What are the causes of colitis?

Causes of Colitis

Colitis can be caused by infections, inflammatory bowel diseases, microscopic colitis, ischemic processes, and medication-induced inflammation, with infectious causes being a common trigger for both acute episodes and chronic inflammatory conditions.

Infectious Causes

• Bacterial pathogens are common causes of infectious colitis, including:

  • Clostridium difficile - particularly in patients with recent antibiotic exposure 1
  • Campylobacter species 1, 2
  • Salmonella species 2, 3
  • Shigella species 2, 3
  • Escherichia coli (especially Shiga toxin-producing strains) 2, 3
  • Yersinia species 3

• Viral infections can cause gastroenteritis with colonic involvement 4

• Parasitic infections can lead to colitis, particularly in endemic regions or after travel 2, 4

• Cytomegalovirus (CMV) infection can cause colitis, especially in immunocompromised patients or those with underlying IBD 1

Inflammatory Bowel Disease (IBD)

• Ulcerative colitis - characterized by continuous inflammation limited to the colon with rectal involvement 1

  • Presents with bloody diarrhea, abdominal pain, urgency, and tenesmus 1
  • Disease extent varies from proctitis to pancolitis 1

• Crohn's disease - characterized by patchy, transmural inflammation that can affect any part of the gastrointestinal tract 1

  • Can be classified by location (terminal ileal, colonic, ileocolic, upper gastrointestinal) 1
  • Can be classified by pattern (inflammatory, fistulating, or stricturing) 1

• Indeterminate colitis/IBD-unclassified - approximately 5% of IBD cases affecting the colon cannot be clearly classified as either UC or CD 1

  • Diagnosis relies on the presence of "overlapping features" or absence of a "clear diagnostic pattern" 1

Microscopic Colitis

• Collagenous colitis - characterized by increased subepithelial collagen and inflammation 1, 5

  • Primarily affects middle-aged women 5
  • Presents with chronic watery (non-bloody) diarrhea 1
  • Normal or near-normal endoscopic appearance 1

• Lymphocytic colitis - characterized by increased intraepithelial lymphocytes 1, 5

  • More equal female-to-male ratio compared to collagenous colitis 5
  • Presents with chronic watery diarrhea 1
  • Normal endoscopic appearance 1

Medication-Induced Colitis

• Non-steroidal anti-inflammatory drugs (NSAIDs) can exacerbate existing colitis or cause new-onset colitis 1

  • Selective COX-2 inhibitors appear to be safer in short-term use 1

• Antibiotics can disrupt normal gut flora, predisposing to C. difficile infection 1, 4

• Various medications have been associated with lymphocytic colitis 5

Other Causes

• Ischemic colitis - due to reduced blood flow to the colon 6

  • More common in older adults with vascular disease

• Radiation colitis - following radiotherapy to the abdomen or pelvis

• Eosinophilic colitis - allergy-associated inflammation 1, 6

• Bile acid malabsorption - can cause diarrhea and inflammation, particularly in microscopic colitis 1

• Food intolerances - maldigestion of fermentable carbohydrates (FODMAPs) and lactose can cause symptoms similar to colitis 1

Pathogenesis Factors

• Genetic susceptibility plays a role in IBD development, with a stronger genetic component in Crohn's disease than in ulcerative colitis 1

• Environmental triggers interact with genetic susceptibility 1

  • Smoking increases risk of Crohn's disease but decreases risk of ulcerative colitis 1
  • Prior appendectomy appears to be protective against ulcerative colitis 1

• Intestinal infections may trigger the onset of IBD or cause flares in established disease 1

• Alterations in gut microbiota contribute to various forms of colitis 1

Clinical Pearls and Pitfalls

• Not all colitis presents with bloody diarrhea - microscopic colitis typically presents with watery, non-bloody diarrhea 1

• Approximately 9% of patients with acute infectious gastroenteritis or colitis develop post-infectious irritable bowel syndrome 4

• Diagnostic uncertainty is common - approximately 15% of patients with non-specific colitis on initial evaluation are later diagnosed with a specific form of IBD 6

• C. difficile infection in IBD patients may not present with typical pseudomembranes, making diagnosis challenging 1

• When evaluating chronic diarrhea, consider microscopic colitis, which requires specific biopsies despite normal endoscopic appearance 1