The Histopathological And Anatomical Basis Of Pull-through Conformal Resection In Ultra Low Rectal Cancer

[Objectives] 1.To measure the distance of intramural lateral spread in low rectal cancer and analyze its risk factors in order to figure out the safe lateral resection margin of PTCR.2.To investigate the influence of neoadjuvant chemoradiotherapy on anal sphincter and evaluate whether the patients who received neoadjuvant chemoradiotherapy are fit for PTCR.3.To observe the space in front of low rectum on cadaver and provide optimal surgical approach for PTCR.[Methods] 1.A total of 83 patients with rectal cancer who received low anterior resection or abdominal-perineal resection in Changhai hospital from December 2015 to March 2016 were enrolled.The distance of intramural lateral spread were measured in the specimens and the risk factors were analyzed.2.From November 2014 to January 2016,a total of 34 specimens in patients who received abdominal-perineal resection in Changhai hospital were divided into two groups based on whether they received neoadjuvant chemoradiotherapy.The physical parameter of internal anal sphincter were measured,the whole-mount sections of the anal sphincter with hematoxylin and eosin(H-E)staining were observed and the external anal sphincter were dissected for observation by transmission electron microscopy.3.Three cadavers provided by the Department of anatomy,the Second Military Medical University from December 2014 to December 2015 were autopsied in order to observe the space in front of low rectum and the structures around.[Results] 1.The overall proportion of intramural lateral spread was 71.08%.The proportion of each direction were 34.94%,26.51%,32.53% and 37.35% respectively.The median distance of lateral spread in each direction was all 0mm and the quartile range were 1mm,0.5mm,0.55 mm and 1mm respectively.The single and multi factor analysis indicated that gender(P=0.0218,OR=0.296,95%CI: 0.100-0.877)and T stage(P=0.0055,OR=3.455,95%CI: 1.439-8.294)were the risk factors of intramural lateral spread.2.The physical parameters of internal anal sphincter were not significant different between neoadjuvant chemoradiotherapy group(length: 22.68±3.56mm;thickness: 5.39±0.74)and control group(length: 21.28±3.62mm;thickness: 5.35±1.12).The ultrastructure of external anal sphincter in neoadjuvant chemoradiotherapy group were severely destroyed,while it did not occurred in control group.3.The Denonvilliers' fascia was a single layer behind the prostate and seminal vesicle.Left/right communicating branches of bilateral pelvic plexuses and vessels run immediately in front of Denonvilliers' fascia.The space between Denonvilliers' fascia and the fascia propria of the rectum was filled with loose connective tissue.[Conclusions] 1.The intramural lateral spread did exist in low rectal cancer,but the distance of lateral spread beyond 5mm was rare.Gender and T stage were the risk factors of lateral spread.2.The neoadjuvant chemoradiotherapy did not change the gross morphology of internal anal sphincter,but it can destroy the ultrastructure of external anal sphincter which may damage the anal function.3.In consideration of oncological safty and nerve-preserving,the plane of total mesorectal excision in front of rectum should be conducted in the space between Denonvilliers' fascia and the fascia propria of the rectum.