Random colonic biopsies in endoscopically normal mucosa are costly and have little utility in ruling out microscopic colitis in patients with chronic diarrhoea, Australian research shows.
An audit of practice in two WA hospitals identified 872 normal colonoscopies where random colonic biopsies were performed by both general surgeons and gastroenterologists.
The most common indications for biopsy were diarrhoea (48.7%), altered bowel habit (26.4%), abdominal pain (8%) and bleeding (3.9%).
The study found there was a 15% yield of abnormal histopathology – “generally minor and not indicative of conditions requiring treatment” – but only 1.5% of the biopsies were positive for microscopic colitis.
“The yield of microscopic colitis in patients with diarrhoea (425 patients) recorded as the indication for colonoscopy was 3.1%,” the study said.
“Of the 13 positive diagnoses of microscopic colitis, 10 of the patients had diarrhoea as a symptom and three did not. Only two patients were reviewed by gastroenterologists and only one received pharmacological treatment for severe diarrhoea.”
Diarrhoea as an indication was significantly associated with a positive diagnosis of microscopic colitis compared to bleeding, altered bowel habit, anaemia or abdominal pain (p = 0.041).
The cost per positive diagnosis of microscopic colitis was calculated at $10,862.42.
The study noted that the British Society of Gastroenterology guidelines for the investigation of chronic diarrhoea in adults recommend biopsy to exclude microscopic colitis.
“However, the yield from this strategy, and the impact of the biopsy results on clinical management was demonstrably minimal in this study,” the WA study said.
“The cost of performing and analysing RCBs of $141,211.45 in this study demonstrates that RCBs are a very costly exercise with very low histopathological yield and low impact on patient outcomes even with a positive diagnosis of microscopic colitis.”
“Although symptoms such as diarrhoea or altered bowel habit, gastrointestinal bleeding are red flags of possible colorectal malignancy and require a colonoscopy, the routine performance of RCBs to rule out microscopic colitis in these settings needs to be further questioned.”
Commenting on the study, Director of Endoscopy and Head of the Inflammatory Bowel Disease Services at Concord Hospital Professor Rupert Leong told the limbic their findings were the opposite of an earlier WA study which found colonic biopsies were useful.
“The sample size is too small and the referral process skewed as patients attending surgical colonoscopy lists would differ from medical lists,” he said.
He said although there were no local guidelines, colonic biopsy to rule our microscopic colitis was fairly standard practice.