二 ) Modern GERD Diagnosis

外賓演講（二）

MODERN GERD DIAGNOSIS

Prakash Gyawali Washington University School of Medicine, USA

GERD does not have a gold standard for diagnosis. A clinical history of typical reflux symptoms and validated questionnaires only have modest performance characteristics compared to objective GERD evidence on invasive testing. Even an empiric trial of PPI does not have high sensitivity or specificity compared to objective evidence. However, empiric PPI therapy is a pragmatic approach to initial diagnosis and management of GERD when presenting symptoms are typical without alarm features. When presenting symptoms are atypical (cough, hoarseness, throat clearing), it is more cost effective to start by performing diagnostic tests up front (endoscopy, ambulatory reflux monitoring, high resolution manometry), and using PPI therapy only when objective GERD evidence exists.

Endoscopy has high specificity but low sensitivity for the diagnosis of GERD, especially when performed while the patient is on PPI therapy, but even in treatment naïve patients. However, endoscopy can identify esophagitis, intestinal metaplasia (Barrett’s esophagus), and peptic strictures, which are considered conclusive GERD evidence. When endoscopy does not reveal conclusive GERD evidence, ambulatory reflux monitoring is pursued. Catheter based testing requires manometry for identification of the lower esophageal sphincter, so the distal pH probe on the reflux monitoring catheter is positioned 5 cm above the sphincter. Acid exposure time and reflux-symptom association are the two standard metrics reported. The addition of impedance electrodes increases value of catheter-based reflux monitoring, since content, directionality and height of refluxate can be recognized. Behavioral disorders such as supragastric belching and rumination syndrome can be diagnosed. New metrics such as baseline impedance and post-reflux swallow induced peristaltic wave can add value to pH-impedance monitoring. However, impedance analysis requires reviewer expertise.

Wireless pH monitoring allows multiple day recordings, and can overcome day-to-day variation in reflux exposure. Multiple days with physiologic reflux exposure rules out reflux disease, while very high acid exposure times on multiple days indicates a need for aggressive reflux management. Wireless pH monitoring may be better tolerated than catheter based monitoring, but this is more expensive since endoscopy is needed for placement.

In patients without GERD evidence, reflux monitoring is performed off acid suppression therapy so that a conclusive diagnosis of GERD can be made. In symptomatic patients with prior GERD evidence, pH-impedance monitoring can be performed on acid suppression, to identify if reflux remains uncontrolled – if so, escalation of management or antireflux surgery might provide benefit. The Lyon Consensus reports testing metrics that are conclusive and borderline for GERD, as well as adjunctive metrics that confirm or refute GERD when evidence is borderline or inconclusive. While the Lyon Consensus criteria mostly apply to testing performed off therapy, recent studies have suggested metrics that can be used for on-therapy tests.

High resolution manometry serves to rule out confounding diagnoses such as achalasia and behavioral syndromes. Manometry can also evaluate for hypomotility disorders and contraction reserve.