Superior vena cava obstruction in fibrosing mediastinitis: demonstration of right-to-left shunt and venous collaterals.

Multiple venous collateral pathways have been described in patients with superior vena cava obstruction. Systemic venous-to-pulmonary venous communication is the most unusual, having been described in a few cases of thoracic malignancy. In a patient with fibrosing mediastinitis radionuclide venography with 99Tcm-macroaggregated albumin demonstrated a systemic venous-pulmonary venous right-to-left shunt in addition to systemic and portal venous collaterals. It is apparent that systemic venous-to-pulmonary venous anastomoses may occur in the absence of malignant disease.