Role of radioisotope renal scans in the choice of nephrectomy side in live kidney donors

Purpose: We determined the role of radioisotope renal scans in the choice of nephrectomy side in potential live kidney donors. Materials and Methods: The study included 300 consecutive potential live kidney donors. In addition to routine laboratory and radiological evaluation, a radioisotope renal scan with selective determination of glomerular filtration rate (GFR) of each kidney was performed for all donors. Results of the first 100 potential donors were used to standardize the technique and to show the normal difference in GFR of both kidneys due to technical and normal physiological variations. The subsequent 200 potential donors who underwent nephrectomy were considered the study group. In the study group kidneys with a GFR difference less than or equal to mean normal difference were considered equal in function. Disparity in function was considered if the GFR difference between both kidneys was greater than normal mean difference. Results: Of the 100 control donors there was no difference between mean GFR +/- SD of the left and right kidney (57.7 +/- 9.09 vs 58.09 +/- 8.93 ml per minute, respectively). The disparity in clearance of both kidneys ranged from 0 to 14.25 ml per minute and averaged 6.12 +/- 0.42. This average difference represents 5.31% +/- 0.27% of average total renographic GFR. Based on control group results a disparity greater than 5.31% of total GFR was considered significant in the study group. Of the 200 study group donors GFR of both kidneys was comparable in 116 cases (58%), the left had better function in 49 (24.5%) and the right had better function in 35 (17.5%). Therefore, a total of 84 donors (42%) had disparity in function between both kidneys. In all these donors the kidney with less function was chosen for nephrectomy regardless of anatomical considerations such as multiplicity of renal arteries. In donors with comparable GFR in both kidneys the harvested kidney was essentially chosen on an anatomical basis. Conclusions: When renal function of 2 kidneys is similar or nearly similar, anatomical factors determine the side of the harvested kidney. When there is a significant difference in clearance value (greater than 6 ml per minute) the kidney with lower clearance is chosen irrespective of anatomical findings. Since this difference is expected in about 40% of healthy individuals, radioisotopic determination of split renal function should be an integral part of the preoperative evaluation of potential kidney donors.