Analysis of the impact of adherent perirenal fat on peri-operative outcomes of robotic partial nephrectomy

Adherent perirenal fat (APF) can be defined as inflammatory fat sticking to renal parenchyma, whose dissection is difficult and makes it troublesome to expose the tumour. Our objective was to evaluate the impact of APF on the technical difficulty of robot-assisted partial nephrectomy (RPN). We analysed data of 202 patients who underwent RPN for a small renal tumour. Patients were divided into two groups according to the presence of APF. Peri-operative data were compared between the two groups. Predictors of APF were evaluated by univariate and multivariate analysis. The validity of the MAP score (radiological scoring system) was also assessed. APF was observed in 80 patients (39.6 %). Tumour complexity and surgeon's experience were similar between both groups. Operative time was 40 min longer in the APF group (188.5 vs. 147.9 min, p < 0.0001). Blood loss was twice higher, and transfusions were more common in the APF group (694 vs. 330 ml, p < 0.0001 and 19 vs. 5.8 %, p = 0.003, respectively). APF was associated with an increased risk of conversion to open surgery (11.2 vs. 0 %, p = 0.0002) or radical nephrectomy (6.2 vs. 0.8 %, p = 0.03). In multivariate analysis, male gender (OR 13.2, p < 0.0001), obesity (OR 1.2, p = 0.007), hypertension (OR 3.7, p = 0.02), and MAP score (OR 3.3; p < 0.0001) were significant predictors of APF. During RPN, APF is associated with increased bleeding and a higher risk of conversion to open surgery and to radical nephrectomy. Male gender, hypertension, obesity, and MAP score are predictors of APF.