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Clostridium difficile (C. difficile) infection (CDI) is the leading identifiable cause of antibiotic-associated diarrhea. While there is an alarming trend of increasing incidence and severity of CDI in the United States and Europe, superimposed CDI in patients with inflammatory bowel disease (IBD) has drawn considerable attention in the gastrointestinal community. The majority of IBD patients appear to contract CDI as outpatients. C. difficile affects disease course of IBD in several ways, including triggering disease flares, sustaining activity, and in some cases, acting as an "innocent" bystander. Despite its wide spectrum of presentations, CDI has been reported to be associated with a longer duration of hospitalization and a higher mortality in IBD patients. IBD patients with restorative proctocolectomy or with diverting ileostomy are not immune to CDI of the small bowel or ileal pouch. Whether immunomodulator or corticosteroid therapy for IBD should be continued in patients with superimposed CDI is controversial. It appears that more adverse outcomes was observed among patients treated by a combination of immunomodulators and antibiotics than those treated by antibiotics alone. The use of biologic agents does not appear to increase the risk of acquisition of CDI. For CDI in the setting of underlying IBD, vancomycin appears to be more efficacious than metronidazole. Randomized controlled trials are required to clearly define the appropriate management for CDI in patients with IBD.

Extra-intestinal manifestations (EIMs) are reported frequently in patients with inflammatory bowel disease (IBD) and may be diagnosed before, concurrently or after the diagnosis of IBD. EIMs in IBD may be classified based on their association with IBD disease activity. The first group has a direct relationship with the activity of the bowel disease and includes pauciarticular arthritis, oral aphthous ulcers, erythema nodosum and episcleritis. The second group of EIMs appears to follow an independent course from the underlying bowel disease activity and include ankylosing spondylitis and uveitis. The third group includes EIMs that may or may not be related to intestinal inflammation, such as pyoderma gangrenosum and probably primary sclerosing cholangitis (PSC). Genetic susceptibility, aberrant self-recognition and immunopathogenic autoantibodies against organ-specific cellular antigens shared by the colon and extra-colonic organs may contribute to the pathogenesis and development of these EIMs. The use of biological agents in the IBD armamentarium has expanded the treatment options for some of the disabling EIMs and these agents form the cornerstone in managing most of the disabling EIMs. PSC is one of the most common hepatobiliary manifestations associated with IBD in which no clear treatment options exist other than endoscopic therapy and liver transplantation. Future research targeting the pathogenesis, early diagnosis and treatment of these EIMs is required.