Anatomical classification of middle rectal arteries regarding detailed vasculature patterns

This study aimed to clarify the anatomy of middle rectal artery and pelvic vasculature patterns, and to provide schematic information in a manner applicable to the total mesorectal excision. Forty sides of pelvis from 20 formalin-embalmed cadavers (10 male, 10 female) were dissected, and all the pelvic vasculatures from the internal iliac artery were investigated, focusing on the middle rectal artery. Middle rectal arteries were classified into major types depending on their vascular origins. Each type was subdivided into minor types according to variability of the pelvic vasculature. A middle rectal artery was identified in 18 out of 20 cadavers, and in 25 out of 40 pelvic sides. In most cases, the middle rectal artery originated from the internal pudendal artery or inferior gluteal artery. These two arteries arose directly from the anterior trunk of the internal iliac artery or were bifurcated from the gluteal-pudendal trunk. In rare cases, these arteries arose from the posterior trunk of the internal iliac artery. The other origins of the middle rectal artery included the gluteal pudendal trunk, inferior vesical artery, internal iliac artery, obturator artery, and the prostatic artery, and the pelvic vasculatures in these cases also presented variability. The detailed anatomical findings related to the middle rectal artery and pelvic vasculatures are noteworthy for their improved clinical applicability.