title: A study into external rectal anatomy: improving patient selection for radiotherapy for rectal cancer.
abstract: OBJECTIVE
  This study was designed to determine the distance from the anal verge to the anterior peritoneal reflection in vivo, thereby improving the selection of patients for preoperative radiotherapy.
  
  
  METHODS
  Measurement of the distance from the anal verge to the anterior peritoneal reflection, confluence of the taenia, and the origin of the sigmoid mesentery in 50 patients in the lithotomy position.
  
  
  RESULTS
  The mean distance from the anal verge to the anterior peritoneal reflection was 11.9 cm (men) and 10 cm (women). To the origin of the sigmoid mesentery, the measurements were 18.8 cm (men) and 19.1 cm (women) and to the confluence of the taenia coli, 20.3 cm (men) and 18.8 cm (women).
  
  
  CONCLUSIONS
  The distance from the anal verge to the origin of the sigmoid mesentery was approximately 19 cm in both men and women. Below this level tumors have limited mobility and should be amenable to radiotherapy.
authors.affiliation: Department of Surgery and Anaesthesia, School of Medicine and Health Sciences, University of Otago Wellington, Wellington, New Zealand.
authors.forename: Sameer
authors.initials: S
authors.lastname: Memon
authors.forename: John P
authors.initials: JP
authors.lastname: Keating
authors.forename: Hugh S
authors.initials: HS
authors.lastname: Cooke
authors.forename: Elizabeth R
authors.initials: ER
authors.lastname: Dennett
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000886:Anthropometry; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012004:Rectal Neoplasms / Q000532:radiotherapy*; D012007:Rectum / Q000033:anatomy & histology*