Microscopic Colitis

An older woman with months of watery stools, urgency and episodes that wake her may have microscopic colitis even when the colonoscopy report says normal. That apparent mismatch is the defining clinical trap: inflammation can evade the endoscopist’s eye but remain visible on biopsy. Collagenous and lymphocytic colitis are different microscopic patterns of the same bedside syndrome, so symptoms do not reliably distinguish them and the first-line treatment pathway is shared. The clinical model is practical. First, decide how much harm the diarrhea is causing—volume depletion, electrolyte loss, kidney injury, skin breakdown and loss of sleep or continence. Then confirm the diagnosis with biopsies from the right and left colon while looking for infection, celiac disease, medication associations, bile acid diarrhea and alarm features that point elsewhere. Once symptomatic microscopic colitis is established, budesonide is guideline-supported first-line therapy, although its use for microscopic colitis is off-label in Canada. Its low systemic exposure is not interaction-proof: strong CYP3A4 inhibitors, regular grapefruit intake and hepatic impairment can increase corticosteroid exposure. Visible blood, fever, progressive severe weight loss or concerning laboratory abnormalities should...