Validation of MAP (Mayo Adhesive Probability) score and preoperative factors to predict adherent perinephric fat in robotic-assisted partial nephrectomy

Mayo Adhesive Probability (MAP) score is based on posterior perinephric fat thickness and perinephric fat stranding and ranges from 0 to 5. We intend to validate the score and identify preoperative factors predictive of Adherent Perinphric Fat (APF) encountered in robotic-assisted partial nephrectomy.

The retrospective and prospective observational study was done at a single tertiary care hospital after appropriate ethical clearance. Sixty-two patients with clinical stage cT1 renal mass planned for robotic-assisted partial nephrectomy were selected over a study period of 3 years after obtaining informed consent. Data that were collected included demographic details and perioperative details including CT renal angiography which was done in all patients preoperatively. Intraoperative and postoperative data were collected. Associations of patient and tumor characteristics with the presence of APF during RAPN were evaluated by multivariable logistic regression models and using Chi-square test to calculate p value.

Out of total 62 patients included; 24 patients (38.7%) had intraoperative Adhesive Perinephric Fat (APF). Three patients required conversion to open surgery and three patients underwent conversion to radical nephrectomy. Thirty-five patients were males. Mean age was 51.27(20–77) years. We noted an increased likelihood of APF with an increase in age (p = 0.003), higher preoperative creatinine (p = 0.003), greater posterior perinephric fat thickness (p = 0.002), and perirenal fat stranding (p < 0.001). From these four variables, posterior perinephric fat thickness and fat stranding were the most predictive. The combined score given to these two highly predictive factors for APF and the calculated score, termed Mayo Adhesive Probability (MAP) score ranges from 0 to 5. APF was seen in 10.7% of patients with a MAP score of 0, 25% with a score of 1, 50% with a score of 2, 44.4% with a score of 3, 88.8% with a score of 4, and 100% of patients with a score of 5 was found. Our study validates the MAP score given by Davidiuk et al. Smoking, high BMI, Sex of patient, tumor size, lateral perinephric fat thickness do not significantly predict APF in our study.

MAP score can be easily calculated from a CT scan. We validate the MAP score in RAPN. Higher MAP score has higher APF which would be useful to all urologists doing RAPN.