A Pseudopheochromocytoma?: Accumulation of I-123 MIBG in the Renal Pelvis

Pheochromocytomas are known to be avid for I-131 or I-123 MIBG. A healthy volunteer was imaged for a control study of the myocardium with I-123 MIBG. The images at 1 hour and at 5 hours depicted a hot spot in the region of the left renal pelvis. The hot spot disappeared on the 24-hour image. It was assumed that the focus was a collection of urinary activity in a benign dilatation of the renal pelvis. Nuclear medicine physicians should be aware of this because this could have been a false-positive scan for a pheochromocytoma.