A 3-year-old girl with idiopathic extrahepatic portal vein obstruction undergoing mesenterico-left portal vein bypass (MLPVB), or Rex shunt, for recurrent variceal bleeding was intraoperatively discovered to have duplicated round ligaments and Rex recessi. The left and right portal veins connected to their respective round ligaments but had minimal communication within the liver. Intraoperative venography identified a better preserved portal system on the left, and standard MLPVB resulted in excellent shunt flow. The shunt remains patent and the patient asymptomatic 9 months after her operation. Abnormal portal anatomy is not a contraindication to MLPVB.