Effects of age and gender on three-dimensional endoanal ultrasonography measurements: development of normal ranges
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- Knowles, A.M., Knowles, C.H., Scott, S.M. et al. Tech Coloproctol (2008) 12: 323. doi:10.1007/s10151-008-0443-5
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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.
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.
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.
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.