Two Years of Vomiting: Multimodality Imaging of a Delayed-Diagnosis Duodenal Web

Background

Duodenal web is a rare congenital cause of intestinal obstruction that may remain undiagnosed when the obstruction is incomplete. We present a case of a term female infant who developed recurrent vomiting after feeding, diarrhea, and poor weight gain from 3 months of age. The symptoms were initially attributed to cow’s milk protein allergy or recurrent gastroenteritis. Despite multiple emergency department visits and three ultrasound examinations performed over the following year to exclude intussusception, no obstruction was identified. At 11 months, an episode of dehydration, electrolyte disturbances, and acute kidney injury occurred.

Case Presentation

At approximately 2 years of age, recurrent vomiting and electrolyte abnormalities prompted repeat ultrasound, which demonstrated marked proximal duodenal dilatation measuring up to 4.6 cm, with distal narrowing suggestive of partial obstruction. Abdominal radiography showed a double-bubble sign with distal bowel gas, supporting incomplete rather than complete obstruction. The differential diagnosis included malrotation with volvulus, annular pancreas, duodenal atresia/stenosis, and superior mesenteric artery syndrome. A normal SMA/SMV relationship argued against malrotation, while the location and intraluminal nature of the obstruction favored a duodenal web.

Upper gastrointestinal contrast study demonstrated proximal duodenal dilatation, a characteristic windsock appearance, and markedly delayed passage of contrast beyond the stenosis. MRCP, performed at the request of the gastroenterologists to clarify the relationship of the papilla to the stenosis, demonstrated critical distal narrowing with the papilla located proximally and a normal biliary tree. Endoscopy confirmed a web in the second portion of the duodenum with preserved bile flow. Endoscopic membranotomy was performed, resulting in significant clinical improvement.

Conclusion

This case highlights that partial duodenal obstruction can present years after birth with nonspecific, intermittent symptoms. Recognition of the windsock sign and complementary use of ultrasound, fluoroscopy, MRCP, and endoscopy can facilitate diagnosis and prevent prolonged diagnostic delay.