Portosystemic shunting in superior vena cava obstruction by tumor demonstrated on ventilation-perfusion lung scan.

Extrapulmonary deposition of macroaggregated albumin particles on lung perfusion scintigraphy occurs in the presence of right-to-left shunting, as demonstrated in this case of portosystemic shunting related to superior vena cava obstruction by germ cell tumor of the mediastinum. The case demonstrates the importance of examining tracer deposition within the entire field of view on (99m)Tc-macroaggregated albumin perfusion lung scintigraphy for extrapulmonary findings.