Imaging Features of Neonatal Bowel Obstruction

A practical radiology review of Imaging Features of Neonatal Bowel Obstruction, focused on imaging findings, differential diagnosis, reporting points, and high-yield teaching pearls.

Classification

• Proximal vs Distal (relative to ligament of Treitz)
• Based on # of dilated loops on X-ray

Proximal Obstruction

• Symptoms: vomiting (bilious/nonbilious), ↔ mild distention

X-ray

1. Single bubble

• Double bubble → duodenal atresia

3. Triple bubble

• Imaging: abdominal XR → UGI contrast / US if needed

Distal Obstruction

• Symptoms: ↔ abdominal distention, meconium ± vomiting
• X-ray: multiple dilated loops
• Imaging: abdominal XR → LGI contrast / US if needed

Emergency

• Free intraperitoneal gas → urgent surgery

Esophageal Atresia (proximal foregut)

• Signs: coiled NG tube, proximal pouch distention
• Often associated: VACTERL, CHARGE, trisomy 21/18
• Can coexist with distal atresias

SINGLE BUBBLE (stomach only)

• Esophageal atresia variants — NG tube coiling in proximal pouch, ± distal bowel gas depending on fistula
• Gastric / pyloric atresia — single bubble with no distal gas (complete obstruction)
• Hypertrophic pyloric stenosis — single bubble with distal gas; US: pyloric muscle ≥3 mm, channel ≥12–16 mm; “caterpillar sign”
• Gastric duplication / antral web — single bubble ± distal gas; filling defect on UGI for web

TEACHING POINTS

• Single bubble without distal gas = atresia; with distal gas = partial/functional
• NG tube coiling = esophageal atresia until proven otherwise

DOUBLE BUBBLE (stomach + proximal duodenum)

• Duodenal atresia — classic double bubble, no distal gas; trisomy 21 frequent
• Annular pancreas — can mimic duodenal atresia; may have some distal gas
• Duodenal web — double bubble with distal gas via central fenestration; “windsock” sign on UGI
• Malrotation ± midgut volvulus — double bubble ± distal gas; US: whirlpool sign, abnormal SMA/SMV & D3 position

TEACHING POINTS

• Double bubble without distal gas = atresia-like
• US first in suspected volvulus — surgery is time-critical

TRIPLE BUBBLE (jejunal pattern)

• Jejunal atresia — few dilated loops in upper abdomen; triple bubble; air–fluid levels
• Apple-peel atresia (type 3b) — absent SMA with twisted short distal bowel around pedicle

TEACHING POINTS

• Triple bubble strongly implies small bowel atresia above ileum
• DISTAL OBSTRUCTION (multiple dilated loops, no distal gas)
• Ileal atresia — diffuse dilated loops, microcolon on enema
• Meconium ileus — microcolon + terminal ileum filling defects (“soap bubble”)
• Segmental volvulus — localized “mini-whirlpool”; may mimic apple-peel
• Colonic atresia — microcolon stopping before cecum; “kink sign”
• Hirschsprung — absent rectal gas, reversed rectosigmoid ratio, sawtooth mucosa
• Functional immaturity — normal rectosigmoid ratio; small left colon; meconium plugs

TEACHING POINTS

• Both ileal atresia + meconium ileus = microcolon — filling defects favor meconium ileus
• Rectosigmoid reversal = Hirschsprung
• Improvement after enema = functional immaturity, not Hirschsprung