Biopsy-Detected Microscopic Colitis and Nonspecific Chronic Inflammatory Change in Patients with Chronic Diarrhea and Normal Colonoscopy: A Two-Case Series

Abstract

Chronic diarrhea may occasionally persist despite macroscopically normal colonoscopy, and in selected patients, random colonic biopsy may reveal histologic abnormalities not apparent endoscopically. We report two illustrative cases of biopsy-detected microscopic or nonspecific inflammatory abnormalities in patients initially managed as having a functional bowel disorder.This retrospective descriptive case series included two adults identified during routine clinical practice over a recent two-year period (approximately 2024–2025) at a tertiary care hospital who underwent colonoscopy with random colonic biopsies despite macroscopically normal colonic mucosa, due to persistent diarrhea-predominant symptoms. Clinical follow-up was available for approximately six weeks in Case 1 and eight weeks in Case 2.In both patients, colonoscopy revealed macroscopically normal colonic mucosa, except for hemorrhoids. In Case 1, histopathology showed preserved crypt architecture, increased intraepithelial lymphocytes, and mild lamina propria inflammation, consistent with lymphocytic microscopic colitis. In Case 2, biopsy showed increased intraepithelial lymphocytes with chronic inflammatory infiltrates in the lamina propria, interpreted as nonspecific chronic inflammatory change. Both patients received colonic-release budesonide with short-term subjective symptomatic improvement on available follow-up.These cases illustrate that biopsy-detected microscopic or nonspecific inflammatory abnormalities may occasionally be identified in selected patients with persistent diarrhea and normal colonoscopy. They should not be interpreted as evidence of routine biopsy yield, but they support individualized biopsy decisions in carefully selected patients after exclusion of more common causes