Abstract
Congenital portosystemic shunts (CPSS) are rare vascular malformations that divert portal blood into the systemic circulation, bypassing hepatic metabolism. Although typically diagnosed in infancy due to associated congenital anomalies or complications such as hepatic encephalopathy, adult presentations are exceptionally uncommon and diagnostically challenging. We report a 71-year-old female patient with recurrent episodes of confusion and drowsiness who was found to have markedly elevated serum ammonia levels despite normal liver function. Extensive investigations excluded infective, metabolic, and structural causes, and a triple-phase liver computed tomography (CT) revealed multiple intrahepatic portosystemic shunts with aneurysmal dilatation, consistent with congenital origin. Due to multiple comorbidities, the patient was deemed unsuitable for shunt closure or liver transplantation but responded well to medical therapy with lactulose, rifaximin, sodium benzoate, glycerol phenylbutyrate, and L-ornithine L-aspartate, with no further episodes of encephalopathy on follow-up. This case underscores the importance of considering CPSS in adults presenting with hyperammonaemia and altered mental status in the absence of hepatic disease. Early recognition and multidisciplinary management are key to preventing recurrence and optimising outcomes.