Acute Abdomen in Pregnancy
Anne Kennedy, MD
DIFFERENTIAL DIAGNOSIS
Common
Placental Abruption
Appendicitis
Renal Stone Disease
Pyelonephritis
Cholecystitis
Less Common
Torsion
Fibroid Degeneration
Trauma
Rare but Important
Uterine Rupture
HELLP Syndrome
ESSENTIAL INFORMATION
Helpful Clues for Common Diagnoses
Placental Abruption
Difficult diagnosis to make sonographically: Occult in up to 50% of cases
Acute clot is isoechoic to placenta, no flow on Doppler evaluation
Clot may be marginal, preplacental, retroplacental
Appendicitis
Appendix is displaced out of pelvis by enlarging gravid uterus
US
Blind ending, non-compressible tube
Diameter > 6 mm
Look for appendicolith: Echogenic focus with distal acoustic shadowing
May see echogenic periappendiceal fat from inflammation
May see focal fluid collection if ruptured
EV sonography very helpful when appendix drops into pelvis, behind pregnant uterus
CT
Same anatomic features
More sensitive for focal perforation, presence of appendicolith, inflammation of fat
MR
Increasingly used if US non-diagnostic as no ionizing radiation
T1, T2, T2 FS sequences (Gadolinium contraindicated in pregnancy)
Same anatomic features as seen with US or CT
Renal Stone Disease
Collecting system dilatation
Ureteric dilatation, particularly suspicious for stone if dilatation stops abruptly
Physiologic dilatation tapers at pelvic brim
Look for ureteric jets with color Doppler
Have patient in decubitus position with side of concern elevated
Measure intrarenal resistive indices (RI)
Physiologic caliectasis does not cause elevated RI
Look for difference of > 0.1 side-to-side
Not specific for renal stone disease, as can also be seen with other other acute renal conditions
Coronal MR, with heavily T2 weighted sequences, shows stones as low signal filling defects within column of high signal urine
Pyelonephritis
US
Enlarged kidney ± parenchymal edema
Look for complicating conditions such as abscess or pyonephrosis (an obstructed, infected system), which require drainage
CT
Delayed ± striated nephrogram
Focal areas of diminished enhancement on delayed images
Cholecystitis
Gallstones
Gallbladder wall thickening
Pericholecystic fluid
Positive sonographic Murphy sign
Remember that right upper quadrant pain and abnormal liver function tests may be seen in preeclampsia
Helpful Clues for Less Common Diagnoses
Torsion
Adnexal mass can undergo torsion in pregnancy
Maximum risk at 12-14 weeks and immediately postpartum
Look for
Ovarian or paraovarian mass as lead point
Echogenic stroma, ovarian enlargement, peripheral follicles from edema
Hemorrhage/necrosis/infarction
Use Doppler to assess flow
Lack of venous flow most suspicious finding
Documentation of flow does not exclude the diagnosis in presence of strong clinical suspicion or other imaging findings of concern
Fibroid Degeneration
Larger fibroids at greater risk for acute red (hemorrhagic) degeneration
Severe abdominal pain may mimic abruption
Often requires narcotic analgesia for control
Inhomogeneous echoes in center of fibroid
No flow in inhomogeneous area on Doppler interrogation
Placental implantation over large fibroid carries increased risk for abruption
Look for changes of abruption, as well as fibroid degeneration, in setting of acute pain
Trauma
Imaging evaluation should not be compromised because the patient is pregnant
When feasible, limit radiation exposure, or use US/MR if possible
Fetus at significant risk even if maternal injuries seem relatively minor
Placental shear injury → abruption, infarction
Maternal hypotension → decreased placental perfusion
Most fetal ischemic injury takes time to be visible on imaging
Wait 10-14 days post injury and consider performance of fetal MR to look for intracranial hemorrhage, ischemic encephalopathy
Helpful Clues for Rare Diagnoses
Uterine Rupture
Most common in labor, uterus ruptures at site of old hysterotomy site
May be a complication of abdominal trauma
Look for disrupted myometrium, continuity of extrauterine fluid with endometrial cavity
HELLP Syndrome
Patients present with preeclampsia and progress to more severe condition with the following
