Does the Renal Parenchyma Adjacent to the Tumor Contribute to Kidney Function? A Critical Analysis of Glomerular Viability in Partial Nephrectomy Specimens

Objective To evaluate the viability of glomeruli in the peritumor parenchyma of partial nephrectomy specimens removed for renal cell carcinoma (RCC) and relate it to kidney function, to better understand the contribution of peritumor parenchyma to renal function. Materials and Methods A retrospective analysis of 53 partial nephrectomies containing RCC was performed. Glomeruli within 0.25-cm increments from the tumor were quantified and histologically assessed for viability. Tumor size, minimum and maximum margin size, and pre- and postoperative estimated glomerular filtration rate (eGFR) were obtained. Results Glomerular viability positively correlated with distance from tumor with mean viable glomeruli in successive 0.25-cm increments of 0-0.25 cm, 58%; 0.25-0.5 cm, 80%; 0.5-0.75 cm, 90%; and 0.75-1.0 cm, 92%. Glomerular viability near the tumor did not correlate with preoperative eGFR, whereas decreased viability further from the tumor did correlate with worse preoperative eGFR. Tumor size showed a nonstatistically significant positive trend with minimum (median 0.15 cm) and maximum margin (median 0.7 cm) sizes. Percent change of glomerular filtration rate did not correlate with margin size ( P  = .190). Conclusion Renal parenchyma immediately adjacent to RCC contains fewer viable glomeruli compared with the parenchyma further from the tumor. Based on this information, attempts to preserve all non-neoplastic renal parenchyma via a surgical margin approaching zero may not necessarily result in clinically relevant differences in the amount of viable glomeruli remaining or the renal function preserved.