The flowing of fluid along the urethra can facilitate the bladder micturition contraction, a reflex appropriate to achieve complete bladder emptying. The response has been observed in animals studied in the decerebrate, spinal, or anesthetized intact state but is difficult to demonstrate in awake, healthy humans. The aim of this study was to investigate this reflex in the awake, intact state using urodynamics in the ewe. The animals were fully awake and lay gently restrained on a recording table. The bladder was catheterized, and urethral flows were obtained by slowly injecting saline at the level of the proximal urethra. Bladder and rectal pressure were monitored, and the responses to urethral flow were tested at various bladder volumes. Urethral flows consistently evoked detrusor contractions in all animals. The response started approximately 2 seconds after the beginning of the flow and largely outlasted the stimulus. Its amplitude was similar to that of the bladder-to-bladder micturition reflex, and, like the latter, it always required some degree of bladder filling to appear. The reflex was selectively suppressed by local anesthesia of the urethral mucosa, indicating that the effect must originate from urethral receptors. Small urethral flows thus appear to elicit large bladder micturition contractions in awake healthy animals, and the reflex could be quite significant during the normal micturition. That this reflex is found in all studied species further supports the notion that the negative results in normal awake humans are owing to descending inhibitory controls rather than to the lack of appropriate pathways.

Urethral implantation of myofibers regenerates as myotubes that exert tonic activity under neural control. This has potential clinical value as a means to create an additional striated urethral sphincter.

The striated urethral sphincter of the female pig shows the morphological and functional features of a tonic muscle. Methods of measuring resting urethral tone generated by the striated urethral sphincter represent original tools for evaluating therapies for intrinsic sphincter insufficiency.

In ewes, we have shown that urethral to bladder micturition reflex involving mechanoreceptors is decreased at temperatures below the physiological range. It is suggested that transient receptor potential vanilloid cation channels (e.g., TRPV4 which is activated by sheer/stress flows at near-body temperature) could be involved in this urethra to bladder reflex. In humans, this reflex has hardly been described and is still a matter of debate. Our results reinforce that its full investigation may require systematic use of a range of saline flows at different temperatures.

International audienceManagement of male severe stress urinary incontinence is currently achieved by the treatment of choice: an artificial urinary sphincter (AUS). This implantable system is designed to exert a constant circumferential force around the urethra. Although continence is totally or partially recovered in most of the patients, this method has some significant drawbacks. Besides the difficulty and discomfort of using the device, the revision rate caused by constant urethral compression, leading to urethral injuries, remains high. We present in this study a new AUS concept, with an ergonomic control, providing a lower exerted pressure on the urethral tissues and improving the continence efficiency. In fact, the implant includes a system which automatically detects circumstances involving high-intravesical pressure and adapts the occlusive pressure accordingly. The device was evaluated using isolated goat urethra, and then, in vivo. Recorded data of 16 human subjects performing different daily exercises were used to assess the detection algorithms. It is shown that occlusive pressure can be controlled by the implant with an accuracy of 1 cm H2O (98 Pa). Acceptable detection performance of seven of the eight targeted activities was observed