A dialysis patient with hyperammonaemia: inferior mesenteric-caval shunt as a cause of portal-systemic encephalopathy

A dialysis patient with hyperammonaemia: inferior mesenteric-caval shunt as a cause of portal-systemic encephalopathy Sir, We report here a rare case of portal-systemic encephalop-athy with occasional loss of consciousness caused by an inferior mesenteric-caval shunt via the internal iliac vein in a peritoneal dialysis (PD) patient who was switched to haemodialysis (HD). A 71-year-old man with end-stage renal disease, who had undergone PD and was shifted to HD, was admitted to our hospital for occasional loss of consciousness. Physical examination showed dysarthria, asterixis and ataxic gait without clinical signs of portal hypertension and liver cir-rhosis. Laboratory studies revealed normal liver function (albumin 2.3 g/dL, total bilirubin 0.62 mg/dL, lactate dehy-drogenase 174 IU/L, aspartate aminotransferase 12 IU/L, alanine transferase 8 IU/L, and gamma-glutamyl transpepti-dase 8 IU/L) and increased ammonia concentration in peripheral blood (151.5 lmol/L, normal range: 17.7–47.0). Neither hepatitis B surface antigen nor antibodies to hepatitis C were detected. Results from the brain computed tomog-raphy (CT) scan and magnetic resonance imaging were normal. An electroencephalogram showed an increase in delta waves. An endoscopy did not find esophageal varices or haemorrhoids. An enhanced abdominal pelvic cavity CT scan detected the presence of the inferior mesenteric vein (IMV)–internal iliac vein shunt. The inferior vena cava (IVC) was enhanced through the shunt in an early phase of enhanced CT. The venous phase of both the superior and inferior mesenteric arteriogram revealed a large shunt between the IMV and left internal iliac vein, with blood flowing from the portal vein to the IVC (Figure 1). Selective venous sampling for blood ammonia levels showed a higher value of 180.3 lmol/L in the shunt vessel in contrast with 132.1 lmol/L in the IVC and 94.5 lmol/L in the left external iliac vein. Portal vein pressure was normal, 10–16 mmHg. A transcatheter coil embolization of the shunt vessel was performed. The high preoperative serum ammonia concentration decreased to the normal range postoperatively. Two years after the embolization, a follow-up enhanced CT scan showed a narrowing of the shunt.