Improvements in intestine transplantation.

Transplantation of the intestine in children has presented significant challenges even as it has become a standard to treat nutritional failure due to short gut syndrome. These challenges have been addressed in part by significant improvements in short and long-term care. Noteworthy enhancements include reduced need for intestine transplantation, drug-sparing immunosuppressive regimens, immune monitoring, and improved surveillance and management of PTLD and non-adherence.

Pediatric small bowel transplantation.

The multivisceral liver-intestine-pancreas-stomach allograft was first described by Starzl nearly 50 years ago. Since then, over 1000 children have received small bowel transplantation (SBTx), alone or with the liver and other organs, for refractory short gut syndrome (SGS) because of a variety of congenital conditions. In 2001, SBTx was approved as definitive therapy for SGS by Medicare. Currently, 1- and 5-year graft survival routinely exceeds 90% and 80%, respectively. The expected outcomes also include freedom from parenteral nutrition, normalization of growth parameters, and quality of life. However, recurrent rejection, complications of high-dose immunosuppression, or chronic rejection, which is more likely to occur after SBTx without a liver graft, account for differences between early and late survival. Future efforts aimed at overcoming such challenges include preventing SBTx through early referral to comprehensive SGS management programs and understanding why the liver protects the small bowel allograft from rejection. Finally, inflammatory mechanisms, which predispose the highly immunogenic small bowel allograft to a protracted risk of resistant rejection must be elucidated, in order to ensure durable success.

Replacing calcineurin inhibitors with mTOR inhibitors in children.

A highly selected subject group comprising pediatric recipients of liver (n = 36) and small intestine alone (n = 1) or multivisceral graft (n = 2) were converted to sirolimus maintenance therapy for tacrolimus-related side effects (n = 32) or by primary intent (n = 7). Indications were nephrotoxicity (n = 14), primary intent (n = 7), post-transplant lymphoproliferative disorder (n = 6), seizures (n = 4), recurrent acute rejection (n = 2), and cardiomyopathy (n = 1). Thirty subjects (78%) experienced successful conversion, with one subject requiring atorvastatin for hypercholesterolemia and hypertriglyceridemia. Nine subjects (22%) were converted back to tacrolimus for serious adverse events including acute rejection (n = 2), elevated liver function tests (n = 1), severe leucopenia (n = 1), non-compliance (n = 2), recurrent malignancy/death (n = 1), steatohepatitis (n = 1), and thrombocytopenic thrombotic purpura (n = 1). Among subjects with nephrotoxicity, significant benefit was seen only in those subjects with shorter time to rescue after transplantation (n = 8 of 14 subjects). Additional benefits included a significant decrease in mean serum creatinine from pretransplant values for the entire population, and elimination of antihypertensive treatment in all five subjects receiving it prior to conversion. Hemoglobin, serum cholesterol and triglycerides, white cell counts and platelets remained within normal limits for the duration of follow-up (36 month). Conversion from tacrolimus to sirolimus is successful in selected pediatric liver and intestine recipients. Chronic nephrotoxicity may be ameliorated by early conversion. Improvement in renal function and hypertension management, and absence of sirolimus-related adverse events argue for prospective evaluation of regimens in which mTOR inhibitors are used without calcineurin inhibitors in children.