Intraoperative identification and neurophysiologic parameters to verify pelvic autonomic nerve function during total mesorectal excision for rectal cancer

BACKGROUND: Preservation of parasympathetic and sympathetic nerves is required to avoid urogenital function disturbances after total mesorectal excision (TME) for rectal carcinoma. This study sought to determine whether intraoperative stimulation of parasympathetic nerves with monitoring of bladder contraction is useful in meeting this demand. STUDY DESIGN: In a prospective pilot study, 17 patients, 11 men and 6 women, underwent TME with pelvic autonomic nerve preservation performed by an experienced surgeon. The parasympathetic nerves were stimulated by an electrostimulation device (Screener 3625, Medronic), and the resulting bladder contraction was measured manometrically in all patients. Variations in pulse rate and voltage were measured to determine optimal stimulation parameters. A standardized questionnaire was used to record urogenital function disturbances. Residual urine volume was measured by ultrasound pre- and postoperatively. Shortterm outcomes data were evaluated to establish a possible association between intraoperative test results and postoperative bladder function. RESULTS: In 15 of 17 patients undergoing TME with pelvic autonomic nerve preservation for rectal carcinoma, the parasympathetic nerves were identified based on nerve stimulation-induced bladder contraction. Two patients with negative results on intraoperative nerve stimulation had persisting bladder dysfunction requiring an indwelling catheter after discharge from hospital. In spite of a short median followup of 2 months (range 1 to 4 months), in 7 of 10 men with intact erectile function prior to surgery, postoperative erectile dysfunction could be excluded. The study showed a pulse rate of 35 Hz and an electric potential of 12 V to be optimal stimulation parameters, associated with a mean intravesical pressure rise of 12.7 cm H(2)O (range 2.8 to 18.0 cm H(2)O). CONCLUSIONS: Intraoperative nerve stimulation with monitoring of intravesical pressure represents a technically simple procedure for the identification and verification of function of pelvic parasympathetic nerves during TME for rectal carcinoma.