Case Report: Adult liver transplantation using a long-standing mesocaval shunt as portal inflow in congenital absence of the portal vein with atypical variceal bleeding and refractory shunt encephalopathy.

Congenital absence of the portal vein (CAPV) is an exceedingly rare vascular malformation in which mesenteric and splenic venous blood bypasses the liver and drains into the systemic circulation. Because congenital portosystemic drainage usually decompresses the splanchnic venous bed, classical portal hypertension is uncommon, and CAPV typically presents with metabolic and vascular complications rather than variceal bleeding. We report the case of a 36-year-old woman with CAPV that presented atypically in early childhood with esophageal variceal hemorrhage, suggesting functional inadequacy or early loss of the native decompressive pathway. At the age of three years, she underwent H-type mesocaval shunting and remained clinically compensated for more than three decades. She later developed refractory shunt-related hyperammonemic encephalopathy with recurrent functional bowel obstruction, without evidence of mechanical obstruction on repeated imaging and laparotomy. Orthotopic liver transplantation was performed using a graft from a brain-dead donor. Because the native portal vein was absent, portal inflow was reconstructed by an end-to-end shunt-to-portal anastomosis using the long-standing mesocaval shunt, avoiding the need for an interposition venous graft. The postoperative course was complicated by a biliary anastomotic stricture managed with staged endoscopic stenting and by late stenosis of the shunt-to-portal anastomosis on postoperative day 212, successfully treated with balloon angioplasty and portal vein stenting. At the 275-day follow-up, the patient remained clinically stable, with no recurrence of encephalopathy and resolution of intestinal dysmotility. This case highlights a rare adult presentation of CAPV requiring liver transplantation and demonstrates that a long-standing mesocaval shunt may serve as a feasible source of portal inflow when the native portal vein is absent.