Scintigraphic detection of 'yo-yo' phenomenon in incomplete ureteric duplication.

'Yo-yo' reflux in an incompletely duplicated renal system was demonstrated on (99m)Tc-mercaptoacetyltriglycine (MAG3) renal scintigraphy in a 7-year-old girl presenting with low-grade fever and pyelonephritis. Incomplete duplication and a bifid renal pelvis, which may be seen in up to 4% of the North American population, occasionally causes symptoms because of recurrent urinary tract infection or loin pain. (99m)Tc-MAG3 renal scintigraphy can demonstrate 'yo-yo' reflux in patients with incomplete renal duplication and should be considered in cases with unexplained loin pain, even if (99m)Tc-dimercaptosuccinic acid (DMSA) renal scintigraphy is normal.