Mastering Medical
USMLE Step 1 · Embryology & Anatomy

Ileal atresia vs Meckel diverticulum

How to tell Ileal atresia and Meckel diverticulum apart when a board question makes them look alike.

Fastest separator

Ileal atresia is neonatal obstruction; Meckel diverticulum is vitelline duct remnant with painless bleeding.

Side by side

Ileal atresiaMeckel diverticulum
Key clue

Ileal atresia causes neonatal bilious vomiting and obstruction from in utero vascular accident, sometimes with apple-peel deformity.

Meckel diverticulum is a vitelline duct remnant with the rule of 2s: 2 inches, within 2 feet of ileocecal valve, age under 2, 2% population, and ectopic gastric or pancreatic tissue.

Mechanism

Ileal atresia causes neonatal bilious vomiting and obstruction from in utero vascular accident, sometimes with apple-peel deformity.

Meckel diverticulum is persistent vitelline duct causing painless bleeding, ectopic gastric mucosa, and rule of twos near terminal ileum.

The repair move

Before naming the answer, force the stem through the separator: Ileal atresia is neonatal obstruction; Meckel diverticulum is vitelline duct remnant with painless bleeding.

Try a free question

Core

A 2-day-old neonate has progressive abdominal distention, bilious vomiting, and failure to pass meconium. Abdominal X-ray shows multiple dilated small bowel loops. At surgery, ileal atresia with an 'apple-peel' deformity is found, with the distal small bowel coiled around a single mesenteric vessel. Which mechanism best explains the atresia?

Show answer and explanation

Answer: A. In utero vascular accident. Ileal atresia (and jejunal atresia) result from in utero vascular accidents (mesenteric vascular insufficiency, often from in utero volvulus, intussusception, or thrombosis), producing segmental small bowel necrosis and atresia. The 'apple-peel' deformity describes distal bowel coiled around a single mesenteric pedicle.

Why the other choices are tempting

  • B. Failure of recanalization causes duodenal atresia (NOT distal ileal atresia).
  • C. Persistent vitelline duct creates Meckel diverticulum, not atresia.
  • D. Aganglionic distal bowel is Hirschsprung disease, not atresia.
  • E. Thick meconium obstruction is meconium ileus in cystic fibrosis.

Flashcards

Tap a card to flip it.

What clue supports Ileal atresia?

Choose Ileal atresia when the stem gives this pattern: Ileal atresia causes neonatal bilious vomiting and obstruction from in utero vascular accident, sometimes with apple-peel deformity.

What clue supports Meckel diverticulum?

Choose Meckel diverticulum when the stem gives this contrasting pattern: Meckel diverticulum is persistent vitelline duct causing painless bleeding, ectopic gastric mucosa, and rule of twos near terminal ileum.

Quick answers

What is the fastest way to tell Ileal atresia from Meckel diverticulum?

Ileal atresia is neonatal obstruction; Meckel diverticulum is vitelline duct remnant with painless bleeding.

What is the key clue for Ileal atresia?

Ileal atresia causes neonatal bilious vomiting and obstruction from in utero vascular accident, sometimes with apple-peel deformity.

What is the key clue for Meckel diverticulum?

Meckel diverticulum is a vitelline duct remnant with the rule of 2s: 2 inches, within 2 feet of ileocecal valve, age under 2, 2% population, and ectopic gastric or pancreatic tissue.