Comparison of Measured Gfr by Tc-99m-dtpawith Estimated Gfr in Potential Kidney Donors at Kenyatta National Hospital

Abstract

Background: Glomerular filtration rate (GFR) is key in assessing the renal function of an individual. GFR cannot be measured directly, but as urinary clearance of an ideal filtration marker. Estimated GFR is vital in detection, evaluation and management of kidney disease. While there are many methods and substances of measuring GFR, nuclear imaging through DTPA is considered to be accurate and more convenient compared with other methods. There is no local study outlining the measured GFR of the kidney donors and there is no local study comparing the variation of DTPA GFR with other GFR estimating formulae like Cockcroft-Gault, CKD- EPI or MDRD. Objective: The aim of the study was to determine the measured GFR by DTPA of the potential kidney donors and compare the measured GFR with three GFR estimating methods among potential kidney donors at KNH. Study design: Retrospective descriptive study. Methodology: The Study population included all potential live kidney donors, aged eighteen years and above, from 2010 who had pre donation work up DTPA done. The participants serum creatinine was obtained from the file and eGFR calculated through the three formulae. This eGFR was then compared with the DTPA mGFR. Data analysis and presentation: Data analysis was done using the Statistical Package for Social Science (SPSS) version 20.0. For continuous variables like age, mean, mode, median, range and standard deviations were calculated. Frequencies of categorical variables e.g. sex were calculated. The Bland-Altman method was used to evaluate the agreement between the measured GFR and the estimated GFR for each of the equations. Data is presented as graphs pie-charts and tables. Results: A total of 130 records were retrieved from the renal and central filing area. Eight had missing data and were therefore excluded from the study. A total of 122 records were reviewed and included. Seventy (57.4%) were male. The average age was 33.9yrs ± 9.2 with a range of 19-58 years. Almost 50% of all donations were from siblings. Forty percent of the right kidneys had a higher GFR than the left. Conversely 60% of the left kidneys had a higher GFR than the right kidneys. The median GFR in the right was 48.67ml/min/1.73m2 and the left was 49.2 ml/min/1.73m2. The means of estimated GFR by the 3 equations were within 10% of mGFR, but variation was marked. Seventy eight (86%) of the nephrectomies were left sided. Out of these, 44(48.9%) were kidneys that had less GFR compared to the contralateral kidney. Conclusion: Most of the donors were young, male and siblings to the recipients. A hundred percent of the donors met the international recommended mGFR of 80 ml/min/1.73m2.The mean and median of split renal function was comparable. The online donor GFR calculator has a potential role in transplantation though needs more validation.