The kidneys filter the blood to remove waste substances such as urea (a nitrogen compound) and salt. This test provides information on the blood supply, function and excretion of urine from the kidneys.

The body discharges these wastes mixed in water as urine. The fluid is collected in the kidneys and discharged through the ureters which join the kidneys to the bladder. The top of the ureter is called the renal pelvis and this joins the kidney to the ureters.

In a renal scan, images are made of the delivery of fluid into the kidneys via the bloodstream, concentration of wastes in the kidney and excretion or flow from the kidneys through the ureters and filling of the bladder.