title: Effects of age and gender on three-dimensional endoanal ultrasonography measurements: development of normal ranges.
abstract: BACKGROUND
  Faecal incontinence is a common and morbid disorder that is often related to anal sphincter dysfunction. High-frequency, three-dimensional (3-D) endoanal ultrasonography (EAUS) allows greater spatial resolution and longitudinal appreciation of the anal canal than conventional 2-D assessment. A robust normal range of values allowing for age and sex is required for subsequent disease comparison.
  
  
  METHODS
  A group of 30 healthy male (n=12) and female (n=18) volunteers (median age, 49 years; range, 31-63 years) underwent 3-D EAUS using a high-frequency 10-MHz transducer. A reconstructed data cube was interrogated to measure anal canal structures in 2-D at high, middle and low levels, and in 3-D for longitudinal measurements.
  
  
  RESULTS
  Men had a significantly longer 3-D external anal sphincter (EAS) and internal anal sphincter (IAS) than women, especially the anterior EAS (mean in men 2.5 cm, mean in women 1.6 cm, p<0.0001). There were no significant differences between the sexes for anal canal length or by 2-D scanning for the thickness of the EAS and IAS. No significant differences were observed between parous and nulliparous women. Age had no significant effect on 3-D length measurements, but 2-D EAUS measurements of the thickness of both the IAS and EAS increased with age significantly (mid canal, p=0.004). On these bases, normal ranges were generated.
  
  
  CONCLUSIONS
  Sphincter measurements, enabled by 3-D reconstruction, vary with age and sex. A normal range incorporating these variations has been produced for future data comparison in disease states.
authors.affiliation: Centre for Academic Surgery Institute of Cellular and Molecular Science Barts and the London, Queen Mary's School of Medicine and Dentistry Whitechapel, London, UK.
authors.forename: A M
authors.initials: AM
authors.lastname: Knowles
authors.forename: C H
authors.initials: CH
authors.lastname: Knowles
authors.forename: S M
authors.initials: SM
authors.lastname: Scott
authors.forename: P J
authors.initials: PJ
authors.lastname: Lunniss
mesh_terms: D000328:Adult; D000367:Age Factors; D001003:Anal Canal / Q000000981:diagnostic imaging*; D000704:Analysis of Variance; D019160:Endosonography / Q000379:methods*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012737:Sex Factors; D018709:Statistics, Nonparametric