A renogram, which may also be known as a MAG3 scan, allows a nuclear medicine physician or a radiologist to visualize the kidneys and learn more about how they are functioning.

The two most common radiolabelled pharmaceutical agents used are 99mTc-MAG3 (MAG3 is also called "mercaptoacetyltriglycine" or "mertiatide") and 99mTc DTPA (diethylenetriaminepentacetate).

[2] After injection into the veins, the compound is excreted by the kidneys, and its progress through the renal system can be tracked with a gamma camera.

Processing then involves drawing a region of interest (ROI) around both kidneys, and a computer program produces a graph of radioactivity inside the kidney with time, representing the quantity of tracer, from the number of counts measured inside in each image (representing a different time point).

[9] 99mTc DTPA is filtered by the glomerulus and may be used to measure the glomerular filtration rate (GFR) (in a separate test), making it theoretically the best (most accurate) choice for kidney function imaging.

[18][19] Initially there was uncertainty as to the usefulness,[20] or best test parameter to identify renal artery stenosis, the eventual consensus was that the distinctive finding is of alteration in the differential function.