Tumor contact surface area is associated with volume loss and functional decline after partial nephrectomy

Purpose: We propose a formula of calculate-based contact surface area (CSA). We examined the correlation of contact surface area and renal volume loss and the predictability for renal function after partial nephrectomy.

Materials and Methods: We conducted a retrospective study in patients who underwent partial nephrectomy between January 2012 and December 2014. Based on abdominopelvic CT and MRI, we calculated the contact surface area with the formula “2* π *Radius*Depth”; while resected and ischemic volume (RAIV) was determined by the equation” [2wˆ2+3w(r+d)+6rd]*w*π)/3”. We evaluated the correlation between CSA, RAIV and perioperative parameters. And we comparatively analyzed the ability of CSA and RAIV to predict the reduction in renal function.

Results: There were 35, 26, and 45 patients receiving OPN, LPN, RPN respectively. The mean±SD contact surface area was 30.7±26.1 cm² , and and the mean±SD RAIV was 19.1±14.4 cm³ . On Spearman correlation analysis we found that CSA and RAIV were highly correlated (coefficient: 0.99, p<0.001). In univariate analysis, BMI (p=0.02), EBL (p=0.001), RAIV (p<0.001), and CSA (p<0.001) significantly affected postoperative renal function. In ROC curve analysis, both CSA and RAIV have good ability to predict more than 10% change of estimated glomerular filtration rate (AUC: 0.86 vs. 0.87). There is no significant difference in AUC between CSA and RAIV. The area difference in PCE10 was 0.002 (p=0.51)

Conclusion: In our study, CSA and RAIV were correlated with several perioperative outcomes and affected post-operative renal function. The ability to predict post-operative renal function between CSA and RAIV was nearly identical. Since CSA was simpler to use, and may possess less interobserver variability in comparison with RAIV, we believe that CSA can represent renal parenchymal loss.