A 5-year-old boy presents with colicky abdominal pain, bilio…
A 5-year-old boy presents with colicky abdominal pain, bilious vomiting, and distension. Abdominal X-ray reveals air-fluid levels consistent with small bowel obstruction. At surgery, a fibrous band is found connecting the ileum to the umbilicus, with a blind-ending pouch along the antimesenteric border. Which embryologic structure failed to involute?