Alimentary Tract
Gastro-oesophageal reflux and interstitial lung disease

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Abstract

Background

Interstitial lung disease is a heterogeneous entity, which encompasses a large number of pulmonary disorders, including idiopathic pulmonary fibrosis. Gastro-oesophageal reflux appears to be more prevalent in idiopathic pulmonary fibrosis than in controls and in patients with secondary pulmonary fibrosis, but its contribution to interstitial lung disease remains unsettled.

Aims

To prospectively evaluate gastro-oesophageal reflux in patients with interstitial lung disease and to define acid reflux patterns in patients with idiopathic and secondary forms of pulmonary fibrosis.

Materials and methods

Twenty-eight patients (15 M, median age 66 years, interquartile range 60–71) were studied by history taking, pulmonary function tests, high resolution computed tomography, oesophageal manometry and 24 h oesophago-gastric pH monitoring.

Results

Sixteen patients (57%) had typical reflux symptoms. All patients completed 24 h pH metry and 14 underwent oesophageal manometry. An abnormal oesophageal acid exposure was observed in 19 patients (68%), 13 of which complained of predominant typical reflux symptoms. A diagnosis of idiopathic pulmonary fibrosis was made in 18 patients, while the remaining 10 patients were classified as secondary pulmonary fibrosis. Secondary pulmonary fibrosis patients had more restrictive lung defect, as expressed as Tiffeneau index (p < 0.05) and greater acid reflux at nighttime (p < 0.05) than idiopathic pulmonary fibrosis patients.

Conclusions

The prevalence of abnormal acid reflux in interstitial lung disease patients is high and, in particular, patients with secondary pulmonary fibrosis show higher oesophageal acid exposure than those with idiopathic form.

Introduction

Gastro-oesophageal reflux (GER) is thought to be potentially implicated in the pathogenesis of different forms of pulmonary disorders, including asthma [1], chronic obstructive pulmonary disease (COPD) [2], chronic cough [3], pneumonia [4], obstructive sleep apnoea [5] and interstitial lung disease (ILD) [6], [7], [8]. Evidences on acid aspiration-induced lung injury date several decades [9] and this is believed to be the main noxious trigger to pulmonary diseases together with vago-vagal reflexes [10]. However, the role of GER as concomitant or causal is far to be elucidated in many of these conditions including ILD.

ILD encompasses a heterogeneous group of acute and chronic disorders characterised by diffuse pulmonary infiltrates with histologic features of pulmonary inflammation, exertional dyspnoea and restrictive lung patterns [11]. Pulmonary fibrosis results from a variety of insults to the lung, including toxic, autoimmune, drug-induced, infectious, or traumatic injuries. Exposure to a known aetiological factor does not always lead to fibrosis and the existence of familial forms of lung fibrosis suggests a genetic predisposition [12]. When the aetiology of ILD is unknown, the disease is classified as idiopathic pulmonary fibrosis (IPF), which is a progressive and fatal syndrome. It usually affects adults in the fifth decade and mortality rates are high, with median survival at the time of diagnosis of 4–5 years [13]. We defined cases with recognisable underlying causes as secondary pulmonary fibrosis (SPF).

Only scant evidences exist suggesting a high prevalence of increased oesophageal acid reflux in patients with pulmonary fibrosis [6], [7], [8], [14]. The aims of our study were to prospectively evaluate GER in consecutive patients with ILD and to define acid reflux patterns in patients with idiopathic and secondary forms of pulmonary fibrosis.

Section snippets

Patients

Twenty-eight consecutive patients diagnosed as being affected by ILD according to predefined criteria [15] were evaluated by thorough medical history, pulmonary function tests, high resolution computed tomography (HRCT), oesophageal manometry and oesophago-gastric pH monitoring. Each patient completed a modified version of the Bowel Disease Questionnaire (BDQ) that is commonly used in our laboratory to evaluate digestive symptoms [16], [17].

Pulmonary function tests

Flow–volume studies, lung volumes, carbon monoxide

Demographics and function pulmonary tests

All patients showed grade III at HRCT (see Section 2). Demographic features, function pulmonary tests and HRCT findings of ILD patients (n = 28, 15 M, 66 years, IQR 60–71) are listed in Table 1. Eighteen patients were diagnosed as being affected by IPF (10 M, 70 years, IQR 61–72) and 10 by SPF, (5 M, 63 years, IQR 55–67). SPF was diagnosed as secondary to extrinsic allergic alveolitis (n = 2), connective tissue disease (n = 5), non-specific interstitial pneumonia (n = 3).

No differences in function

Discussion

A potential causative role of GER in a variety of pulmonary diseases [1], [2], [3], [4], [5], [6], [23], [24] including ILD [25] has long been hypothesised. An increased prevalence of hiatal hernia and GER has been reported in IPF compared with SPF [12]. Studies on correlations between lung function tests and oesophageal dysmotility in ILDs and between DLCO and pH monitoring, have provided controversial results [26]. Experimental models showed that pulmonary fibrosis can occur after acid

Conflict of interest statement

None declared.

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