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Comparison of single-injection multisample renal clearance methods with and without urine collection
1Division of Nuclear Medicine, University of Alabama Hospital, Birmingham 35233, USA.
Summary
Urine-free methods accurately measure renal clearance for tubular agents like 99mTc-MAG3 and 131I-OIH, eliminating the need for urine collection except at very low clearance levels.
Area of Science:
- Nuclear medicine
- Renal physiology
- Diagnostic imaging
Background:
- Renal clearance measurement traditionally involves urine collection, which can be cumbersome.
- Single-injection plasma clearance methods are sometimes viewed skeptically due to data extrapolation requirements.
- Concerns exist regarding the accuracy of urine-free methods for rapidly cleared tubular agents compared to glomerular filtration rate agents.
Purpose of the Study:
- To compare the accuracy of urine-based and urine-free renal clearance measurement methods.
- To evaluate the utility of urine-free methods for tubular agents like 99mTc-MAG3 and 131I-OIH.
Main Methods:
- Dual-tracer plasma data collected from 18 patients over 90 minutes (nine samples).
- Urine collected for 90 minutes, with residual bladder activity corrected using gamma camera imaging.
- Comparison of clearance calculations between urine-based and urine-free methods.
Main Results:
- Minimal difference in measurements for 99mTc-MAG3 (1 +/- 5 ml/min) and 131I-OIH (23 +/- 8 ml/min) between methods.
- Regression analysis showed no significant deviation from the line of identity for 99mTc-MAG3.
- High correlation coefficients (0.94) observed for both agents, indicating strong agreement.
Conclusions:
- Urine collection is not essential for accurate renal clearance measurement of tubular agents.
- Urine-free methods are reliable even for rapidly cleared agents, except in cases of very low clearance.
- This simplifies the process of renal clearance assessment in clinical settings.