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Introduction
Chronic kidney disease (CKD) is associated with risk of all-cause mortality. Radical nephrectomy (RN), or nephron sparing surgery (NSS), results in immediate renal functional decline. Patients may develop CKD after RN or NSS, termed, surgical CKD (CKD-S); however, recent work suggests preexisting CKD (CKD-M) may be a stronger predictor of overall survival (OS) than CKD-S.
Methods
Surgically treated patients from 1994-2014 with available pre/post-operative renal function data were identified in our prospectively maintained institutional registry. Kaplan-Meier (KM) survival curves with log rank statistic were used to assess OS based on pre/post-operative renal function. Multivariable analysis (MVA) was performed using Cox proportional hazard model to evaluate variables for independent association with OS.
Results
On MVA, CKD-S was not associated with a statistically significant difference in mortality compared with No-CKD (HR 1.2, 95% CI 0.9-1.6, p=0.21). Further, when compared to CKD-M, CKD-S and No-CKD groups had significantly lower risk of mortality (HR 0.76, 95% CI 0.57-1.00, p=0.05 and HR 0.63, 95% CI 0.47-0.86, p=0.003, respectively). Renal functional decline was significantly higher in patients with CKD-M than in patients with CKD-S (P=0.0013).
Conclusion
Renal function before and after kidney surgery predicts OS. Survival impact appears to be immediate, suggesting CKD status is a surrogate metric of mortality risk and likely not its primary cause. CKD-S has an attenuated correlation with OS compared to patients with CKD-M. Renal functional decline in CKD-S has slower kinetics compared with CKD-M. As such, these findings support the concept of CKD-S as a distinct subtype of CKD.