De novo inflammatory bowel disease and its mimics after organ transplantation.

Diarrhea is a common symptom after solid organ transplantation or hematopoietic stem cell transplantation, with a reported prevalence up to 72%. One of the uncommon causes for diarrhea in the posttransplant setting is development of de novo inflammatory bowel disease (IBD). The incidence of posttransplantation de novo IBD was shown to be higher than that in the general population (206 versus 20 per 100,000 cases annually). The frequency seems to be much higher following orthotopic liver transplantation than the transplantation of other solid organs. De novo IBD has also been described in the setting of bone marrow transplantation though not as commonly as after SOT. While IBD is considered an immune-mediated disorder and responds favorably to immunosuppressive, de novo IBD or IBD-like conditions can occur in the posttransplant period despite antirejection immunosuppressive therapy. Damage or pathogen-associated molecular pattern molecules and their associated ongoing inflammation within the transplanted organ and the recipients' intestine have been implicated as possible etiologies. Various viral, bacterial, and protozoal infections can mimic IBD in postorgan transplantation. Common IBD mimickers in the postbone marrow transplant setting are graft-versus-host disease, infectious enteritis/colitis, and less commonly "cord colitis" that is described in detail below. In this article, we discuss the epidemiology, clinical features, and outcomes of de novo IBD after transplantation and highlight their differences in presentation, diagnosis, and management.