Microscopic colitis

Microscopic colitis syndrome is defined by the triad of:

• chronic watery diarrhoea
• normal mucosal appearance on colonoscopy
• characteristic histological changes in the mucosal biopsy
  
  
• chronic watery diarrhoea
  • most common symptom in microscopic colitis is chronic, non-bloody, watery, diarrhoea, frequently associated with faecal urgency, the passage of stools at night, and faecal incontinence
  • may also complain of cramping abdominal pain
• microscopic colitis affects 0.12% of the population
• Coeliac disease is present in 3%–4% of patients with microscopic colitis, reflecting an overlap with other autoimmune conditions
• median age at diagnosis is 60 years of age
• risk factors include:
  • smoking
  • long-term use of proton-pump inhibitors, non-steroidal anti-inflammatory drugs, and selective serotonin reuptake inhibitors
• diagnosis:
  • depends on characteristic histological findings
  • normal mucosal appearance on colonoscopy - 4.77% of patients with normal colonoscopy findings have microscopic colitis confirmed on histology from biopsies
  • characteristic histological changes in the mucosal biopsy:
    • lymphocytic infiltration in the lamina propria - when this is marked the disease may be termed lymphocytic colitis
    • variable thickening of the subepithelial collagen layer - when fibrosis is marked the disease may be termed collagenous colitis

Reference:

• Barrett K.Microscopic colitis: a guide for general practice British Journal of General Practice 2021; 71: 41–42. DOI: https://doi.org/10.3399/bjgp21X714593