Comparison of inulin, iothalamate, and 99mTc-DTPA for measurement of glomerular filtration rate.

Clearances of inulin, 125I-iothalamate, and 99mTc-Sn-DTPA were measured simultaneously in five mongrel dogs exhibiting a wide range of glomerular filtration rates (GFR). Standard constant-infusion inulin clearance was compared to radionuclide clearances after subcutaneous injection of the emitters mixed with aqueous epinephrine. All three substances were found to have virtually identical clearances. The accuracy, accessibility, low cost, low radiation hazard, and short half-life of 99mTc-Sn-DTPA make it an excellent substance for measuring GFR. The subcutaneous technique offers an accuracy comparable to the more difficult constant-infusion method.