A magnetic device for increasing the urethral resistance to flow: an experimental study in female dogs

Abstract

Objective To test a new magnetic device for increasing the urethral resistance to¯ow in a dog model, and thus provide a potential mechanical device for the treatment of incontinence in women. Materials and methods The study comprised 12 female mongrel dogs; three dogs were used to study the effect on urethral resistance of inserting a vaginal magnet (control experiment) and ®ve were assessed in a urodynamic study. With the animals under general anaesthesia, the bladder and the urethra were exposed by a low midline incision. One magnet, embedded in a silicon layer, was placed on the anterior side of the urethra 3 cm distal to the bladder neck and ®xed with a few sutures. To increase the urethral resistance as required, a second magnet was inserted into the vagina and the device activated. Urethral pressure pro®les and leak-point pressures were recorded in the anaesthetized animals under resting conditions and after the urethra was compressed between the magnets. Recordings were also made after pharmacological blockade of the urethral musculature. In four additional dogs, chronic experiments were conducted to evaluate the effect of continuous compression of the urethra and the vaginal wall for 14 days. Results Urethral compression between the magnets resulted in a doubling of the maximal pressure in the proximal urethra and in a threefold increase of the leak-point pressure. After pharmacological denervation of the urethra the differences between the control pressures and those after activating the device were even greater, although not signi®cantly so. After 2 weeks of continuous compression of the vaginal wall and the urethra between the magnets there was no detectable tissue damage. Conclusion These results suggest that the magnetic device can ef®ciently increase urethral pressure and that prolonged compression caused no apparent damage to the urethra or vagina. It may therefore be a useful potential method of providing urinary continence in women.

Novel Artificial Urinary Sphincter in the Canine Model: The Tape Mechanical Occlusive Device

“…No histologic evidence of vascular congestion or edema was detected in the transitional epithelium, lamina propria, muscularis mucosa or tunica muscularis but some was present in the serosa. The total irritation index score was 5 which indicated a mild irritative response [10-11]. …”

“…After 2 weeks, the TMOD was activated (ON mode) except for night time and three times a day (30 minutes each) to simulate the natural voiding pattern of the animals. At 6 and 9 weeks post-implantation, following administration of appropriate anesthetics, the urethral sphincter was temporarily paralyzed in 3 female dogs with 0.1 mg/kg succinyl choline to simulate sphincter damage [10]. Urethral pressure profilometry was then performed by the catheter based perfusion method with TMODs ON & OFF.…”

Urodynamic effects of a percutaneously controlled static hydraulic urethral sphincter in canine cadavers

“…Analysis of results of our study also confirmed our hypothesis that a simple, percutaneously controlled HUS could be used to improve urodynamic variables in canine cadavers. Although they will never supersede objective evaluation of clinical outcome in dogs with naturally developing USMI, urodynamic variables have served as 1 of the few objective means of comparing the effects of medical or surgical treatment in controlled studies 4,7,[24][25][26][27][28][29][30][31][32][33] and have been reported consistently in the veterinary literature. Studies 7,20,[25][26][27]29,30 of diagnostic or surgical techniques for USMI are often performed in clinically normal animals or on cadavers, making it impossible to quantify the degree of incontinence.…”

“…Although they will never supersede objective evaluation of clinical outcome in dogs with naturally developing USMI, urodynamic variables have served as 1 of the few objective means of comparing the effects of medical or surgical treatment in controlled studies 4,7,[24][25][26][27][28][29][30][31][32][33] and have been reported consistently in the veterinary literature. Studies 7,20,[25][26][27]29,30 of diagnostic or surgical techniques for USMI are often performed in clinically normal animals or on cadavers, making it impossible to quantify the degree of incontinence. Consequently, studies 7,20,[25][26][27]29 have often relied on urodynamic variables to describe the mechanism of action of medical and surgical interventions for USMI.…”

“…Studies 7,20,[25][26][27]29,30 of diagnostic or surgical techniques for USMI are often performed in clinically normal animals or on cadavers, making it impossible to quantify the degree of incontinence. Consequently, studies 7,20,[25][26][27]29 have often relied on urodynamic variables to describe the mechanism of action of medical and surgical interventions for USMI. Evaluation of intraoperative and postoperative urodynamic variables has also been recommended specifically during use of the PCHUS in human patients.…”