C i.e. Tc99 DTPA 99mTcDMSA (gold standard) and 99mTc- GFIA are morphologic agents. Dimercaptosuccinic acid (DMSA) labelled with technetium-99m is most satisfactory tracer for imaging renal anatomyQ (e.g. in renal ectopia and anomalies like horseshoe kidney), differentiating functional renal masses (with radiotracer uptake) from pseudomassesQ (abscess, cysts or tumors which show no uptake of DMSA and appear photon deficient on renal images) and detecting infection and scarringQ. 99Tc-DMSA scan is most accurate (non invasive) method for estimating distribution of function between two kidneysQ. It is used to locate functional renal tissue, to find out scar or non-functioning areas of renal parenchymaQ (or to differentiate renal coex form soft tissue masses in or near kidney) and to estimate the functional contribution of each abnormal kidney. Dimercaptosuccinic acid (DMSA) labelled with technetium-99m is most satisfactory tracer for imaging renal anatomyQ (e.g. in renal ectopia and anomalies like horseshoe kidney), differentiating renal masses (with radiotracer uptake) from pseudomassesQ abscess, cysts or tumors which show no uptake of DMSA and appear photon deficient on renal images) and detecting infection and scarringQ. 99mTc-MAG3 (preferred), 99mTc-DTPA (preferred in emergency) and 1311OIH, (ohoiodohippurate) are functional agents. Functional agents are used for assessment of renal perfusion, renal plasma flow, glomerular filtration and tubular secretion and are applied in dynamic radionuclide studies of urinary tract obstruction. (obstructive uropathy), vesico-ureteral reflux, renovascular hypeension, and acute renal failure. (anuria/oliguria). Radionucleide that are excreted almost entirely by glomerular filtration can be used to estimate GFR and these are - Tc99 in- labelled DTPA (diethylenetriaminepenta acetic acid)Q and Chromium 51- labelled - EDTAQ