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The estimate of glomerular filtration rate during urography. Acceptability of a nonionic contrast medium as a marker
1Department of Urology, Stepping Hill Hospital, Stockport, United Kingdom.
Rationale And Objectives:
An estimate of glomerular filtration rate (GFR) may be obtained at the same time as urography by measuring the plasma clearance of the radiographic contrast medium using an x-ray fluorescence technique. It must be established whether the function measured or one modified by an effect of the contrast medium itself represents a true value.
Methods:
Technetium 99m-DTPA (99mTc-DTPA) plasma clearance was measured in 21 patients using a single-injection technique, before, during, and after an intravenous injection of 50 mL of 350 mg I/mL iohexol. Iohexol clearance also was determined using an alternative single-injection, two-sample technique.
Results:
The mean 99mTc-DTPA clearances before, during, and after contrast were 71.2, 71.5, and 70.7 mL/minute, respectively. The within-patient standard deviation in clearance values was 3.84 mL/minute. One factor repeat measures analysis of variance indicated no significant difference between the three measurements (F ratio = 0.24). Contrast and 99mTc-DTPA clearances performed simultaneously agreed closely (r = .976; ClDTPA = 1.02ClCon - 1.35).
Conclusion:
The authors conclude that no change in function is observed during or 48 hours after contrast injection. Imaging doses of iohexol can be used for GFR measurement during urography.