Misinterpreting Diarrhea-Predominant Irritable Bowel Syndrome and Functional Diarrhea: Pathophysiological Highlights

J Clin Med. 2023 Sep 5;12(18):5787. doi: 10.3390/jcm12185787.


Giusi Desirè Sciumè 1Ginevra Berti 1Christian Lambiase 1Italia Paglianiti 2Vincenzo Villanacci 3Francesco Rettura 1Antonio Grosso 1Angelo Ricchiuti 1Nicola de Bortoli 1Paolo Usai Satta 4Gabrio Bassotti 5Massimo Bellini 1


Author information

1Gastrointestinal Unit, Department of Translational Sciences and New Technologies in Medicine and Surgery, University of Pisa, 56010 Pisa, Italy.

2Nuclear Medicine Unit, Department of New Technologies and Translational Research in Medicine and Surgery, University of Pisa, 56010 Pisa, Italy.

3Institute of Pathology ASST-Spedali Civili, University of Brescia, 25121 Brescia, Italy.

4Gastrointestinal Unit, 'P. Brotzu' Hospital, 09121 Cagliari, Italy.

5Gastroenterology & Hepatology Section, Department of Medicine, University of Perugia Medical School, 06129 Perugia, Italy.



Irritable bowel syndrome with predominant diarrhea (IBS-D) and functional diarrhea (FD) are disorders of gut-brain interaction characterized by recurring symptoms which have a serious impact on the patient's quality of life. Their pathophysiology is far from being completely understood. In IBS-D growing evidence suggests that bile acid malabsorption (BAM) could be present in up to 30% of patients. Microscopic colitis (MC) is a well-known cause of watery diarrhea and some patients, at first, can be diagnosed as IBS-D or FD. Both BAM and MC are often responsible for the lack of response to conventional treatments in patients labelled as "refractory". Moreover, because BAM and MC are not mutually exclusive, and can be found in the same patient, they should always be considered in the diagnostic workout when a specific treatment for BAM or MC is unsatisfactory. In the present review the possible shared pathogenetic mechanisms between BAM and MC are discussed highlighting how MC can induce a secondary BAM. Moreover, a brief overview of the current literature regarding the prevalence of their association is provided.

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