Unusual location of a liver 'hot spot' in a patient with superior vena caval obstruction

This case represents yet another instance of focal liver 'hot spot' secondary to superior vena caval obstruction. The scintigraphic finding in this case that is of particular interest is that the focal zone of hyperconcentrated activity was superiorly located at the junction of the right and left lobes rather than in the mid-inferior portion of the liver. Holmquest and Burdine first showed with radionuclide angiography that caval portal shunting through collateral venous, channels was the cause of the abnormal 'hot spot'. They pointed out that the major abnormal vessel approaching the liver was the umbilical vein, which enters the liver at its mid-inferior portion. Since the umbilical vein terminates rather abruptly, in contrast to the extensive intrahepatic branching characterizing the portal vein, there is a very heavy local deposition of the labeled colloid. This accounts for the inferior location of the liver 'hot spot' secondary to superior vena caval obstruction. In the current case, it would appear that the umbilical vein did not enter the liver in its usual inferior location, but instead terminated much more superiorly. The possibility of other aberrant venous channels being involved also must be considered but would appear less likely than the above explanation.