Relationship between new-onset proteinuria and the volume of the non-donated kidney before and after donation in living kidney donors.

Abstract

Introduction: Some living kidney donors (LKDs) experience proteinuria after donation. Based on several studies, preoperative non-donated side kidney volume (pre-KV) and postoperative percentage change in preserved kidney hypertrophy (%PKH) are associated with proteinuria. This study explored the association of the combination of pre-KV and %PKH with new-onset proteinuria.

Methods: This single-center, retrospective, observational study included eligible LKDs who underwent donor nephrectomy between January 2008 and July 2022 (N = 195). Among those, LKDs in whom KV and either urinary protein or albumin were obtained both pre-donation and 1 year post-donation were finally included (N = 70). The LKDs were assigned to four groups according to the mean body surface area-adjusted pre-KV and %PKH, and their association with the occurrence of proteinuria or albuminuria was investigated.

Results: Among the 70 LKDs, mean age was 59.8 ± 7.9 years, and 50 (71.4%) were females. The mean preoperative estimated glomerular filtration rate, %PKH, and pre-KV was 78.0 ± 13.6 mL/min/1.73 m², 20.3 ± 7.0%, and 161.4 ± 24.1 cm³/1.73 m², respectively. During the 2.4 year follow-up period, there was no significant difference in the occurrence of proteinuria among the four groups (log-rank test, P = 0.111). However, after adjustment, the large pre-KV and small %PKH group had a significantly higher hazard ratio (HR) for proteinuria than the small pre-KV and large %PKH groups (adjusted HR 3.12, 95% confidence interval: 1.09-8.91, P = 0.033).

Conclusions: Proteinuria is more likely to occur postoperatively in LKDs whose kidneys are already enlarged before donation and cannot appropriately hypertrophy.