A false positive I-131 MIBG due to dilated renal pelvis: a case report.

A case of false positive I-131 MIBG imaging for detection of pheochromocytoma is presented. There was an area of increased tracer uptake in the left renal region that showed steadily reducing activity over a period of three days. This raised the suspicion of a dilated renal pelvis, which was later confirmed by Tc-99m DTPA imaging. It is advisable in cases of ambiguous I-131 MIBG imaging to use Tc-99m DTPA rather than Tc-99m DMSA for localizing the kidneys and renal pelvis.