Pediatric Nuclear Medicine II

GENITOURINARY SYSTEM Radionuclide studies of the genitourinary system have wide application in pediatric patients. They include renal scintigraphy, radionuclide cystography, and testicular scintigraphy. Renal Scintigraphy Early diagnosis and treatment of urinary abnormalities in children have made it possible to reduce the morbidity and mortality associated with these disorders. Radionuclide studies of the kidneys have become valuable diagnostic methods which complement radiology and ultrasonography of the genitourinary system. While information about the size, position, and shape of the renal units is available in scintigraphy, its most unique contribution is that of providing quantitative information regarding renal function. The radionuclide evaluation is done with an intravenous injection of a very small volume of radiopharmaceutical and recording with a gamma camera-computer system. Several radiopharmaceuticals can be used. The technetium-99m labeled compounds include those excreted by glomerular filtration, such as 99mTc-Sn-diethylenetriamine pentaacetic acid (DTPA), and also agents Showing varying degrees of retention by tubular cells. These include 99mTc-iron ascorbate DTPA, 99mTc-gluco-heptonate and 99mTc-dimercapto-succinic acid (DMSA). Orthoiodohippurate, labeled with 123I or 131I, is eliminated primarily by tubular excretion and is not normally retained by the kidney (Table 1). The study carries no risk and the radiation dose to the patient is lower than that of intravenous urography. Perfusion studies are obtained by rapid imaging of the kidneys following the intravenous injection of any of the technetium radiopharmaceuticals.