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

A. Barium swallow
B. Endoscopy
C. Computed tomography (CT) scan
D. Esophageal manometry

**Core Concept:**
Zenker's diverticulum is a bulging out pouch in the posterior wall of the hypopharynx, which can cause symptoms such as odynophagia (painful swallowing), dysphagia (difficulty in swallowing), and regurgitation of food particles. This condition is typically diagnosed using radiological, endoscopic, or manometric investigations.

**Why the Correct Answer is Right:**
The correct answer is **Endoscopy (B)**, as it directly visualizes the Zenker's diverticulum and allows for biopsy, diagnosis, and treatment if needed. Although **Barium swallow (A)** can sometimes show the diverticulum, endoscopy offers more accurate diagnostic information and therapeutic options. **Computed tomography (CT) scan (C)** can also demonstrate the diverticulum, but it is less direct and invasive compared to endoscopy. **Esophageal manometry (D)** is a specialized procedure to study the motility of the esophagus and is not typically used for diagnosing Zenker's diverticulum.

**Why Each Wrong Option is Incorrect:**
A. **Barium swallow (A)** is a less invasive imaging study; however, it is less direct and may overlook the diagnosis due to not directly visualizing the diverticulum.
B. **Endoscopy (B)** is more direct and offers therapeutic options, making it the preferred diagnostic tool.
C. **Computed tomography (CT) scan (C)** can show the diverticulum, but endoscopy is more accurate and less invasive. CT scans may not always be necessary for diagnosis.
D. **Esophageal manometry (D)** is a specialized procedure for studying esophageal motility and is not typically used for diagnosing Zenker's diverticulum, as it focuses on motility rather than direct visualization of the diverticulum.

**Clinical Pearl:**
Zenker's diverticulum is a common clinical entity, often misdiagnosed as it can mimic other conditions like gastroesophageal reflux disease (GERD) or laryngeal cancer. A detailed clinical history, physical examination, and appropriate investigations are essential to arrive at the correct diagnosis.