Anatomical study on the relationship between the middle rectal artery and the mesorectum        WANG Qing-ming*, FU Chuan-gang, MENG Rong-gui，et al. *Department of Colorectal Surgery, Changhai Hospital, the Second Military Medical University, Shanghai 200433, China
Corresponding author: FU Chuan-gang, E-mail: fugang416@126.com
Abstract    Objective    To observe the anatomical relationship between the middle rectal artery and the mesorectum. Methods    10 pelvises (7 males and 3 females) harvested from cadavers were studied by dissection. Results    The middle rectal artery was present in 9 cases, bilaterally (3 cases) or unilaterally (6 cases), originating from the internal pudendal (10/12，83.33%). 6 middle rectal arteries just run along the surface of the levator ani, and join into the rectum through the muscular at the junction between the levator ani muscle and rectum. Another 5 vessels penetrate the medial visceral fascia of the vesicohypogastric fascia into the mesorectum. Conclusion    The middle rectal artery is a more constant present vessel for the rectal blood supply, unilateral ones are more than the bilateral ones. There are two contacting forms between the middle rectal artery and the rectum: One is that the vessel runs into the rectum at the junction between the rectum and the levator ani muscle , another is  that the vessel runs into the mesorectum across the fasica. Crossing the mesorectum may be taken as the judge basis for unilateral or bilateral middle rectal artery in pelvis. The middle rectal artery not entering the mesorectum will not be damaged  during rectum related operation.