Atypical forms of inflammatory bowel disease.

Atypical forms of IBD include the microscopic colitides, collagenous and lymphocytic colitis, and two macroscopic colitides, SRUS and diversion colitis. Clinical presentations include chronic, watery diarrhea and intermittant rectal bleeding. Constitutional symptoms are typically absent; laboratory data are often nonspecific. Colonoscopic evaluation and mucosal biopsy are essential in establishing these diagnoses and excluding more classic forms of IBD (i.e., Crohn's disease or idiopathic ulcerative colitis). Prognosis and response to treatment are variable; potential therapeutic options include dietary manipulations, topical or systemic anti-inflammatory agents, and, in refractory cases, surgical intervention.