**Question:** Investigation of choice for Zenker's diverticulum is -

A. Barium Swallow
B. Endoscopy
C. CT Scan
D. Ultrasound

**Correct Answer:** B. Endoscopy

**Core Concept:**
Zenker's diverticulum is a herniation of the mucosa and submucosa through the cricopharyngeal muscle complex at the level of the upper esophagus. This condition is characterized by dysphagia, odynophagia, and regurgitation of food particles.

**Why the Correct Answer is Right:**
Endoscopy is the appropriate investigation for diagnosing Zenker's diverticulum due to its ability to directly visualize the affected area and confirm the presence of a diverticulum. A barium swallow and ultrasound can identify the anomaly but do not provide direct visualization of the diverticulum. CT scan is a valuable imaging modality for detecting cervical spine abnormalities, but it is not as sensitive in diagnosing Zenker's diverticulum as endoscopy.

**Why Each Wrong Option is Incorrect:**
A. Barium swallow: Although barium swallow can detect the presence of a cervical esophageal diverticulum, it does not allow for direct visualization of the affected area, making endoscopy a more reliable diagnostic tool.

B. CT scan: CT scan is valuable for cervical spine imaging but lacks sensitivity for detecting cervical esophageal diverticulum compared to endoscopy.

C. CT scan: Similar to option B, CT scan is useful for cervical spine imaging but not as effective as endoscopy in diagnosing Zenker's diverticulum.

D. Ultrasound: Ultrasound is a valuable diagnostic tool for conditions affecting the neck and chest but is less sensitive than endoscopy in detecting cervical esophageal diverticulum.

**Clinical Pearl:**
Zenker's diverticulum is a common clinical presentation in the field of gastroenterology and should be considered in patients with dysphagia, odynophagia, and regurgitation of food particles. Endoscopy remains the gold standard for diagnosis as it provides direct visualization and allows for biopsy if needed.