Introduction: Proteinuria is considered both a known marker for the severity of chronic kidney disease (CKD) and a robust predictor of future renal function and cardiovascular morbidity and mortality in a general population. The urological community has long overlooked proteinuria as a marker of renal function. Recently, the American Urological Association (AUA) clinical practice guideline addressed this issue and suggested introducing proteinuria assessment prior to kidney cancer surgery. The aim of this systematic review was to provide evidence of proteinuria as a predictor of renal function impairment and survival outcomes after kidney surgery for renal tumors.
Evidence acquisition: A systematic search was performed by using three search engines (PubMed, Embase®, and Web of Science) from January 2010 to November 2020. Study selection followed the PRISMA guidelines. After screening, ten articles and abstracts fully compatible with the PICOS were included in this systematic review.
Evidence synthesis: Overall, a total of 11,705 patients who underwent partial nephrectomy (PN) or radical nephrectomy (RN) were analyzed. When used as a binomial variable, proteinuria prior to surgery was detected from 10% to 33% of patients. Relying on both proteinuria and estimated glomerular filtration rate (eGFR) in the assessment of renal function yielded up to 33% higher rates of patients with preoperative renal impairment. Moreover, proteinuria increased the risk of long-term renal impairment after PN and RN as well as patients with preoperative proteinuria undergoing PN exhibited a greater risk of postoperative acute kidney injury (AKI). Among eligible studies, proteinuria was associated with diabetes, obesity, metabolic syndrome, hypertension and cardiovascular disease. Finally, proteinuria was an independent predictor of overall mortality, but not of cancer-specific mortality.
Conclusions: Proteinuria yields a prognostic power beyond that provided by estimated glomerular filtration rate (eGFR) among patients undergoing renal cancer surgery, supporting its introduction in the preoperative assessment of renal function. However, well-designed multicenter prospective studies would be necessary to corroborate these results and provided urological community with high-grade recommendation for clinical practice.