Gaspari F, Perico N, Ruggenenti P, Mosconi L, Amuchastegui CS, Guerini E, Daina E, Remuzzi G
Plasma clearance of nonradioactive iohexol as a measure of glomerular filtration rate

J Am Soc Nephrol (Aug) 6:257-263 1995

Gaspari et al. describe their experience in the use of non-radioactive contrast media as a measurement of GFR in humans in the hope of providing an alternative method to inulin clearance. The method involves the injection of iohexol as a single dose followed by repetitive blood sampling to define the plasma disappearance curve of the compound. As the latter curve becomes linear only after 120 minutes of injection of the dye, useful sampling is required beyond this time point and at least 4 blood samples or more at sixty minutes intervals are required for accuracy. The plasma concentration of iohexol is measured by HPLC. This procedure would require around one hour and a half per patient studied. The data are then fitted to either a two or one compartment model and clearance is calculated. Compared to inulin clearance by standard methods, the iohexol clearance gives accurate estimates of GFR, but only when several blood samples are used over a long period of time.

Comment: The use of non-radioactive contrast media for measurement of GFR has been described previously by several authors. Most of these methods are aimed at replacing inulin because of the difficulties in inulin measurements. The adavantage of no urine collection with contrast media is not much different than the use of the so called "single shot" inulin. The application of these non-radioactive methods requires development of the assay techniques in clinical laboratories, a proposition less simple than assumed. For the practicing clinical nephrologist, these new methods offer little benefit. Their usefulness resides in the area of clinical research. (Mujais)

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Assessing renal function : Creatinine clearance