Evaluation of Perirenal Fat as a Predictor of cT1a Renal Cortical Neoplasm Histopathology and Surgical Outcomes

Background and Purpose: With the increasing detection of small renal cortical neoplasms (RCNs), the preoperative prediction of histopathology has become increasingly important. Because perirenal fat (PF) is known to be metabolically active, we evaluated PF as a predictor of renal tumor histopathology. Patients and Methods: We retrospectively evaluated patients who underwent laparoscopic nephron-sparing procedures for cT(1a) RCN at two institutions. PF was measured using the digital measuring tool function on standard imaging software, at the level of the renal hilum as the perpendicular distance between the posterior surface of the kidney and the external margin of the psoas muscle. The Mann-Whitney test and logistic regression were used to examine PF, selected demographic, clinical, and operative parameters, and their association with tumor histopathology. Results: Data from 250 patients were included in this study. There were 157 (63%) men and 93 (37%) women with a median body mass index (BMI) of 28 kg/m(2). Median tumor size was 2.4 cm, and the median PF distance was 12 mm. Significant correlations were noted between PF and sex and BMI. No significant correlations were found between PF and the operative parameters. Results of a multivariate logistic regression analysis revealed that PF (P < 0.01), age (P < 0.04), and tumor location (P < 0.04) were significant predictors of clear-cell renal-cell carcinoma (RCC) histopathology. Conclusions: In this study, PF, location of tumor, and age were significant predictors of clear-cell RCC histopathology. The correlation of PF and histopathology may be useful in preoperative decision-making and surgical planning in the management of small RCN.