Ultrasound Criteria for Bowel Obstruction in Babies
Ultrasound is not the primary diagnostic tool for bowel obstruction in babies, with plain radiographs being the recommended initial imaging modality, followed by contrast studies depending on the specific presentation. 1
Initial Diagnostic Approach
- Plain abdominal radiographs should be the first imaging study for suspected bowel obstruction in infants, as they can demonstrate key findings such as dilated bowel loops, air-fluid levels, and the presence or absence of distal gas 1
- The classic "double bubble" sign on radiographs indicates duodenal atresia, while a "triple bubble" sign suggests jejunal atresia 1, 2
- For proximal obstructions with classic radiographic findings, additional imaging with ultrasound is generally not supported by current evidence 1
Ultrasound Findings When Used
When ultrasound is employed in the evaluation of suspected bowel obstruction in infants, key findings include:
- Differential dilation of bowel loops (dilated proximal loops with collapsed distal loops) 3, 4
- Bowel wall thickening, which is present in 82.54% of small bowel obstructions 5
- Abnormal peristalsis, including hypokinesis (90.46% of cases) or akinesis 5
- Free peritoneal fluid (74.60% of cases), which correlates with more advanced stages of obstruction 5
- Prominent valvulae conniventes (intestinal folds) in the dilated segments 5
Type-Specific Findings
Proximal Obstructions (Duodenal/Jejunal Atresia)
- For duodenal atresia, ultrasound may show the "double bubble" appearance with gastric and duodenal dilation 6
- In jejunal atresia, a "triple bubble" appearance may be visible on ultrasound 2
- Absence of peristalsis in the dilated segments is a key functional sign 4
Distal Obstructions (Ileal Atresia, Hirschsprung's)
- Multiple dilated loops with absent or decreased distal gas 1
- Microcolon may be visualized due to lack of contents moving through the bowel 2
- Free fluid between bowel loops, which increases with the severity of obstruction 5
Emergency Findings
- "Do Not Miss" ultrasound findings requiring emergent intervention include:
Clinical Application Limitations
- Despite the potential utility of ultrasound, the American College of Radiology guidelines note there is limited literature supporting the use of ultrasound in evaluating neonates with suspected bowel obstruction 1
- For suspected distal obstruction, contrast enema is the diagnostic imaging procedure of choice rather than ultrasound 1
- For suspected malrotation or midgut volvulus, upper GI series remains the reference standard 1
Emerging Applications
- Recent improvements in ultrasound techniques including higher resolution probes, color Doppler, harmonic and panoramic imaging are improving detection of bowel pathology in children 7
- Ultrasound is increasingly used for monitoring patients undergoing conservative treatment of bowel obstruction, allowing assessment of loop distension and peristalsis recovery 4