MR evaluation of the portal vein in pediatric liver transplant candidates.

Nine pediatric liver transplant candidates underwent preoperative MR evaluation of the portal vein and the inferior vena cava. Sonographic correlation was available in all patients and angiographic correlation was available in five. Pathologic correlation was obtained in seven cases either at liver transplantation or autopsy. MR demonstrated portal vein patency in three cases when it was not seen by angiography and confirmed portal vein patency in one patient when it was questionably identified on sonography. The portal vein was not seen on MR imaging in two cases when it was seen on sonography and angiography: in one case, it was small and to-and-fro flow was demonstrated angiographically; in the second case, the portal vein was occluded by tumor thrombus. Two vessels in two patients were misidentified by sonography and identified correctly by MR. These were an azygous continuation of the inferior vena cava and a large collateral vein in the portal region. Knowledge of the anatomy and documentation of vascular patency are essential in evaluation of patients before liver transplantation. In patients with complex anatomy or hemodynamics, it may be necessary to obtain this information from several imaging techniques (sonography, angiography, and MR).