The surgical treatment of post-prostatectomy urinary incontinence (PPI) is based on returning the function of urethral sphincter mechanism by increasing urethral pressure either through artificial urinary sphincter (AUS) or male slings (adjustable or non-adjustable)

Adjustable trans-obturator male system (ATOMS ®, A.M.I., Feldkirch, Austria) has demonstrated effectiveness for the treatment of PPI both in multicentre studies performed in Europe and Canada and meta-analysis. However, unlike AUS there is no possibility to deactivate it. Consequently, the increase in urethral pressure is maintained throughout the voiding phase. 

Studies performed on females after incontinence surgery have shown an increase of urethral resistance that leads to bladder outlet obstruction (BOO) in a non-negligible number of patients (1)  . This kind of studies have not been conducted with ATOMS device. Consequently, our purpose is to assess the changes in the voiding phase after ATOMS implantation in male patients with PPI.

Study Design. Longitudinal prospective

Materials and Methods. A prospective longitudinal study was carried out between October 2020 and March 2021 in a cohort of patients submitted to ATOMS implantation to treat PPI. Inclusion criteria were patients with a previous urodynamic study before ATOMS implant and informed consent to be included in the study. Exclusion criteria were bladder outlet obstruction due to bladder neck contracture or urethral stricture proved by urethroscopy and patients who underwent urinary tract surgery between preoperative and postoperative urodynamics (e.g., transurethral resection of bladder tumour, ureteroscopy).

The urodynamic study consisted on a pressure flow study. The polygraph used was a Uro 2000 (MMS, Enschede, The Netherlands). The study was made according to the specifications of the International Continence Society (ICS) and the protocols of Good Urodynamic Practices (GUP) The diagnostic of BOO was made when the URA value was equal to or greater than 29 cm H2O.

The sample size was calculated according to Kraus et al (1) to find a difference in bladder outlet obstruction index (BOOI) before and after the sling procedure of 18 cm H2O with a standard deviation of BOOI of 31 cm H2O an alpha error of 5% and a statistical power of 80%. This gave a minimum sample size of 25 patients. The initial sample of patients screened with preoperative urodynamic study was 84 cases, with a mean age of 70 ± 5.5 years (mean ± SD). Their preoperative urodynamic study was performed 15 ± 15.3 months before surgery. The final sample was composed of 45 patients with a mean age of 70 ± 6.5 years. Three patients died of another disease during follow-up, 22 patients did not give consent to undergo postoperative urodynamic study, 8 had urethral stenosis, 3 had bladder neck contracture, 2 patients had irregular urethra in which no urodynamic catheter could be inserted, and one was not able to urinate because of perineal contraction. The postoperative urodynamic study was performed 37 ± 20.5 months after surgery.

Statistical analysis was performed using the SPSS version 22 platform and consisted of the following tests of statistical significance: mean comparison test for dependent groups (Student’s t test) for parametric variables and Wilcoxon signed-rank test for non-parametric variables.  Parametric distribution of variables was tested by the Kolmogorov-Smirnoff test. The significance level was set at 95 % bilateral.

The main urodynamic voiding variables before and after ATOMS implantation are shown in table 1. We observed a statistically significant difference in maximum flow rate (greater before surgery, p=0.008), BOOI (greater after surgery, p=0.025) and bladder contractility index (BCI) (greater before surgery, p=0.044). Preoperatively we found that 2 patients had BOO versus none postoperatively (non-significant difference, p =0.157).

Voiding dynamics is based on two variables: urethral resistance and detrusor contractility. Our results show that ATOMS implantation resulted in an increase of urethral resistance measured by increased BOOI but without any postoperative case of BOO, and a decrease in BCI.

Unlike in women, stress urinary incontinence in males is due exclusively to a deficiency of the urethral sphincter mechanism. Different surgical methods attempt to restore continence using sub-urethral slings. It is a common belief that if such sling can pull strongly enough it will increase urethral pressure. However, a sling can only apply a force from side to side and we know that this will not increase urethral pressure. If a sling is pulled excessively it will deform and kink the urethra causing bladder outlet obstruction. Schaefer (2)  has proved that the only way to increase urethral pressure is by a device that surrounds the entire urethra, such as AUS does. Studies of voiding phase in men after PPI surgery are scarce and, often they do not provide any parameter of urethral resistance. Engel et al (3)  in six patients with PPI who underwent a bulbourethral sling procedure observed a mean postoperative URA of 104 cm H2O that is clearly obstructive. Our study showed an increase in BOOI, but without producing bladder outlet obstruction (all patients had an URA parameter of less than 29 cm H2O). Patients with PPI without bladder neck contracture or urethral strictures have an abnormal decrease in their urethral resistance. Consequently, the increased BOOI we observed could be explained by the recovery of urethral function. Our results suggest that the mechanism of action of ATOMS differs from that of AUS or sling procedures because it lengthens the urethra and this action can lead to an increase of urethral pressure according to Laplace’s law without kinking or constricting the urethral lumen and, consequently, without creating a bladder outlet obstruction.

An unsuspected finding in our study was the significant decrease in bladder contractility after ATOMS surgery.  Contrary to our results Engel et al (3) found an increase in BCI after bulbourethral sling placement, although this increase was not statistically significant, probably due to the scarce number of patients (n=6). These authors also found an increase in bladder work that can be attributed to increased urethral resistance. It is well known that a chronic obstruction such as that which occurs in prostatic hyperplasia is associated with compensatory detrusor hyperplasia and increased detrusor power. The absence of increased or decreased detrusor contractility in our study also confirms that bladder outlet obstruction does not occur after ATOMS placement. On the other hand, this decrease of detrusor contractility did not lead to any voiding dysfunction because the post void urinary residue did not vary significantly.

The ATOMS implantation in male patients with PPI results in an increase of urethral resistance, without any case of bladder outlet obstruction, and a decrease in bladder contractility. These findings suggest that these changes may reflex a return to a more physiological voiding condition.

Tran H, Rutman M. Female outlet obstruction after anti-incontinence surgery. Urology.;112:1-5.
Schäfer W. Some biomechanical aspects of continence function. Scand J Urol Nephrol Suppl. 2001;(207):44-60.
Engel JD, Jacobs D, Konsur B, Megaridis CM, Bushman W. Urodynamic evaluation of the human bladder response to an increase in outlet resistance. Neurourol Urodyn. 2002;21(6):524-8.