Early Initiation of Kidney Replacement Therapy for Hyperammonemia in Acute Liver Failure: A Case Report and Literature Review

Introduction: Hyperammonemia is a key contributor to cerebral edema, especially in acute liver failure (ALF). While renal replacement therapy (RRT) is well established for managing hyperammonemia in pediatric patients with metabolic disorders, evidence in adult populations remains sparse. Case Description: A 19-year-old female with no prior medical history presented with ALF of unknown etiology. Her initial serum ammonia was 877 µmol/L, and she showed signs of cerebral edema. Despite extensive evaluation, including liver biopsy, no underlying cause was found. Continuous venovenous hemodialysis (CVVHD) was initiated promptly and continued until ammonia levels dropped below 100 µmol/L. Adjunctive measures included lactulose, hypernatremia induction, and controlled hyperventilation. Her cerebral edema improved in parallel with biochemical markers and ventilatory function. Discussion: The liver detoxifies ammonia via the urea cycle. In ALF, impaired clearance leads to rapid ammonia accumulation. Although the kidneys can increase ammonia excretion in acidotic states, they are often insufficient to control severe elevations. Standard therapy involves protein restriction, sodium correction, and agents such as lactulose and rifaximin. In suspected urea cycle disorders, additional therapies like sodium benzoate, arginine, and carnitine may be trialed. Ammonia, being small and non–protein-bound, is highly dialyzable. While some suggest initiating RRT at ammonia levels >3× the upper limit of normal or with encephalopathy, newer data support earlier initiation—even without acute kidney injury—especially if cerebral edema is present. In this case, CVVHD was chosen due to hemodynamic instability, using high blood and dialysate flow rates to maximize clearance. RRT was stopped once ammonia dropped below 100 µmol/L, with neurological and respiratory recovery serving as surrogate markers of improvement. Conclusion This case illustrates the benefit of early RRT in adult ALF with severe hyperammonemia, regardless of kidney function. It emphasizes a proactive approach and highlights the need for standardized guidelines on RRT initiation and cessation in this setting.