Microscopic colitis
Microscopic colitis is a cause of chronic watery, non-bloody diarrhea in older women with a grossly normal colonoscopy, diagnosed only by random colon biopsy showing lymphocytic or collagenous histology. Management starts with stopping culprit drugs and antidiarrheals, then oral budesonide for induction and, if needed, maintenance.
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What this article covers
- Overview
Definition: microscopic colitis is an inflammatory disease of the colon that causes chronic watery, non-bloody diarrhea despite a grossly and radiographically normal colon, with the diagnosis made only on histology of random colon biopsies.
- Epidemiology
Age and sex: most common in the seventh and eighth decades of life and affects women far more often than men.
- Risk factors
Older age and female sex: the dominant demographic risk factors, with a strong predominance in middle-aged and older women.
- Pathophysiology
Mucosal inflammatory infiltrate without gross injury: an abnormal immune or inflammatory response within the lamina propria and epithelium produces chronic diarrhea while leaving the mucosal surface…
- Clinical features
Chronic watery, non-bloody diarrhea: the hallmark and defining symptom, typically several loose stools per day, without gross blood, in an older woman.
- Differential diagnosis
Irritable bowel syndrome with diarrhea: chronic diarrhea with abdominal pain related to defecation and normal biopsies; distinguished from microscopic colitis by the absence of histologic…
- Diagnosis
Establish the diagnosis by histology on random colon biopsy, then subtype by the specific finding: because the colon is endoscopically normal by definition, colonoscopy with random biopsies of the…
- Management
Stop offending medications first: discontinue NSAIDs, PPIs, SSRIs, statins, or other implicated drugs where clinically feasible, as the first step regardless of symptom severity.
- Complications
Dehydration and electrolyte disturbance: from chronic high-volume watery diarrhea, particularly in older or frail patients.
- Prognosis
Generally benign course: most patients respond to antidiarrheal therapy or budesonide, and the disease does not shorten life expectancy.
- Prevention
Avoid or discontinue culprit medications when possible: NSAIDs, PPIs, SSRIs, and statins in a patient with a history of microscopic colitis, to reduce relapse risk.
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