Zenker's diverticulum is a hypopharyngeal diverticulum above the upper esophageal sphincter that causes regurgitation of undigested food, foul breath, coughing, and obstructive symptoms.

• A. A gastric diverticulum causing regurgitation.
• B. A hypopharyngeal diverticulum above the upper esophageal sphincter causing regurgitation of undigested food and foul breath.
• C. A duodenal diverticulum causing postprandial pain.
• D. A diverticulum below the upper esophageal sphincter causing difficulty swallowing.

Answer: (B)

The key idea is recognizing Zenker's diverticulum by its location and the way it presents. Zenker's diverticulum is a false pouch in the hypopharynx, just above the upper esophageal sphincter, typically on the posterior wall where the cricopharyngeus muscle and other fibers meet (Killian’s dehiscence). Food can get trapped in this pouch, so people experience regurgitation of undigested food, foul breath, coughing, and block-like symptoms from the retained material.

This description matches exactly: a hypopharyngeal diverticulum above the upper esophageal sphincter that causes regurgitation of undigested food and foul breath. The other scenarios describe diverticula in different locations with different symptom patterns—gastric in the stomach, duodenal in the duodenum with postprandial pain, or a diverticulum below the UES causing dysphagia—which don’t fit the classic presentation of Zenker’s.