Ascites

Karen Y. Oh, MD

DIFFERENTIAL DIAGNOSIS

Common

Less Common

ESSENTIAL INFORMATION

Helpful Clues for Common Diagnoses

Pseudoascites (Mimic)
- Abdominal wall musculature can mimic ascites
  - Surrounds the anterolateral liver margin but not seen posteriorly
- More prominent with slightly oblique scan angle
- True ascites is seen in other parts of abdomen, outlines organs
Hydrops
- Fluid in 2 body spaces
  - Skin edema, pleural effusion, ascites, pericardial effusion
- Nonimmune or immune hydrops
- Polyhydramnios and placentomegaly also commonly present
Bladder Rupture
- Initial ultrasound may show markedly enlarged bladder
  - Look for evidence of posterior urethral valves or urethral atresia
  - Less commonly due to prune belly or megacystis-microcolon
- Bladder rupture results in urinary ascites
  - Thick-appearing bladder wall after decompression
- Follow all fetuses with large bladder
  - Likely transient finding if otherwise normal urinary tract
Bowel Perforation
- Initial ultrasound may show dilated bowel
  - Underlying atresia(s), volvulus, intussusception, meconium ileus
- Often perforation event is occult, with ascites being the only finding
- Look for signs of meconium peritonitis to confirm diagnosis
  - Intraperitoneal calcifications
  - Meconium pseudocyst
Infection
- Ascites may be isolated, but more commonly, is part of generalized hydrops
- Look for hepatic or cerebral calcifications
- Correlate with clinical history for maternal signs of infection or exposures

Helpful Clues for Less Common Diagnoses

Tachyarrhythmia
- Sustained heart rate > 180-200 bpm
- Ascites may be isolated and first sign of impending failure/hydrops
- Always check heart rate in setting of isolated ascites