Opinion Review
Copyright ©The Author(s) 2021. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Hepatol. Dec 27, 2021; 13(12): 1816-1827
Published online Dec 27, 2021. doi: 10.4254/wjh.v13.i12.1816
Non-alcoholic fatty liver disease in irritable bowel syndrome: More than a coincidence?
Huw Purssell, Peter J Whorwell, Varinder S Athwal, Dipesh H Vasant
Huw Purssell, Varinder S Athwal, Hepatology, Manchester University NHS Foundation Trust, Manchester M23 9LT, United Kingdom
Huw Purssell, Peter J Whorwell, Varinder S Athwal, Dipesh H Vasant, Division of Diabetes, Endocrinology and Gastroenterology, University of Manchester, Manchester M23 9LT, United Kingdom
Peter J Whorwell, Neurogastroenterology Unit, Wythenshawe Hospital, Manchester University NHS Foundation Trust, Manchester M23 9LT, United Kingdom
Dipesh H Vasant, Neurogastroenterology Unit, Department of Gastroenterology, Manchester University NHS Foundation Trust, Wythenshawe Hospital, Manchester M23 9LT, United Kingdom
Author contributions: Purssell H and Vasant DH did the main literature review and drafted the manuscript; Whorwell PJ and Athwal VS critically reviewed the manuscript; and all authors approved the final version of the manuscript for publication.
Conflict-of-interest statement: None of the authors have any conflicts of interest to disclose.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Dipesh H Vasant, MBChB, MRCP, PhD, Senior Lecturer, Neurogastroenterology Unit, Department of Gastroenterology, Manchester University NHS Foundation Trust, Wythenshawe Hospital, Southmoor Road, Manchester M23 9LT, United Kingdom. dipesh.vasant@manchester.ac.uk
Received: April 17, 2021
Peer-review started: April 17, 2021
First decision: July 27, 2021
Revised: August 1, 2021
Accepted: October 27, 2021
Article in press: October 27, 2021
Published online: December 27, 2021
Processing time: 253 Days and 17.8 Hours
Abstract

Irritable bowel syndrome (IBS) and non-alcoholic fatty liver disease (NAFLD) are amongst the most common gastrointestinal and liver conditions encountered in primary and secondary care. Recently, there has been interest in the apparent co-incidence of NAFLD in patients with IBS mainly driven by improved understanding of their shared risk factors and pathophysiology. In this paper we summarize the shared risk factors which include; overlapping nutritional and dietary factors as well as shared putative mechanisms of pathophysiology. These include changes in the gut microbiome, gut permeability, immunity, small bowel bacterial overgrowth and bile acid metabolism. This paper describes how these shared risk factors and etiological factors may have practical clinical implications for these highly prevalent conditions. It also highlights some of the limitations of current epidemiological data relating to estimates of the overlapping prevalence of the two conditions which have resulted in inconsistent results and, therefore the need for further research. Early recognition and management of the overlap could potentially have impacts on treatment outcomes, compliance and morbidity of both conditions. Patients with known IBS who have abnormal liver function tests or significant risk factors for NAFLD should be investigated appropriately for this possibility. Similarly, IBS should be considered in patients with NAFLD and symptoms of abdominal pain associated with defecation, an altered bowel habit and bloating.

Keywords: Irritable bowel syndrome; Non-alcoholic fatty liver disease; Metabolic syndrome; Obesity; Prevalence; Pathophysiology

Core Tip: Irritable bowel syndrome (IBS) and non-alcoholic fatty liver disease (NAFLD) are amongst the most common gastrointestinal and liver conditions encountered in primary and secondary care. There has been interest in the apparent co-incidence of NAFLD in patients with IBS mainly driven by improved understanding of their shared risk factors and pathophysiology. In this paper we summarize the shared risk factors which include; overlapping nutritional and dietary factors as well as shared putative mechanisms of pathophysiology. Physicians should be aware of the possibility of co-existence of IBS and NAFLD and consider investigating patients with IBS or NAFLD with clinical features of the other condition.