Idiopathic colitis following cardiac transplantation: three pediatric cases.

Colitis can cause significant morbidity in pediatric solid organ transplant recipients. In many cases, despite intensive evaluation, a specific infectious, inflammatory, or immunologic etiology is not identified, and idiopathic colitis may be the ultimate diagnosis. We defined idiopathic colitis as the presence of gastrointestinal symptoms (vomiting, diarrhea, abdominal pain) with inflammatory changes seen on intestinal biopsy in the absence of identifiable bowel disease. We describe three cases of idiopathic colitis following cardiac transplantation. In each case, the post-transplant course was complicated by persistent abdominal pain, diarrhea, and in two cases, vomiting. All three patients' post-transplant courses were marked by multiple graft rejection episodes, and all received intensified immune therapy in addition to usual maintenance immunosuppression. Differential diagnosis of the patients' gastrointestinal symptoms included drug side effect, indolent opportunistic infections, inflammatory bowel disease, post-transplant lymphoproliferative disease, and microvascular ischemic colitis. Continued symptoms led these patients to extensive evaluation including imaging studies, endoscopy and tissue biopsy, and stool, blood and tissue cultures for viral, bacterial and parasitic pathogens. Definitive differentiation presented significant diagnostic challenge, and once identifiable etiologies were excluded, the diagnosis of idiopathic colitis was assigned. We conclude that idiopathic colitis following pediatric cardiac transplantation can be a cause of significant morbidity. Endoscopic evaluation of patients who present with gastrointestinal symptoms after transplant is warranted to identify the presence of idiopathic colitis once common causes are ruled out. Further study is needed to identify its incidence, etiology, therapeutic options and prognosis.