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Right biopsy protocol for microscopic colitis: Reduced workload and carbon footprint while maintaining diagnostic accuracy
Edric Leung, Yasir Alshareefy, Conor Costigan, Sandeep Sihag, Sarah Delaney, Sarah O’Donnell, Niall Breslin, Anthony O’Connor, Barbara Ryan, Abdul Zaheer, Ion Cretu, Fintan O’Hara, Deirdre McNamara
Edric Leung, Yasir Alshareefy, Conor Costigan, Sandeep Sihag, Sarah O’Donnell, Niall Breslin, Anthony O’Connor, Barbara Ryan, Fintan O’Hara, Deirdre McNamara, Department of Gastroenterology, Tallaght University Hospital, Dublin D24 NR0A, Ireland
Edric Leung, Conor Costigan, Sandeep Sihag, Deirdre McNamara, Trinity Academic Gastroenterology Group, Trinity College, Dublin D24 NR0A, Ireland
Sarah Delaney, Department of Cellular Pathology, Tallaght University Hospital, Dublin D24 NR0A, Ireland
Abdul Zaheer, Ion Cretu, Department of Gastroenterology, Naas General Hospital, Kildare W91 AE76, Ireland
Author contributions: Leung E and Alshareefy Y acquired and curated the data; Leung E and McNamara D conceived and designed the study, analyzed and interpreted the data, and drafted and critically revised the manuscript; Alshareefy Y, Costigan C, Sihag S, Delaney S, O’Donnell S, Breslin N, O’Connor A, Ryan B, Zaheer A, Cretu I, and O’Hara F contributed to the study design and critical review of the manuscript. All authors approved the final manuscript.
Institutional review board statement: This study was approved by the Clinical Audit Manager of Tallaght University Hospital. Formal ethics committee approval was not required owing to the retrospective study design.
Informed consent statement: Patients were not required to give informed consent for the study, as the analysis used anonymized clinical data obtained after each patient had provided written consent for treatment.
Conflict-of-interest statement: All the authors report no relevant conflicts of interest for this article.
STROBE statement: The authors have read the STROBE Statement-checklist of items, and the manuscript was prepared and revised according to the STROBE Statement-checklist of items.
Data sharing statement: sharing statement: The data underlying this article are available from the corresponding author upon reasonable request.
Corresponding author: Edric Leung, Department of Gastroenterology, Tallaght University Hospital, Tallaght, Dublin D24 NR0A, Ireland.
edric.leung@tuh.ie
Received: September 9, 2025
Revised: November 13, 2025
Accepted: January 27, 2026
Published online: June 5, 2026
Processing time: 263 Days and 18.5 Hours
BACKGROUND
Histological findings of microscopic colitis (MC) are patchy, with potential for missed diagnoses. While guidelines recommend biopsies from the right and left sides of the colon, the optimal approach remains uncertain.
AIM
To interrogate diagnostic biopsies in a cohort of patients with confirmed MC with a view to improving biopsy protocols.
METHODS
We conducted a retrospective study of index colonoscopies in patients with MC over a 14-year period. We recorded demographics, symptoms, total number and location of biopsies, and whether they revealed features of lymphocytic or collagenous colitis.
RESULTS
A total of 228 index colonoscopies were included: 64% (145/228) lymphocytic colitis and 36% (83/228) collagenous colitis. The median age at diagnosis was 60 (interquartile range: 48-72) years, with 27% (61/228) aged < 50 years. Overall, 71% (162/228) of the patients were female, similar across subtypes. Males were older at diagnosis than females (62 vs 56, P = 0.03). Symptoms were known in 86% of patients (196/228), of whom 98% (192/196) had diarrhea. Among 150 cases with biopsies from the right colon, MC features were present in the right-colon specimens in 100%, with a patchy distribution in only 2% (3/150). In contrast, among 158 cases with biopsies from the left colon, MC features were present in the left-colon specimens in 92%. Among cases with paired right and left biopsies, 10% (13/136) had positive right-sided biopsies with negative left-sided biopsies; the converse was never observed. Regarding specimen containers, those from the left colon were more likely to be negative [9% (17/199) vs 2% (4/209), odds ratio: 4.79, P = 0.0025].
CONCLUSION
In the era of green endoscopy, our data support a protocol of taking biopsies from at least two sites in the right colon only, processed in a single container.
Core Tip: Current guidelines recommend biopsies from both the right and left colon for diagnosing microscopic colitis; however, the optimal strategy remains uncertain. In this retrospective study of 228 index colonoscopies in patients with microscopic colitis, right colon biopsies were diagnostic in all cases, while left colon biopsies had a significantly lower yield and provided no additional diagnostic value. These findings suggest that a simplified protocol of two right colon biopsies in a single container could preserve diagnostic accuracy while reducing workload, cost, and carbon footprint, consistent with green endoscopy principles.
