Applied Anatomical Study Of The Layers Associated With Lateral Lymph Node Dissection In Rectal Cancer

Objective: In this study,the anatomical layers of lateral lymph node dissection of rectal cancer was studied by dissecting human pelvic specimens.To improve the surgeon’s anatomical understanding of lateral lymph node dissection of rectal cancer and reduce the occurrence of surgical complications and improve the quality of patients’ life after surgery.Methods: Anatomical experiments were performed on 10 human pelvic specimens(Provided by the Human Anatomy Experimental Center of Xi’an Medical University and the Anatomy Teaching and Research Section of the Medical Department of Xi’an Jiaotong University),including 6 male specimens and 4 female specimens.Treatment of specimens:(1)Treatment of intact corpses: take a supine position,transect with a hacksaw at the upper edge of the 4th lumbar vertebra and the upper 1/3 of the bilateral femurs,pay attention to protect the pelvic tissue from damage and obtain a complete pelvic specimen.(2)Treatment of pelvic specimens: Cut along the median sagittal position with a hacksaw to obtain 20 half-pelvic specimens.The sagittal half-pelvic dissection approach was used to finely dissect the lateral layers,blood vessels and nerves of the rectum.During the dissection,important structures were stained with acrylic paint and photographed and recorded.Results:1.The layers around the rectum are the rectum and its mesentery,urogenital stratum,pelvic visceral vascular layer and obturator vascular layer in order from inside to outside.2.Urogenital Stratum: UGS from the inside to the outside contains the hypogastric nerve,ureter,vas deferens into the pelvic cavity.UGS was distributed in the posterior direction of rectum and its mesentery,and fused with the rectum proper fascia at the 4th sacral level.The space between the visceral layer of UGF and the proper fascia of rectum is the posterior space of rectum.The presacral space is formed between the UGF wall layer and the anterior sacral fascia.UGS is distributed outside the rectum and its mesentery on the lateral surface of the rectum,bladder,and seminal vesicles(vaginae).The visceral layer of UGF terminates in the caudal side of the seminal vesicle and thenforms the fascia around the rectum.The UGF wall layer merges with the intrinsic fascia of the bladder.The pelvic visceral nerves formed by the sacral 2,3,and 4 nerves enter the UGS at the level of the 4th sacral vertebra and participate in the formation of the inferior hypogastric nerve plexus.3.Pelvic Visceral Vascular Layer: The anterior sacral fascia is distributed laterally and covers the surface of the internal iliac blood vessels,sacral nerve plexus and its branches,and continues with the anterior transverse abdominal fascia.The structure formed by the anterior sacral fascia covering the vascular branches of the pelvic organs such as the bladder and prostate is called the pelvic visceral vascular layer.The main arteries present at this level are: umbilical artery,superior bladder artery,inferior bladder artery,and prostate artery(Uterine artery).The pelvic visceral vascular layer and UGS are fused to the inherent fascia of the pelvic organ.The vascular branches in the pelvic visceral vascular layer and the nerve branches of the inferior hypogastric nerve plexus in the UGS together reach the corresponding pelvic organ.4.Obturator Vascular Layer: The anterior sacral fascia is coated on the surface of obturator vessels and obturator nerves to form the obturator vessel layer.The fascia on the surface of the pelvic visceral vascular layer and the fascia on the surface of the obturator vascular layer are continuous with each other.The obturator vascular layer comes from the pelvic visceral vascular layer.Conclusion:1.The UGS is an independent functional layer containing tissues and organs of urogenital function.2.The UGS and the pelvic visceral vascular layer fuse in the intrinsic fascia of the pelvic organs,forming the common mesangial structure of the pelvic organs.3.There are three surgical levels in lateral lymph node dissection of rectal cancer,which are the inner urogenital stratum,the middle pelvic visceral vascular layer and the outer obturator fascia layer.The urogenital stratum is the "nerve layer" in LLND,which is a watershed that protects the nerves.Protecting the urogenital layer during surgery can protect the pelvic plexus.The pelvic visceral vascular layer is the area of lymph node dissection in No.263,and the front boundary of the dissection is the fusion of the urogenital stratum and the pelvic visceral vascular layer.The obturator fascial layer is the range of lymph node dissection in No.283,during the operation,we should pay attention to the variation of obturator artery and the protection of obturator nerve.