[Validity of iohexol clearance in patients with chronic renal failure and normal renal function in comparison to (99m)Tc-DTPA-clearance]

The most common method used for testing dynamic renal function is creatinine clearance, but it has some limitations, e. g. variable muscle mass and tubular secretion of creatinine. The use of radionuclides as an exact method is limited in terms of availability, cost and time needed for examination. We compared the plasma clearance of iohexol with the established (99m)Tc-diethylenetriaminepentaacetate acid (DTPA) clearance. The aim of the present study was to validate iohexol clearance as a simple and suitable method for measuring to determine GFR with a comparable sensitivity to radioisotopic methods.

120 patients (49 females, 71 males), mean age of 56 (range 20 to 84) years with normal renal function and different stages of renal failure, mean creatinine clearance of 61.6 +/- 44,9 (range 1.8 - 181.1) ml/min/1.73 m2 received a bolus injection of 10 ml iohexol, a non-ionic low osmolar x-ray contrast medium. Using the one-compartment model, plasma samples were taken after 150, 240 and 480 minutes. The total plasma disappearance of iohexol was measured by x-ray fluorescence analysis and the clearance was calculated. The (99m)Tc-DTPA clearance was determined in accordance with a standard protocol.

A high correlation was found between the clearance of iohexol and (99m)Tc-DTPA (r = 0.95). The average deviation between Iohexol and (99m)Tc-DTPA clearance was 7.4 ml/min/1.73 m2. Allergic and nephrotoxic side effects were not observed.

Iohexol clearance is a valid method for measuring GFR in patients at any stages of renal failure. It is easy to perform and inexpensive.