Renal parenchymal damage [RPD] is a key determinant of kidney transplant receivers’ prognosis. However, biopsy of non-tumour tissue is not contemplated in patients treated with radical nephrectomy [RN] for a renal mass and no data on its potential application in urologic patients are available. Our hypothesis stated that RPD is associated with functional outcomes in patients treated with RN.
A prospective study involving 172 patients treated with RN for a renal mass was performed. The variable of interest was RPD, assessed using an established classification system (Remuzzi score) based on glomerulosclerosis, interstitial fibrosis, tubular atrophy, and vascular damage. Two separate samples from each kidney were evaluated by an expert genito-urinary pathologist. RPD was defined as the average score of the two samples and categorized as absent (0), moderate (0.5 – 1.5) or severe (>1.5). The outcome of the study was the estimated glomerular filtration rate [eGFR] measured by CKD-EPI and BIS1 equations. Before RN and during the first 12 months after RN, 396 individual eGFR observations were recorded. Multivariable linear regression analysis [MVA] was used to investigate the impact RPD on the pattern of renal function detriment after accounting for all the potential confounders. RPD-specific patterns of renal function detriments were investigated using Loess regression function.
RPD resulted absent, moderate or severe in 26, 42 and 32% of the study population. At MVA, severe RPD was associated with lower eGFR relative to absent RPD (estimate -7; p=0.01). Conversely, moderate RPD was associated with virtually the same eGFR relative to absent RPD (estimate 4; p=0.1). Age, hypertension, tumour clinical size and time from surgery were also associated with lower eGFR (all p<0.05). Diabetes was associated with higher eGFR (p<0.05). Accordingly, the pattern of renal function detriments after RN resulted similar in patients with absent or moderate RPD whereas in patients with severe RPD renal function detriment after RN was more pronounced (Fig 1).
RPD resulted an independent predictor of renal function in patients treated with RN for a renal mass and deserves special consideration as a prognostic parameter. These observations support renal biopsy of non-tumour tissue for the analysis of RPD at final pathology after RN and imply a paradigm shift in the current pathology protocols.