Kaplan USMLE Step 1: Intermittent abdominal pain in a young patient

If you’re preparing for the United States Medical Licensing Examination® (USMLE®) Step 1 exam, you might want to know which questions are most often missed by test-prep takers. Check out this example from Kaplan Medical, and read an expert explanation of the answer. Also check out all posts in this series.

A 10-year-old boy is brought to the physician because of intermittent right lower quadrant abdominal pain for the past 18 months. The appendix appears normal on imaging. A technetium-99m pertechnetate scan is performed and heterotopic gastric mucosa is found. The heterotopic mucosa is most likely in which of the following locations?

A. Ascending colon 

B. Cecum

C. Duodenum

D. Ileum

E. Sigmoid colon

The correct answer is D.

This patient most likely has a Meckel diverticulum, which results from a failure of complete obliteration of the omphalomesenteric (vitelline) duct. The two main complications are bleeding and obstruction, and the two main types of heterotopic tissues seen are gastric and pancreatic mucosa. Meckel diverticula are most often found 2 feet proximal to the ileocecal valve in the ileum.

Choice A: The patient presents with a Meckel diverticulum, which is a congenital anomaly most commonly located in the ileum. The ascending colon is not a likely location for a Meckel diverticulum.