Partial nephrectomy for renal tumors in solitary kidneys: postoperative renal function dynamics

Objective: To describe renal functional outcomes after partial nephrectomy (PN) for a tumor in a solitary kidney using the estimated glomerular filtration rate eGFR (MDRD equation).

Patients and methods: A retrospective review of 103 cases of PN in a solitary kidney at Memorial Sloan-Kettering Cancer Center from December 1989 to July 2010 was conducted. The postoperative eGFR measurements were broken into three timeframes: 1-10 days after PN, 10 days-8 weeks after PN, and 4-12 months after PN. Several factors were analyzed for their impact on postoperative eGFR on univariate and multivariable analyses. To illustrate the change in eGFR after surgery over time, a univariate generalized estimating equation (GEE) model was constructed.

Results: Median preoperative eGFR was 47 ml/min/1.72 m(2) (IQR 39, 58). Higher preoperative eGFR, younger age at the time of PN, less estimated blood loss during PN, increased time between PN and previous radical nephrectomy, and decreased arterial clamp (ischemia) time were all significantly associated with increased postoperative eGFR in the early postoperative period on multivariable analysis. Younger age and higher preoperative eGFR were the only variables significantly associated with increased postoperative eGFR at all three time points. From the GEE model, postoperative eGFR continues to rise after PN until it reaches a plateau approximately 1 month after PN without attaining preoperative levels.

Conclusion: PN for tumors in a solitary kidney is feasible and safe. In our model, non-modifiable factors predict the long-term postoperative eGFR: Young patients with healthy kidneys have superior renal functional results.