Gastrointestinal complications are common after kidney, liver, pancreas, heart, and lung transplantation. Complications can include gastrointestinal conditions preceding the transplantation, viral, fungal, and bacterial gastrointestinal infections, and gastrointestinal side effects of medications including immunosuppressive agents. Establishing the etiology of gastrointestinal complaints is often difficult because any one or a combination of these factors might be contributory in the same patient.