Stimulated smooth muscle neosphincter in male intrinsic sphincter deficiency: Proof of principle studies in a rabbit model

Aims Intrinsic sphincter deficiency (ISD) causes significant disability and impairment of quality of life despite a range of treatment options. We investigated a novel method to improve sphincter function that does not appear to have been previously attempted, that is, transplantation to create a smooth muscle cuff, that subsequently becomes innervated, around the urethra. Methods Bladder pressure and passage of urine were measured in conscious, sedated rabbits of three groups: 6 control (unoperated) rabbits, 8 rabbits rendered incontinent by incision of their urethral wall, and 12 lesioned rabbits treated by transplantation of a circumferential strip of autologous dartos muscle whose innervation was later stimulated electrically. Effects of stimulation were tested up to 6 months after surgery. Results Lesions of the proximal urethra caused the bladder to leak at filling volumes that previously caused no leak. The volume added to cause first leak was less than half the volume added to cause a voiding reflex in unoperated rabbits. Transplantation of dartos to the lesioned bladder neck did not affect urodynamic parameters. However, electrical stimulation of the innervation of the transplant increased the bladder volume necessary to cause voiding and restored voiding pressures and filling volumes towards normal. These effects were maintained for 6 months and were not related to spontaneous healing. Conclusions Free transplants of smooth muscle that become innervated offer promise as a treatment for ISD that is unlikely to cause urethral erosion and will not require a pump to restore continence. Neurourol. Urodynam.