Choosing the larger kidney on CT volumetry: a study on the early post-donation kidney function of living donors

Background Selecting the smaller kidney for donation has been advocated if there is a size difference of > 10% between the 2 kidneys but has never been prospectively evaluated. With increase in donor nephrectomies, it is important to evaluate this to minimize loss of renal function to donors. Methods 75 consecutive donor nephrectomy patients were included in our longitudinal study. The Split Renal Volume (SRV) of bilateral kidneys were measured using contrasted computer tomography scans and patients segregated into 2 groups depending on donated kidney having more (Group 1) or less than (Group 2) 52.5% of SRV. Results Patients in Group 1 (n = 19) and 2 (n = 56) were of similar age (43.8 vs. 48.3), BMI (22.4 vs. 25.2), sex (57.9 vs. 55.4% women), respectively. Although total kidney volumes were similar in both groups, Group 1 had significantly smaller right kidney volumes (120.4 ± 24.9 vs. 142.7 ± 28.4 mls, p = 0.003). EGFR pre-operatively (116.3 ± 20.8 vs. 106.3 ± 23.8 mL/min/1.73 m 2 ) and at 6-months (65.7 ± 13.3 vs. 66.9 ± 15.5 mL/min/1.73 m 2 ) were not different between groups. However, patients in Group 1 had significantly greater absolute (50.6 ± 14.9 vs. 39.5 ± 14.7 mL/min/1.73 m 2 ) and relative decline (43.0 ± 8.6 vs. 36.3 ± 10.6%) in eGFR at 6 months (p = 0.06, 0.009). Conclusion With a SRV difference of 5% between the 2 sides, removal of the larger kidney for living kidney donation resulted in greater early decline of renal function than kidney donors whose larger or equivalent kidney is preserved.