Introduction Patients investigated for diarrhoea often have macroscopically normal colonoscopies. Biopsies are, however, required in order to diagnose microscopic colitis (MC). Obtaining colonoscopic biopsies for persistent diarrhoea is an auditable JAG standard. The aim of this study, carried out in a single large NHS Teaching Hospitals Trust was (1) To measure the incidence of MC in patients with diarrhoea who had a “normal” colonoscopy. (2) To examine whether the discipline of the colonoscopist affected whether biopsies were taken in this situation or not. (3) To assess which biopsy protocols were being used.

Methods An analysis was performed of all colonoscopies with the indication of diarrhoea, with normal findings, undertaken in 2010. Interrogation of the endoscopy recording system (ERS), looked at endoscopist discipline, if biopsies were taken, biopsy sites and histology results.

Results A total of 4753 colonoscopy records were examined, of which 750 (15.8%) were performed for diarrhoea. 313/750 (41.7%) were described as being entirely normal. Of the 313 “normal” colonoscopies, 132 (42.2%) were performed by physicians; 40 (12.8%) surgeons; 124 (39.6%) nurses; 17 (5.4%) not specified. 294 (93.9%) colonoscopies had biopsies taken and MC was confirmed histologically in 14 (4.8%). Among the different professional groups, there was variation in the frequency of obtaining biopsy specimens: physicians 126/132 (95.5%), surgeons 35/40 (87.5%) and nurses 118/124 (95.2%). The difference between physicians and surgeons was not statistically significant (χ²=3.55, p=0.06). Positive biopsy for MC was similar between the different groups: physicians 5 (3.8%), surgeons 2 (5.0%), nurses 5 (4.0%) (p=NS). Of the patients who did have biopsies performed, 274/294, (93%) had both right and left colon sampled.

Conclusion The vast majority (93.9%) of patients presenting with diarrhoea and a normal colonoscopy in our unit are having colonic biopsies performed to exclude a diagnosis of microscopic colitis. The histology positivity rate was 5%, comparable to similar published series. A majority of all professional colonoscopists perform colonic biopsies appropriately in the setting of diarrhoea and normal colonoscopy. There is variability, but this is not statistically significant.

Competing interests None declared.