Tacrolimus-induced Segmental Renal Artery Vasoconstriction in the Setting of Nicardipine Administration after Renal Transplantation

Immediate postoperative complications in renal transplants include renal artery thrombosis and dissection both of which carry significant risk for loss of the graft. We present an unusual case in which apparent devascularization of the upper pole of the transplant kidney was due to reversible vasospasm as a result of a drug interaction. Tacrolimus, a calcineurin inhibitor, is used for post-transplant immunosuppression. The antihypertensive medication nicardipine impairs liver metabolism of tactolimus and, in this case, the combination of drugs resulted in supratherapeutic levels of tacrolimus causing acute nephrotoxicity as well as profound vasoconstriction which was most pronounced in the upper pole branch renal artery and simulated devascularization of almost half of the transplant kidney. This case highlights the fact that not all abnormal post-transplant Doppler findings are due to surgical technique or embolic events and illustrates the importance of drug interactions in this group of patients with complex medical conditions.