ileocolitis

Ileocolitis refers to inflammation affecting both the ileum and the colon. It is a pattern of inflammatory bowel disease that most often reflects Crohn's disease, but it can also result from infectious, ischemic, or drug-related processes, as well as from radiation therapy or postoperative changes. In Crohn's disease, ileocolitis is a common phenotype characterized by transmural inflammation that can affect any region from the terminal ileum to the colon, often with skip lesions.

Clinical features typically include abdominal pain, usually in the lower right abdomen, chronic or intermittent diarrhea, sometimes with blood, weight loss, and fatigue. Fever may occur with infection or active inflammatory disease. The presentation can mimic other forms of bowel disease, so careful evaluation is needed.

Diagnosis relies on a combination of history, laboratory tests, endoscopy with ileal and colonic visualization, histology, and imaging. Colonoscopy with intubation of the terminal ileum and biopsies helps distinguish Crohn's ileocolitis from other disorders; histology may show transmural inflammation, granulomas (less commonly), and chronic inflammatory changes. Imaging such as CT or MR enterography can assess the extent and complications like strictures or fistulas. Fecal calprotectin is a useful noninvasive marker of intestinal inflammation, while stool studies help exclude infection.

Management is tailored to the underlying cause. Crohn's ileocolitis is typically treated with a stepwise approach including corticosteroids or budesonide for induction, and immunomodulators or biologic therapies for maintenance. Antibiotics are used for specific infectious ileocolitis. Ischemic or radiation-related disease focuses on removing the underlying cause and supportive care; surgery may be required for complications or refractory disease. Nutritional support is important in all forms.