Although it is commonly staged according to glomerular filtration rate, an international work group recommended classifying chronic
kidney disease by cause, glomerular filtration rate and albuminuria. Data on nonsurgical patients with chronic
kidney disease indicate proteinuria to be an independent predictor of renal function decrease and mortality. We evaluated whether preoperative proteinuria impacted survival in patients undergoing nephrectomy.
Materials and Methods
An institutional registry was queried for information regarding preoperative creatinine/glomerular filtration rate and urinalysis in 900 patients, including 362 and 538 treated with partial and radical nephrectomy, respectively. Patients were grouped according to glomerular filtration rate level (G1 to G5), proteinuria level (A1 to A3) and chronic kidney disease risk classification (low to very high). Kaplan-Meier and Cox proportional hazards analyses of overall survival were performed.
Results
The preoperative glomerular filtration rate was less than 60 ml/minute/1.73 m2 in 30% of patients (median 73, IQR 56–91) and 20% of patients had baseline proteinuria. According to the KDIGO (Kidney Disease Improving Global Outcomes) classification 23% of patients were at moderately increased, 11% were at high and 8% were at very high risk for chronic kidney disease progression. Kaplan-Meier analysis revealed that the preoperative glomerular filtration rate, proteinuria and chronic kidney disease risk group were associated with poor overall survival. In Cox proportional hazard models accounting for age, gender, race, tumor size, clinical stage and surgery type the glomerular filtration rate, proteinuria and chronic kidney disease risk group were highly significant predictors of overall survival (p <0.0001).
Conclusions
Preoperative proteinuria is a significant predictor of overall survival in patients who undergo nephrectomy. Classification according to preoperative glomerular filtration rate and proteinuria more accurately predicts survival than using the glomerular filtration rate alone after accounting for cancer stage. This information supports routine evaluation of proteinuria in patients with kidney cancer.
