“Normal Values of 24H Multichannel Intraluminal Impedance pH-Metry in a Greek Obese Population Based on Montreal Definition of Gerd”

Esophageal high-resolution manometry and 24 h pH-impedance monitoring normative values in patients with obesity candidate for bariatric and metabolic surgery

Obesity is linked to increased risk of gastroesophageal reflux disease (GERD) and esophageal motility disorders, both of which may impact outcomes in metabolic and bariatric surgery (MBS). GERD pathophysiology in obesity includes elevated intraabdominal pressure and altered esophagogastric junction (EGJ) function. High resolution manometry (HRM) and 24-h esophageal pH-impedance (MII-pH) monitoring are vital in evaluating GERD, yet normative values specific to populations with obesity are limited, risking misdiagnosis if lean data are used. This study establishes normative HRM and MII-pH values in asymptomatic individuals with obesity, compared to normal-weight controls, to guide accurate diagnosis and treatment. A retrospective analysis was conducted on asymptomatic patients with obesity (BMI ≥ 30) and normal-weight controls (BMI 20-25) who underwent HRM and MII-pH prior to MBS between 2015 and 2024. Exclusion criteria included GERD symptoms, esophagitis, and prior gastrointestinal surgery. Key HRM parameters (LES pressure, EGJ morphology) and MII-pH metrics (acid exposure time, reflux episodes) were recorded and analyzed. Of the 96 patients with obesity and 25 normal-weight participants, significant differences in HRM and MII-pH results were observed. Individuals with obesity showed increased intra-gastric pressure, gastroesophageal pressure gradient, and higher acid exposure time. While LES pressure and EGJ morphology were similar to controls, participants with obesity exhibited distinct reflux patterns, especially postprandial, suggesting obesity-specific physiological changes. This study establishes normative HRM and MII-pH values for asymptomatic individuals with obesity, highlighting critical differences from normal-weight controls. Obesity-specific diagnostic criteria are essential for accurate GERD diagnosis, particularly for MBS candidates, to improve management and predict potential postoperative complications.

Study of gastroesophageal reflux. Interpretation of functional tests in the obese patient

Overweight and obesity are a public health problem and in 1997 obesity was recognized as a global epidemic by the World Health Organization (WHO). Overweight and obesity affect almost 60% of adults and one in three children in Europe according to the most recent WHO report. Objectively, gastroesophageal reflux disease (GERD) is defined as the presence of characteristic esophageal mucosal damage assessed by endoscopy and/or the demonstra-tion of pathological acid exposure by reflux monitoring studies. The prevalence of GERD is increased in obese patients In overweight and obese patients, the clinical symptoms of GERD are especially present in the supine position and this correlates with more frequent episodes of nocturnal reflux in the 24-h pH monitoring, there is also an increase in the number of refluxes with content acid. In the population with symptoms, digestive endoscopy detects data of erosive esophagitis in 50% of patients, while 24-h pH-impedanciometry diagnoses 92% of patients with non-erosive reflux disease (NERD) The presence of persistent GERD in the mucosa affects esophageal motility and patients may develop ineffective esophageal motility-type disorders, so we will review the interpre-tation of the functional tests that determine motility, which is esophageal manometry, and those that determine reflux gastroesophageal, acid and non-acid, which is the pH measure-ment with or without 24-h impedanciometry.

Normal values and regional differences in oesophageal impedance-pH metrics: a consensus analysis of impedance-pH studies from around the world

OBJECTIVE

Limitations of existing impedance-pH thresholds include small sample size of normative studies, inclusion of artefactual pH drops and incorrect identification of impedance reflux events. We aimed to obtain new impedance-pH thresholds from expert consensus analysis of tracings from a large number of healthy subjects.

DESIGN

Of 541 studies performed worldwide using two different systems (Diversatek, USA, and Laborie, Netherlands), 150 tracings with oesophageal diagnoses, behavioural disorders and study-related artefacts were excluded. The remainder studies were subject to two reviewer consensus analysis, in-person or through video conference, consisting of editing meals and pH drops, identification of impedance reflux and postreflux swallow-induced peristaltic wave (PSPW) using strict pre-established criteria and measurement of distal mean nocturnal baseline impedance (MNBI).

RESULTS

Consensus analysis was performed in 391 tracings (age 32.7 years, range 18-71, 54.2% female). Normative thresholds were significantly different between Diversatek and Laborie (total acid exposure time: 2.8% and 5%; reflux episodes: 55 and 78; MNBI at 3 cm: 1400 and 1500 ohms, at 5 cm: 1400 and 1800 ohms). Males had higher acid exposure, more reflux episodes and lower MNBI. Significant regional differences were identified, including higher PSPW scores in Western countries, and higher MNBI in Asia using Diversatek, and higher acid exposure in the Netherlands, higher MNBI in Asia and South Africa, and lower MNBI in Turkey using Laborie.

CONCLUSION

Normal impedance-pH monitoring thresholds have regional and system-related differences. Clinical interpretation needs to use normal thresholds valid for the system used and world region, following careful editing of the tracings.

Can Impedance-pH Testing on Medications Reliably Identify Patients with GERD as Defined by Pathologic Esophageal Acid Exposure off Medications?

INTRODUCTION

Impedance-pH testing (MII-pH) while patients are on acid suppression medications is frequently used to evaluate persistent reflux symptoms. The aim of this study was to determine whether MII-pH on medications can reliably identify patients with gastroesophageal reflux disease (GERD) as defined by pathologic esophageal acid exposure off medications, and to determine if there is a threshold of total reflux episodes on medications where pH testing off medications may be unnecessary.

METHODS

A retrospective review identified all patients between 1/2010 and 4/2017 who underwent MII-pH testing on PPI medications and subsequently had pH testing off medications. GERD was defined on pH testing off medications by an abnormal DeMeester Score (DMS) and on MII-pH on medications by ≥ 48 total reflux episodes. Patients with an abnormal DMS by MII-pH on medications were excluded.

RESULTS

There were 71 patients, (22 males; 49 females), with a median age of 52 years. Based on ≥ 48 total reflux episodes by MII-pH testing on medications, 42 patients (59%) had GERD. When tested off medications, an abnormal DMS was present in 44 patients (62%). Among those with GERD based on impedance testing on medications, 31% did not have GERD based on pH testing off medications. Further, in the 29 patients with ≤ 48 total reflux episodes on MII-pH (normal test), 15 patients (52%) had pathologic acid exposure off medications. When there were > 73 reflux events with MII-pH on medications, all 15 patients in our series had pathologic acid exposure on pH testing off medications.

CONCLUSION

MII-pH testing on medications in patients with refractory GERD symptoms does not reliably correlate with a diagnosis of GERD as defined by pathologic esophageal acid exposure off medications. The commonly used abnormal MII-pH test value of ≥ 48 total reflux episodes is not validated and should not be used. However, in our series, patients with > 73 total reflux episodes had a high likelihood of having pathologic acid exposure off medications. Overall, the preferred strategy to evaluate patients with persistent GERD symptoms on acid suppression therapy should be pH testing off medications.