Systematic review with meta‐analysis: diagnostic overlap of microscopic colitis and functional bowel disorders

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Summary Background Microscopic colitis shares certain common clinical manifestations with functional bowel disorders, especially diarrhoea‐dominant irritable bowel syndrome ( IBS ) and functional diarrhoea. However, the exact relationship between microscopic colitis and functional bowel disorders has not been systematically assessed. Aim To conduct a systematic review and meta‐analysis on the diagnostic overlap between functional bowel disorders and microscopic colitis. Methods We searched MEDLINE , EMBASE and SCOPUS databases, as well as the abstract books of the major gastroenterology meetings, to investigate the prevalence of microscopic colitis among patients with functional bowel disorders (considering all subtypes of both disorders) and vice versa. Data were pooled with a random‐effects model. Results Of 227 references identified, data were collected from 26 studies and a total of 5,099 adult patients. The pooled prevalence any type of functional bowel disorders in patients who present diagnostic criteria of microscopic colitis was 39.1% (95% CI : 22.8–56.6%; I 2 : 97%) and was higher for lymphocytic colitis than for collagenous colitis (40.7% vs. 28.4%, respectively; P = 0.58). The prevalence of microscopic colitis in functional bowel disorders patients was 7% (95% CI : 3.6–11.4%), reaching 9.8% (95% CI : 4.4–17.1%; I 2 : 95%) in patients exhibiting diarrhoea‐dominant IBS , nonsignificantly higher than microscopic colitis rates among patients with constipation‐dominant IBS (1.3%) or mixed‐dominant IBS (1.9%). Conclusions There is a significant overlap of symptoms between microscopic colitis and functional bowel disorders, especially in diarrhoeal subtypes. The high proportion of microscopic colitis among diarrhoea‐dominant functional syndromes should serve as a call for more active diagnosis in selected patients.