Perioperative impact of body mass index on upper urinary tract and renal robot-assisted surgery: a single high-volume centre experience.

To assess the impact of body mass index (BMI) on peri-operative outcomes of kidney and upper tract robot-assisted surgery. Medical audit of patients who underwent robot-assisted kidney and upper tract cancer surgery at a single institution between 2017 and 2019, categorized on BMI into obese patients with a BMI ≥ 30 kg/m and a control group with BMI < 25 kg/m. Patient and tumour characteristics, surgery time, intraoperative blood loss, intraoperative adverse events (AE) according to the European Association of Urology Intraoperative Adverse Incidents Classification (EAUiaiC), conversion- to-open/radical rate as well as 30-day postoperative AE according to Clavien-Dindo (CD) and length of inpatient stay were analyzed. 366 patients were identified, 141 with a BMI < 25 (normal-weight) and 225 BMI ≥ 30 (obesity). There were no significant differences between the groups in terms of age, gender, comorbidities, tumour size, TNM stage and type of surgery. Obese patients had a higher estimated blood loss (198.05 ml), surgery time (171.75 min), intraoperative AE (all grades) (14.67%, 95% CI (0.10-0.19) as well as adherent perinephric fat (APF) (14.22%, 95% CI (0.09-0.19)) in contrast to the control group (86.85 ml, 148.29 min, 7.04% and 2.12%, respectively). Hospital stay, major intraoperative AE (≥ 3) and major postoperative AE (CD > 2) distributed equally between groups. Robotic kidney and upper tract surgery in obese patients showed an increase in surgery time and blood loss potentially related to APF. However, obesity was not associated with conversion to open surgery or radical nephrectomy in nephron-sparing procedures, length of stay, major intraoperative AE or postoperative complications.