Focal increased activity in the liver on 18F-FDG PET scan secondary to brachiocephalic vein and superior vena cava obstruction.

We present 2 cases demonstrating focal increased activity in the liver on 18F-fluorodeoxyglucose positron emission tomography scans resulting from central venous obstruction and increased blood flow to select regions of the liver via collateral veins. Collateral venous pathways from anterior chest wall veins to the portal veins can form via paraumbilical veins (including the vein of Burrow and the superior and inferior veins of Sappey) or subcapsular veins of the liver via musculophrenic vessels. Imagers should be familiar with the phenomenon of focally increased uptake of 18F-fluorodeoxyglucose in the liver secondary to collateral blood flow to avoid mischaracterizing the liver abnormalities as malignant in etiology.