Neurophysiological basis of sympathetic nerve-preserving surgery for lower rectal cancer - A canine model

BACKGROUND/AIMS: The relative contribution and interrelated compensation of sympathetic signals among sympathetic components in pelvic plexus remain undefined. This study was designed to investigate the genitourinary function in response to autonomic nerve preservation and severance using a canine model. METHODOLOGY: Eighteen mongrel dogs were randomly divided into 3 groups which received severance of the hypogastric nerves on either the right side, left side, or on both sides. The hypogastric nerves and sacral sympathetic trunks were electrically stimulated and the contraction pressure of the internal urethral orifice was measured immediately, at 1- and 3-month intervals. The ejaculation function and the length of time required to reach sexual orgasm were evaluated by manual penis-stimulation. RESULTS: The difference between the left and right sides of the normal hypogastric nerve in contribution to sympathetic signals was insignificant. Compared with the hypogastric nerve, the bilateral sacral sympathetic trunks were functionally trivial in controlling the closure of the internal urethral orifice. The preserved side of the hypogastric nerve compensated for the loss of sympathetic signals of the severed side within 1 month and, thereafter, remained stationary. In contrast, the functional compensation of bilateral sacral sympathetic trunks for the severed bilateral hypogastric nerves was insignificant. When the hypogastric nerve was preserved in one or both sides, all dogs maintained normal antegrade ejaculation. If bilateral hypogastric nerves were severed, 50.0% (3/6) of the dogs lost both emission and ejaculation function; 33.3% (2/6) presented with retrograde ejaculation; and, 16.7% (1/6) presented with combined retrograde ejaculation and reduced antegrade ejaculation. The time required to reach sexual orgasm was not affected by the severance of the hypogastric nerve. CONCLUSIONS: The normal genitourinary function could be maintained only when at least one side of the hypogastric nerve was preserved.