Yes, Microscopic Colitis Causes Chronic Watery Diarrhea
Microscopic colitis is definitively characterized by chronic watery diarrhea caused by colonic inflammation, making diarrhea the hallmark presenting symptom of this disease 1.
Clinical Presentation
The diarrhea in microscopic colitis has specific characteristics:
- Profuse watery diarrhea (non-bloody) is the classic presentation 2, 3
- Nocturnal or early morning diarrhea is particularly common 2
- Patients frequently experience fecal urgency and incontinence 2, 3
- Abdominal pain accompanies the diarrhea in many cases 4, 3
In a recent cohort study, 98% of patients with microscopic colitis presented with diarrhea 4, confirming this as the dominant symptom. The study also found that nocturnal diarrhea (OR = 4.26) and abdominal pain (OR = 4.62) were significantly associated with microscopic colitis diagnosis 4.
Why This Matters Clinically
The critical diagnostic challenge is that the colon appears endoscopically normal in microscopic colitis 1, 2, 3. This creates a significant risk of misdiagnosis as irritable bowel syndrome, particularly since:
- Over half of patients with active microscopic colitis have fecal calprotectin <100 µg/g 5
- Many healthcare systems use calprotectin thresholds that miss microscopic colitis cases 5
- The disease can only be diagnosed through histological examination of colonic biopsies 1, 2
Diagnostic Approach
When evaluating chronic diarrhea:
- Perform colonoscopy with biopsies from multiple colonic segments, particularly the right colon 1
- Take biopsies even when the colon appears normal endoscopically 2, 3
- Consider microscopic colitis in patients over 60 years old, especially women 1, 2
- Look for associated features: nocturnal diarrhea, abdominal pain, weight loss 4, 3
Inflammatory markers can aid diagnosis: ESR >14 mm/h and fecal calprotectin >64 mcg/g showed excellent diagnostic validity (AUC 0.94 and 0.97 respectively) 4, though normal values do not exclude the diagnosis.
Impact on Quality of Life
Microscopic colitis significantly impairs quality of life despite not increasing mortality 1. The chronic watery diarrhea, fecal incontinence, and unpredictable symptoms substantially affect patients' daily functioning and well-being 2.
The disease occurs in 7.5% of patients undergoing evaluation for chronic diarrhea 1, with incidence comparable to ulcerative colitis and Crohn's disease 5, making it a common and frequently underdiagnosed cause of chronic diarrhea.