Pathophysiology and Management of Hyperammonemia in Organ Transplant Patients

Neurologic complications are common after solid-organ transplantation, occurring in one-third of patients. Immunosuppression-related neurotoxicity (involving calcineurin inhibitors and corticosteroids), opportunistic central nervous system infections, seizures, and delirium are some of the causes of neurologic symptoms following solid-organ transplantation. An uncommon often missed complication posttransplantation involves buildup of ammonia levels that can lead to rapid clinical deterioration even when treated. Ammonia levels are not routinely checked due to the myriad of other explanations for encephalopathy in a transplant recipient. A treatment of choice for severe hyperammonemia involves renal replacement therapy (RRT), but there are no guidelines on the mode or parameters of RRT for reducing ammonia levels. Hyperammonemia in a transplant recipient poses specific challenges beyond the actual condition because the treatment (RRT) involves significant hemodynamic fluctuations that may affect the graft. In this review, we describe a patient with posttransplantation hyperammonemia and discuss the pathways of ammonia metabolism, potential factors underlying the development of hyperammonemia posttransplantation, and choice of appropriate therapeutic options in these patients.