Radioisotope Renography: Graphic tracing over a time period of radioactivity measured externally over the kidneys following intravenous injection of a radionuclide which is taken up and excreted by the kidneys.Technetium Tc 99m Mertiatide: A technetium diagnostic aid used in renal function determination.Iodohippuric Acid: An iodine-containing compound used in pyelography as a radiopaque medium. If labeled with radioiodine, it can be used for studies of renal function.Technetium Tc 99m Pentetate: A technetium imaging agent used in renal scintigraphy, computed tomography, lung ventilation imaging, gastrointestinal scintigraphy, and many other procedures which employ radionuclide imaging agents.Hydronephrosis: Abnormal enlargement or swelling of a KIDNEY due to dilation of the KIDNEY CALICES and the KIDNEY PELVIS. It is often associated with obstruction of the URETER or chronic kidney diseases that prevents normal drainage of urine into the URINARY BLADDER.Radioisotopes: Isotopes that exhibit radioactivity and undergo radioactive decay. (From Grant & Hackh's Chemical Dictionary, 5th ed & McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Hypertension, Renovascular: Hypertension due to RENAL ARTERY OBSTRUCTION or compression.Zinc Radioisotopes: Unstable isotopes of zinc that decay or disintegrate emitting radiation. Zn atoms with atomic weights 60-63, 65, 69, 71, and 72 are radioactive zinc isotopes.Ureteral Obstruction: Blockage in any part of the URETER causing obstruction of urine flow from the kidney to the URINARY BLADDER. The obstruction may be congenital, acquired, unilateral, bilateral, complete, partial, acute, or chronic. Depending on the degree and duration of the obstruction, clinical features vary greatly such as HYDRONEPHROSIS and obstructive nephropathy.Captopril: A potent and specific inhibitor of PEPTIDYL-DIPEPTIDASE A. It blocks the conversion of ANGIOTENSIN I to ANGIOTENSIN II, a vasoconstrictor and important regulator of arterial blood pressure. Captopril acts to suppress the RENIN-ANGIOTENSIN SYSTEM and inhibits pressure responses to exogenous angiotensin.Furosemide: A benzoic-sulfonamide-furan. It is a diuretic with fast onset and short duration that is used for EDEMA and chronic RENAL INSUFFICIENCY.Iodine Radioisotopes: Unstable isotopes of iodine that decay or disintegrate emitting radiation. I atoms with atomic weights 117-139, except I 127, are radioactive iodine isotopes.Renal Artery Obstruction: Narrowing or occlusion of the RENAL ARTERY or arteries. It is due usually to ATHEROSCLEROSIS; FIBROMUSCULAR DYSPLASIA; THROMBOSIS; EMBOLISM, or external pressure. The reduced renal perfusion can lead to renovascular hypertension (HYPERTENSION, RENOVASCULAR).Pentetic Acid: An iron chelating agent with properties like EDETIC ACID. DTPA has also been used as a chelator for other metals, such as plutonium.Radiopharmaceuticals: Compounds that are used in medicine as sources of radiation for radiotherapy and for diagnostic purposes. They have numerous uses in research and industry. (Martindale, The Extra Pharmacopoeia, 30th ed, p1161)Technetium: The first artificially produced element and a radioactive fission product of URANIUM. Technetium has the atomic symbol Tc, atomic number 43, and atomic weight 98.91. All technetium isotopes are radioactive. Technetium 99m (m=metastable) which is the decay product of Molybdenum 99, has a half-life of about 6 hours and is used diagnostically as a radioactive imaging agent. Technetium 99 which is a decay product of technetium 99m, has a half-life of 210,000 years.Radioisotope Dilution Technique: Method for assessing flow through a system by injection of a known quantity of radionuclide into the system and monitoring its concentration over time at a specific point in the system. (From Dorland, 28th ed)Strontium Radioisotopes: Unstable isotopes of strontium that decay or disintegrate spontaneously emitting radiation. Sr 80-83, 85, and 89-95 are radioactive strontium isotopes.Krypton Radioisotopes: Unstable isotopes of krypton that decay or disintegrate emitting radiation. Kr atoms with atomic weights 74-77, 79, 81, 85, and 87-94 are radioactive krypton isotopes.Kidney Pelvis: The flattened, funnel-shaped expansion connecting the URETER to the KIDNEY CALICES.Diuretics: Agents that promote the excretion of urine through their effects on kidney function.Chlormerodrin: A mercurial compound that has been used as a diuretic but is now superseded by more potent and less toxic drugs. The radiolabeled form has been used as a diagnostic and research tool.Indium Radioisotopes: Unstable isotopes of indium that decay or disintegrate emitting radiation. In atoms with atomic weights 106-112, 113m, 114, and 116-124 are radioactive indium isotopes.Sodium Radioisotopes: Unstable isotopes of sodium that decay or disintegrate emitting radiation. Na atoms with atomic weights 20-22 and 24-26 are radioactive sodium isotopes.Renal Plasma Flow: The amount of PLASMA that perfuses the KIDNEYS per unit time, approximately 10% greater than effective renal plasma flow (RENAL PLASMA FLOW, EFFECTIVE). It should be differentiated from the RENAL BLOOD FLOW; (RBF), which refers to the total volume of BLOOD flowing through the renal vasculature, while the renal plasma flow refers to the rate of plasma flow (RPF).Radioactivity: The spontaneous transformation of a nuclide into one or more different nuclides, accompanied by either the emission of particles from the nucleus, nuclear capture or ejection of orbital electrons, or fission. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Barium Radioisotopes: Unstable isotopes of barium that decay or disintegrate emitting radiation. Ba atoms with atomic weights 126-129, 131, 133, and 139-143 are radioactive barium isotopes.Urography: Radiography of any part of the urinary tract.Radionuclide Imaging: The production of an image obtained by cameras that detect the radioactive emissions of an injected radionuclide as it has distributed differentially throughout tissues in the body. The image obtained from a moving detector is called a scan, while the image obtained from a stationary camera device is called a scintiphotograph.Yttrium Radioisotopes: Unstable isotopes of yttrium that decay or disintegrate emitting radiation. Y atoms with atomic weights 82-88 and 90-96 are radioactive yttrium isotopes.Tin Radioisotopes: Unstable isotopes of tin that decay or disintegrate emitting radiation. Sn atoms with atomic weights 108-111, 113, 120-121, 123 and 125-128 are tin radioisotopes.Technetium Tc 99m Dimercaptosuccinic Acid: A nontoxic radiopharmaceutical that is used in the diagnostic imaging of the renal cortex.Kidney: Body organ that filters blood for the secretion of URINE and that regulates ion concentrations.Dilatation, Pathologic: The condition of an anatomical structure's being dilated beyond normal dimensions.Carbon Radioisotopes: Unstable isotopes of carbon that decay or disintegrate emitting radiation. C atoms with atomic weights 10, 11, and 14-16 are radioactive carbon isotopes.Sensitivity and Specificity: Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed)Organometallic Compounds: A class of compounds of the type R-M, where a C atom is joined directly to any other element except H, C, N, O, F, Cl, Br, I, or At. (Grant & Hackh's Chemical Dictionary, 5th ed)Iron Radioisotopes: Unstable isotopes of iron that decay or disintegrate emitting radiation. Fe atoms with atomic weights 52, 53, 55, and 59-61 are radioactive iron isotopes.Hypertension, Renal: Persistent high BLOOD PRESSURE due to KIDNEY DISEASES, such as those involving the renal parenchyma, the renal vasculature, or tumors that secrete RENIN.Copper Radioisotopes: Unstable isotopes of copper that decay or disintegrate emitting radiation. Cu atoms with atomic weights 58-62, 64, and 66-68 are radioactive copper isotopes.Phosphorus Radioisotopes: Unstable isotopes of phosphorus that decay or disintegrate emitting radiation. P atoms with atomic weights 28-34 except 31 are radioactive phosphorus isotopes.Renal Artery: A branch of the abdominal aorta which supplies the kidneys, adrenal glands and ureters.Beta Particles: High energy POSITRONS or ELECTRONS ejected from a disintegrating atomic nucleus.Diuresis: An increase in the excretion of URINE. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Gamma Cameras: Electronic instruments that produce photographs or cathode-ray tube images of the gamma-ray emissions from organs containing radionuclide tracers.