Functional urinary bladder wall substitute using a free innervated latissimus dorsi muscle flap.

This study was designed to investigate the ability of the latissimus dorsi muscle in situ to evacuate a bladder reservoir and to study the functional, anatomic, and histopathologic results of partial or subtotal bladder reconstruction with an innervated free latissimus dorsi muscle in mongrel dogs. In group I (four dogs), the latissimus dorsi muscle was dissected and tailored in situ. Then the so-formed pedicled latissimus dorsi muscle flap was wrapped around tissue expanders of varying sizes (volumes of 50, 100, and 150 cc, respectively) to form a bladder-like reservoir. Electromyography and intraluminal pressure measurements were done at the time of surgery and 6 months thereafter using a standard electromyograph and a Dantec urodynamic unit. In group II (four dogs), the dome of the bladder wall was removed, with up to 50 percent of the mucosal layer being left intact. The resulting muscular defect was repaired with a free innervated latissimus dorsi muscle flap. The transferred latissimus dorsi muscle was shaped and wrapped around the bladder in a spiral form, with particular attention to the resting tension. The thoracodorsal vessels were anastomosed to the pelvic branches of the hypogastric vessels, and the thoracodorsal nerve was coapted to a pelvic motor nerve that was selected by use of a nerve stimulator. Cystography and urodynamic studies were performed after 3, 6, and 9 months. Electromyography was done after 9 months, before sacrifice of the animals, which was followed by regular histologic and electron microscopic examinations. Stimulation of the thoracodorsal nerve of the reconfigured latissimus dorsi muscle reservoirs in situ after 6 months yielded average intraluminal pressures of 190 cmH2O at maximum capacity and 35 cmH2O at a minimum capacity of 10 to 15 cc. Stimulation of the latissimus dorsi muscle transferred to the bladder resulted in a visible and measurable contraction of the transplanted muscle after 9 months. Urodynamic values preoperatively and postoperatively were basically unchanged. During cystography, the bladder outline was smooth during both filling and voiding. Light and electron microscopic examinations confirmed viable, reinnervated muscle. The reconfigured pedicled latissimus dorsi muscle has the ability to evacuate a bladder-like reservoir after nerve stimulation. A detrusor function of the bladder can be induced through the contractility of a reinnervated free latissimus dorsi muscle that was wrapped around the bladder. An innervated free latissimus dorsi muscle flap does not undergo severe muscle fibrosis, contracture, and atrophy such as occur after transfer of completely or partially denervated, pedicled muscle. This means that a functional bladder reconstruction/augmentation can be achieved by microneurovascular transfer of a latissimus dorsi muscle flap.