Stress urinary incontinence (SUI) is a highly prevalent condition in the general female population, and has a large impact on patients’ quality of life. It has been proposed that an important mechanism in the prevention of leakage of urine, during episodes of high intra-abdominal pressure, is the extent to which the urethra is capable of kinking (1). An important factor influencing the kinking capabilities of the urethra is bladder neck mobility. The kinking mechanism is assumed to serve as a supplementary closure mechanism supporting the urethral sphincter. Previous studies have investigated the use of an intravesical balloon to alleviate symptoms if SUI, and have confirmed its therapeutic effectivity (2). Here, we evaluated a potential mechanism of action for this therapy. We have previously confirmed that the implantation of an intravesical balloon inwardly pushes the bladder upwards, causing the bladder to obtain a more vertically oriented shape. We hypothesize that this change in bladder shape may change bladder mobility and or orientation and consequently may cause a reduction in incontinence episodes or volume.

The current study was approved by the local ethical committee, and informed consent was obtained from each of our participants. We recruited 10 female patients with SUI according to ICS criteria (mean age: 55.6, SD 7.8). The video urodynamic studies of 5 patients could be evaluated for this analysis before and after balloon implantation (5 patients had missing data due to technical difficulties). In order to visualize differences in bladder position and mobility before and after implantation of an intravesical balloon, our participants were subjected to two video urodynamic studies in which the bladder was filled with 100ml of saline and patients were asked to cough with increasing intensity: the first before implantation of the intravesical balloon and the second one week following implantation of the balloon. To test our hypothesis, we used a custom written script to identify the bladder in each frame of the video urodynamic investigation and subtract information regarding the location of the caudal limit of the bladder.

For each video urodynamic investigation, we normalized the displacement by subtracting the mean displacement. Then we plotted the location of the caudal limit of the bladder during coughing episodes at 100ml to identify the maximum displacement. Before and after intravesical balloon implantation displacement values were then statistically compared using a Wilcoxon Signed-Rank Test. The mean normalized maximum displacement was 7.56mm before implantation of the intravesical balloon, and 14.48mm one week following implantation. The difference between maximum displacement of the caudal bladder limit before and after implantation of the intravesical balloon was significant at the 0.05 level (one-sided p = 0.034). Additionally, after implantation of the intravesical balloon the participants’ average number of daily involuntary urine loss decreased from 4.4 to 1.8 (two-sided p = 0.02), and average daily pad use decreased from 3 pads per day before implantation to 1.3 pads per day (two-sided p = 0.02) after implantation of the intravesical balloon.

Our results indicate that the displacement of the caudal limit of the bladder during coughing episodes at a bladder volume of 100ml increases significantly after implantation of an intravesical balloon. Furthermore, we have observed a significantly positive effect on patients’ daily involuntary urine loss and pad use. We propose that the observed effect on the caudal bladder limit mobility indicates an increased kinking capacity of the bladder neck and urethra area. This mechanism might help to prevent involuntary urine loss during episodes of high intra-abdominal pressure, and decreases symptoms of SUI.

Implantation of an intravesical balloon in patients with SUI complaints significantly improves patients’ symptoms. After implantation of an intravesical balloon the caudal bladder limit shows an increased mobility in response to coughing. This increase in mobility may indicate an increased kinking of the bladder neck and urethra area.

Petros, P. E. P., & Ulmsten, U. I. (1993). An integral theory and its method for the diagnosis and management of female urinary incontinence. Scandinavian University Press.
Wyndaele, J. J., De Wachter, S., Tommaselli, G. A., Angioli, R., de Wildt, M. J., Everaert, K., ... & Van Koeveringe, G. A. (2016). A randomized, controlled clinical trial of an intravesical pressure-attenuation balloon system for the treatment of stress urinary incontinence in females. Neurourology and urodynamics, 35(2), 252-259.