The Anatomy of the Perineal Body in Relation to Abdominoperineal Excision for Low Rectal Cancer

The perineal body (PB) is poorly understood. In abdominoperineal excision (APE), there is no natural dissection plane through the PB. Knowledge of the PB is essential to avoid straying in to incorrect planes leading to tumour perforation and unnecessary urogenital and anorectal injuries. This study describes the anatomy of the PB and the implications for APE. Six human adult cadaveric specimens (three males, three females) were obtained from the Leeds GIFT Research Tissue Programme. Paran-embedded mega-blocks containing the PB were produced and serially sectioned at 50 and 250 µm intervals. Sections were stained to reveal collagen and elastin, and with an antibody against α-smooth muscle actin. The PB is formed of a bromuscular mass, which was thicker and wider in female specimens compared to males, extending from the external anal sphincter to the rectogenital septum. Muscles from the urogenital diaphragm and anterior rectal wall anchored into the PB. The longitudinal muscle (LM) of the rectal muscularis propria extended in anterolateral directions and intertwined with the somatic pelvic oor muscles to create strong xation of the anorectum. The LM plays a dominant role in the formation of the PB. Surgeons should be aware of the complex course of the LM through the PB to prevent injuries to the urogenital organs and perforation of the anterior rectal wall. The perineal phase of an APE starts with excellent exposure followed by proper tension on the PB to allow safe dissection through the densely-packed bromuscular mass.