Exploration Of Membrane Anatomy In Colorectal Cancer Surgery

Part Ⅰ Anatomical Observation of the Right Retroperitoneal Fascia and its Clinical Significance in Complete Mesocolic Excision for Right Colon CancerObjective:To investigate the anatomic characteristics of the right retroperitoneal fascia and its surgical implementation while performing complete mesocolic excision(CME)for right colon cancer.Methods:A descriptive study was carried out.(1)Clinicopathological data and surgical videos of 17 non-consecutive patients undergoing laparoscopic right hemicolectomy(extended right hemicolectomy)with CME for right colon cancer in our department between January 2020 and October 2020 were retrospectively collected.The construction of right retroperitoneal fascia was observed from caudal dorsal direction and caudal ventral direction.(2)Three postoperative specimens from 3 cases undergoing laparoscopic right hemicolectomy with CME for right colon cancer in June 2020 were prospectively included to observe anatomy and examine histology.(3)Five abdominal cadaver specimens were enrolled.Anatomical observation and histological studies were performed from the cranial approach and the caudal dorsal approach.Masson staining was used.Results:(1)Surgical video observation:The typical structure of right retroperitoneal fascia could be observed in all the 17 patients.The fascia was a rigid barrier between the posterior space of the ascending colon and the anterior pancreaticoduodenal space behind the transverse colon.The right retroperitoneal fascia should be sharply cut to communicate between the two spaces to avoid entering the right mesocolon by mistake.The severed ventral stump of the right retroperitoneal fascia ran along the dorsal side of the right hemicolon to the lateral side,and the dorsal stump covered the level of the duodenum caudally,and continued to move downward,covering the surface of Gerota’s fascia.(2)Observation of surgical specimens:The dorsal side of the right mesocolon was smooth and intact,which could be anchored in the corresponding area of the lateral edge of the duodenum.The ventral stump of the right retroperitoneal fascia could be seen,which attached to the dorsal side of the right mesocolon semi-circularly.Masson staining observation:The ventral stump of the right retroperitoneal fascia ran cephalad,fused with the dorsal side of the right mesocolon tightly and curled.The caudal side of confluence and the dorsal side of the right mesocolon presented a bilobed structure.(3)Anatomy of cadaveric specimens:The right retroperitoneal fascia was a thin fascia structure,which was a rigid barrier between the anterior pancreaticoduodenal space behind the transverse colon and the posterior space of the ascending colon.Histological examination showed that the ventral stump of the right retroperitoneal fascia fused with the dorsal side of the right mesocolon by the cephalic side,and the dorsal side of the right hemi-mesocolon on the fusion level by caudal side gradually separated into a double-layer loose fascial structure.The dorsal stump of the right retroperitoneal fascia covered the surface of the duodenum level,moved on from the ventral side to the surface of the prerenal fascia,and continued to the caudal side.Conclusions:The right retroperitoneal fascia is a rigid barrier between the anterior pancreaticoduodenal space behind the transverse colon and the posterior space of the ascending colon.During the operation,this fascia should be identified and cut to penetrate the anterior pancreaticoduodenal space behind the transverse colon and the posterior ascending colon space,which helps to ensure the integrity of the dorsal side of the right hemi-mesocolon.Part Ⅱ Anatomical Observation and Clinical Significance of the Left Parietal Peritoneum for Left Retro-mesocolic Space DissectionObjective:To investigate the anatomic characteristics of the left parietal peritoneum and its surgical implementation while dissecting in left retro-mesocolic space.Methods:First phase:between January 2018 and December 2018,surgical videos of 35 patients who underwent laparoscopic radical resection of colorectal cancer were reviewed.Second phase:the left parietal peritoneum was observed in 5 cadaveric models though gross and histopathological examination with Masson staining.Third phase:retrospective observation of 5 specimens and prospective observation of 4 retrieved specimens after laparoscopic radical resection of colorectal cancer.Results:(1)Intraoperative observation of "staggered layer phenomenon" and left parietal peritoneum was possible in 77.1%(27/35)of patients when the left retro-mesocolic space was separated from the lateral and central approaches respectively.The left parietal peritoneum acted as a rigid fascia barrier between the lateral and central approaches,which was a translucent dense connective tissue fascia.(2)Specimens after operation:observation of the dorsal side of the left mesocolon showed the dorsal edge of the left parietal peritoneum.The lateral side of the broken edge was the exposed dorsal lobe of the left half mesocolon,which moved downward to continue with the proper fascia of the rectum.(3)Abdominal cadaveric specimens:the left retro-mesocolic space was separated through lateral approach and central approach respectively,and the rigid fascia barrier was encountered.Cross-section view showed that the left parietal peritoneum could be further detached from the dorsal lobe of the left mesocolon from the outside,but could not be further dissected from the inside out.(4)Three undivided regions of cadaveric specimens were selected for histological verification:IMA root region:there was no obvious fascia structure in the root region of IMA,Outside the root region of IMA,the left trunk of inferior mesenteric plexus was observed penetrating Gerota fascia;the middle region:there were 4 layers of fascias in this region,including the ventral lobe of the left mesocolon,the dorsal lobe of the left mesocolon,left parietal peritoneum and Gerota’s fascia,small vessels were observed between the dorsal lobe of the left mesocolon and the left parietal peritoneum;lateral region:renal tissue and renal fascia were observed;aside from them,three layers of fascia structures were observed,including the dorsal lobe of the left mesocolon,left parietal peritoneum,and Gerota’s fascia.Conclusion:The left parietal peritoneum is the anatomical basis of the "staggered layer phenomenon" between the lateral or central approaches during the separation of left retro-mesocolic space.The small blood vessels in the dissection plane were the anatomic basis of intraoperative microbleeds,which need coagulation.The central part of Gerota fascia was penetrated by the branches of the inferior mesenteric plexus,which resulted in a relatively dense surgical plane.Thus,during the dissection through the central approach,it is easy to come into wrong surgical plane by deeper.Part Ⅲ Anatomical Observation and Clinical Significance of An Intrasheath Separation Technique for Nerve-Sparing High Ligation of the Inferior Mesenteric Artery in Colorectal Cancer SurgeryObjective:To investigate the relationship between the left trunk of the inferior mesenteric plexus(IMP)and the vascular sheath of the inferior mesenteric artery(IMA)and to explore anatomical evidence for autonomic nerve preservation during high ligation of the IMA in colorectal cancer surgery.Methods:We evaluated the relationship in 23 consecutive cases of laparoscopic or robotic colorectal surgery with high ligation of the IMA at our institute.Anatomical dissection was performed on 5 formalin-fixed abdominal specimens.A novel anatomical evidence-based operative technique was proposed.Results:Anatomical observation showed that the left trunk of the IMP was closely connected with the IMA and was involved in the composition of the vascular sheath.Based on anatomical evidence,we present a novel operative technique for nerve-sparing high ligation of the IMA that was successfully performed in 45 colorectal cancer surgeries with no intraoperative complications and satisfactory postoperative urogenital functional outcomes.Conclusion:The left trunk of the IMP is involved in the composition of the IMA vascular sheath.This novel anatomical evidence-based operative technique for nerve-sparing high ligation of the IMA is technically safe and feasible.Part Ⅳ Anatomical Observation and Clinical Significance of Denonvilliers’ Fascia for Anterior Surgical Plane in Total Mesorectal ExcisionObjective:To investigate the course of Denonvilliers’ fascia(DVF)and its relationship with neurovascular bundles(NVB)to identify the safe anterior surgical plane to reduce the damage of pelvic autonomic nerve in total mesorectal excision(TME).Methods:The course of Denonvilliers’ fascia and its relationship with neurovascular bundles(NVB)were evaluated through anatomical dissection of 3 formalin-fixed pelvic cadaver specimens.Sixteen postoperative specimens from male patients with low rectal cancer who underwent TME surgery in our department between September and December 2019 were continuously collected for histological analysis.TME with partial preservation of DVF was performed in 176 male patients with low rectal cancer and its oncological and functional results were assessed.Results:1)Cadaveric specimens:the head of DVF originated the peritoneal reflection,and the caudal side of DVF fused with the prostatic capsule near the base of the seminal vesicles.The connecting branches of the bilateral NVB could be found above the caudal attachment edge.2)Histology of the postoperative specimens:the head of DVF of all(16/16)patients originated above the lowest point of peritoneal reflection,and the fascia propria of the rectum of 81.3%(13/16)patients also started above the peritoneal reflection and was close to DVF,while the fascia propria of the rectum of only 18.7%(3/16)patients emanating from the lowest point of peritoneal reflection.Based on anatomical evidence,we confirmed that TME with partial preservation of DVF which incised 1.0 cm above the peritoneal reflection helps to maintain the integrity of the anterior rectal mesorectum and it was successfully performed in 176 male patients with no intraoperative complications.The circumferential resection margin was positive in 1 patient.The incidence of erectile dysfunction(5-item version of the International Erectile Function Index Questionnaire score[IIEF-5]≤11)and urinary dysfunction(International Prostate Symptom Score[IPSS]≥8)at postoperative month 12 were 7.6%(7 of 92 patients with normal preoperative erectile function)and 2.0%(3 of 147 patients with normal preoperative urinary function),respectively.At a median follow-up of 46 months,the local recurrence rate and cumulative 3-year recurrence-free survival rate were 4.0%and 80.4%,respectively.Conclusion:The head of DVF originated above the lowest of the peritoneal reflection,and most of the fascia propria of the rectum also starts above the peritoneal reflection.TME with partial preservation of DVF is oncologically and functionally safe and feasible.Part Ⅴ Anatomical Observation and Clinical Significance of the Prostatic Part of Neurovascular Bundle for Total Mesorectal ExcisionObjective:To investigate the anatomic characteristics of the prostatic part of NVB in TME.Methods:A descriptive cohort study was carried out.A total of 38 male patients with rectal cancer who underwent TME in our department between November 2013 and March 2015 were included.A total of 4 hemipelvis were examined.The following outcomes were observed:1)the clinical significance of bleeding of the prostatic part of NVB:surgical videos were reviewed and the incidence of bleeding was recorded.The urogenital function was assessed using the International Prostate Symptom Score(IPSS)and International Index of Erectile Function(IIEF)score.The correlation between prostatic part bleeding and postoperative urogenital function was evaluated.2)anatomical observation:the vessels,nerve fibers,as well as their surrounding fatty tissue from the prostatic part were treated as a whole,namely,the fat pad of the prostatic part.The anatomical architecture of the prostatic part in the surgical videos was reviewed and interpreted with the cadaveric findings.Results:1)the clinical significance of bleeding of the prostatic part of NVB:the overall incidence of bleeding was 55.3%(21/38).The urinary function significantly decreased in patients in the bleeding group compared to non-bleeding group according to IPSS score after the 3rd month of the surgery(6.8±6.0 vs 1.5±1.1,P=0.031).There was no difference regarding the IPSS score between the two groups after the 6th month and 1 year of the surgery(P>0.05).With a total of 23 patients with normal preoperative sexual activity(IIEF-5≥18)included,87.5%(7/8)of patients in the non-bleeding group can expect to return to their preoperative baseline sexual activity,meanwhile IIEF-5 decreased by less than 3 points at 1 year after operation,this incidence was significantly higher than that of only 40%(6/15)in the bleeding group(P=0.029).2)anatomical observation:for cadaveric observation,the prostatic part of NVB was located in the narrow triangular space composed of anterolateral walls of the rectum,the posterolateral surface of the prostate and the medial surface of the levator ani musculature.The tiny vascular branches and nerve fibers from the prostatic part were hard to identify.The cavernosal nerves cannot reliably be distinguished from the neural supply to the prostate,rectum and levator ani.In the cross-section of levels of prostatic base and mid-prostate in cadaveric hemipelvis specimens,the boundary of the prostatic part fat pad was partly overlapped and merged with the boundary of the mesorectum.Intraoperative observation showed that the areas of overlap referred to the rectal branches from the prostatic part piercing the fascia propria of the rectum to supply the mesorectum,which carried the largest tension and high risk of bleeding during circumferential dissection toward the perirectal plane.The ultrasonic scalpel was required to pre-coagulate the rectal branches at the point close to the fascia propria of the rectum to prevent bleeding.In the cross-section of the prostatic apex level,the prostatic part approached ventrally and its boundary was away from the boundary of the mesorectum.Conclusion:NVB prostatic part injury is one of the causes of urogenital dysfunction after TME.The nerve fibers from the prostatic part were tiny,and its functional zones cannot be distinguished during operation.Therein,the fat pad of the prostatic part should be protected as a whole.Understanding the morphology of the fat pad of the prostatic part provides invaluable surgical guidance to dissect this critical area.When dissecting around the anterolateral rectal wall,appropriate anti-traction tension should be maintained and the rectal branches from the prostatic part should be coagulated with an ultrasonic scalpel to prevent bleeding.