The Gold standard investigation for Gastro-Oesophageal reflux disease is:
**Core Concept**
The diagnosis of Gastro-Oesophageal reflux disease (GERD) involves assessing symptoms, anatomical changes, and physiological alterations in the lower oesophageal sphincter (LOS) and oesophageal mucosa. The gold standard investigation aims to confirm the presence of mucosal injury and assess the severity of reflux disease.
**Why the Correct Answer is Right**
Ambulatory 24-hour pH monitoring is considered the gold standard investigation for GERD. This test objectively measures the frequency, duration, and pattern of acid reflux episodes, providing valuable information on the relationship between symptoms and acid reflux. It involves placing a catheter through the nose into the oesophagus, connected to a portable recorder that monitors acid reflux over 24 hours. This procedure helps to distinguish between gastro-oesophageal reflux and other conditions that may mimic GERD symptoms.
**Why Each Wrong Option is Incorrect**
**Option A:** Endoscopy is a useful diagnostic tool for GERD, but it is not the gold standard investigation. Endoscopy can visualize mucosal damage, erosive oesophagitis, and stricture formation, but it may not detect non-erosive reflux disease (NERD) or symptoms that do not correlate with mucosal injury.
**Option B:** Upper GI series (barium swallow) is a radiological examination that visualizes the oesophagus and stomach, but it is not sensitive for detecting acid reflux or mucosal injury. It may show signs of oesophageal dilatation or stricture formation but is not specific for GERD.
**Option C:** Oesophageal manometry measures the motility and pressure of the oesophagus, which can be useful in diagnosing achalasia or diffuse oesophageal spasm. However, it is not the primary tool for diagnosing GERD.
**Clinical Pearl / High-Yield Fact**
When interpreting 24-hour pH monitoring results, a DeMeester score ≥ 14.7 is considered abnormal, indicating a high likelihood of GERD.
**Correct Answer: C. 24-hour pH monitoring.