SECTION 1
Ectopic Pregnancy
KEY POINTS Ectopic pregnancy is an important cause of maternal
morbidity and mortality in the United States. It occurs
1. The majority of ectopic pregnancies are tubal in location. when a fertilized ovum implants on any tissue other than
2. Serum hCG levels are variable and not predictive of the endometrial lining of the uterus. Ectopic pregnancies
account for approximately 1 to 2% of all pregnancies, but
pregnancy location. cause approximately 3% of pregnancy-related deaths.(1)
3. Ultrasound cannot be used to definitively rule out the Despite an increase in the incidence of ectopic pregnancy
in the United States, there has been a significant decline
presence of ectopic pregnancy in all cases. in mortality since the 1980’s.(2) The cause for increased
incidence has been attributed to increases in risk factors,
including prior sexually transmitted diseases, use of assisted
reproductive techniques, prior tubal surgery, tobacco abuse,
intrauterine device use, and previous ectopic pregnancy.(3,4)
However, half of patients diagnosed with ectopic pregnancy
have no risk factors at all, so it is important that clinicians
always consider the possibility of ectopic pregnancy when
evaluating the symptomatic first trimester patient.(3,4)
51
Patients with ectopic pregnancy will usually present with ultrasound findings. A single hCG level may be viewed as a
acute lower abdominal pain or vaginal bleeding (Movie 6.1). guide to gestational age but gives no information on pregnancy
While the clinical triad of vaginal bleeding, lower abdominal location. The emergency clinician must be careful when
pain, and adnexal mass is considered to be specific for the utilizing serum hCG level since levels in women with ectopic
diagnosis of ectopic pregnancy, the presence of any of these pregnancy are extremely variable and not predictive of rupture.
findings should prompt further investigation to exclude ectopic (6, 8) The presence of a low quantitative hCG level should not
pregnancy. In a 1980 study of 283 patients presenting with dissuade the emergency clinician from performing a pelvic
symptoms concerning for ectopic pregnancy, the clinical triad ultrasound in a symptomatic patient.
had a positive predictive value of only 14%.(5) A 2006 study
notes the following odds ratios in comparing patients with There are multiple possible anatomic locations for ectopic
ectopic pregnancy with other symptomatic pregnancy patients: pregnancy, with tubal being most common (90-95 %).(9) Non-
prior ectopic pregnancy (2.98), history of pelvic inflammatory tubal locations include interstitial, ovarian, cervical, cesarean
disease (1.5), pain at presentation (1.4), vaginal bleeding at section scar and abdominal (Gallery 6.1). Ultrasound frequently
presentation (1.42) and human chorionic gonadotropin (hCG) is helpful in confirming the location of the pregnancy and
level between 501-2000 mIU/ml (1.73).(4) In patients with shock “ruling in” an ectopic pregnancy, but it is essential to understand
and symptoms concerning for ectopic pregnancy, standard that ultrasound alone cannot be used to “rule out” the presence
resuscitative measures should be undertaken with early of an ectopic pregnancy. Sonographic findings in patients
obstetric consultation for operative intervention. with ectopic pregnancy may include definitive visualization
of the ectopic pregnancy, findings suspicious for an ectopic
The liberal use of ultrasound and hormonal testing in this pregnancy, or a normal pelvic ultrasound (pregnancy of
patient population has played a significant role in the recent unknown location).
decline in maternal mortality.(6) Centers with ectopic
pregnancy monitoring programs have managed more patients Free Fluid (Movie 4.5)
successfully non-surgically and decreased their negative
laparoscopy rates.(7) Ultrasound plays an integral role in the Clinical Pearls:
evaluation of the symptomatic first trimester pregnancy. Serum • Identifying peritoneal free fluid is a key part of point-of-care
hCG levels are generally obtained in pregnant patients with
possible ectopic pregnancy and utilized in conjunction with first trimester ultrasound.
• Free fluid can either appear anechoic or echogenic.
52
• Echogenic free fluid should be considered to be Sonographically, fluid can either appear anechoic (simple) or
hemoperitoneum until proven otherwise in a patient with echogenic (complex). Distinguishing between simple and
suspected ectopic pregnancy. complex free fluid is imperative. Echogenic free fluid in the
setting of a pregnant patient with abdominal pain accurately
• The presence of fluid in Morison’s pouch is highly predictive correlates with hemoperitoneum and should be considered
of the need for operative intervention in patients with to be hemoperitoneum until proven otherwise.(11) Other
suspected ectopic pregnancy. causes of complex free fluid include a ruptured hemorrhagic
corpus luteum cyst, pelvic inflammatory disease, and ovarian
In addition to identifying the presence or absence of an torsion. The rate of ruptured ectopic pregnancy in patients
intrauterine pregnancy, one of the main goals of point-of- with moderate to large free fluid is significantly higher than
care first trimester ultrasound is evaluating the female pelvis in patients with only trace to mild free fluid.(12) When
for the presence of free fluid. Identifying and quantifying free hemoperitoneum has had time to clot, a pelvic hematoma can
fluid should be part of every focused first trimester ultrasound form which will appear as an echogenic fluid collection. This
examination. The sonologist should start by examining the isoechoic or hyperechoic fluid may be misleading to the novice
pouch of Douglas (or posterior cul-de-sac) for the presence of sonologist and care must be taken to avoid the pitfall of only
free fluid since this is the most dependent portion of the pelvis evaluating for anechoic free fluid.
in the supine patient. Physiological free fluid is commonly seen
in both the pregnant and non-pregnant female pelvis and is Imaging the right upper quadrant to evaluate for peritoneal
typically seen low in the pelvis. As the amount of fluid in the free fluid is an important adjunctive view to the standard
pelvis increases, it extends along the posterior uterine wall pelvic views and should be included in any exam when more
towards the uterine fundus. Free fluid is considered small if it than a small amount of free fluid is visualized in the pelvis.
extends one-third up the posterior uterine wall, moderate if it Identification of fluid in Morison’s pouch is predictive of the
extends two-thirds up the posterior uterine wall and large if it need for operative intervention in patients with suspected
extends beyond two-thirds of the posterior wall, spills into the ectopic pregnancy and should lead to prompt obstetrical
anterior cul-de-sac or extends up into Morison’s pouch.(10) It consultation.(13)
is important to evaluate the anterior cul-de-sac in patients with
a normal posterior cul-de-sac as some patients may have free 53
fluid isolated to the anterior cul-de-sac, particularly in patients
with a retroverted uterus.(11)
Endometrial Findings (Movie 6.2) A gestational sac is one of the earliest sonographic findings
in a normally developing intrauterine pregnancy. It is usually
Clinical Pearls: located eccentrically within the endometrial canal. In the
• Endometrial thickness cannot be used to rule in or rule out setting of an ectopic pregnancy, a false, or pseudogestational,
sac can form. A pseudogestational sac is thought to be the
the presence of an ectopic pregnancy. result of fluid in the endometrial canal caused by endometrial
• Pseudogestational sacs are seen in about 10% of ectopic breakdown. The sonographic finding was first described in 1979
with a reported incidence of approximately 20 %.(18) More
pregnancies. recent studies have found a lower frequency of approximately
• Trilaminar appearance of the endometrium is specific but not 10 %.(19-21)
sensitive for the diagnosis of ectopic pregnancy. A pseudogestational sac can potentially be confused with a
normal gestation sac. The shape and location of the sac may
In patients with a clinically suspected ectopic pregnancy be helpful in distinguishing between the two types of sacs.
and no definitive sonographic evidence of an intrauterine or Pseudogestational sacs are typically located centrally within
extrauterine pregnancy, evaluation of the endometrial pattern the endometrial canal, as opposed to true gestational sacs
or thickness may provide useful information. Sonographic which tend to implant eccentrically within the endometrial
findings of the endometrium in patients with ectopic cavity. (slideshow) The shape of the sac is important, as a
pregnancy include the presence of a pseudogestational sac, pseudogestational sac is often oval, has pointy edges, and
a normal endometrium, a thickened endometrium, a thinned conforms to the shape of the uterine cavity while a normal
endometrium, or a trilaminar endometrium. Additionally, gestational sac is typically round. Pseudogestational sacs can
the endometrium may have either a homogenous or be of a variety of sizes and therefore size cannot be used to
heterogeneous appearance. distinguish a gestational sac from a pseudogestational sac. In
a recent evaluation of 229 patients with ectopic pregnancy,
Numerous studies have evaluated endometrial thickness as only 2 patients (0.9%) had smooth walled anechoic fluid within
a predictor of ectopic pregnancy.(14-17) These studies have the uterus which could be confused for a normally developing
shown that the width of the endometrial stripe is thinner in gestational sac.(22) From a statistical standpoint, the presence
patients with ectopic pregnancies, but no specific cut-off value
could be determined.(14-17) Therefore, endometrial thickness 54
should not be used to rule-in or rule-out the presence of an
ectopic pregnancy in patients with pregnancy of unknown
location.
of an intrauterine anechoic sac is much more likely to be a • Transducer mobilization may help distinguish a tubal ectopic
developing normal IUP and not a pseudogestational sac.(22) pregnancy from a corpus luteum cyst.
The trilaminar endometrium is formed during the late • The tubal ring sign or “ring of fire” is very sensitive but poorly
proliferative phase of the normal menstrual cycle. It consists specific for the diagnosis of a tubal ectopic pregnancy.
of an echogenic basal layer and a hypoechoic inner layer
that is surrounded by a thin echogenic layer that represents The majority of ectopic pregnancies are tubal in location (>90%)
the interface with the endometrial lumen. (slideshow) The with implantation occurring in the isthmic, ampullary, or fimbrial
trilaminar endometrial pattern can also develop in patients portions of the fallopian tube.(25) The sonographic appearances
with ectopic pregnancy. This pattern is highly specific (> 90 %) of the tubal ectopic pregnancy will depend on the gestational
but poorly sensitive (approximately 20%) for the diagnosis of age of the pregnancy, the location of implantation in the tube,
ectopic pregnancy.(16,23,24) In the prediction of ruptured and the viability of the pregnancy.
ectopic pregnancy, a trilaminar endometrial pattern had a
sensitivity of 60%, a specificity of 95.7%, a positive predictive Definitive sonographic findings of tubal ectopic pregnancy
value of 85.7%, and a negative predictive value of 84.6%.(24) include a tubal mass with a visible yolk sac or embryo, with or
Therefore, in patients without sonographic evidence of an without cardiac activity. These findings carry positive predictive
intrauterine pregnancy, the diagnosis of ectopic pregnancy values (PPV) for ectopic pregnancy of 100% but are only seen in
should be strongly considered when this trilaminar endometrial approximately 13-22% of ectopic pregnancies.(12,26,27)
pattern is present
Sonographic findings that are suspicious but not definitive
Tubal Ectopic (Movie 6.3) for tubal ectopic pregnancy include tubal rings and adnexal
masses. A tubal ring without yolk sac separate from the
Clinical Pearls: ipsilateral ovary is seen in approximately 20-25% of cases and
• Definitive evidence of ectopic pregnancy includes carries a PPV of 90-95%.(12,26,27) Sonographically the tubal
ring appears as a hypoechoic circular structure with hyperechoic
visualization of an adnexal mass containing a yolk sac or outer ring. The most common finding of an ectopic pregnancy,
viable embryo. seen in approximately 54-58% of cases, is a nonspecific complex
• Suspicious findings of ectopic pregnancy include adnexal or solid adnexal mass and has a PPV of 90-95%.(12,26,27)
masses and tubal rings.
The corpus luteum is an integral part of the development
of normal pregnancy and it can have multiple different
55
sonographic appearances. A corpus luteum cyst can be very • Ultrasound findings include an eccentrically located
difficult to distinguish from the non-specific adnexal mass of gestational sac with less than 5 mm of myometrium
a tubal ectopic pregnancy.(28) Transducer pressure can be surrounding the gestational sac.
employed to help distinguish between a corpus luteum cyst
and a tubal mass with attempts made to mobilize the suspected • A cornual pregnancy occurs in a horn of a bicornuate uterus
tubal mass. If the mass moves with the ovary, it is likely a corpus and is associated with a better prognosis compared to that of
luteum cyst. An ectopic pregnancy will move separately from an interstitial ectopic.
the ovary.(29)
An interstitial ectopic pregnancy occurs when a fertilized ovum
Traditionally, color Doppler has been used to visualize the implants in the myometrial portion of the fallopian tube where
vascular flow around a tubal ring or adnexal mass and is it traverses the wall of the uterus to enter the endometrium
described as “ring of fire.” “Ring of fire” is very sensitive but poorly and is estimated to comprise 2-4% of ectopic pregnancies.
specific for the diagnosis of a tubal ectopic pregnancy. This (30) Patients with interstitial pregnancies that advance past
sign can be seen in both corpus luteum cysts and tubal ectopic 12 weeks of gestational age are at particularly high risk for
pregnancy and should not be used to distinguish between rupture. The insertion site for interstitial pregnancies tends to
the two entities.(9) Color Doppler may also allow for detection be located closely to the uterine artery and rupture can cause
of a tubal ectopic pregnancy surrounded by loops of bowel. brisk hemorrhage, leading to increased morbidity and mortality
However, the presence of significant bowel peristalsis will result compared to ruptured tubal pregnancies.(31) While interstitial
in artifact that may obscure the “ring of fire.” ectopic pregnancy and cornual pregnancy are often used
interchangeably, they are two distinct entities and should not
Interstitial Ectopic (6.4) be confused. Cornual pregnancies are pregnancies that occur in
a horn of a bicornuate uterus. They are associated with higher
Clinical Pearls: complication rates but can still result in viable pregnancies,
• An interstitial ectopic is a dangerous subtype of ectopic while interstitial ectopic pregnancies do not result in viable
pregnancies.(32)
pregnancy in which the ovum implants in the portion of the
fallopian tube that traverses the uterine wall. Sonographic recognition and diagnosis of interstitial pregnancy
is challenging as the gestational sac is located outside of the
endometrium but still within the uterus; therefore careful
analysis of the surrounding anatomy is key.(33) Criteria for
56
diagnosis of an interstitial pregnancy include an empty uterus, Miscellaneous Ectopic Pregnancies (Movie 6.5)
an eccentrically located gestational sac, and a thin myometrial
mantle.(34) The myometrial mantle is measured at the thinnest Clinical Pearls:
portion of myometrium from the free uterine wall to the • Non-tubal ectopic pregnancies are rare.
endometrium. A measurement of 5 mm or less should be • Knowledge of potential locations and sonographic
considered highly suspicious for the presence of an interstitial
ectopic pregnancy. Some have suggested using an 8 mm appearances of non-tubal ectopic pregnancies is important
cutoff; while this would increase the sensitivity it would also when performing point-of-care first trimester ultrasound.
result in a higher false-positive rate.(30) The currently used • Because of anatomical considerations, non-tubal ectopic
cutoff criteria is based on data from small studies and case pregnancies are associated with increased morbidity and
series and there is no prospective study available that offers a mortality.
conclusive measurement.(9) Uterine contractions resulting in
an eccentrically located but normally implanted gestational Less than 10% of ectopic pregnancies involve implantation of
sac, an early intrauterine pregnancy in a bicornuate uterus, the fertilized egg in locations other than the fallopian tubes.
and a uterine fibroid in a pregnant patient without a visualized (6) These locations include the cervix, cesarean section scar,
intrauterine pregnancy can all be mistaken for an interstitial ovary, and abdomen. Despite their rarity, knowledge of
ectopic pregnancy. In cases where the 2D ultrasound is the sonographic appearance of these ectopic pregnancies
inconclusive, 3D ultrasound or MRI may play a role.(31) is important when performing point-of-care first trimester
ultrasound as they can be challenging to diagnose.
The interstitial portion of the fallopian tubes is visualized
sonographically as an echogenic line that connects Cervical Ectopic
endometrium to the uterine serosa. An interstitial ectopic may A cervical ectopic pregnancy occurs when there is implantation
be visualized in the middle of this echogenic line, termed the of a fertilized ovum in the endocervical canal and represents
interstitial line sign, and is thought to be very specific for the less than 1% of ectopic pregnancies.(36) Patients usually
diagnosis of interstitial pregnancy.(35) present with painless vaginal bleeding during the first trimester.
Cervical ectopic is considered a high-risk subtype of ectopic
pregnancy because of the increased vascularity of the cervix
and the amount of bleeding that can occur with rupture.(37)
57
A cervical ectopic pregnancy can easily be confused with the the anterior myometrium and subsequent implantation at
cervical phase of a spontaneous miscarriage.(38) Findings this site.(40) Findings on pelvic ultrasound include an empty
suggestive of a spontaneous abortion include an irregularly uterine cavity, an empty cervical canal, development of a
shaped gestational sac that is not adherent to the cervix. gestational sac in the anterior portion of the uterine isthmus
Clinically, an open cervical os strongly suggests spontaneous at the presumed site of cesarean scar, and absence of healthy
abortion. If an embryo with cardiac activity is visualized below myometrium between the bladder and the gestational sac.(40)
the internal cervical os, cervical ectopic is the diagnosis. If the The gestation can develop prominent vascularity; thus bleeding
gestational sac is in the same position and has the same shape can be severe when cesarean scar pregnancies rupture.(40)
on repeat ultrasound examination, cervical ectopic is likely.(37) Additionally, there is high risk of significant maternal morbidity
Correct diagnosis is imperative, since treating a cervical ectopic and mortality if rupture occurs.(40)
as a cervical phase of a spontaneous abortion with dilation and
curettage can cause severe life-threatening hemorrhage.(33) Ovarian Ectopic
Ovarian ectopic pregnancy occurs when a fertilized ovum is
Nabothian cysts can be confused with the sac of a cervical retained in an ovary. Ovarian ectopic pregnancy is estimated
ectopic. Nabothian cysts, however, will not have an echogenic to comprise 1-3% of ectopic pregnancies and is associated
ring present and are frequently far enough away from the with IUD usage.(25) Sonographically, most ovarian ectopic
cervical canal to prevent confusion. pregnancies appear cystic and have an echogenic outer ring.
A yolk sac or embryo is not commonly visualized. Applying
Cesarean Scar Ectopic transducer pressure augmented by manual abdominal pressure
Cesarean scar pregnancy occurs when there is implantation of can help distinguish between a tubal and an ovarian ectopic.
a fertilized ovum in the anterior lower uterine segment at the (33) However, it can be very difficult to distinguish between a
site of a cesarean scar. Cesarean scar pregnancies represent corpus luteum and an ovarian ectopic and some patients will
6% of ectopic pregnancies in women with a prior cesarean need repeat ultrasound examinations to assess for sonographic
section.(39) The incidence is low, representing less than 1% changes in the concerning ovarian mass.(41)
of all ectopic pregnancies, but thought to be rising because
of increasing rates of cesarean deliveries.(39) The underlying Abdominal Ectopic
pathophysiology is unknown but the predominant theory Abdominal ectopic pregnancy occurs when there is
is that poor healing of the scar leads to a wedge defect in implantation of a fertilized ovum anywhere in peritoneal cavity.
58
Abdominal ectopics are exceedingly rare, representing < 1% spontaneous heterotopic pregnancy is about 1 in 30,000;
of all ectopic pregnancies.(25) Abdominal ectopic pregnancy however, risk in women receiving assisted reproductive
can be defined as primary or secondary.(42) Primary abdominal technology (ART) is significantly increased at 1 to 3 in 1000.
ectopic pregnancy is very rare and occurs when a fertilized (45) Because of its rarity, diagnosis is often delayed and most
ovum implants itself initially on an abdominal organ, while cases are missed on initial presentation.(46) Both ectopic and
secondary abdominal ectopic pregnancy occurs when the heterotopic pregnancies are considered serious complications
fertilized ovum is implanted in the fallopian tube or uterus of ART. Rupture of the ectopic pregnancy can have deleterious
and then escapes into the peritoneal cavity through rupture. effects on the intrauterine pregnancy; however, if expeditiously
(42) Anatomically, they are most commonly found in the diagnosed and treated properly, the intrauterine pregnancy can
posterior cul-de-sac or adjacent to the fundus of the uterus. frequently be brought to term.
(43) Diagnosis tends to be delayed and inaccurate. Abdominal
ectopic pregnancies are associated with high maternal Women undergoing ART are potentially at increased risk of
mortality, upwards of 18%, because of the aforementioned ectopic pregnancy given the high likelihood of underlying tubal
delay in diagnosis as well as anatomic considerations leading to dysfunction. When ovarian hyperstimulation and embryonic
a high rate of rupture and subsequent hemorrhage.(44) transfer techniques are utilized, the risks of both ectopic
pregnancy and heterotopic pregnancy are increased.(47)
Heterotopic Pregnancy (Movie 6.6)
Routine evaluation of the adnexa during first-trimester point-
Clinical Pearls: of-care ultrasound will help evaluate for the potential of
• Heterotopic pregnancy is defined as the presence of both an heterotopic pregnancy, with particular attention given to
patients undergoing ART. Even in the presence of intrauterine
IUP and simultaneous ectopic pregnancy. pregnancy, echogenic and/or a moderate amount of pelvic
• Heterotopic pregnancies are rare but occur with much more free fluid should prompt the sonologist to further scrutinize the
adnexa.(48)
frequency in patients undergoing assisted reproduction.
• In symptomatic patients undergoing assisted reproduction, 59
pelvic ultrasound should thoroughly examine the pelvis.
Heterotopic pregnancy is by definition the presence of an
intrauterine and simultaneous ectopic pregnancy. Risk of
Pregnancy of Unknown Location For patients with PUL, deciding whether therapy for ectopic
pregnancy should be initiated is the key question. If there is a
Clinical Pearls: chance of a viable IUP, conservative management is paramount
• Pregnancy of unknown location (positive hCG level and and should include a follow-up hCG level and ultrasound. The
consequences of a false positive (i.e. an inappropriate diagnosis
a normal uterus and adnexa on ultrasound) is a complex of non-viability) are severe, as treating a desired viable IUP as
clinical scenario. an ectopic pregnancy can have catastrophic repercussions.
• Every effort should be made to eliminate false positive results The consequence of a false negative (i.e. incorrect diagnosis
(inappropriate diagnosis of non-viability). of potential viability) is much less dire and usually amounts to
• When in doubt, a repeat hCG level and ultrasound is close follow-up with a minimal delay in treatment for a patient
indicated. without an adnexal mass on ultrasound. Clinical decision trees
are currently being evaluated to stratify PUL into low and high
When a pregnancy cannot be definitely called intrauterine, risk for ectopic pregnancy and monitor for adverse outcomes.
ectopic, or failed, the location of the pregnancy is temporarily (51-53) Test specificity for ectopic pregnancy needs to be as
unable to be identified, thus termed pregnancy of unknown close to 100% as possible, and all attempts should be made to
location (PUL). Between 5-42% of symptomatic pregnant eliminate any chance of a false positive result.(54)
women being evaluated for abnormal first trimester pregnancy
are diagnosed with PUL.(49) Compared with ectopic Recent research has substantially changed current thinking
pregnancies that are identified on initial ultrasound, ectopic regarding PUL and the “discriminatory zone.” The discriminatory
pregnancies which are initially diagnosed as PUL have lower zone is the hCG level above which an intrauterine gestational
mean gestational age and mean initial hCG level.(26) A 2004 sac should be seen on US in normal pregnancy. Traditional
study of symptomatic first trimester patients presenting to an levels are 6500 mIU/ml IRP for transabdominal imaging and
urban academic emergency department noted a PUL rate of between 1000-2000 mIU/ml IRP for transvaginal imaging. These
20%.(50) The outcomes of patients with PUL in this study were single value thresholds are not acceptable given the need to
poor, with approximately 50% pregnancy failure, 15% ectopic limit false positive diagnoses of nonviable pregnancies. There
pregnancy, and 30% IUP.(50) Notably, fewer patients in the are published cases of term deliveries after an initially empty
PUL follow-up group with ectopic pregnancy required surgical uterus and hCG levels above 3000 mIU/mL IRP. Even in a patient
treatment (36% vs 83%).(50) with a PUL and an hCG level of greater than 2000 mIU/ml, a
60
nonviable IUP is twice as likely as an ectopic pregnancy. For a 5. Schwartz RO, Di Pietro DL. beta-hCG as a diagnostic aid for
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33. Chukus A, Tirada N, Restrepo R, Reddy NI. Uncommon Implantation review of the literature. J Obstet Gynaecol Can. 2009 Jan;31(1):57-
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Mass. Radiographics. 2015 May-Jun;35(3):946-59.
43. Goh TH, Rahman SA. Primary peritoneal pregnancy implanted on
34. Timor-Tritsch IE, Monteagudo A, Matera C, Veit CR. Sonographic the uterine fundus. Aust N Z J Obstet Gynaecol. 1980 Nov;20(4):240-
evolution of cornual pregnancies treated without surgery. Obstet 1.
Gynecol. 1992 Jun;79(6):1044-9.
44. Atrash HK, Friede A, Hogue CJ. Abdominal pregnancy in the United
35. Ackerman TE, Levi CS, Dashefsky SM, Holt SC, Lindsay DJ. Interstitial States: frequency and maternal mortality. Obstet Gynecol. 1987
line: sonographic finding in interstitial (cornual) ectopic pregnancy. Mar;69(3 Pt 1):333-7.
Radiology. 1993 Oct;189(1):83-7.
45. Fernandez H, Gervais A. Ectopic pregnancy after infertility
36. Cerveira I, Costa C, Santos F, Santos L, Cabral F. Cervical ectopic treatment: modern diagnosis and therapeutic strategy. Hum
pregnancy successfully treated with local methotrexate injection. Reprod Update 2004;10(6):503-13.
Fertil Steril. 2008 Nov;90(5):2005 e7- e10.
46. Talbot K, Simpson R, Price N, Jackson SR. Heterotopic pregnancy.
37. Frates MC, Laing FC. Sonographic evaluation of ectopic pregnancy: J Obstet Gynaecol 2011 [cited 31 1]; 7-12]. Available from: http://
an update. AJR Am J Roentgenol. 1995 Aug;165(2):251-9. www.ncbi.nlm.nih.gov/pubmed/21280985
38. Leeman LM, Wendland CL. Cervical ectopic pregnancy. Diagnosis 47. Refaat B, Dalton E, Ledger WL. Ectopic pregnancy secondary to in
with endovaginal ultrasound examination and successful treatment vitro fertilisation-embryo transfer: pathogenic mechanisms and
with methotrexate. Arch Fam Med. 2000 Jan;9(1):72-7. management strategies. Reprod Biol Endocrinol. 2015;13:30.
39. Seow KM, Huang LW, Lin YH, Lin MY, Tsai YL, Hwang JL. Cesarean 48. Yamamoto R, Murakoshi H, Yamashita Y, Ejima Y, Yoshida S,
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2004 Mar;23(3):247-53. onset of severe symptoms: case report. Clin Exp Obstet Gynecol.
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40. Osborn DA, Williams TR, Craig BM. Cesarean scar pregnancy:
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64
CHAPTER 7
Incidental Findings
Joseph Minardi, MD
65
SECTION 1
Incidental Findings
KEY POINTS While point-of-care pelvic ultrasound is not meant to be
comprehensive, the sonologist should recognize common
1. Common incidental findings include nabothian cysts and incidental uterine and adnexal findings. . In this chapter,
fibroids. we will review some common normal variants as well as
some common abnormal, but non-emergent findings that
2. Pregnancy in the setting of an IUD is an ectopic pregnancy may be encountered. It is important that these findings are
until proven otherwise. not mistaken for pathology. Further, recognizing common
findings allows the clinician to create a more complete
3. Periuterine vasculature may be distinguished from other sonographic and clinical picture in order to make more
entities using color Doppler. informed treatment and follow-up decisions.
4. Normally, fallopian tubes cannot be visualized with Uterine Findings (Gallery 7.1)
ultrasound.
Clinical Pearls:
5. Any complex ovarian cyst requires a follow up ultrasound. • Nabothian cysts are located in the myometrial portions of
the lower uterine segment and cervix, have thin walls and
typically contain simple fluid
66
• Leiomyomas or fibroids are common and may be variable in Leiomyomas/Fibroids
location. Leiomyomas, commonly known as fibroids, are the most
common uterine mass. A 1997 longitudinal study of US nurses
• Fibroids have a heterogeneous appearance with streaking found fibroids occur in 8.9 per 1000 white women and 30.6
attenuation artifacts often obscuring other structures. per 1000 black women.(5) They are often an asymptomatic
incidental finding on pelvic ultrasound. However, they may
• Pregnancy occurring with an intrauterine device (IUD) in cause symptoms including pain and/or bleeding. Their location
place is an ectopic pregnancy until proven otherwise. is categorized as intramural, submucosal, or subserosal.
Nabothian cysts • Intramural - confined to the myometrium
Nabothian cysts are a common, normal finding in the lower • Submucosal - project into the uterine cavity
uterine segment and cervix of young women. They may be • Subserosal - lie on the outer borders or peritoneal surfaces of
seen on physical inspection of the cervix as well as visualized
sonographically.(2) They are typically small, thin walled, the uterus, and may even appears as pedunculated masses
circular, fluid filled cysts found in the lower uterine segment
and cervix (see nabothian 1 and 2). Nabothian cyst walls are Submucosal fibroids may lead to problems with infertility and
nearly invisible by ultrasound. Fluid within the cysts is typically can increase the risk of spontaneous abortion.(6) Additionally,
hypoechoic or anechoic, but more echogenic material is fibroids located in the lower uterine segment or cervix may
sometimes present. They are typically small, 2-4 mm in diameter, interfere with vaginal delivery.(6) Pregnant women with fibroids
but larger cysts, measuring up to 4 cm may be found. Posterior may experience acute pain from degeneration characterized on
acoustic enhancement may be noted, but may be difficult ultrasound by hypoechoic areas within the fibroid.(7-9)
to appreciate with smaller cysts (see nabothian 3 and 4).(3, 4)
Nabothian cysts could potentially be mistaken for a gestational The sonographic appearance of fibroids is variable, typically
sac of a cervical ectopic pregnancy. Noting the location in consisting of a hypoechoic or heterogeneous mass, distorting
the myometrial portion of the uterus, the simple nature of the the uterine contour. Attenuation and shadowing is common,
contents and the very thin, nearly invisible walls should allow often making visualization of other important anatomy difficult
the clinician to differentiate these cysts from ectopic pregnancy, (see fibroid 4). (Insert various fibroid US pics)
gestational sac, or other dangerous pathology
Fibroids are generally benign and malignant transformation is
rare. Specific follow up is recommended only for symptomatic
lesions. Fibroids may be mistaken for other malignant lesions
67
or possibly ectopic pregnancy and consultative ultrasound will as these cases carry seven times higher risk of morbidity and
be required when the diagnosis is in doubt. However, recalling mortality compared to tubal ectopic pregnancies.(13)
the general high prevalence of fibroids and noting the typical
appearance should help the clinician avoid confusion. Intrauterine Device (IUD)
IUDs are a commonly used and highly effective form of
Bicornuate Uterus (Movie 7.2) contraception. They consist of a T-shaped polyethylene frame
Bicornuate uterus is a uterus composed of two uterine “horns” with a copper wire or a levonorgestrel-containing collar around
separated by a septum as a result of abnormal fusion in the stem. Complications associated with IUD placement
embryogenesis. It is a variation of normal anatomy that occurs include expulsion out of the cervical canal, fragmentation
in 0.4 % of women, although it is likely underestimated.(10) It of the IUD, displacement, uterine perforation and infection.
is commonly referred to as a heart-shaped uterus. While this (14) Non-visualization of IUD strings on clinical examination
anatomical variation was once thought to cause infertility, or excessive pelvic pain following recent IUD insertion should
recent research does not support this.(11) These pregnancies prompt ultrasound evaluation of IUD location. Appropriate IUD
are typically considered high risk due to the potential for position should be recognized on ultrasound. The long axis of
increased adverse effects including recurrent pregnancy the IUD stem should follow the exact path of the endometrial
failure, preterm birth, malpresentation, and fetal deformities. canal. The arms of the IUD should extend laterally at the fundus.
(12) However, patients can have a relatively normal pregnancy Copper IUDs will be more easily visualized on ultrasound than
course depending on the extent of anatomic variation and hormonal IUDs which have echogenic proximal and distal
implantation site of the fetus. Due to the abnormal anatomy ends only. (include pics). Partial expulsion out of the cervical
of the uterus, a pregnant bicornuate uterus can be mistaken canal requires evaluation by gynecology due to inefficacy of a
for an interstitial ectopic as often the pregnancy will appear partially expulsed IUD.(15) Management of an asymptomatic
to be implanted off- center. Because of this possibility it is malpositioned IUD in the myometrium, which occurs in up
important that the practitioner make sure to thoroughly sweep to 25% of patients with IUDs, is variable with some patients
through the uterus and ensure that there is at least 5 mm electing removal and others deciding on observation.(16) If
of myometrium surrounding the GS. Emergency medicine an IUD is not visualized on ultrasound, plain films should be
literature suggests being even more conservative and ensuring performed to rule out uterine perforation.(17)
8 mm of myometrium surrounding the gestational sac.(13)
Ruling out an interstitial pregnancy is extremely important 68
IUDs are 97-99% effective in preventing pregnancy (copper IUD the ovarian architecture. In addition, ovaries typically contain
97.5% effective versus hormonal IUD 99.5% effective).(18) When visible stromal tissue and a thin oval capsule. Periuterine
pregnancy occurs with an IUD in place, implantation is unlikely vasculature should also be differentiated from paraovarian and
to occur in the endometrial cavity. Therefore, these patients ovarian cysts. Color Doppler is useful for this purpose as flow
should be suspected of having an ectopic pregnancy until should be visible within non-thrombosed vessels and absent
proven otherwise.(19) from paraovarian and ovarian cysts.(20)
Adnexal/Miscellaneous Findings (Gallery 7.2) Bowel
Bowel within the female pelvis is commonly seen and can
Clinical Pearls: be confused with normal ovaries, dilated fallopian tubes, and
• Periuterine vasculature may mimic the appearance of ovarian other pathologic findings. Normal bowel, when decompressed
is made up of alternating hypo and hyperechoic layers that
follicles, but is less organized and color Doppler should show distinguish it from ovaries or other adnexal structures.(21)
internal flow.
• Decompressed bowel has distinctly visible alternating Alternating intestinal layers from innermost to external:
hypoechoic and echogenic layers. Bowel filled with fluid,
stool, or air will have an irregular shape compared to ovaries • Superficial mucosa – hyperechoic
and frequently undergoes peristalsis • Deep mucosa - hyperechoic
• Hydrosalpinx and pyosalpinx consist of serpiginous fluid- • Deep mucosa/muscularis propria interface - hyperechoic
filled structures adjacent to the ovaries and uterus without • Muscularis propria - hypoechoic
internal flow and are commonly seen with tubo-ovarian • Serosa – hyperechoic
abscess.
When bowel becomes fluid or stool filled, the walls become
Periuterine vasculature stretched and the layered architecture is not typically visible. The
The periuterine vasculature in females of gestational age may relatively homogeneous appearance of bowel contents, as well
be prominent and appear very similar to ovarian follicles. Using as the irregular contours should assist in proper identification.
color Doppler may be useful to demonstrate internal flow in the In addition, observing for peristalsis will confirm a structure
vasculature whereas ovarian follicles should not have internal as bowel rather than ovary, dilated fallopian tube, or another
flow. The periuterine vasculature is less organized compared to adnexal structure. Care should be taken when observing the
69
bowel as intestinal pathology may be identified including Ureteral Stones:
appendicitis, intussusception, colitis, and constipation.(21-23) Symptomatic ureteral stones in pregnancy occurs at a rate
similar to that of nonpregnant women of child-bearing age.
Hydrosalpinx/Pyosalpinx Distal ureteral stones may be visualized during performance
Normally, fallopian tubes are not visualized by ultrasound. of the transabdominal pelvic ultrasound examination since
However, if they become filled with fluid, they may be visible. the urinary bladder is visualized. The ureteral stones will be
A fluid-filled fallopian tube is referred to as hydrosalpinx.(24) echogenic and round or oval in shape. Posterior shadowing
Hydrosalpinx may be a normal finding after hysterectomy or may be present depending on stone composition and size.
tubal ligation, but may also be a manifestation of tubo-ovarian
abscess (TOA). The appearance is that of a serpiginous, fluid- Ovarian Findings (Gallery 7.3)
filled structure adjacent to the uterus that is distinct from
the ovaries. If the fluid is more echogenic or complex, this is Clinical Pearls:
referred to as pyosalpinx and is even more likely to represent a • Simple cysts are thin walled, round or ovoid containing
TOA. Occasionally, blood may collect within the fallopian tubes,
which is referred to as hematosalpinx, giving the fluid a more simple fluid.
echogenic or complex appearance as well.(25-27) Ultrasound • Corpus luteal cysts have thicker, vascular walls and occur in
cannot distinguish between pyosalpinx and hematosalpinx.
early pregnancy.
Hydrosalpinx or pyosalpinx may be mistaken for ectopic • Hemorrhagic cysts have thin walls and contain some internal
pregnancy, paraovarian or ovarian cyst, or even normal
structures such as bowel or vasculature. Proper identification echogenic material and always require follow-up imaging.
is aided by following the course of the structure, imaging from • Dermoid cysts are fat containing masses with mixed
at least two different planes, interrogating with color Doppler,
and identifying the uterus and ovaries as distinct, separate echogenic areas and attenuation artifacts.
structures. As always, the sonographic findings should be
interpreted in the clinical context. In unclear cases, surgical Follicular Cysts
exploration may be the only means to a definitive diagnosis. Nearly all simple ovarian cysts are follicular in origin. They are
one of the most common findings in pelvic ultrasound. By
definition, they are thin-walled, round or ovoid, contain simple
hypoechoic or anechoic fluid, and display posterior acoustic
enhancement.(28) Follicular cysts are simply enlargement of the
normal ovarian follicles, beyond 2.5 cm.(28) They may be very
70
large and can obscure visualization of the ovarian parenchyma. Hemorrhagic Cysts
Follicular cysts, especially larger ones, may cause pelvic pain. Hemorrhagic cysts are another common finding in pelvic
Rupture of follicular cysts occasionally causes acute pelvic pain. ultrasound. Hemorrhagic cysts demonstrate the following
Follicular cysts require follow-up only if symptomatic. characteristics:
Corpus Luteal Cysts • Thin, smooth walls
Corpus luteal cysts are often seen in first trimester pregnancies. • Complex internal echoes and/or septations
The corpus luteum forms during ovulation and, when • Typically exhibit posterior acoustic enhancement
pregnancy occurs, secretes progesterone to maintain • Contents do not demonstrate color Doppler flow.(28, 33, 34)
endometrial growth and sustain pregnancy.(29) These cysts
average about 2 cm in size, regress by 10-13 weeks’ gestation, Leaked hemorrhagic contents from a ruptured hemorrhagic cyst
and have thicker walls than follicular cysts.(30) The contents may cause acute pain. In some cases, frank hemoperitoneum
may be simple, but septations and internal debris are frequently with echogenic fluid in the cul-de-sac and Morison’s pouch may
present. Color flow to the rim of the corpus luteal cyst peaks be present, which can mimic a ruptured ectopic pregnancy.
at 5 weeks’ gestational age (GA) and makes differentiation from
ectopic pregnancy difficult at times.(31) TOA and endometriomas may have a similar sonographic
appearance and may not be distinguishable without other
Contextual information can assist in interpretation of the clinical information.(35) In comparison to ectopic pregnancy,
sonographic findings. For instance, if an intrauterine pregnancy hemorrhagic cysts typically have thin walls and the internal
has been identified, a corpus luteal cyst is much more likely to contents are disorganized and largely hypoechoic.(33) Follow-
be present than a heterotopic pregnancy. Acutely presenting up for these complex cysts is recommended in 6-12 weeks
pregnant patients with presumed ruptured corpus luteal cysts or sooner depending on the clinical concerns.(36) A true
require obstetric consultation and risk stratification for operative hemorrhagic cyst should decrease in size or resolve within this
intervention.(32) timeframe.(35) Follow-up consultative ultrasound is warranted
for anything other than simple ovarian cysts.
Endometrioma
Endometriomas are common benign tumors made up
of ectopic endometrial tissue that are a manifestation of
71
endometriosis.(36, 37) Sonographically, they have a very described adnexal cysts. Often, they are recognized incidentally
similar or nearly identical appearance to a hemorrhagic cyst. as they are usually asymptomatic.(28) They may, however,
The primary difference is that they do not change and may present acutely as a torsed ovary or ruptured cyst.
even increase in size over the course of a few menstrual cycles.
Clinically, endometriomas cause more indolent or chronic Sonographically, they have a highly variable appearance that
pain compared to hemorrhagic cysts, which tends to be usually contains prominent echogenic fatty material.(40, 41)
present more acutely. Differentiating an endometrioma from a Sebaceous material, hair, and calcified teeth may also be seen.
hemorrhagic cyst is difficult in the acute setting. Sonographic (40) Guttman’s 1977 article describes the dermoid “tip of the
findings of pelvic inflammatory disease and TOA may also iceberg sign” in which the highly echogenic cyst contents
have a very similar appearance. All patients with hemorrhagic produces a bright edge with posterior attenuation that
cysts who are able to be discharged home require a follow-up obscures other structures.(42) A dermoid plug (“dermoid plug”
consultative ultrasound in 6-12 weeks.(36) sign), which is an area of echogenic material projecting from an
ovarian cyst may also be seen.(43) Dermoid plugs often contain
Paraovarian cysts calcific, dental, adipose, hair and/or sebaceous components.
Paraovarian cysts appear similar to follicular cysts, but are Dermoid cysts don’t typically exhibit internal vascularity with
distinctly separate from the ovaries, often lying along the course color Doppler analysis.(40)
of the fallopian tubes. They are thin walled, typically round, with
simple, hypoechoic or anechoic contents as well as posterior As with most adnexal masses, torsion is the most emergent
acoustic enhancement.(38) Color Doppler should reveal no possible complication. The heterogeneous appearance and
internal flow. These cysts are usually benign and unlikely to highly echogenic fat with attenuation artifacts should assist
cause symptoms. Rarely, they may hemorrhage, rupture, or in differentiating from ectopic pregnancy and other adnexal
be lead to adnexal torsion. Follow up is recommended for masses. Follow-up consultative ultrasound should be obtained
cysts greater than 5 cm diameter in premenopausal women or for these and any other complex adnexal masses.
greater than 1 cm in postmenopausal women.(39)
Ovarian Torsion
Dermoid cysts Ovarian torsion occurs when the ovary twists on its vascular
Dermoid cysts are also known as cystic teratomas. Dermoid pedicle and obstructs venous return, leading to stromal edema,
cysts are less commonly seen compared to the previously hemorrhage, and necrosis of ovarian tissue if unrecognized.
Any ovarian mass, especially larger than 5 cm, may increase the
72
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Radiol. 2001 Jun;74(882):556-62. ovarian torsion. Radiographics. 2008 Sep-Oct;28(5):1355-68.
38. Athey PA, Cooper NB. Sonographic features of parovarian cysts. AJR 48. Chang EM, Kim A, Kim JW, Yoon TK. Ultrasound-guided transvaginal
Am J Roentgenol. 1985 Jan;144(1):83-6. aspiration as initial treatment for adnexal torsion following
ovarian hyperstimulation. Eur J Obstet Gynecol Reprod Biol. 2010
39. Savelli L, Ghi T, De Iaco P, Ceccaroni M, Venturoli S, Cacciatore Sep;152(1):60-3.
B. Paraovarian/paratubal cysts: comparison of transvaginal
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49. Gaspar-Oishi MA, Kawelo RM, Bartholomew ML, Aeby T.
Transvaginal ovarian cystectomy for adnexal torsion during
pregnancy. J Minim Invasive Gynecol. 2012 Mar-Apr;19(2):255-8.
50. Erdemoglu M, Kuyumcuoglu U, Kale A. Pregnancy and
adnexal torsion: analysis of 20 cases. Clin Exp Obstet Gynecol.
2010;37(3):224-5.
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CHAPTER 8
STreicmoensdt/eTrhPirredgnancy
Kelly Gibson, MD FACOG
Justin Lappen, MD FACOG
77
SECTION 1
Second/Third Trimester
KEY POINTS Clinical pearls:
• The determination of fetal presentation and lie is essential
1. Six essential components of the second and third trimester
ultrasound examination include the determination of: fetal to planning for optimal delivery and need for additional
lie and presentation, cardiac activity, fetal number, amniotic resources.
fluid volume, placental localization, and biometry. • Placental location relative to the cervix determines the
need for cesarean section.
2. Vaginal bleeding and abdominal pain in the second and • Rapid options to estimate gestational age in order to
third trimester requires timely evaluation with ultrasound determine fetal viability include fundal height and femur
to guide maternal and fetal management. length.
3. Point-of-care pelvic ultrasound is part of the secondary Point-of-Care ultrasound (POCUS) components:
survey in the evaluation of the pregnant trauma patient. 2nd/3rd trimester examination
4. Goals for point-of-care ultrasound in active labor include Essential Components of Obstetric Ultrasound in the 2nd/3rd
fetal presentation, placenta location, and fetal viability. Trimester of Pregnancy (Movie 8.1)
1. Fetal Lie and Presentation
2. Fetal Cardiac Activity
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3. Fetal Number (singleton, twin, triplet or higher order should be suspected and a mid-sagittal view of the fetal spine
multiple gestation) should be obtained to assess the relative angle of the fetal and
maternal spines.
4. Amniotic Fluid Volume
To determine fetal lie and presentation, place the transducer
5. Placental Localization/Placental Assessment over the maternal lower abdomen, just above the pubic
symphysis, in a transverse orientation. Angle the transducer
6. Fetal Biometry inferiorly toward the cervix to identify the presenting part of the
fetus (head, buttocks/sacrum, or other/none).
Fetal Lie and Presentation (Movie 8.2)
Fetal lie is defined as the orientation of the fetal spine relative to The determination of fetal lie and presentation are critical to
the maternal spine. Determination of fetal lie requires obtaining choosing the optimal mode of delivery. Attempting breech
a mid-sagittal view of the fetal spine. Longitudinal fetal lie vaginal delivery may be appropriate based on clinical factors,
occurs when the fetal and maternal spinal columns are parallel experience of the health care provider, and the care setting.(1)
(along the same axis), which is the most common fetal lie in the External cephalic version may be recommended to women with
second and third trimester. Cephalic and breech presentation oblique lie or breech presentation at term. Persistent transverse
are both examples of a longitudinal fetal lie. Transverse lie lie requires cesarean delivery. However, a classical cesarean
occurs when the fetal spine is positioned perpendicular to the delivery is required if the fetal back is “down” (fetal spine in lower
maternal spine. When the fetal spine is in an oblique direction uterine segment) as the thorax and abdomen obstruct delivery
to the maternal spine (at an angle between a longitudinal and through a hysterotomy in the lower uterine segment.
transverse lie), the fetal lie is considered to be oblique.
Fetal Cardiac Activity (Movie 8.3)
Fetal presentation refers to which anatomical part of the fetus The determination of fetal cardiac activity is an essential
is closest to the pelvic inlet. The presentation may be cephalic, component of any basic ultrasound examination. The presence
breech, or shoulder. Determination of fetal presentation or absence of normal fetal cardiac activity in the second and
is technically easier than lie, therefore we recommend third trimester has significant management implications and
assessing fetal presentation first. A fetus in cephalic or breech may provide an early window into severe maternal or fetal
presentation, by definition, has a longitudinal lie. If the fetal pathologic processes. Furthermore, the presence of normal
head or sacrum is not visible in the lower uterine segment cardiac activity provides an important opportunity for patient
(technique described below), then transverse or oblique lie
79
reassurance. As such, confirmation of cardiac activity should be Fetal Number (Movie 8.4)
performed early in the ultrasound examination. Multiple gestations are associated with many pregnancy
complications, including preterm delivery, preeclampsia,
Documentation of fetal cardiac activity can be performed abnormal labor, fetal malpresentation as well as fetal, neonatal
by storing a cine-loop (video clip) of the moving fetal heart and infant mortality.(3) Determination of fetal number is
or by obtaining a static M-mode or pulsed-wave Doppler critical to antenatal care, patient counseling, fetal surveillance,
image. Measurement of fetal heart rate can be determined by and delivery planning. Given the rarity of higher order
many modalities, two of which will be presented here. First, multiples, the remainder of this section will focus on twin
pulsed-wave Doppler can be used to calculate the fetal heart pregnancy (though similar principles and techniques apply
rate. Obtain a four chamber view of the fetal heart. With the to higher-order multiples). On a second or third trimester
gate width set at 3 mm, place the Doppler gate at the level ultrasound examination, a twin gestation is suspected when
of the mitral valve, activate the Doppler signal and record two fetal crania are detected. However, the presence of two
the flow waveform. Place the calipers between consecutive separate fetal bodies is necessary to confirm the diagnosis.
ejections to calculate the fetal heart rate (R-R interval). It is Additionally, the overwhelming majority of twins will have
important to note that some manufactures have a 2 beat peak- a dividing membrane, indicating dichorionic-diamniotic or
to-peak calculation system. Concerns for heat production on monochorionic-diamniotic placentation. Less than 1% of all
developing organs by focused Doppler waveform in the first twins are monochorionic-monoamniotic, a subtype without a
trimester fetus are less concerning in the second and third dividing membrane.
trimester.(2) M-mode, a function available on most ultrasound
machines, can also be used to document fetal cardiac activity To assess fetal number, the entire uterine cavity should be
and to determine the rate by detecting motion of the cardiac assessed in a standardized, systematic manner with attention
chambers. When M-mode is activated, a line appears on the to the number of fetal crania identified. If more than one
screen which detects motion through the tissue it intersects. head is identified, confirmation of twins should be performed
The deflections on the M-mode display correspond to the by assessing other body parts and evaluation for a dividing
anatomic structures through which the M-mode line passes. membrane. The uterine cavity should be evaluated in two
Measuring the distance between consecutive deflections planes: transverse and sagittal. In the transverse plane, the
(ventricular ejections, for example), can be used to assess fetal uterus should be imaged in a superior to inferior (between
heart rate. uterine fundus and lower uterine segment) in sequential
80
parallel planes until the entire cavity has been evaluated. the amniotic fluid index (AFI). The techniques for both methods
Sequential parallel scanning should then be repeated in the are described below. MVP is the preferred methodology given
sagittal orientation, from the left to right aspect of the maternal the simplicity of the technique and lower false positive rate
abdomen. Keep the ultrasound transducer perpendicular to the for the diagnosis of oligohydramnios, which results in fewer
maternal abdomen to prevent a false diagnosis of twins, which obstetric interventions without an increase in adverse perinatal
can result from imaging the same head at various angles. outcomes.(10) Furthermore, MVP was also supported by a
recent multidisciplinary, multi-society consensus workshop.(11)
Amniotic Fluid Volume (Movie 8.5)
Amniotic fluid is necessary for normal human development and The MVP is defined as the measurement of the single largest
may protect the fetus against mechanical trauma or intrauterine vertical pocket of amniotic fluid within the uterine cavity that is
infection.(4) The primary source of amniotic fluid in the second free of umbilical cord or fetal parts. Amniotic fluid is anechoic
and third trimester is fetal urine. Disorders of amniotic fluid in appearance. With the transducer in the sagittal orientation
volume may suggest underlying maternal or fetal pathology. and perpendicular to the floor, the uterine cavity should be
Oligohydramnios, or decreased amniotic fluid volume for a assessed in its entirety (from left to right and from the fundus to
particular gestational age, can be caused by premature rupture the lower uterine segment) to identify the single largest pocket
of membranes, uteroplacental insufficiency (hypertension, of amniotic fluid. After identification, the pocket is measured
preeclampsia, and intrauterine growth restriction), (in centimeters) by placing the calipers in a vertical straight
postterm pregnancy or fetal genitourinary abnormalities. line. Normal MVP ranges from 2-8 cm.(4) Oligohydramnios
Polyhydramnios, or increased amniotic fluid volume for a and polyhydramnios are defined as a MVP < 2 cm and > 8 cm
particular gestational age, can be idiopathic (approximately 50% respectively.(4)
of cases) or related to gestational/pre-gestational diabetes, fetal
infection, alloimmunization, or fetal structural or chromosomal To perform an AFI, the uterus is divided into four equal
abnormalities.(4) Importantly, both oligohydramnios and quadrants, within which the deepest vertical pocket of fluid
polyhydramnios are associated with an increased risk of is measured. All four measurements are then summed to
perinatal morbidity and mortality.(5-9) generate the AFI. The technique is the same as for the MVP.
Normal AFI is gestational age dependent, however in the
Two methodologies for assessing amniotic fluid volume are second and third trimester typically ranges from 5-20 cm.(4)
commonly employed: the maximal vertical pocket (MVP) and Oligohydramnios and polyhydramnios are defined as < 5 cm
and > 20 cm respectively.(4)
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Placental Localization/Assessment (Movie 8.6) occurs when the placenta covers the internal cervical os. Ideally,
Placental implantation can occur on any uterine surface: the urinary bladder should be partially full since an overly full
anterior, posterior, lateral, fundal or overlying the internal os of urinary bladder can simulate a previa by causing apposition of
the cervix. The latter situation, called placenta previa, represents the anterior and posterior walls of the lower uterine segment
one of the most common causes of bleeding during the second while an empty urinary bladder can make visualization of the
and third trimester of pregnancy. Placenta previa requires a lower uterine segment/cervical region difficult. If the patient
cesarean delivery. Therefore, antenatal identification of placenta was experiencing a contraction during the examination, the
previa allows for an appropriately planned, prelabor cesarean examination should be repeated after the contraction has
delivery, which is recommended at a late preterm to early term resolved since the contraction can distort the placenta and
gestational age.(12) Additionally, placenta previa (and other myometrium making it appear as though a placenta previa is
types of abnormal placentation, such as accreta) increase the present. The diagnosis of placenta previa should be confirmed
risk of hemorrhage and other complications. (or ruled out) by performance of a transvaginal (TV) or
translabial ultrasound if the transabdominal (TA) ultrasound is
With the transducer in sagittal orientation and perpendicular to non-diagnostic.
the mattress or backboard/wedge, scan in parallel, longitudinal
paths from superior to inferior (uterine fundus to lower uterine Vasa previa is assessed via a TA sagittal image of the lower
segment) along the maternal abdomen from the left to right uterine segment/cervical region with color Doppler to assess
side. Starting at the uterine fundus will ensure that a fundal for the presence of fetal vessels in the membranes overlying the
placenta will not be overlooked. Overlying fetal parts may cervical os. Assessment of placenta accreta, increta, percreta
shadow and obscure a posterior placenta. Avoid this artifact and abruptio placenta requires systematic TA scanning of the
by placing the transducer lateral on the maternal abdomen. placenta in both the sagittal and transverse planes.
After the placenta is localized, the inferior or lower edge must
be identified and the relationship of this edge to the cervix Fetal Biometry (Movie 8.7)
must be evaluated. A low-lying placenta occurs when the Fetal biometry refers to the anatomic measurements of
placental edge is within 2 cm of the internal cervical os but the fetus that can be used to estimate both fetal age and
does not touch the internal cervical os. A marginal placenta fetal weight. The common biometric parameter used for
previa occurs when the placental edge touches the internal estimation of gestational age and fetal size in the second or
cervical os but does not cover it. A complete placenta previa third trimester include: head circumference (HC), biparietal
82
diameter (BPD), abdominal circumference (AC) and femur BPD, activate the biometry software on the ultrasound console
length (FL). It is important to remember that ultrasound and select BPD. The upper caliper should be placed on the
evaluation of an embryo or fetus in the first trimester (crown- outer edge of the proximal parietal bone and the lower caliper
rump length through 13 6/7 weeks’ gestation) is the most should be placed on the inner edge of the distal parietal bone.
accurate method to determine gestational age.(13) The The line between the calipers should be perpendicular to the
gestational age (or estimated due date) of a pregnancy dated midline falx.
by first trimester ultrasonography should not be changed
by subsequent biometric assessment in the second or third The HC can be measured in the same plane as the BPD. After
trimester. Therefore, the earliest ultrasound in pregnancy should selecting HC from the biometry menu, position the calipers
be used for gestational dating. When dating a pregnancy, we on the two outer edges of the proximal and distal parietal
recommend use of recent guidelines supported by American bones. The line between the calipers should be perpendicular
Congress of Obstetricians and Gynecologists(ACOG), Society for to midline falx. Open and fit the ellipse over the contour of the
Maternal-Fetal Medicine(SMFM) and the American Institute of fetal skull. The ellipse can be adjusted to improve the fit over
Ultrasound in Medicine(AIUM).(13) the fetal skull by adjusting the position of the calipers.
If the goal in a critically ill medical or surgical patient is to The AC is measured in a symmetrical, circular, transverse section
determine if the fetus is potentially viable outside of the uterus of the fetal abdomen. Anatomic landmarks to identify the
and fundal height cannot be assessed on physical examination proper plane of measurement include: visualization of the
due to obesity, a quick femur length or fundal height could vertebrae in cross section along with the stomach bubble, and
be assessed with ultrasound. Provided a uterine fibroid is intrahepatic umbilical vein with portal sinus. The fetal kidneys
not present, fundal height assessment could provide a good should not be visualized. Measuring the AC with the fetal spine
estimate of gestational age but this should not be used to at 3 o’clock or 9 o’clock will minimize shadowing. Similar to
replace traditional measurements when the patient is stable. measurement of the HC, after selecting AC from the biometry
menu, calipers will appear. Place the proximal and distal calipers
BPD and HC should be measured in a transverse section of on the outer edges of the fetal skin such that the line between
the head at the level of the thalami and cavum septi pellucidi. them is perpendicular to the midline. Open and fit the ellipse
Other landmarks include the midline falx and a symmetric over the contour of the fetal abdomen. The ellipse can be
appearance to the bilateral cerebral hemispheres. The adjusted to improve the fit by adjusting the caliper position.
cerebellar hemispheres should not be visible. To measure the
83
FL should be measured with the full length of the bone infection, trauma, or cervical carcinoma among other etiologies.
perpendicular to the ultrasound beam, excluding the epiphysis. Time permitting, the six-step systematic scanning approach
The measurement is obtained by selecting FL from the biometry should be followed with particular emphasis on placental
menu and placing the calipers at the ends of the ossified assessment and placental location. It is important to note that
diaphysis. all steps do not need to be performed if the patient has already
previously been scanned and the exam can be tailored to the
Typically, ultrasound machines have software that derives the clinical circumstance. While transvaginal (TV) imaging is the
estimated fetal weight from the biometric measurements preferred methodology for placental imaging, the following
using a mathematical formula. A complete discussion of the sections will focus on abdominal ultrasound, which is typically
methodology of estimation of fetal weight is beyond the scope more readily available in the setting of an acutely bleeding
of this iBook. patient.
Vaginal Bleeding Placenta previa
Placenta previa occurs when the placenta covers the internal
Clinical Pearls: os of the cervix and affects approximately 1 in 200 pregnancies
• The differential diagnosis of second and third trimester at term.(16) A recent consensus workshop changed the
nomenclature for placenta previa, which is defined as any
vaginal bleeding includes multiple obstetric complications placenta that overlies the cervical os to any degree.(11) All
that are associated with increased maternal and fetal placentas that approach, but are not overlying, the cervical
morbidity and mortality. os are termed “low lying”.(11) Risk factors for placenta previa
• Bleeding in the second and third trimester requires timely include a history of cesarean delivery, dilation and curettage,
maternal/fetal clinical assessment and ultrasonography, previous placenta previa, advanced maternal age, and tobacco
which will guide diagnosis and management abuse.(17) Importantly, while many placentas extend into the
lower uterine segment in early pregnancy, the majority “migrate”
Vaginal bleeding in the second or third trimester complicates away from the cervix with advancing gestation as the lower
approximately 6% of all pregnancies.(14, 15) The differential uterine segment develops and as placental growth progresses
diagnosis of bleeding in the latter half of pregnancy includes toward the better vascularized (fundal) portion of the uterus
labor/preterm labor, cervical insufficiency, placenta previa, (trophotropism). Persistence of placenta previa until delivery
placental abruption, uterine rupture, vasa previa as well as
cervical or vaginal pathology such as polyps, inflammation/ 84
is associated with a later gestational age at diagnosis and a or interventions, thromboembolism, infection, ARDS) while
greater distance of extension of the placenta over the internal fetal morbidity is increased secondary to prematurity.
cervical os.(18, 19) Classically, placenta previa presents with Comprehensive reviews on the diagnosis, management and
painless vaginal bleeding, however some women may present morbidity of placenta accreta have been published recently.
with uterine contractions and bleeding which may overlap with (17, 20) Ultrasound is the cornerstone of antenatal diagnosis
the clinical presentation of placenta abruption. The diagnosis of placenta accreta. Ultrasound findings suggesting placenta
of placenta previa requires delivery by cesarean section. The accreta include multiple vascular lacunae within the placenta
sonographic findings of placenta previa will be based on the (“Swiss cheese appearance”) with or without turbulent flow,
relationship of the placental edge to the internal cervical os. loss of the normal hypoechoic retroplacental area, abnormal
A complete placenta previa will cover the internal cervical os appearance of the interface of the uterine serosa and bladder,
completely while a marginal placenta previa extends to the and retroplacental myometrial thickness < 1 mm.(21)
edge of the internal cervical os but does not cover it.
Placental abruption (abruptio placenta
Placenta accreta Placental abruption (Gallery 8.1), or premature placental
Placenta accreta describes abnormal placental implantation separation with bleeding at the placental-decidual interface,
where trophoblastic invasion and placental villi extend beyond affects approximately 1% of all pregnancies and is associated
the normal decidual boundary (Nitabuch’s layer) and is defined with an increased risk of maternal and fetal morbidity
according to the depth of placental invasion. The term placenta and mortality.(22, 23) Numerous risk factors for placental
accreta refers to the attachment of chorionic villi to the abruption have been identified and risk factors include:
myometrium. Placenta increta and percreta refer to invasion chronic hypertension, gestational hypertension, preeclampsia
into the myometrium and to or beyond the uterine serosa or eclampsia, premature rupture of membranes, trauma,
respectively. Placenta accreta is associated with multiple risk cocaine use, prior placental abruption, polyhydramnios, and
factors, the strongest of which are placenta previa and previous intrauterine growth restriction. Importantly, the diagnosis of
uterine surgery (especially cesarean delivery). Importantly, placental abruption is based on clinical findings, including
placenta accreta is associated with a marked increase in vaginal bleeding accompanied by abdominal or uterine
maternal morbidity and mortality.(20) The majority of maternal pain. Examination may reveal uterine tenderness, frequent
complications result from massive hemorrhage (DIC, massive uterine contractions (≥ every 2 minutes or uterine tetany)
transfusion, multiorgan failure, additional surgical procedures or constant abdominal pain. Back pain may occur if the
85
placenta is posterior. The majority of cases of clinical placental Prior to the incorporation of ultrasound into prenatal care, the
abruption will not be detected by ultrasound so the absence morbidity from vasa previa was thought to be unavoidable.
of sonographic findings of placental abruption does not rule However, in the era of ultrasound the majority of morbidity
out the diagnosis.(24) Sonographic findings include the from vasa previa is circumvented with prenatal diagnosis and
presence of a hematoma that is the result of the separation. cesarean delivery prior to the onset of labor.
The hematoma will usually be located retroplacental but
it can also be located preplacental (subamniotic). The Flow within the vessels overlying the internal cervical os will be
sonographic appearance of the hematoma can vary and may seen with TA ultrasound. The diagnosis of vasa previa can be
be hypoechoic, isoechoic, or hyperechoic to the surrounding confirmed on TV ultrasound with color Doppler documenting
tissue. Visualization of a retroplacental clot has a high positive the presence of fetal vessels overlying the internal os. Pulsed
predictive value for abruption, however this typically correlates Doppler should be performed to ensure the vascular flow
with a substantial quantity of bleeding and/or placental is fetal in origin (and not maternal/uterine). Consideration
separation. should be given to performing or repeating the study in the
Trendelenburg position or after the patient moves around to
Vasa previa ensure a funic (umbilical cord) presentation is ruled out.
Vasa previa (Gallery 8.2), a rare but potentially catastrophic
complication, occurs when fetal vessels are present in the Abdominal Pain
membranes covering the cervical os. A vasa previa can form in
the following two scenarios: Clinical Pearls:
• The physiologic and anatomic changes of pregnancy
• Velamentous insertion of umbilical cord, with umbilical
vessels coursing through the fetal membranes before may alter the clinical presentation and examination of the
inserting into placental disk pregnant woman with acute abdominal pain
• Point-of-care ultrasound provides a rapid, safe and effective
• Bilobed or succenturiate placenta, with connecting fetal way to distinguish between some of the obstetric and non-
vessels in the membranes overlying the cervix obstetric etiologies of acute abdominal pain
Undiagnosed vasa previa carries a perinatal mortality rate of The approach to acute abdominal pain in pregnancy, while
approximately 60% as a result of fetal/neonatal exsanguination similar to the non-pregnant state, also includes the challenges
upon spontaneous or artificial rupture of membranes.(25) of the physiologic and anatomic changes of pregnancy,
86
obstetric etiologies of pain, as well as maternal and fetal (2) Rectus sheath hematoma: Rectus sheath hematomas,
implications of the underlying pathologic process. The primary either traumatic or spontaneous, represent a rare cause of acute
goal in the evaluation of patients with acute abdominal pain abdominal pain; however, pregnancy is a known risk factor.
is to identify those with serious etiologies that require urgent (26) Ultrasound is an appropriate screening test prior to CT or
intervention. Rather than present a comprehensive review surgical intervention.(27) Transverse imaging of the abdominal
of the differential diagnosis and management of the acute wall (perpendicular to the rectus bellies) will demonstrate a
abdomen, this section will focus on elements of the differential heterogeneous appearance and intra-abdominal free fluid will
diagnosis that may be identified or ruled out with point-of- be absent. It is important to note that ultrasound cannot be
care ultrasound. These patients should undergo the six-step used to distinguish a hematoma from an abscess.
systematic approach along with additional abdominal scanning
to assess non-obstetrical causes of abdominal pain based on (3) Hernia: While ventral and groin hernias are typically readily
the individual clinical circumstance. It is beyond the scope of identified with abdominal and groin examination, ultrasound
this iBook to discuss the sonographic evaluation and findings of may be used as an adjunct to physical examination. Ultrasound
the non-obstetrical abdominal ultrasound examination. over the suspected hernia site may detect fascial defects,
protrusion or herniation of fat or small bowel, and may detect
This section will highlight examples of point-of-care ultrasound other pathologies such as fluid collections.(28)
findings and techniques to aid diagnosis in the setting of the
acute abdomen in pregnancy. Examples covered elsewhere in (4) Ovarian torsion: While primarily a clinical diagnosis,
this iBook will not be discussed. numerous ultrasound findings may suggest ovarian torsion in
a symptomatic patient with an adnexal mass of appropriate
(1) Pregnancy-related liver disease: Subcapsular hepatic size (approximately 5cm or greater).(29, 30) While torsion can
hematoma (with or without rupture) is a rare complication of occur at any point in pregnancy, diagnosis prior to 20 weeks
HELLP syndrome that is a surgical emergency. Performance is more common given that the gravid uterus may prevent
of a FAST ultrasound may detect intra-abdominal free fluid. A ovarian torsion due to intra-abdominal space constraints. (30)
more thorough evaluation of the right upper quadrant with Ultrasound findings suggestive of torsion include.(31)
transverse view of the liver may reveal a subcapsular hematoma,
as evidenced by a curvilinear, anechoic collection between the • Enlarged ovary with cyst or mass
liver and the capsule. • Heterogeneous appearance to ovarian stroma (due to edema
and/or hemorrhage)
87
• Decreased or absent ovarian Doppler flow Management of Obstetric Trauma
• Abnormal ovarian location (example: anterior to uterus)
• Free pelvic fluid Clinical Pearls:
• The priority in treating a pregnant trauma victim is
Given that the ovary has dual arterial supply (from both the
ovarian artery and collateral supply from the uterus through the stabilization of the mother.
utero-ovarian ligament), diminished or absent flow, particularly • Ultrasound evaluation as part of the secondary survey in
as an isolated finding, does not accurately predict ovarian
torsion.(32) pregnant trauma patients should focus on the determination
of gestational age and the presence of fetal cardiac activity
(5) Fibroid degeneration: While the majority of fibroids (viability), placental location, fetal number, and fetal
remain asymptomatic in pregnancy, fibroid degeneration can presentation.
occur in pregnancy when rapid fibroid growth results in a • While periviable birth occurs between 20-25 weeks’ GA, in the
relative decrease in perfusion leading to ischemia and necrosis. United States, interventions for fetal benefit are not typically
Larger fibroids are at a greater risk to undergo degeneration performed before 23-24 weeks’ GA..
in pregnancy.(33) In addition to localized pain, the release of • Position the second/third trimester trauma patient in the left
prostaglandins from degenerating fibroids may also result in lateral decubitus position to avoid compressing the inferior
the clinical findings of fever, nausea or mild leukocytosis. By vena cava.
ultrasound, degenerating fibroids may demonstrate cystic,
central degeneration. Additionally, the performance of Trauma complicates as many as 1 in 12 pregnancies and is the
ultrasonography overlying the degenerating fibroid typically leading cause of non-obstetric maternal mortality in the United
reproduces patient abdominal pain. Lastly, a degenerating States.(34, 35) Maternal trauma is associated with multiple
pedunculated fibroid (particularly with lateral location) may adverse obstetric outcomes including premature rupture
mimic a cystic ovarian mass. of membranes, preterm labor and preterm birth, placental
abruption, cesarean delivery, uterine rupture and intrauterine
fetal demise.(36) While pregnancy does not appear to impact
morbidity and mortality related to trauma, the physiologic
changes of pregnancy may alter clinical presentation, for
example by masking early signs of severe hemorrhage.
Additionally, the gravid uterus may alter patterns of injury,
particularly for penetrating trauma.(37)
88
In this chapter we will review the use of ultrasound applications pregnant trauma patients can be found in recent publications
in the setting of trauma in pregnancy. Recent evidence and proposed management algorithms.(36, 39, 40)
demonstrates a decrease in the rate of preterm delivery for
pregnant women with traumatic injuries who receive care in a Viability determination
designated trauma center, which suggests that a coordinated The gestational age at which “viability” is determined is
approach to trauma care may improve maternal and neonatal dependent on local resources for neonatal resuscitation, with
outcomes.(38) As such, we encourage a standardized approach large discrepancies between resource-rich and resource-poor
to the triage and evaluation of pregnant trauma patients settings.(41, 42). As such, decisions regarding interventions for
based on the local availability of resources. The six-step fetal benefit may vary widely by country or practice setting.
systematic approach should be tailored to the individual clinical In the United States, as outlined by a recent multi-society
circumstance and the eFAST examination should be performed consensus workshop, periviable birth is defined as delivery
if there is concern for blunt thoracic and/or abdominal trauma at 20 0/7 to 25 6/7 weeks of gestation.(43) In general in the
(Gallery 8.1). An overview of the eFAST examination is beyond United States, management decisions based on fetal indications
the scope of this iBook so it is recommended that the ACEP (fetal monitoring, cesarean delivery) are incorporated into care
Trauma App be downloaded (no cost) from Apple’s App Store beginning at 23-24 weeks of gestation.
for a comprehensive discussion of the eFAST examination.
Determining gestational age of the fetus should be done
Management of the Pregnant Trauma Patient by physical examination with assessment of fundal height.
The primary management goal in caring for the pregnant If this cannot be done, then a quick assessment of fundal
trauma patient is maternal stabilization. Fetal outcomes directly height in relationship to the umbilicus should be performed.
correlate with early and aggressive maternal resuscitation, and Provided that the patient does not have uterine fibroids, the
as such pregnancy should not result in under-diagnosis or fundal height measurement will provide a good estimate of
treatment secondary to fears of any adverse fetal effects.(36, gestational age and help the clinician in determining if the
39) Simultaneous evaluation of pregnant trauma patients by fetus is independently viable. Femur length may also be used
emergency, trauma and obstetrical teams should be undertaken to estimate GA. If fetal viability is confirmed, the initiation of
when possible to provide the most rapid, comprehensive continuous external fetal monitoring is recommended along
assessment. A comprehensive review detailing the care of with external tocometry to assess for clinical evidence of
preterm labor or placental abruption.
89
(1) Ultrasound for Secondary Obstetric Survey: (2) Focused Assessment with Sonography for Trauma (FAST)
Ultrasound evaluation as part of the secondary survey in The American Institute of Ultrasound in Medicine published
pregnant trauma patients should focus on the determination a detailed description of FAST practice guidelines in 2014.(45)
of gestational age and the presence of fetal cardiac FAST may be used in both the non-pregnant and pregnant
activity (viability), placental location, fetal number, and patient populations to diagnose traumatic injuries. A large
fetal presentation. Knowledge of placental location and retrospective cohort study has demonstrated that the sensitivity
fetal presentation provide useful information for delivery and specificity of FAST for the detection of free intraperitoneal
planning should delivery become indicated. The technique fluid or intraabdominal injury is similar between pregnant and
for performing these evaluations does not differ from those non-pregnant trauma patients.(46)
described earlier in this book. However, the point-of-care
sonologist must remain attentive to the mechanism of injury The technique for performance of a FAST exam in a pregnant
and the time required to perform the obstetric assessment as trauma does not differ compared with a non-pregnant patient.
this ultrasound exam should be performed in a purposeful, However, remember to consider the impact of a gravid
timely manner. For example, determination of gestational age uterus on the anatomic location of other abdominal viscera.
in the setting of critical maternal illness can be determined Additionally, a FAST exam in a supine pregnant woman should
rapidly by assessment of fundal height or FL alone. be performed with left lateral displacement if possible.
Importantly, the use of ultrasound for the diagnosis of placental Management of the Critically Ill Obstetric Patient
abruption remains limited. The sensitivity of ultrasound for
the detection of placental abruption is low (24% in one study), Clinical Pearls:
however when a clot is visualized the positive predictive value • Goals of point-of-care ultrasound in second and third
for the detection of abruption at delivery is high.(24) In this
2002 study, 50% of women with a clinical abruption, confirmed trimester critically ill patients include determining fetal
at delivery, had negative sonographic findings.(24) Clinically, number, viability, and gestational dating.
a substantial quantity of blood must collect to be evident Point-of-care ultrasound in critically ill obstetric patients
by ultrasound. Additionally, since most abruptions are not
concealed, vaginal bleeding may preclude the development of The second or third trimester patient with a critical illness
a sonographically evident abruption. (medical or surgical/traumatic) requires rapid evaluation and
resuscitation. The primary goal of the point-of-care second
90
or third trimester ultrasound examination in a patient with an at all should be very brief and should not distract from the
unknown prenatal/OB history should be determination of fetal resuscitative efforts.
number, viability, and gestational age. Ideally in these critically
ill patients, assessment of the placenta and its location would Active Labor/Imminent Delivery
not be of clinical significance since the method of delivery
in these unstable obstetrical patients would be by cesarean Clinical Pearls:
section. In patients with routine prenatal care and ultrasound • POCUS in the active labor patient should focus on fetal
examinations, fetal viability may be the only element that
needs to be determined if the patient’s records can be quickly presentation, placenta location, and fetal viability.
assessed by another member of the healthcare team while
resuscitative efforts are continued. The decision to perform POCUS in the evaluation of the patient
in active labor should be based on the patient’s history and
Perimortem Cesarean Delivery current examination. Patients who have had routine prenatal
In the setting of maternal cardiac arrest (or severe maternal care with prenatal ultrasound examinations at most would
injury or illness requiring cardiopulmonary resuscitation), a require a very brief tailored examination. The patient without
perimortem cesarean section on a viable pregnancy may prenatal care would, time permitting, require a sonographic
improve maternal and neonatal mortality. While the data evaluation that would include most (or all) of the six steps. In
is limited to retrospective case reports and series, cesarean patients in active labor, the examination should focus on fetal
delivery performed within 4 minutes of unsuccessful maternal presentation and placental localization along with fetal viability
cardiopulmonary resuscitation (CPR) may improve maternal and in order to determine the need for cesarean delivery. In patients
infant survival.(47) Theoretically, and supported by anecdotal with imminent delivery, it would be very unlikely that POCUS
evidence, delivery in the setting of unsuccessful maternal would be helpful and it would most likely interfere with delivery
CPR may improve hemodynamics and resuscitative efforts. efforts and medical management.
(48, 49) Prior to viability, a cesarean section would be unlikely
to impact the mechanical and volume hemodynamics of the Postpartum Hemorrhage (PPH)
pregnant uterus on maternal resuscitation. In the setting of
maternal cardiac arrest, point-of-care ultrasound if performed Clinical Pearls:
• POCUS can assist in the diagnosis and management of
primary and secondary postpartum hemorrhage.
91
• Procedures for the treatment of postpartum hemorrhage can to initial medical management with uterotonic agents (uterine
be performed under direct ultrasound guidance. tamponade or packing) can be performed under ultrasound
guidance to minimize the risks of uterine perforation and to
In the postpartum period, POCUS may be helpful in the assess the adequacy of treatment.
diagnosis and management of postpartum hemorrhage (PPH).
PPH, which affects approximately 6% of all deliveries, remains Uterine Tamponade
one of the leading causes of maternal death worldwide, with Uterine tamponade, either with a balloon catheter or packing, is
approximately 140,000 deaths annually.(50, 51) Classically, an effective treatment for PPH secondary to uterine atony. We
PPH is defined based on the quantity of blood loss, most recommend the use of uterine balloons, if available, over uterine
commonly as ≥ 500 mL after a vaginal delivery and ≥ 1000 mL packing given that they can be placed quickly and easily, allow
after a cesarean delivery. PPH can also be defined as primary for objective quantification of ongoing blood loss, and are likely
(occurring in the first 24 hours after delivery) or secondary more effective than packing.(52, 53) Furthermore, early use
(occurring from 24 hours to 12 weeks after delivery).(50) In this of balloon tamponade is associated with a decreased risk of
chapter, we will review ultrasound applications useful in the transfusion, ICU admission, and hysterectomy.(54) If a balloon
management of primary and secondary PPH. A full discussion is not available, gauze or kerlix can be used to pack the uterine
of the epidemiology, identification, management, and cavity and can be impregnated with thrombin (5000 units of
prevention of PPH is beyond the scope of this text. thrombin in 5mL of sterile saline) to enhance clotting.
Primary PPH Uterine balloons or packing can be placed under ultrasound
Primary PPH may result from uterine atony, tissue trauma or guidance. The transducer should be placed in sagittal position
lacerations, retained products of conception, coagulopathy, or superior to the pubic symphysis in the midline of the maternal
a combination of these factors. In the setting of primary PPH, abdomen. By convention, the notch should be pointing to the
point-of-care ultrasound can provide a useful tool to assist with maternal head, which will allow for the fundus to be on the
diagnosis and treatment. For example, ultrasound may aid left side of the screen. In this position, a uterine balloon can be
in the identification of retained placenta (in conjunction with inserted and filled under direct visualization.
clinical exam/uterine exploration) or abnormal placentation
(placenta accreta). Additionally, procedures for retained 92
placenta (such as uterine curettage) or uterine atony refractory
Retained Placenta between the findings in normal and pathologic states.(55, 56)
Ultrasound can be used to identify retained placental tissue. A As such, the interpretation of postpartum uterine ultrasound
thin endometrial echo should be present after delivery with images can be challenging. In both the normal postpartum
complete placental expulsion. Retained placental tissue can be state and secondary PPH, the uterus may be empty or contain
identified as an irregular, echoic mass adjacent to the uterine fluid or echogenic material. Echogenic intrauterine material
lining. In the setting of acute, or primary PPH, retained placental with vascularity on color Doppler suggests retained placenta.
tissue should demonstrate vascular flow by Doppler. While a lack of vascularity may indicate that intrauterine material
is a blood clot, avascular or necrotic retained placenta cannot
Assessment for retained placenta by ultrasound requires be excluded. While rare, gestational trophoblastic disease and
assessment of the uterus both the sagittal and transverse uterine arteriovenous malformations are part of the differential
planes. The sagittal plane can be assessed with the same diagnosis which can be assessed by ultrasound. In conjunction
technique as described for uterine tamponade. For transverse with ultrasound, serum quantitative hCG may be useful for the
assessment, rotate the transducer 90° (transverse on maternal detection of retained products of conception, choriocarcinoma,
abdomen) and scan from the fundus to the lower uterine or a new pregnancy. The technique for uterine imaging in the
segment in the midline of the maternal abdomen. Uterine setting of secondary PPH is similar to that described for primary
curettage can be performed under ultrasound guidance using a PPH.
sagittal in-plane technique through the long axis of the uterus.
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