Is DtPa the Gold Standard for Glomerular Filtration Rate Estimation in Voluntary Kidney Donors before and after Donor Nephrectomy?

Abstract

Introduction: Precise assessment of renal function of voluntary kidney donors has important implications for both donor and recipient health outcome. The ideal test for assessment of overall renal function is measurement of Glomerular Filtration Rate (GFR). Various centres use various creatinine based formulae to calculate the GFR, however when compared to GFR measurements by 99mTc-diethylenetriaminepentaacetic acid (DTPA) isotope clearance, their performance remain inconclusive. Aim: To assess the efficacy of creatinine-based GFR estimating equations in comparison to DTPA scan in voluntary kidney donors before and after donor nephrectomy. Materials and Methods: This study was conducted on 50 voluntary kidney donors who underwent donor nephrectomy at Army Hospital (R&R), New delhi. This study was conducted from November 2016 to March 2018 as a single centre, prospective, longitudinal cohort study on living related kidney donors with follow up at 1 and 3 months after kidney donation. The predictive capabilities of GFR estimation by Cockroft Gault (CG) equation, CG equation corrected for GFR and 24-hour urine Creatinine Clearance (CrCl) corrected for Body Surface Area (BSA), for both pre- and postdonor nephrectomy at 90 days, were assessed and further compared with DTPA-GFR as reference GFR. Individual quantitative parameters were compared using Student t test. For the normally distributed GFR data, Pearson’s correlation coefficient was also calculated. Statistical Package for the Social Sciences (SPSS), version 24.0, software and MS Excel were used for analysis. Results: Out of 50 subjects studied, 38 (76%) were females and 12 (24%) were males. Majority of donors were spouses. The mean GFR measured by 99mTc-DTPA scan was 99.47±14.4 ml/min/1.73m2 and 62.1±11.5 ml/min/1.73 m2 pre and postdonation respectively. All the equations being evaluated in this study underestimated the GFR as measured by 99mTc DTPA renal scan prior to kidney donation whereas GFR estimation postdonor nephrectomy by CG CrCl and CG GFR overestimated the GFR values while Urine CrCl underestimated it. Conclusion: All the equations performed unsatisfactorily. Even the best performing equation urine-CrCl was also found to be suboptimal for donor evaluation. More accurate methods of GFR estimation, should, thus be used keeping the potential risks of living kidney donation in perspective.