Advancements in the use of 24-hour impedance-pH monitoring for GERD diagnosis

Abstract

Gastro-esophageal reflux disease (GERD) occurs in about 25% of the general population. The complexity of the disease and the multiplicity of its clinical manifestations impair the availability of a singular diagnostic test. The majority of GERD patients do not have any endoscopically visible lesions, the so-called non-erosive reflux disease (NERD). This latter population consists of several subgroups characterized by: 1. excess of acid; 2. normal acid, but hypersensitivity to acid or weakly acidic reflux; 3. normal acid, but lack of any relationship between symptoms and reflux episodes. At present, 24-h impedance-pH monitoring represents the best diagnostic tool to detect abnormal reflux and to correlate symptoms to reflux episodes. Moreover, the recent adoption of novel impedance metrics, such as mean nocturnal baseline impedance and post-reflux swallow-induced peristaltic wave index, seem to be able to improve the diagnostic yield of 24-h impedance-pH monitoring, making this test the most accurate in diagnosis of GERD.

Introduction

Gastroesophageal reflux disease (GERD) is a chronic and benign condition, affecting up to 20% of the general population in western countries while it is less prevalent in Asian populations [1]. According to the Montreal classification [2], it develops when the reflux into the esophagus of gastric contents (meals and secretions) causes troublesome symptoms and/or complications.

Until the end of the second millennium, GERD was identified with erosive esophagitis (EE), but in the past two decades we have realized that the majority of patients with this illness do not present any inflammatory lesions of the distal part of the esophagus at endoscopy [3]. This non-erosive form of GERD has been named as NERD (non-erosive reflux disease) on the exclusive basis of the absence of endoscopic damage, but subsequent functional studies have clearly shown that it is markedly heterogeneous from a pathophysiological point of view, because we can distinguish various phenotypes [4]: patients with acid excess (true NERD); patients with normal acid, but positive correlation between heartburn and reflux episodes (reflux hypersensitivity) and patients with normal acid, but without any relationship between symptoms and reflux events (functional heartburn = FH). In other words, the most typical symptom of GERD, that is heartburn, can be due not only to acid, but also to other factors not depending on increased esophageal acid exposure [5].

Beyond the typical symptoms of GERD (heartburn and regurgitation), this disorder can manifest with extraesophageal symptoms (chronic cough, hoarseness, asthma), but this association has been questioned in last years, because it seems to be much less frequent than previously estimated [6].