An implantable computerized electrical stimulation system designed to induce bladder evacuation in animal models (dogs) after spinal cord transection has been realized and evaluated. This fully programmable system is based on a handheld device and generates a wide range of stimuli through multichannel implantable miniaturized stimulator. Using the new bladder stimulator and inducing reversible fatigue to the external sphincter via the pudendal nerve enables us to reduce the bladder outlet resistance, resulting in the proper emptying of the bladder during stimulation without the need for sacral nerve rhizotomies and the pudendal nerve neurectomies. Four chronically affected dogs were studied to determine the optimal stimulation parameters for inducing a sphincter fatigue that would reliably empty the bladder for the duration of the experiment. These parameters were: maximum amplitude of 1.5 mA +/- 0.5 SD, stimuli composed of a high frequency signal of 200 Hz +/- 50 SD modulated by a low frequency signal of 10 Hz +/- 5 SD, pulse width controlled by a duty-cycle of 20% +/- 10 SD, sacral nerve stimulation of 50 s +/- 25 SD and fatiguing duration of 20 s +/- 5 SD.