Morphological study of the neurovascular bundle to elucidate nerve damage in pelvic surgery

Purpose Postoperative sexual and urinary dysfunction may occur after rectal cancer surgery involving the pelvis, but this problem cannot be solved. The aim of this study was to examine the nerve morphology of the neurovascular bundle in cadavers to determine possible causes of nerve damage during surgery. Methods Twenty-two formalin-fixed cadavers were used in the study. The cadavers were donated to the Tokyo Medical University. The study comprised histological evaluation of paraffin-embedded bilateral neurovascular bundle specimens from the cadavers. Four slides of 3-cm thick were made every 1 cm in a plane perpendicular to the rectum towards the pelvic floor from the peritoneal reflection in bilateral neurovascular bundles in 22 cadavers. The number of nerves, the mean nerve area, and the mean nerve diameter were measured in each slide. Results The results were categorized into cases with high (group H) and low (group L) positions of the pelvis 1 cm above and 2 cm below the peritoneal reflection, respectively. There was no significant difference in the number of nerves between these groups. The nerve area and nerve diameter were significantly smaller in group L, and these characteristics were more marked in males. Conclusions Our results show that the nerves of the neurovascular bundle became smaller in the deep pelvis. This may cause these nerves to be more susceptible to injury, resulting in nerve damage in the deep pelvis that leads to postoperative dysfunction. Particularly, this type of nerve damage may be a cause of postoperative sexual dysfunction in males.