Reflections on the etiology of hot spots on liver scans.

Liver scintigraphy demonstrated areas of increased radiocolloid uptake in three cases with obstruction of the superior vena cava and extensive collateral circulation through the veins of the thoracic wall. The pattern of the hyperactive zones is indicative of predominant vascularization of the liver via the umbilical vein, with high colloid particle deposition in the quadrate lobe and adjacent part of the right lobe. These liver regions vascularized by the first intrahepatic branches of the umbilical vein as demonstrated by postmortem angiography, probably extract a great portion of the tracer dose, resulting in localized hyperactivity. An identical liver scan image was, however, found in a fourth case without evident superior vena cava syndrome. In this patient, presenting with a bronchus carcinoma with paratracheal metastatic lymph nodes, there is no explanation metastatic lymph nodes, there is no explanation (collateral circulation without vena cava obstruction?) for the abnormal tracer distribution within the liver.