The “right” biopsy protocol for microscopic colitis: reduced workload and carbon footprint while maintaining diagnostic accuracy

Aims Histological findings of microscopic colitis are patchy and the potential for missed diagnoses is recognized. While current guidelines recommend biopsies from at least the right and left side of the colon, the optimal approach is uncertain. We interrogated diagnostic biopsies in a cohort of patients with confirmed microscopic colitis with a view to improving biopsy protocols.

Methods We conducted a multi-centre retrospective cohort study of index colonoscopies in microscopic colitis patients over a 14 year period. We recorded patient demographics and symptoms along with the total number and location of biopsies and whether they revealed features of lymphocytic or collagenous colitis. Patients were excluded if histology was not definitive and clinical evidence was lacking.

Results 228 index colonoscopies between 2010 and 2024 with confirmed microscopic colitis were included, 64% (145/228) lymphocytic colitis and 36% (83/228) collagenous colitis. The median incidence was 9 cases and this was stable over the study period. Median age at diagnosis was 60 (IQR 48-72) for both subtypes, while 27% (61/228) were less than 50 years old. As expected, there was a female predominance overall (71%, 162/228) and was similar for both subtypes. Of interest, males were significantly older than females at the time of diagnosis (62 vs 56 years respectively, p=0.03) and females were twice as likely to be diagnosed under the age of 50 years (OR=1.96). Symptoms were known in 86% (196/228), 98% (192/196) had diarrhoea and only 2% (4/196) had other symptoms. The median number of individual colonic biopsies taken was 6 (IQR 4–7). 26% (60/228) had biopsies labelled “random colon biopsies”, 4% (8/226) had serial colonic biopsies, 37% (84/226) had biopsies labelled “right colon” and “left colon”, and 33% (76/228) had some other combination of biopsies. In 150 subjects who had any biopsy identified from the right colon, 100% had microscopic colitis features in the right colon and only 2% (3/150) had a patchy distribution. While some subjects had positive right colon biopsies with negative left colon biopsies (10%, 13/136), the converse was not true. Furthermore, looking just at containers identified as being from the right or left colon, those from the left were statistically more likely to be negative (9% (17/199) vs. 2% (4/209), OR 4.79, p=0.0025). Both lymphocytic colitis and collagenous colitis were equally likely to have negative left colon biopsies. 51% (117/228) had rectal biopsies and 75% (88/117) of these had microscopic colitis features.

Conclusions These findings support the need for a full colonoscopy for patients of all ages presenting with diarrhoea. In the era of green endoscopy, our data would support a protocol of taking biopsies from at least two sites in the right colon only, processed in a single specimen container, as opposed to the current recommendation for distinct right and left colon biopsies.

Conflicts of Interest

Authors do not have any conflict of interest to disclose.

Publication History

Article published online:
27 March 2025