Renal cortical retention of Tc-99m MAG3 in hypotension

A three-year-old boy with a history of resected posterior urethral valves had persistent bilateral megaureter and ureterohydronephrosis. Renal scintigraphy was performed within 1 hour of cystoscopy. The initial scintigrams showed prompt cortical uptake of Tc-99m MAG3 with persistence of cortical activity both before and after the administration of furosemide. The patient's cystoscopy had been conducted under heavy general anesthesia and episodic hypotension accompanied the anesthesia. The patient was found to be significantly dehydrated during the initial diuretic renogram. The persistence of cortical activity, similar to the postcaptopril effect in renovascular hypertension, reflects the hypotension that resolved on follow- up evaluation with adequate hydration. Hypotension should be added to the differential diagnosis of persistent cortical activity.