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