Optimizing scintigraphic evaluation of split renal function in living kidney donors using the geometric mean method: a preliminary retrospective study

Background Accurate assessment of pre-transplant split renal function in candidates for living kidney donation is indispensable for side-selection and a sufficient long-term residual renal function. Objective To analyse the need of depth correction in the assessment of split renal function in potential living kidney donors. Methods In 13 consecutive patients screened for living kidney donation split renal function was measured with four different methods including conventional posterior MAG-3-scintigraphy, the geometric mean method in MAG-3-scintigraphy, MAG-3-scintigraphy with CT-based depth correction and CT-volumetry. Correlation and agreement of methods were analyzed using Spearman's rho correlation coefficient and the Bland-Altman method. Results Despite good correlation and agreement between the different radioisotopic methods there were clinically relevant differences in split renal function in 2/13 patients (15 %) between conventional posterior MAG-3 scan and the geometric mean method. The best correlation was found between the two scintigraphic methods with depth correction. Comparing radioisotopic methods with CT-volumetry, significant differences were found in up to 6/13 patients (46 %). Conclusions Our results clearly indicate that in the case of living kidney donation further assessment concerning the accuracy and reliability of measuring split renal function is necessary. As there are no differences in duration of examination, costs and radiation exposure between techniques with and without depth correction, but clinically relevant differences in up to 46 % of patients, kidney depth should be incorporated in daily clinical practice of living kidney donor evaluation. The geometric mean method could significantly improve future patient assessment in cases of living kidney donation.