title: Anatomical considerations for transanal minimal-invasive surgery: the caudal to cephalic approach.
abstract: OBJECTIVE
  Nerve-sparing surgery during laparoscopic rectal mobilization is still limited by anatomical constraints such as obesity, the narrowness of the male pelvis, an ultra low rectal cancer or all of these. The transanal approach for total mesorectal excision has overcome the shortcomings of limited access to the rectal 'no-man's land' close to the pelvic floor. The aim of this anatomical study was to define a roadmap of anatomical landmarks for the caudal to cephalic approach so as to standardize nerve-sparing rectal mobilization procedures.
  
  
  METHODS
  Macroscopic dissections of the pelvis in a caudal to cephalic direction were performed in eight alcohol-glycerol embalmed cadavers. A roadmap of anatomical landmarks was created at different levels of section to demonstrate the sites of nerve injury.
  
  
  RESULTS
  Extrinsic autonomic nerves to the urogenital organs and the internal sphincter muscle are closely adjacent to the lowest portion of the rectum above the pelvic diaphragm.
  
  
  CONCLUSIONS
  This anatomical guide for the pelvic surgeon should facilitate a safe and nerve-sparing dissection of the mesorectal plane with a meticulous overview of the lowest autonomic nerve fibres. New anatomical insights by a 'caudal to cephalic' approach to the 'no-man's land' should help overcome anatomical constraints of a narrow, obese and male pelvis during rectal mobilization procedures.
authors.affiliation: Department of Visceral, Transplant and Thoracic Surgery, Innsbruck Medical University, Innsbruck, Austria.|Department for General, Visceral and Transplantation Surgery, Charité Universitätsmedizin, Berlin, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Aigner
authors.affiliation: Department of Anatomy, Histology and Embryology, Division for Clinical and Functional Anatomy, Innsbruck Medical University, Innsbruck, Austria.
authors.forename: R
authors.initials: R
authors.lastname: Hörmann
authors.affiliation: Department of Anatomy, Histology and Embryology, Division for Clinical and Functional Anatomy, Innsbruck Medical University, Innsbruck, Austria.
authors.forename: H
authors.initials: H
authors.lastname: Fritsch
authors.affiliation: Department of Visceral, Transplant and Thoracic Surgery, Innsbruck Medical University, Innsbruck, Austria.|Department for General, Visceral and Transplantation Surgery, Charité Universitätsmedizin, Berlin, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Pratschke
authors.affiliation: Department of Abdominal Surgery, University Hospitals Gasthuisberg, Leuven, Belgium.
authors.forename: A
authors.initials: A
authors.lastname: D'Hoore
authors.affiliation: Department of Anatomy, Histology and Embryology, Division for Clinical and Functional Anatomy, Innsbruck Medical University, Innsbruck, Austria.
authors.forename: E
authors.identifier: http://orcid.org/0000-0001-6739-1198
authors.initials: E
authors.lastname: Brenner
authors.affiliation: National Centre for Bowel Research and Surgical Innovation, Centre for Digestive Diseases, Barts and the London School of Medicine and Dentistry, Queen Mary University London, London, UK.
authors.forename: N
authors.initials: N
authors.lastname: Williams
authors.affiliation: Department of Visceral, Transplant and Thoracic Surgery, Innsbruck Medical University, Innsbruck, Austria.|Department for General, Visceral and Transplantation Surgery, Charité Universitätsmedizin, Berlin, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Biebl
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D059925:Anatomic Landmarks / Q000033:anatomy & histology*; D001341:Autonomic Nervous System / Q000033:anatomy & histology*; D017776:Autonomic Pathways; D002102:Cadaver; D004210:Dissection / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017773:Pelvic Floor / Q000294:innervation* / Q000601:surgery; D012007:Rectum / Q000294:innervation* / Q000601:surgery; D000067368:Transanal Endoscopic Surgery / Q000379:methods*
keywords: Transanal; anatomy; mesorectum; neurovascular bundles; surgery