What is Diversion Colitis?
Diversion colitis is a non-specific mucosal inflammation that develops in the defunctionalized segment of the colon or rectum following surgical diversion of the fecal stream via colostomy or ileostomy. 1, 2
Pathophysiology
The condition arises from several key mechanisms:
- Nutritional deficiency of the colonic epithelium occurs due to the absence of luminal short-chain fatty acids (SCFAs), which are the preferred metabolic substrates for colonic epithelial cells 3
- Microbial alterations include an increase in aerobic bacteria and altered microbiome composition in the diverted segment 1
- Immune dysregulation contributes to the inflammatory process, though the exact pathogenesis remains incompletely understood 1
Clinical Presentation
The clinical spectrum varies considerably:
- Most patients remain asymptomatic despite endoscopic and histologic evidence of inflammation 2, 4
- Symptomatic patients may present with hemorrhagic purulent rectal discharge, rectal bleeding, abdominal pain, and tenesmus 3, 5
- Endoscopic findings reveal granular, friable mucosa with evidence of linear ulceration and inflammation that mimics idiopathic inflammatory bowel disease 3, 5
- Histologic examination shows a distinctive pattern of mucosal inflammation that resolves more slowly than gross endoscopic appearance 3
Prevalence and Natural History
- Nearly all patients with surgical diversion develop some degree of diversion colitis, though most remain asymptomatic 2
- The condition persists indefinitely unless the excluded segment is reanastomosed or removed 3
- Potential complications include stricture formation and, in inflammatory bowel disease patients with prior dysplasia/cancer history, an increased cancer risk reaching 4.5 per 1,000 diverted patient-years 4
Special Considerations in IBD Patients
When diversion colitis occurs in patients with underlying inflammatory bowel disease (termed diversion proctocolitis):
- Differential diagnosis is challenging as distinguishing diversion-related inflammation from underlying IBD activity is often unclear 4
- Surveillance is critical for IBD patients who undergo subtotal colectomy with end-ileostomy, requiring close endoscopic monitoring due to cancer risk 4
- Patient distribution among IBD subtypes includes approximately 50.6% ulcerative colitis, 43.3% Crohn's disease, and 5.4% IBD-unclassified 4