Figure 844

Before Furosemide After Furosemide

10 min.

15 min.

Before Furosemide After Furosemide

10 min.

15 min.

Lt Rt Lt Rt

Mercaptoacetyltriglycine-3 renal scan with furosemide in a newborn with left ureteropelvic junction obstruction. A diuretic renal scan using 99mtechnetium-mercaptoacetyltriglycine (99mTc-MAG-3) showing differential renal function (47% right kidney; 53% left kidney) at 1 to 2 minutes after radionuclide administration is seen. A significant amount of radionuclide remains in each kidney 15 minutes after administration. After administration of furosemide, however, the isotope is seen to disappear rapidly from the right kidney (t1/2 of radioisotope washout in 4.9 minutes) but persists in the hydronephrotic left kidney (t1/2 in 50.1 minutes). A t1/2 of the radioisotope in less than 10 minutes is thought to reflect a lack of significant obstruction. A t1/2 of over 20 minutes is suggestive of obstruction. Intermediate values of washout are indeterminate. The most appropriate therapy for infants with delayed renal pelvic radioisotope washout and diagnosis of ureteropelvic junction obstruction is controversial. Some authors advocate pyeloplasty to alleviate the obstruction based on renal scan results, whereas others advocate withholding surgery unless renal function deteriorates or hydronephrosis progresses.

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