AUA 2018: Renal Function Variability: Simple Method to Identify Subclinical Kidney Disease before Nephrectomy

San Francisco, CA ( Kidney function variability has been associated with worse renal outcomes for patients with chronic kidney disease (CKD). The authors sought to determine if variability in preoperative kidney function was associated with development of significant CKD and overall survival following radical and partial nephrectomy in a large integrated health care system.  

The authors identified all patients who underwent radical or partial nephrectomy from 2002 to 2014 in the Veterans Health Administration (VHA) (n=18617). From this database clinical and demographic information was extracted, as well as all available outpatient kidney function measurements from 12 months prior to surgery until the end of the study period. Patients with less than 3 preoperative kidney function measurements or a baseline preoperative estimated glomerular filtration rate (eGFR) < 30 mL/min/1.73 m2 were excluded. Preoperative variability was defined as the coefficient of variation (CV) of the outpatient eGFR measurements. The primary outcome was time to significant CKD (eGFR < 30). The final analytic cohort was stratified by radical nephrectomy (n=8189) and partial nephrectomy (n=4082). Uni- and multi-variable proportional hazard models controlling for clinical and tumor characteristics were performed.  

In this cohort of 12271 patients, the median number of outpatient preoperative kidney function measurements was 5 (IQR 4 to 6) and the median preoperative eGFR was 68.8 (IQR 54.2 to 84.6). The mean CV was 0.13 (SD 0.08) and 0.11 (SD 0.07) prior to radical and partial nephrectomy, respectively. The CV was associated time to eGFR < 30 (HR 1.32, 95%CI 1.26 to 1.37). In fully adjusted models, the CV remained independently associated with time to eGFR < 30 (HR 1.05, 95% CI 0.99 to 1.10 after radical nephrectomy; HR 1.24, 95% CI 1.12 to 1.37 after partial) and overall survival (HR 1.28, 95%CI 1.16 to 1.42 after radical; HR 1.12, 95%CI 1.07 to 1.17 after partial).  

The authors concluded that preoperative kidney function variability can identify subclinical CKD and is associated with renal outcomes and mortality after nephrectomy. According to the authors, using commonly available data, this simple metric may improve prognostication for patients undergoing kidney cancer surgery. 

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Presented By: Andrew Sun, Stanford, CA, USA

Written by: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre Twitter: @GoldbergHanan at the 2018 AUA Annual Meeting - May 18 - 21, 2018 – San Francisco, CA USA
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