title: US identification of the anal sphincter complex and levator ani muscle in neonates: infracoccygeal approach.
abstract: OBJECTIVE
  To identify the anal sphincter complex and levator ani muscle at transperineal ultrasonography (US) with the infracoccygeal approach.
  
  
  METHODS
  Infracoccygeal US was performed with a 7-MHz linear-array transducer in 40 healthy neonates. The babies were placed in the supine position, and both legs were drawn up to the chest. The buttocks were accordingly lifted up. The approach site was just inferior to the coccyx and posterior to the anus. Scanning was performed to obtain transverse images of the anorectal area. The thickness of the anal sphincter complex and the puborectalis muscle were measured.
  
  
  RESULTS
  Infracoccygeal US revealed the internal anal sphincter (IAS), the external anal sphincter (EAS), and the puborectalis muscle in all babies. The IAS and EAS were depicted as inner and outer hypoechoic ringlike structures, respectively. A round, hyperechoic space (intersphincteral space) was present between the hypoechoic IAS and EAS. The puborectalis muscle was identified as a U-shaped hypoechoic structure. The bulbocavernosus and ischiocavernous muscles were also identified. Mean thicknesses were as follows: IAS, 1.3 mm +/- 0.3 (SD) (range, 0.8-1.9 mm); EAS, 1.6 mm +/- 0.3 (range, 1.2-2.3 mm); and puborectalis muscle, 1.1 mm +/- 0.3 (range, 0.6-1.9 mm).
  
  
  CONCLUSIONS
  Infracoccygeal transperineal US is an excellent diagnostic modality for demonstrating the anal sphincter complex and levator ani muscle in neonates.
authors.affiliation: Departments of Radiology, Eulji University School of Medicine, Taejon 301-726, South Korea. tihan@emc.eulji.ac.kr
authors.forename: T I
authors.initials: TI
authors.lastname: Han
authors.forename: I O
authors.initials: IO
authors.lastname: Kim
authors.forename: W S
authors.initials: WS
authors.lastname: Kim
authors.forename: J Y
authors.initials: JY
authors.lastname: Chung
authors.forename: K
authors.initials: K
authors.lastname: Choeh
authors.forename: M K
authors.initials: MK
authors.lastname: Song
authors.forename: Y G
authors.initials: YG
authors.lastname: Yoon
mesh_terms: D001003:Anal Canal / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D009132:Muscles / Q000000981:diagnostic imaging*; D012016:Reference Values; D014463:Ultrasonography