Introduction: There are cases of persistent urinary incontinence after robot-assisted radical prostatectomy (RARP). Urinary incontinence is one of the factors that significantly reduce quality of life, and there is a need to elucidate predictive factors for urinary incontinence to assist in treatment selection. On the other hand, it has been reported that decreased skeletal muscle mass is a risk factor for perioperative complications and poor prognosis, and we considered that it could also be a predictor of urinary incontinence after RARP. Therefore, we measured cross sectional area of psoas major muscle (CSA-PMM), which has been one of the indicators of skeletal muscle volume, and analyzed the relationship between the systemic skeletal muscle and urinary incontinence after RARP. Methods: Altogether, 539 (average 67.0 ± 5.18 years old) who underwent RARP were enrolled in this study. CSA-PMM were measured by tracing the bilateral psoas major muscles at the upper border level of cross section L4 on preoperative CT. Urinary continence was defined as =2 g on a 1-hour pad test and was assessed at 1, 3, 6, 9, and 12 months after RARP. The correlation analysis between patient factors such as CSA-PMM, age, BMI, and eGFR and postoperative urinary continence was performed. The median of CSA-PMM was divided into two groups, high or low CSA-PMM groups, and used for analysis. Results: The continence rates at 1, 3, 6, 9, and 12 months after RARP were 31.9%, 53.6%, 66.0%, 70.3%, and 70.8%, respectively. The median of CSA-PMM was 19.72 (10.39-33.16) ?. CSA-PMM was a significant predictor of urinary continence at 6, 9, and 12 months after RARP in univariate analysis (p < 0.01, p<0.01, p=0.03). Furthermore, in multivariate analysis, it was a significant predictor of urinary continence at 3, 6, 9, and 12 months after surgery (p=0.02, p<0.01, p<0.01, p<0.01). Conclusions: CSA-PMM was a significant predictor of long-term urinary incontinence after RARP. Since the psoas major muscle is one indicator of total body skeletal muscle mass, patients with low CSA-PMM had lower pelvic floor muscle mass. This might be related to urinary incontinence. SOURCE OF Funding: Nothing
