Radionuclide liver spots: indicator of liver disease or a blood flow phenomenon.

Abnormal areas of increased uptake on liver scan have been controversial. While often said to be associated with superior vena caval obstruction, three distinctly different findings are possible: hot spot, warm spot, and no spot. All of these changes can be readily explained by distinct, separate anatomic venous collateral pathways. Four cases of superior vena caval obstruction with isotopic liver flow studies are presented. Anatomy of the venous collateral system is reviewed, and the potential significance of the liver "warm spot" is considered.