**Question:** Motility disorders of the oesophagus are best diagnosed by -

A. Manometry
B. Endoscopy
C. Barium swallow
D. Esophageal pH monitoring

**Core Concept:**
Motility disorders are conditions characterized by abnormalities in the coordinated and coordinated contractions of the esophageal smooth muscles, leading to impaired swallowing and food passage. These disorders include achalasia, diffuse esophageal spasm, and nutcracker esophagus.

**Why the Correct Answer is Right:**
Manometry is the gold standard for diagnosing motility disorders of the oesophagus. It measures the pressure inside the oesophagus during swallowing, allowing for assessment of the contractile patterns and evaluating the function of the lower oesophageal sphincter (LES). This method is highly specific and sensitive in diagnosing motility disorders.

**Why Each Wrong Option is Incorrect:**

B. Endoscopy: While endoscopy can reveal structural abnormalities, it does not directly assess the motility of the oesophagus.

C. Barium swallow: This test evaluates the transit of barium through the oesophagus but does not provide information about the contractile patterns or LES function.

D. Esophageal pH monitoring: This test measures the pH of the oesophageal content and is primarily used for diagnosing gastroesophageal reflux disease (GERD), not motility disorders.

**Clinical Pearls:**

1. Manometry is the most reliable test to diagnose oesophageal motility disorders.
2. Combining manometry with pH monitoring can help diagnose both GERD and motility disorders simultaneously.
3. Differentiation between primary (motility) and secondary (reflux) oesophageal symptoms is crucial for appropriate management.