Introduction Cesarean Section - Jefferson

Cesarean Section Introduction

US and CT of Acute and Chronic • Cesarean delivery accounts for approximately 1/3 of all
Complications births in the US.

Mindy M. Horrow, MD, FACR, FSRU, FAIUM • Typical symptoms requiring acute post-operative
imaging : fever with poor response to antibiotics over 2-3
Director of Body Imaging days, dropping hemoglobin, unexpectedly heavy vaginal
Albert Einstein Medical Center bleeding, pain.
Associate Professor of Radiology
Thomas Jefferson University • Acute diagnoses include a variety of unusual
hematomas, abscesses, wound infections and
dehiscence, uterine rupture and pelvic thrombophlebitis.

• Chronic findings include uterine adhesions resulting in
difficult sonographic imaging. The C-section scar also
may result in several rare, but unique diagnoses that are
now made with increasing frequency.

Acute Complications following Overview
Cesarean section
• “Normal” acute post C-section appearance: US and CT
• Hematomas

– Peritoneal: hemoperitoneum
– Extraperitoneal: Bladder flap, subfascial, prevesical (space of Retzius)
– Retroperitoneal
• Infections
– Phlegmon and abscess
– Uterine dehiscence and rupture
– Superficial and deep incision infection and dehiscence
– Septic pelvic

• Other: ureteral and bowel injuries

• Choice of imaging modality: Depending upon the clinical situation, cost,
availability and contraindications for intravenous contrast, one may use
ultrasound, CT and/or MR. Our experience has been predominantly with
ultrasound and CT.

Four different “normal” studies CT and US in same patient with “normal” findings of small
hematoma in myometrial incision
Staples in Pfannenstiel incision
Myometrial sutures
Tiny focus of air
in endometrium

Blood in endometrial canal

Uterine incision

Small
bladder flap
hematoma

Small myometrial and extrauterine Routine findings 4 days post C-section
hematomas
History: breech twins, abruptio placenta, post-operative fever not responding to
antibiotics, probable endometritis

1. Uterine incision
2. Air in subcutaneous incision (air in

bladder from Foley catheter)
3. Expanded endometrial canal with

subacute blood (lochia)

Normal CT Imaging post C-section Normal US Imaging post C-section

• Obvious uterine discontinuity is common in the • Small, often linear, echogenic foci within uterine incision
immediate postpartum period. represent continuous sutures in myometrium.

• Other findings which are common and not clinically • Small indistinct mass-like region in incision representing
important include: small amounts of endometrial air and a small hematoma is a common “normal” finding.
blood, small parametrial collections, and small bladder
flap hematomas (< 2cm in thickness) • Small bladder flap hematomas are not uncommon.
• Endometrial clot and debris and occasional foci of air are
• Our recommendations:
common findings with endometritis but also may be seen
– If using CT for evaluation, intravenous contrast should be used if in normal healthy patients.
possible. • Our recommendation: Use a variety of frequencies and
approaches to obtain optimal images: transabdominal
– Best to image perpendicular to the plane of incision, using sagittal (when the uterus is still large) and transvaginal or
and coronal reconstructions. transperineal to visualize the lower uterus and the scar.

Small bladder flap hematoma, Infected bladder flap hematoma
hemoperitoneum
gas containing (echogenic foci) 5 x 6 x 7 cm collection
∗
History: Persistent pain and fever 9 days after C-section
∗ Classical transverse incision best visualized in sagittal plane
Bladder

TA SAG TV SAG

TA TRV TV TRV

Bladder Flap Hematoma Subfascial and abdominal wall
hematomas
• A complication of a low uterine transverse incision.
• The uterine incision is covered by a fold of peritoneum Bladder

that is incised from myometrium and bladder
• Bleeding from uterine incision is usually confined by

overlying peritoneum, but can spread to broad
ligaments, retroperitoneum and peritoneum.
• Can be considered “normal” if less than 2-5 cm, and
may occur in up to 50%
• Surgical evacuation requires incision of peritoneum.

Infected rectus/subfascial hematoma Subfascial Hematoma

Required surgical debridement • Extraperitoneal hemorrhage from inferior
epigastric vessels and their branches
Bladder flap
hematoma • Blood accumulates in prevesical space, posterior
to rectus and transversalis muscles and anterior
to peritoneum continuous with space of Retzius,
potentially accommodating as much as 2.5 liters
without a palpable mass.

• May be evacuated without entering the
peritoneum.

Fever several days after C-section History: Premature rupture of membranes
and chorioamnionitis
Uterine Dehiscence
TA TRV TA TRV

Uterine dehiscence
Infected bladder flap hematoma

Ileus

Infection resolved with conservative management Re-admitted 12 days later for A
including antibiotics and catheter drainage purulent drainage, progression to

Follow up CT several days later large bladder flap abscess,
requiring hysterectomy

AA A

Uterine Dehiscence Ruptured uterus with broad ligament (B),
extra- and retroperitoneal hematomas (H)
• Defined as infected and necrotic uterine incision with
dehiscence at suture line, intact serosa. Uterine incision Uterine incision
B B
• Very difficult imaging diagnosis post C-section because H
of overlap with normal appearance of uterine incision.
Uterus H
• Paucity of reports in the literature. Some claim that MR
is preferred over CT because of multiplanar capabilities
and better soft tissue contrast.

• Presence of large (> 5cm) bladder flap hematoma may
be related to underlying uterine dehiscence.

• Difficult to differentiate partial from complete dehiscence.
• Our recommendation is to look for gas in the uterine

incision with possible extrauterine extension. Use
sagittal and coronal reformatted images from
multidetector CT.

Follow-up: Resolution of Uterine Rupture
hematomas; tethered uterus
• Defined as complete muscular separation of
Adhesion myometrium

SAG • Accompanied by hemoperitoneum and/or other
hematomas

• High morbidity and mortality
• Patients attempting vaginal delivery after c-

section (VBAC) at risk

Subcutaneous Wound Infection Subcutaneous wound infection with dehiscence,
small left rectus hematoma required drainage

∗

∗ Sub-acute blood in endometrium

Stat C-section for fetal distress with left extension, post-op fever unresponsive to antibiotics

Increased bleeding and persistent fever one Ruptured bladder flap abscess
week post C-section
History: Fever, abdominal pain and free air on CXR,
2 weeks after routine C-section

Retained products of conception = Bladder flap abscess contains gas (dotted arrow), associated with
focal enhancing endometrial “mass” pneumoperitoneum (solid arrows), free fluid and infiltration of the

Abscess omentum (dashed arrow).

Extrauterine Infection Chorioamnionitis and failure to progress at
41 weeks gestation
• Extrauterine infections include infected
hematomas, abscess and cellulitis. Dilated R ovarian vein with central
thrombus and hyperenhancing wall
• Infection usually occurs in the region of incision,
but can extend to the parametrium after IVC
cesarean section.

• Frequency and severity of post partum infections
are significantly greater after Cesarean section
compared to vaginal delivery.

Right ovarian vein septic thrombophlebitis
Small focus retained products of conception

Unexplained post partum fever Two different patients with diffuse septic
pelvic vein thrombophlebitis
RO
Patient also had herniation of uterus at incision.
Septic Thrombophlebitis: Right Ovarian Vein U
UU
Ovarian and Pelvic Septic
Thrombophlebitis Thrombophlebitis - numerous veins with enhancing walls
containing hypodense thrombus.
• 1/600 deliveries, though likely underestimated.
• Usually unilateral, right more frequent than left. Pelvic pain one month post C-section

Right ovarian vein thrombus may extend to IVC. Obstructed uterus: Hematometros
• CT and MR are techniques of choice.

Sonography may be difficult due to bowel gas.
• Findings include enlarged ovarian and other

pelvic veins with low-density thrombus within the
lumen surrounded by an enhancing vessel wall.
Inflammation may be present in surrounding fat.

Chronic Complications Overview
following Cesarean Section
• Normal scar : ultrasound and CT
examples

• Complications of Cesarean scar:

- “Niche”
- Malpositioned IUD
- Ectopic pregnancy
- Placenta accreta
- Endometrial implant

Sonography and the Cesarean scar What is wrong with this uterus?

• In some patients, the scar causes significant distortion of Adhesions of Cesarean section scar cause
the normal uterine position tethering of uterus, elongation of cervix

• When the cervix is elongated and the lower uterus is
tethered to the anterior abdominal wall, transvaginal
imaging allows excellent visualization of the cervix, but
the corpus of the uterus is poorly demonstrated.

• In this situation, transabdominal imaging is also limited,
because the distended bladder will not serve as a
“sonographic window” to the body of the uterus.

• Our recommendation is to try a higher frequency curved
transducer directly over the uterus, when the body
habitus permits.

CT and simulated transvaginal view of
a similar patient

Scar simulating a myoma US and CT views of tethered uterus:

Scar ovaries may also be pulled ventrally

Simulated myoma Endometrium may be pulled into the scar
with thinning and irregularity of the overlying

myometrium

SAG COR

Blood can accumulate in the scar, causing Retroflexed uterus with fluid in scar - CT and US
inter-menstrual bleeding.
COR
SAG COR SAG

Blood in endometrial canal and scar

Fluid in scar after miscarriage

History of heavy menses and inter-menstrual bleeding The Cesarean Scar “pouch” or

M “niche”
SIS
• Fluid may occasionally be present in scar during routine
Intracavitary myoma and prominent niche transvaginal scanning.

• By filling the scar with fluid, sonohysterography can
better delineate the defect and measure the depth.

• Hysteroscopy correlates well with the findings on
sonohysterography.

• Routine hysterosalpingography can also demonstrate the
scar.

• The scar can act as a reservoir for blood and thus be a
cause of abnormal bleeding.

• What percentage of women with prior C-section will have
a demonstrable “niche” is unknown.

IUD Malpositioned in Scar TA/TV US confirms IUD partially in
cervix, extending into scar

2005 immediate 2006 IUD Malpositioned, partially in scar
post C-section

CT several days after C-section Several months later patient is
pregnant with bleeding

Cesarean Scar Ectopic Pregnancy

SAG Two days later

After treatment with systemic Surgery Required
methotrexate, follow up

study 5 days later showed
growth of sac and cardiac
activity. Second dose of

methotrexate given.

COR

One month later returns
with bleeding

History Cesarean section x 1 Ectopic Pregnancy in Cesarean Scar
Interpreted as abortion in progress
• A gestation completely surrounded by myometrium, but
separated from endometrium and fallopian tube.

• Several reports of occurrence within months of Cesarean
delivery suggesting incomplete healing of scar may
contribute to this ectopic implantation.

• Probable mechanism is invasion of myometrium through
a microscopic tract. Similar to interstitial pregnancy.

• US Findings: empty uterine cavity, empty cervical canal,
sac in anterior lower uterus

C-section scar implantation (ectopic) with retained
products of conception

Ectopic Pregnancy in Cesarean Scar 30 weeks pregnant with hematuria,
history of Cesarean section
• Differential diagnosis: spontaneous abortion in progress
and cervical ectopic. Placenta Percreta:
Placental invasion of bladder
• Rupture can occur early and delayed diagnosis limits
treatment options. Courtesy of Dr. Sandra Allison
Georgetown University
• Because this type of ectopic pregnancy is so rare, no
specific guidelines for treatment. Can try medical
therapy, but only surgery will allow removal of the
pregnancy and repair of the defect

• Appears to be increasing in incidence
• Distinctly different from placental implantation over the

scar resulting in placenta accreta.

Placenta Accreta Placenta Accreta

• Accreta: villi in direct contact with myometrium without • Modalities: ultrasound (TA, TV, with Doppler), MR
intervening decidua (usually without gadolinium)

• Increta: deeper myometrial invasion – Sensitivities and specificities may be similar
• Percreta: invasion to serosa and sometimes to adjacent – With anterior placenta ultrasound is better
– With posterior placenta MR is often better
bladder and bowel
• Risk factors: Cesarean section, instrumentation, • Criteria for suspecting placental invasion by ultrasound

placenta previa – Loss of retroplacental hypoechoic myometrial zone
• Can result in life threatening hemorrhage at delivery – Numerous vascular lacunae in placenta
– Disruption of hyperechoic boundary between uterine serosa and
because placenta will not separate from myometrium
bladder
– Nodular projection beyond uterine edge

★Similarities between placenta accreta (myometrial invasion)
and C-section scar ectopic (abnormal implantation site)★

Endometriosis in Scar - US Endometriosis in Scar - CT

Endometrial implant Adhesions

History of increasingly painful C-section scar with mass Endometrial implant is a nodular subcutaneous lesion in the Cesarean section
scar with enhancement greater than adjacent muscles.

Endometrial Implant in Scar Incarcerated Ventral Hernia
at site of scar
• Due to endometrial tissue spread outside of uterus
during surgical procedure. History of 3 prior Cesarean Sections

• Symptoms include: pain and tenderness, worsening
symptoms with menses, cyclic bleeding.

• Variable appearance: cystic, mixed, solid; related to
distribution of hemorrhagic and fibrotic material; often
spiculated secondary to fibrosis.

• Color Doppler frequently demonstrates dilated vessels.
• Differential diagnosis: desmoid, mesenchymal tumors,

hematoma.
• Typically enhance dramatically with contrast.

References References (cont.)

• Antonelli E, Morales A, et al. Sonographic detection of fluid collections and • Monteagudo A, Carreno C, Timor-Tritsch IE. Saline infusion sonohysterography in
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• Baker ME, Bowie JD, Killam AP. Sonography of post-cesarean-section bladder-flap • Rivlin ME, Patel RB, Carroll CS, Morrison JC. Diagnostic imaging in uterine incisional
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Medicine 2005;50:928-932.
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• Cheung VYT, Constaninescu OC, Ahluwalia BS. Sonographic evaluation of the lower • Seow KM, Huang LW, Lin YH, Lin MY, Tsai YL, Hwang JL. Cesarean scar
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• Silver RM, et al. Maternal morbidity associated with multiple repeat cesarean
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2003;22:695-700.
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• Hamilton BE, Margin JA, Ventura SJ. Births: preliminary data for 2005. National Vital Statistics • Twickler DM, et al. Imaging of puerperal septic thrombophlebitis: prospective
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• Hensen JH, Van Breda Vriesman AC, Puylaert JB. Abdominal wall endometriosis: • Twickler DM, Setiawan AT, Harrell RS, Brown CEL. CT appearance of the pelvis after
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• Maldjian C, Milestone B, Schnall M, Smith R. MR appearance of uterine dehiscence
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References (cont.)

• Wiener MD, Bowie JD, Baker ME, Kay HH. Sonography of subfascial hematoma after
cesarean delivery. AJR 1987;148:907-10.

• Woo GM, et al. The pelvis after cesarean section and vaginal delivery: Normal MR
findings. AJR 1993;161:1249-52.

• Zuckerman J, et al. Imaging of pelvic postpartum complications. AJR 1997;168:663-8.