The clearance of creatinine has been shown to overestimate GFR in patients with renal disease and in kidney transplant recipients. Alternate means for measuring GFR involve the use of constant infusion and, frequently, of radioisotpes. We report herein the measurement of GFR with the use of a radiocontrast agent (diatrizoate meglumine) injected subcutaneously with a small amount of epinephrine (0.05 ml of 1:1000). The concentrations of this marker of glomerular filtration in blood and in urine were measured with high-performance liquid chromatography. The results demonstrate that with this method of administration stable blood levels are observed for at least three hours. Furthermore, creatinine clearance overestimated GFR by 50% and by 68% in patients with renal disease and in renal transplant recipients, respectively. This method offers several advantages: 1) the use of commonly available and inexpensive materials; 2) obviates the need for the use of constant infusions; and 3) avoids the use of radioisotopes.
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