title: The anthropometric definition of the rectum is highly variable.
abstract: OBJECTIVE
  The precise definition of the rectum is essential for localizing colorectal pathology, yet current definitions are nebulous. The objective of this study is to determine the anthropometric definition of common pelvic landmarks in relation to patient characteristics.
  
  
  METHODS
  Seventy-one patients underwent open proctectomy with intra-operative measurements from the anal verge to various pelvic landmarks, and patient characteristics were evaluated. Analyses were performed using Spearman correlation and Wilcoxon rank sum.
  
  
  RESULTS
  The mean landmark distance was dentate line = 1.7 cm (range 0.8-4.0 cm), puborectalis muscle = 4.2 cm (range 2.0-8.0 cm), anterior peritoneal reflection = 13.2 cm (range 8.5-21.0 cm), sacral promontory = 17.9 cm (range 13.0-26.0 cm), and confluence of the taenia = 25.5 cm (range 16.0-44.0 cm). Men had longer mean distances to the dentate line (p = 0.0003), puborectalis muscle (p = 0.03), and anterior peritoneal reflection (p = 0.02). Patient weight significantly correlated with distance to all landmarks except for the confluence of the taenia, which did not correlate with any patient factor.
  
  
  CONCLUSIONS
  The location of common pelvic landmarks is highly variable. The use of predefined absolute measurements from the anal verge to localize rectal pathology is inaccurate and fails to account for patient variability.
authors.affiliation: Department of Surgery, Northwestern University, Chicago, IL, USA.
authors.forename: Molly A
authors.initials: MA
authors.lastname: Wasserman
authors.affiliation: Department of Surgery, Northwestern University, Chicago, IL, USA. mmcgee1@nm.org.|Division of Gastrointestinal and Oncologic Surgery, Feinberg School of Medicine, Northwestern University, 676 N. St. Clair, Suite 650, Chicago, IL, 60611, USA. mmcgee1@nm.org.
authors.forename: Michael F
authors.initials: MF
authors.lastname: McGee
authors.affiliation: Department of Surgery, Northwestern University, Chicago, IL, USA.|Department of Preventative Medicine, Northwestern University, Chicago, IL, USA.
authors.forename: Irene B
authors.initials: IB
authors.lastname: Helenowski
authors.affiliation: Department of Surgery, Northwestern University, Chicago, IL, USA.|Division of Gastrointestinal and Oncologic Surgery, Feinberg School of Medicine, Northwestern University, 676 N. St. Clair, Suite 650, Chicago, IL, 60611, USA.
authors.forename: Amy L
authors.initials: AL
authors.lastname: Halverson
authors.affiliation: Department of Surgery, Northwestern University, Chicago, IL, USA.|Division of Gastrointestinal and Oncologic Surgery, Feinberg School of Medicine, Northwestern University, 676 N. St. Clair, Suite 650, Chicago, IL, 60611, USA.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Boller
authors.affiliation: Department of Surgery, Northwestern University, Chicago, IL, USA.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Stryker
mesh_terms: D000886:Anthropometry; D001827:Body Height; D015992:Body Mass Index; D001835:Body Weight; D003108:Colonic Diseases / Q000601:surgery; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010388:Pelvis / Q000033:anatomy & histology; D012002:Rectal Diseases / Q000601:surgery; D012007:Rectum / Q000033:anatomy & histology* / Q000601:surgery; D012189:Retrospective Studies; D012737:Sex Factors
keywords: Anatomy; Cancer; Colon; Endoscopy; Rectum