Determination of glomerular filtration rate with radionuclide renography and direct urinary activity quantitation.

Objective. The direct urinary activity quantitation method is quick (approximately 40 minutes), requires only a single blood sample, is performed as part of standard renal scanning and shows high accuracy compared with 24-hour creatinine clearance. The purpose was to evaluate the practical application and accuracy of this technique at our clinic. Design. Direct urinary activity quantitation was done in patients scheduled for routine radionuclide renography and compared to standard multiple-blood-sample techniques by means of Cr-51-EDTA and Tc-99m-DTPA. Setting. Academic Medical Complex, Department of Nuclear Medicine, Universitas Hospital, Bloemfontein. Participants. Fifteen patients scheduled for routine radionuclide renography (glomerular filtration rate (GFR) determination) were voluntarily enrolled in the study. The GFRs of selected patients varied over a wide range. Possible obstructive uropathy was excluded. Main outcome measures. GFRs obtained by the direct urinary method were compared with GFRs determined by multisample Cr-51-EDTA and Tc-99m DTPA. Results. GFRs from the direct urinary method compared with multisample Tc-99m-DTPA showed differences from -19,85 to 22,95 ml/min with a mean of 0,2 (± 12,25) ml/min (r = 0,93). When compared with multisample Cr-51 EDTA, differences ranged from -34,35 to 21,05 ml/min with a mean of -4,25 (± 16,08) ml/min (r = 0,90). Conclusion. The direct urinary activity technique is easily applied and highly accurate compared with previous standardised multisample radionuclide techniques for determination of GFR.