The clearance is the elimination of substances like drugs, chemicals and secondary products from the body. Although clearance may also involve other organs than the kidney, it is almost synonymous with renal clearance or renal plasma clearance. Each material has a specific organ clearance that depends on its filtration characteristics.

The excretion of body wastes and toxic substances are the primary function of the kidneys. The functional excretion unit is the nephron. Each kidney contains about one million nephrons. The nephron has three primary regions that function in the renal excretion process, the glomerulus, proximal tubule, and the distal tubule.
The kidney clearance is a measurement of the renal excretion ability. The excretion of the radiopharmaceutical used for kidney clearance begins approx. four minutes after application.

(EDTA) Ethyl diamine tetra acetic acid is used in decontamination applications as well as for the kidney clearance in connection with 99mTc to assign the glomerular kidney filtration.