Our previous study reported that preoperative lower bladder contractility index (BCI) was a predictive factor of postoperative detrusor underactivity (DU) at 1 month after robot-assisted radical prostatectomy (RARP). This result suggested that the decrease in reserve capacity of bladder function preoperatively might contribute to the development of postoperative DU in relatively early phase after RARP. In addition, in this study, the patients with postoperative DU at 1 month after RARP have the deterioration of lower urinary tract symptoms including International Prostatic Symptom Score (IPSS) and Overactive Bladder Symptom Score (OABSS). However, the long-term prognosis of lower urinary tract function and symptoms including voiding and storage in the patients with lower bladder contractility remained unclear. In our prospective study, we analyzed the time-dependent change of lower urinary tract function and symptoms in the patients who underwent RARP.

One-hundred-fifteen patients (mean age 66.6 ± 5.0 years) who underwent RARP in our institution were enrolled in this study. Urodynamic study (UDS) was performed before RARP for all of these patients. These patients were divided into two groups, impaired bladder contractility group (patients with BCI<100: impaired group; n=45) and preserved bladder contractility group (patients with BCI>100: preserved group; n=70). In these two groups, lower urinary tract function including maximum flow rate (Qmax), voiding volume, or postvoiding residual volume and lower urinary tract symptom including IPSS, Quality of Life (QOL) score, or OABSS was evaluated at 1, 3, 6, 9, and 12 months after RARP, respectively. Furthermore, in order to determine the risk factors for lower BCI, we performed univariate and multivariate logistic regression analysis by using patient parameters including age, body mass index, prostate weight, diabetes, LDL-cholesterol.

Qmax at 1, 3, 9, and 12 months after RARP were significantly lower in impaired group than in preserved group (p<0.05, respectively). Voiding volume at 3 months after RARP was also significantly lower in impaired group than in preserved group (p<0.01). In addition, the IPSS voiding scores at 1, 3, 6, 9, and 12 months after RARP were significantly higher in impaired group than in preserved group (p<0.05, respectively). On the other hands, no significant difference was observed in the 1-hour pad test and OABSS between impaired group and preserved group throughout the testing period. High LDL-cholesterol was identified as a risk factor for preoperative low BCI (p=0.03, odds ratio 1.02).

Our results showed that the patients with lower bladder contractility had the voiding dysfunction including a decrease of Qmax and voiding volume throughout the testing period. Furthermore, these patients had also the deterioration of voiding symptoms including IPSS voiding score in some degree. In our previous study, the patients with lower bladder contractility were reported to develop postoperative detrusor under activity (DU) in early period after RARP. Detrusor nerves are reported to be abundantly located dorsal to bladder neck around ureterovesical junction. Therefore, the partial denervation of detrusor nerves due to surgical operation might induce a decrease of postoperative bladder contractile force. In addition, our analysis showed that metabolic parameters abnormality including high LDL-cholesterol affected the decrease of bladder contractility in preoperative period. Therefore, both the preoperative lower bladder contractility by metabolic abnormality and detrusor nerve impairment by surgical operation might affect voiding dysfunction not only in early periods but also in late periods after RARP as a synergic effect.

Preoperative lower bladder contractility was associated with prolonged deterioration of voiding function. It was suggested that the dyslipidemia might be associated with decrease in bladder contractility.

Hata J, Onagi A, Kojima Y, et al. Prevalence and predictors of postoperative detrusor underactivity after robot-assisted radical prostatectomy: a prospective observational study. Int J Urol. in press, 2021.