Single-nephron estimated glomerular filtration rate and postoperative adverse kidney outcomes following partial nephrectomy

The primary goal in treating renal cell carcinoma is to ensure patient survival through complete tumor resection, with kidney function preservation pursued whenever feasible. Nevertheless, long-term renal outcomes remain variable. Hyperfiltration of the remaining nephrons, which may influence postoperative kidney function, can be quantified as an elevated single-nephron estimated glomerular filtration rate (SNeGFR). Although maintaining postoperative kidney function is a key surgical consideration, the degree of SNeGFR elevation may directly drive progressive kidney injury via glomerular hypertension. This study therefore aimed to investigate the association between SNeGFR and both postoperative kidney function decline and long-term renal prognosis in patients undergoing partial nephrectomy.

We conducted a retrospective cohort study of 105 patients who underwent partial nephrectomy for renal cell carcinoma between April 2009 and March 2017. SNeGFR was calculated as eGFR (mL/min) divided by twice the estimated nephron number per kidney, where nephron number was estimated using preoperative computed tomography–derived cortical volume and non-sclerotic glomerular density from normal kidney regions adjacent to tumors. The primary endpoint was the annual postoperative eGFR slope. A linear mixed-effects model (MMRM) assessed the association between SNeGFR tertiles and eGFR slope, adjusting for age, sex, baseline eGFR, diabetes mellitus, hypertension, dyslipidemia, tumor diameter, clinical T stage, and operative time. The secondary endpoint was a composite kidney outcome, defined as ≥30 % decline in eGFR from baseline or initiation of kidney replacement therapy. Cumulative incidence was compared among SNeGFR tertiles using the Kaplan-Meier method with Log-rank trend test. Hazard ratios (HR) were calculated using Cox proportional hazards models adjusted for age and sex.

Baseline characteristics of the 105 patients were as follows: mean age 57.3 years, 81.0 % male, 12.4 % with diabetes mellitus, 30.5 % with hypertension, and a median baseline eGFR of 65.0±15.6 mL/min/1.73 m2. The mean SNeGFR was 47.3±17.2 nL/min. In the multivariable adjusted MMRM, SNeGFR tertiles were independently associated with a steeper postoperative eGFR slope (P for trend = 0.023; Figure 1). In contrast, nephron number tertiles were not significantly associated with the eGFR slope (P for trend = 0.53). The composite kidney outcome occurred in 20 patients (19.0 %). Higher SNeGFR tertiles were associated with significantly greater cumulative incidence of the composite outcome (Log-rank P for trend = 0.009; Figure 2). Age- and sex-adjusted Cox regression analysis demonstrated increased risk across the SNeGFR tertiles (P for trend = 0.008), with the HR of 10.0 (95 % confidence interval [CI]: 1.27–79.4) for Tertile 2 and 12.3 (95 % CI: 1.57–96.3) for Tertile 3 compared with Tertile 1.

Elevated baseline SNeGFR is independently associated with both accelerated kidney function decline and adverse kidney events after partial nephrectomy. This association was observed even though total nephron number itself was not directly related to the postoperative eGFR slope. These findings suggest that the degree of compensatory stress reflected by SNeGFR is linked to subsequent kidney outcomes in patients undergoing partial nephrectomy.