In a renal transplant recipient with persistently poor graft function, the flow phase of a renal scan incidentally revealed multiple venous collaterals with focally increased vascular activity near the left lobe of the liver (quadrate lobe). This was initially assumed to represent superior vena cava (SVC) obstruction. A renal biopsy was contemplated to exclude acute rejection because of a nondiagnostic flow phase (loss of a bolus effect). However, because the possibility of venous obstruction at the level of the subclavian and/or brachiocephalic veins (without involving the SVC) also existed, another renal scan was performed, with injection of radiotracer into the contralateral arm. This showed a patent SVC and reasonably preserved renal perfusion consistent with acute tubular necrosis. Subsequently, left subclavian vein obstruction was identified. The graft function improved with conservative management for acute tubular necrosis. These findings illustrate the danger of considering only SVC obstruction when collateral flow patterns and focal hot spots in the liver are present.