title: Transrectal ultrasound and the diagnosis of rectovaginal endometriosis: a prospective observational study.
abstract: BACKGROUND
  Rectovaginal endometriosis is a severe form of pelvic endometriosis in which pharmacological treatment is relatively ineffective (Vercellini et al., Fertil Steril. 2005;84:1375-87). Laparoscopic surgical treatment is effective, but has the potential risks of bowel perforation and colostomy formation (Darai et al., Am J Obstet Gynecol. 2005;192:394-400). Transrectal ultrasound scanning can be applied as a preoperative tool to predict the presence of rectovaginal endometriosis and bowel wall involvement (Abrao et al., J Am Assoc Gynecol Laparosc. 2004;11:50-4).
  
  
  METHODS
  Thirty-two women underwent transrectal ultrasound followed by therapeutic laparoscopy. Likelihood ratios and post-test prevalences were calculated with Fagan's normogram. This was then extrapolated with the aid of a mathematical model to a low-risk population.
  
  
  RESULTS
  A positive likelihood ratio was found to be 10.89 (95% confidence ratio (CI): 1.62-73.15) and a negative likelihood ratio was found to be 0.24 (95% CI: 0.1-0.57). The pre-test prevalence of rectovaginal endometriosis was 56%. The positive post-test prevalence probability was 93%, and the negative post-test prevalence probability was 23%.
  
  
  CONCLUSIONS
  Preoperative transrectal ultrasound scanning for rectovaginal endometriosis is an extremely accurate predictive test, and strongly predicts the need for extensive laparoscopic dissection and potential bowel resection.
authors.affiliation: Department of Obstetrics and Gynaecology, University Hospital of Wales, Heath Park, Cardiff, UK. assw21@dsl.pipex.com
authors.forename: Anthony
authors.initials: A
authors.lastname: Griffiths
authors.forename: Roxani
authors.initials: R
authors.lastname: Koutsouridou
authors.forename: Sue
authors.initials: S
authors.lastname: Vaughan
authors.forename: Richard
authors.initials: R
authors.lastname: Penketh
authors.forename: S Ashley
authors.initials: SA
authors.lastname: Roberts
authors.forename: Jared
authors.initials: J
authors.lastname: Torkington
mesh_terms: D004715:Endometriosis / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D016013:Likelihood Functions; D011446:Prospective Studies; D012002:Rectal Diseases / Q000000981:diagnostic imaging*; D012007:Rectum / Q000000981:diagnostic imaging; D012680:Sensitivity and Specificity; D014463:Ultrasonography; D014623:Vaginal Diseases / Q000000981:diagnostic imaging*