title: Exoanal ultrasound of the anal sphincter: normal anatomy and sphincter defects.
abstract: OBJECTIVE
  To describe the sonographic appearance of normal anal sphincter anatomy and sphincter defects evaluated with a conventional 5 MHz convex transducer placed on the perineum.
  
  
  METHODS
  Prospective, single-blind study.
  
  
  METHODS
  Department of Obstetrics and Gynecology, University of Michigan Medical Center, USA.
  
  
  METHODS
  Twenty-five women with symptoms of faecal incontinence, 11 asymptomatic nulliparous women, and 32 asymptomatic parous women.
  
  
  METHODS
  A convex scanner was placed on the perineum with the woman in lithotomy position. Images were taken at three levels of the sphincter canal. Pictures were evaluated by two examiners who were blinded to the case history of the women and to the results of each other for the presence or absence of sphincter defects.
  
  
  METHODS
  Description of anal sphincter appearance on endoanal ultrasound. Reproducibility of the evaluation of sphincter defects.
  
  
  RESULTS
  The internal anal sphincter is visible as a hypoechoic circle; the external anal sphincter shows a hyperechoic pattern. Proximally the sling of the puborectalis muscle is visible. Sphincter defects were detected in 20 women. In all five women who subsequently underwent surgery, the presence and location of the defect was confirmed at the time of surgery. Examiners were in agreement 100% of the time on the presence or absence of internal defects. They disagreed in one patient on the presence of an external defect.
  
  
  CONCLUSIONS
  Exoanal ultrasound provides information on normal anatomy and on defects of the anal sphincter.
authors.affiliation: Department of Obstetrics and Gynecology, University of Michigan Medical Center, Ann Arbor, USA.
authors.forename: U M
authors.initials: UM
authors.lastname: Peschers
authors.forename: J O
authors.initials: JO
authors.lastname: DeLancey
authors.forename: G N
authors.initials: GN
authors.lastname: Schaer
authors.forename: B
authors.initials: B
authors.lastname: Schuessler
mesh_terms: D000328:Adult; D001003:Anal Canal / Q000000981:diagnostic imaging*; D001004:Anus Diseases / Q000000981:diagnostic imaging*; D005242:Fecal Incontinence / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008875:Middle Aged; D015588:Observer Variation; D011446:Prospective Studies; D016037:Single-Blind Method; D014463:Ultrasonography