Advantages of robotic surgery for rectal cancer compared to laparoscopic surgery: pelvic anatomy and its impact on urinary dysfunction.

The anatomical dimensions and the shape of the pelvis influence surgical difficulty for rectal cancer. Compared to conventional laparoscopic surgery, robot-assisted surgery is expected to improve surgical outcomes due to the multi-joint movement of its surgical instruments. The aim of this study was to investigate the impact of pelvic anatomical indicators on short-term outcomes of patients with rectal cancer. A retrospective analysis was conducted using data from 129 patients with rectal cancer who underwent conventional laparoscopic low anterior resection (L-LAR) or robot-assisted low anterior resection (R-LAR) with total mesorectal excision or tumor-specific mesorectal excision between January 2014 and December 2022. The transverse diameter of the lesser pelvis and the sacral promontory angle were used as indicators of pelvic anatomy. The sacral promontory angle was not associated with age and sex while the pelvic width was smaller in male than in female. The pelvic width did not affect postoperative complications in both L-LAR and R-LAR. In contrast, postoperative urinary dysfunction occurred more frequently in patients with a small sacral promontory angle (p = 0.005) in L-LAR although there was no impact on short-term outcomes in R-LAR. Multivariate analysis demonstrated that a small sacral promontory angle was an independent predictive factor for urinary dysfunction (p = 0.032). Sharp angulation of the sacral promontory was a risk factor for UD after L-LAR. Robot-assisted surgery could overcome anatomical difficulties and reduce the incidence of UD.