A 10-year-old girl with a patent ductus venosus associated with multiple autoimmune disorders presented with hypoxia, cyanosis of her lips, and exertional dyspnea. Ultrasonography and abdominal computed tomography of the liver showed a communication between the portal vein and the inferior vena cava through a patent ductus venosus. Portography showed flow from the portal vein directly into the inferior vena cava via the portosystemic shunt. The portosystemic venous shunt ratio was estimated to be 71.8% by scintigraphy using 123I-IMP. Intraoperatively, the authors diagnosed this portosystemic shunt as patent ductus venosus because of the absence of the ductus venosus on real anatomic position. The portal venous pressure was 8.2 cm H2O, which increased to 17.7 cm H2O when the ductus venosus was temporarily occluded. After surgical ligation of the ductus venosus, the color of liver improved, indicating restored liver circulation. The postoperative course was uneventful, and the patient has been asymptomatic for 6 months.