title: The challenges with NOTES retroperitoneal access in humans.
abstract: BACKGROUND
  Animal studies have supported natural orifice transluminal endoscopic surgery (NOTES) retroperitoneal access. NOTES also may offer unique retroperitoneal access in humans.
  
  
  OBJECTIVE
  This study was designed to assess the feasibility of endoscopic transgastric and transrectal retroperitoneal access in a cadaver model using prone and supine positioning, and to compare NOTES retroperitoneal examination with endoscopic ultrasound.
  
  
  METHODS
  Using a multidisciplinary team, this institutional review board-approved study evaluated transgastric and transrectal retroperitoneal examination in six cadavers (3 male, 3 female; body mass index range, 25-37 kg/m(2)). Endoscopic ultrasound retroperitoneal examination preceded NOTES access. Transgastric Access: Using a prototype dual channel endoscope, a needle knife gastrotomy was created on the preantral posterior gastric wall. Retroperitoneal examination specifically targeted the pancreas and surrounding structures with the cadaver supine and prone. Transrectal Access: Using the same endoscope, a posterior needle knife rectotomy distal to the upper valve of Houston provided extraluminal access. Retroperitoneal examination proceeded with the cadaver prone and supine. Open dissection followed procedure completion.
  
  
  RESULTS
  Access into the retroperitoneum succeeded at all sites. Significant challenges locating identifiable landmarks were faced-mostly transrectal and improved transgastric prone. All cadavers, despite body mass index or sex, had significant retroperitoneal adipose tissue limiting the endoscopic view.
  
  
  CONCLUSIONS
  Although porcine studies have highlighted successful NOTES retroperitoneal procedures, the abundant human retroperitoneal adipose tissue challenged the translation of porcine research to humans. Additionally, although access to the retroperitoneal space and dissection within this space were accomplished easily, the appearance of cadaveric tissue and lack of blood flow made confident landmark identification impossible. Further study should continue in this area and focus on confident landmark identification for directed dissection. In a cadaveric model, this would best be improved by pre-NOTES anatomic marking or active perfusion of vasculature along with consideration of direct entry into the retroperitoneum from a targeted intraperitoneal site in clinical patients.
authors.affiliation: Division of General Surgery, Department of Surgery, Mayo Clinic College of Medicine, Rochester, MN, USA.
authors.forename: E A
authors.initials: EA
authors.lastname: Moran
authors.forename: J
authors.initials: J
authors.lastname: Bingener
authors.forename: F
authors.initials: F
authors.lastname: Murad
authors.forename: M J
authors.initials: MJ
authors.lastname: Levy
authors.forename: C J
authors.initials: CJ
authors.lastname: Gostout
mesh_terms: D015992:Body Mass Index; D002102:Cadaver; D004210:Dissection; D019160:Endosonography; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000033:anatomy & histology; D008297:Male; D057605:Natural Orifice Endoscopic Surgery / Q000379:methods*; D009928:Organ Specificity; D010179:Pancreas / Q000033:anatomy & histology / Q000098:blood supply / Q000601:surgery; D016684:Prone Position; D012007:Rectum; D012187:Retroperitoneal Space / Q000033:anatomy & histology; D013045:Species Specificity; D013270:Stomach; D016683:Supine Position