Microscopic colitis is a common cause of watery diarrhea. This debilitating disease is easy to treat, but the diagnosis can be challenging. Without lesions to target, guidelines recommend colonoscopy with at least two biopsies from the right, transverse, descending, and sigmoid colon (total: eight-plus biopsies). With little evidence to guide this recommendation, this time-consuming protocol was proposed to minimize the risk of false-negative results.

This study by Virine and colleagues again demonstrates that microscopic colitis is a patchy colonic disease and that biopsy yield varies by anatomic location. Most importantly, the authors determined that a colonoscopy with two biopsies from the ascending and two biopsies from the descending colon (total: four biopsies) detects all patients with microscopic colitis. Biopsies of the rectosigmoid alone were insufficient. This work suggests that we can rule out a diagnosis of microscopic colitis by taking at least 50% fewer biopsies.

A more efficient and less invasive procedure is better for patients as sedation time and sampling the colon are associated with risks. In the future, a prospective, colonoscopy-based study in patients with diarrhea will allow us to confirm the optimal number and location of biopsies needed to establish a diagnosis of microscopic colitis. This work will be important to inform diagnostic guidelines and change practice.

Anne F. Peery, MD, MSCR, is assistant professor of medicine, division of gastroenterology and hepatology, University of North Carolina School of Medicine, Chapel Hill. She has no conflicts of interest.