Hypothesis / aims of study
In recent decades, more localized prostate cancer patients received the surgery of robotic-assisted radical prostatectomy (RaRP). Post-prostatectomy incontinence (PPI) is a bothersome and common complication with a negative impact on quality of life. However, the urodynamic investigation of the lower urinary tract function after RaRP is limited. Therefore, this study investigated the changes of lower urinary tract (LUT) function in prostate cancer patients after RaRP.
Study design, materials and methods
We prospectively enrolled 61 localized prostate cancer patients who underwent RaRP. Their voiding conditions and parameters in videourodynamic studies (VUDS) were investigated before and during the first year (at 3-6, and 12 months) after the surgery. VUDS during follow-up were compared with the baseline data.
The mean age was 69.5 ± 8.2 years old with a mean prostate volume of 35.6±17.0 mL. In compared with the preoperative VUDS parameters, reduced detrusor voiding pressure (Pdet) and bladder outlet obstruction index (BOOI) were noted at 1 year postoperatively (Table 1). The changes of VUDS parameters including Pdet, maximum flow rate (Qmax), and BOOI were different between patients with and without preoperative bladder outlet obstruction (BOO). De novo detrusor overactivity (DO) developed in 25.0% of the patients, and the remission rate of DO was 21.1%. In general, patients without pre-operative BOO (30.6%) did not have significant change of LUT function or bladder outlet dysfunction at 1 year postoperatively. In contrast, patients with pre-operative BOO (69.4%) had more bladder outlet dysfunction (32%), including intrinsic sphincter deficiency (12%), BOO (12%), detrusor underactivity (4%), and dysfunctional voiding (4%). At 1 week after the removal of the urinary catheter, 37.9% of patients were pad-free and continent. Both stress (SUI) and urge (UUI) urinary incontinence rates were gradually reduced at 3 months (22.2%, 15.9%), at 6 months (8.3%, 6.6%), and at 12 months (9.8%, 5.9%) (Fig. 1A). The largest degree of the recovery of urinary continence developed during the first 6 months after the surgery. After subgroup analysis (Fig. 1B-E), enlarged prostate volume (≥40 mL), the presence of pre-operative BOO, peri-operative neuromuscular bundle scarification, and post-operative radiotherapy had negative impacts on urinary incontinence recovery.
Interpretation of results
After RaRP, Pdet and BOOI significantly decreased during the first-year follow-up. The BOOI reflected the bladder outlet resistance; the “detected” Pdet, being a compensatory mechanism, might change according to the bladder outlet resistance if there is no significant impairment in detrusor contractility. Male continence mechanisms include the prostate gland, urethral sphincteric system, and urethral supportive system. After RaRP, the residual functions of the urethral sphincteric and supportive systems determine the urinary continence status, and the surgical removal of the prostate gland resulted in the reduction of bladder outlet resistance (causing reduced Pdet, increased Qmax, and reduced BOOI in VUDS). All of the pre-operative (prostate volume, and the presence of BOO), peri-operative (neuromuscular bundle sacrification), and post-operative (radiotherapy) factors would affect the rate of PPI. Patients with pre-operative BOO might have enlarged prostate volume, which might cause the more peri-operative sphincter and bladder neck destruction. In addition, these patients had the higher rate of DO, which might aggravate the symptoms of urinary incontinence. In summary, patients with pre-operative BOO had non-only the higher rate of PPI but also the tendency to develop bladder outlet dysfunction.
At 1 year after RaRP, the patients with pre-operative BOO had significant changes of LUT function and more bladder outlet dysfunctions, in compared with those without BOO. The SUI and UUI rates gradually improved, with the continence rates more than 90% at 1 year. The key phase of urinary continence recovery was the first 6 months. Pre-operative enlarged prostate volume and BOO, peri-operative neuromuscular bundle scarification, and post-operative radiotherapy had negative impacts on urinary incontinence recovery.