Estimated glomerular filtration rate, renal scan and volumetric assessment of the kidney before and after partial nephrectomy: a review of the current literature.

INTRODUCTION: The best method for assessing renal function after partial nephrectomy (PN) continues to be a matter of debate. Early studies evaluated kidney function by measuring serum creatinine (sCr) and/or the estimated glomerular filtration rate (eGFR), potentially underestimating the contribution of the contralateral kidney in masking alterations in renal function. Since then, researchers have studied the operated renal unit with the aid of nuclear renal scans (RS). However, taking into consideration the importance of the amount of renal parenchyma spared or sacrificed during PN, many novel methods have been proposed for determining kidney volume before and after PN. This review presents a critical analysis of the literature concerning renal function assessment using eGFR, renal scan and volumetric methods before and after PN.

EVIDENCE ACQUISITION: The literature review was carried out using the Pubmed database and the keywords "eGFR", "renal scan" and "volumetric assessment" in combination with "partial nephrectomy" or "nephron-sparing surgery". The search was limited to English language articles published between June 2006 and June 2016.

EVIDENCE SYNTHESIS: Of the available formulas, the Chronic Kidney Disease Epidemiology Collaboration and Modification of Diet in Renal Disease equations should be used as they provide the best estimation of GFR. MAG3 RS is the most widely used method in current practice, presenting several distinct advantages. According to studies on volumetric assessment, as a general rule, renal tumors should be removed with resection of a thin rim of healthy parenchyma or by enucleation following the tumor pseudocapsule plane, as a histologic tumor-free resection margin, irrespective of the width of the margin, is sufficient to achieve local control during PN. There are no clear recommendations regarding the best modality to use.

CONCLUSIONS: The use of serum creatinine alone should be avoided. The use of glomerular filtration rate, as estimated by means of available formulas, could be a viable option. If available, a nuclear RS should be adopted, whilst taking into account the limitations of this imaging methodology. Volumetric assessment continues to lack certainty. To date, no single proposed method for volumetric assessment appears to be superior above the others.