A 55-year-old man with alcoholic cirrhosis and a history of spontaneous bacterial peritonitis (SBP) presents with worsening ascites and oliguria. His creatinine is 3.0 mg/dL, BUN 55 mg/dL, and urine output <500 mL/day. He is started on albumin and terlipressin. What is the definitive treatment for hepatorenal syndrome?