Congenital absence of the portal vein.

A 14-year-old girl presented at the hospital after discovering an abdominal tumor. CT scan and ultrasonography indicated a hepatic tumor and also revealed the absence of the portal vein. The patient was admitted to excise the hepatic tumor. It was found that the venous blood from the small intestines flowed into the left renal vein and then emptied directly into the inferior vena cava. A tumor extending from the right lobe through the middle portion of the liver was excised. The postoperative course was satisfactory and marked regeneration of the residual hepatic tissue was observed. Also the blood level of ammonia in the superior mesenteric vein was low, approximately 120 micrograms/dl, compared to the normal value of 350 micrograms/dl in the portal vein. This low blood level may indicate the presence of some homeostatic control mechanism.