What are the symptoms and diagnostic workup for microscopic colitis?

Symptoms and Diagnostic Workup for Microscopic Colitis

Microscopic colitis is characterized primarily by chronic watery, non-bloody diarrhea, and diagnosis requires colonoscopy with biopsies showing characteristic histological changes despite normal-appearing colonic mucosa. 1

Clinical Presentation

Primary Symptoms

• Chronic watery, non-bloody diarrhea (hallmark symptom) 1, 2
• Nocturnal diarrhea (reported in approximately 70-80% of cases) 3
• Fecal urgency 2
• Abdominal pain (occurs in approximately 50-60% of patients) 2, 3

Secondary Symptoms

• Weight loss (mild to moderate) 2, 3
• Abdominal bloating and flatulence 3
• Arthralgias (joint pain) 2

Risk Factors

• Increasing age (most common in patients over 60 years) 1, 2
• Female sex (female predominance) 2, 4
• Presence of other autoimmune diseases 2
• Medication use:
  • Proton pump inhibitors 2, 3
  • Nonsteroidal anti-inflammatory drugs 2, 3
  • Selective serotonin reuptake inhibitors 2
  • Statins 2

Diagnostic Workup

Initial Assessment

• Evaluate for chronic watery diarrhea without blood
• Rule out infectious causes (including C. difficile) 1
• Consider symptom overlap with IBS-D (irritable bowel syndrome with diarrhea) 1, 3

Definitive Diagnosis

1. Colonoscopy with biopsies (gold standard) 1, 5

   • Endoscopic appearance is typically normal or near-normal 1, 2
   • Multiple biopsies should be taken from normal-appearing mucosa 1, 3
   • Biopsies should include samples from both right and left colon 3

2. Histopathological examination (required for diagnosis) 1, 2

   • Two main subtypes:
     • Lymphocytic colitis: Increased intraepithelial lymphocytes and infiltration of the lamina propria 1, 6
     • Collagenous colitis: Thickening of the collagen subepithelial layer 1, 6

Differential Diagnosis

• Irritable bowel syndrome with diarrhea (IBS-D) 1, 3
• Celiac disease 5, 6
• Inflammatory bowel disease 5, 6
• Infectious colitis 5
• Bacterial overgrowth 5

Important Clinical Considerations

Diagnostic Challenges

• Symptoms overlap significantly with IBS-D, leading to potential misdiagnosis 3
• Studies have found that approximately 6% of patients initially diagnosed with IBS-D actually have microscopic colitis 3
• Normal endoscopic appearance can lead to missed diagnosis if biopsies are not taken 1, 2

Key Diagnostic Pearls

• Always consider microscopic colitis in patients over 60 with chronic watery diarrhea 1, 2
• Nocturnal diarrhea is an important distinguishing feature from IBS-D 3
• Colonoscopy with multiple biopsies is essential even when the mucosa appears normal 1, 3
• Medication history is crucial as several common drugs can trigger or exacerbate microscopic colitis 2, 3

Pitfalls to Avoid

• Relying solely on endoscopic appearance without biopsies 1, 2
• Failing to obtain biopsies from both right and left colon 3
• Missing the diagnosis in patients with IBS-D symptoms, particularly in older women 3, 4
• Not considering medication-induced microscopic colitis 2, 3