**Question:** Normal lower oesophageal sphincter pressure is

A. 5-15 cmH2O
B. 15-20 cmH2O
C. 20-30 cmH2O
D. 30-40 cmH2O

**Correct Answer:** A. 5-15 cmH2O

**Core Concept:**

The lower oesophageal sphincter (LES) is a ring of smooth muscle located at the junction of the oesophagus and stomach. It plays a crucial role in preventing the regurgitation of stomach contents into the oesophagus. Normal lower oesophageal sphincter pressure refers to the resting pressure of the LES, which is essential for maintaining its function.

**Why the Correct Answer is Right:**

The correct answer (5-15 cmH2O) represents the normal range of resting pressure for the lower oesophageal sphincter. This pressure helps to prevent regurgitation of stomach contents into the oesophagus and ensures proper gastroesophageal function.

**Why Each Wrong Option is Incorrect:**

A. 30-40 cmH2O (Option D) is an excessively high pressure, which would make it difficult for food to pass through the LES and into the stomach. This would lead to impaired gastroesophageal function.

B. 15-20 cmH2O (Option B) is within the range of the correct answer but still too high, resulting in similar issues as in option D.

C. 20-30 cmH2O (Option C) is also within the correct answer range but still too high, leading to gastroesophageal dysfunction.

**Clinical Pearl:**

The normal lower oesophageal sphincter pressure is crucial for maintaining gastroesophageal integrity and preventing gastroesophageal reflux disease (GERD), a common condition caused by impaired gastroesophageal function, including decreased LES pressure. Adequate LES pressure ensures a smooth passage of food from the oesophagus into the stomach and prevents stomach contents from flowing back into the oesophagus. Any deviation from the normal pressure range (5-15 cmH2O) can lead to gastroesophageal dysfunction and the risk of GERD.