Normal Values of Anal Sphincter Biometry by 4-Dimensional Translabial Ultrasound: A Retrospective Study of Pregnant Women in Their Third Trimester

Julie Magpoc Mendoza, Friyan Turel Fatakia, Ixora Kamisan Atan, Hans Peter Dietz

Research output: Contribution to journalArticle

Abstract

OBJECTIVES: Exoanal 4-dimensional translabial ultrasound (TLUS) is increasingly used to image the anal sphincter. The aim of this study was to define the limits of normality for assessment of external and internal anal sphincters with TLUS. METHODS: This study was a retrospective analysis using data sets of nulliparous women seen antenatally. All women had a 4-dimensional TLUS examination at a mean gestational age ± SD of 36 ± 0.7 (range, 32.9-37.3) weeks. Anal sphincter biometry, including external anal sphincter (EAS) length and thickness, EAS proximal rotational asymmetry, and internal anal sphincter thickness, was assessed blinded against other data. RESULTS: A test-retest series showed good repeatability (intraclass correlation coefficients, 0.619-0.849) of all parameters. The mean age of the women (n = 111) was 30.9 (range, 18.8-40.5) years. None reported anal incontinence. On tomographic imaging, none showed anal sphincter defects. The mean EAS length was 17.5 (range, 8.4-34.8) mm, being shorter dorsally at 16.4 (range, 7.0-32.7) mm versus 18.7 (range, 7.5-36.9) mm ventrally (P < .001). The ventral EAS reached farther cranially by 0.8 ± 2.5 (range, -4.8-5.1) mm on average. The mean EAS thickness was 3.4 (range, 2.0-5.8) mm, being thicker dorsally than ventrally (P < .001). CONCLUSIONS: Anal sphincter biometry can be assessed with good repeatability by TLUS. The EAS seems longer ventrally. Asymmetry of the EAS could result in a false-positive diagnosis of defects in women in whom the ventral EAS terminates more caudally than its dorsal aspect, which seems uncommon. Hence, the likelihood of a false-positive diagnosis of substantial defects of the EAS using the published method seems low.

Original languageEnglish
Pages (from-to)2733-2738
Number of pages6
JournalJournal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine
Volume38
Issue number10
DOIs
Publication statusPublished - 1 Oct 2019

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Biometry
Third Pregnancy Trimester
Anal Canal
Pregnant Women
Reference Values
Retrospective Studies

Keywords

  • 3-/4-dimensional ultrasound
  • anal sphincter
  • anal sphincter biometry
  • exoanal ultrasound
  • obstetric anal sphincter injury

ASJC Scopus subject areas

  • Radiological and Ultrasound Technology
  • Radiology Nuclear Medicine and imaging

Cite this

@article{c51f7cef796c4f8b9472925cd0a50df8,
title = "Normal Values of Anal Sphincter Biometry by 4-Dimensional Translabial Ultrasound: A Retrospective Study of Pregnant Women in Their Third Trimester",
abstract = "OBJECTIVES: Exoanal 4-dimensional translabial ultrasound (TLUS) is increasingly used to image the anal sphincter. The aim of this study was to define the limits of normality for assessment of external and internal anal sphincters with TLUS. METHODS: This study was a retrospective analysis using data sets of nulliparous women seen antenatally. All women had a 4-dimensional TLUS examination at a mean gestational age ± SD of 36 ± 0.7 (range, 32.9-37.3) weeks. Anal sphincter biometry, including external anal sphincter (EAS) length and thickness, EAS proximal rotational asymmetry, and internal anal sphincter thickness, was assessed blinded against other data. RESULTS: A test-retest series showed good repeatability (intraclass correlation coefficients, 0.619-0.849) of all parameters. The mean age of the women (n = 111) was 30.9 (range, 18.8-40.5) years. None reported anal incontinence. On tomographic imaging, none showed anal sphincter defects. The mean EAS length was 17.5 (range, 8.4-34.8) mm, being shorter dorsally at 16.4 (range, 7.0-32.7) mm versus 18.7 (range, 7.5-36.9) mm ventrally (P < .001). The ventral EAS reached farther cranially by 0.8 ± 2.5 (range, -4.8-5.1) mm on average. The mean EAS thickness was 3.4 (range, 2.0-5.8) mm, being thicker dorsally than ventrally (P < .001). CONCLUSIONS: Anal sphincter biometry can be assessed with good repeatability by TLUS. The EAS seems longer ventrally. Asymmetry of the EAS could result in a false-positive diagnosis of defects in women in whom the ventral EAS terminates more caudally than its dorsal aspect, which seems uncommon. Hence, the likelihood of a false-positive diagnosis of substantial defects of the EAS using the published method seems low.",
keywords = "3-/4-dimensional ultrasound, anal sphincter, anal sphincter biometry, exoanal ultrasound, obstetric anal sphincter injury",
author = "{Magpoc Mendoza}, Julie and {Turel Fatakia}, Friyan and {Kamisan Atan}, Ixora and Dietz, {Hans Peter}",
year = "2019",
month = "10",
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doi = "10.1002/jum.14981",
language = "English",
volume = "38",
pages = "2733--2738",
journal = "Journal of Ultrasound in Medicine",
issn = "0278-4297",
publisher = "American Institute of Ultrasound in Medicine",
number = "10",

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T1 - Normal Values of Anal Sphincter Biometry by 4-Dimensional Translabial Ultrasound

T2 - A Retrospective Study of Pregnant Women in Their Third Trimester

AU - Magpoc Mendoza, Julie

AU - Turel Fatakia, Friyan

AU - Kamisan Atan, Ixora

AU - Dietz, Hans Peter

PY - 2019/10/1

Y1 - 2019/10/1

N2 - OBJECTIVES: Exoanal 4-dimensional translabial ultrasound (TLUS) is increasingly used to image the anal sphincter. The aim of this study was to define the limits of normality for assessment of external and internal anal sphincters with TLUS. METHODS: This study was a retrospective analysis using data sets of nulliparous women seen antenatally. All women had a 4-dimensional TLUS examination at a mean gestational age ± SD of 36 ± 0.7 (range, 32.9-37.3) weeks. Anal sphincter biometry, including external anal sphincter (EAS) length and thickness, EAS proximal rotational asymmetry, and internal anal sphincter thickness, was assessed blinded against other data. RESULTS: A test-retest series showed good repeatability (intraclass correlation coefficients, 0.619-0.849) of all parameters. The mean age of the women (n = 111) was 30.9 (range, 18.8-40.5) years. None reported anal incontinence. On tomographic imaging, none showed anal sphincter defects. The mean EAS length was 17.5 (range, 8.4-34.8) mm, being shorter dorsally at 16.4 (range, 7.0-32.7) mm versus 18.7 (range, 7.5-36.9) mm ventrally (P < .001). The ventral EAS reached farther cranially by 0.8 ± 2.5 (range, -4.8-5.1) mm on average. The mean EAS thickness was 3.4 (range, 2.0-5.8) mm, being thicker dorsally than ventrally (P < .001). CONCLUSIONS: Anal sphincter biometry can be assessed with good repeatability by TLUS. The EAS seems longer ventrally. Asymmetry of the EAS could result in a false-positive diagnosis of defects in women in whom the ventral EAS terminates more caudally than its dorsal aspect, which seems uncommon. Hence, the likelihood of a false-positive diagnosis of substantial defects of the EAS using the published method seems low.

AB - OBJECTIVES: Exoanal 4-dimensional translabial ultrasound (TLUS) is increasingly used to image the anal sphincter. The aim of this study was to define the limits of normality for assessment of external and internal anal sphincters with TLUS. METHODS: This study was a retrospective analysis using data sets of nulliparous women seen antenatally. All women had a 4-dimensional TLUS examination at a mean gestational age ± SD of 36 ± 0.7 (range, 32.9-37.3) weeks. Anal sphincter biometry, including external anal sphincter (EAS) length and thickness, EAS proximal rotational asymmetry, and internal anal sphincter thickness, was assessed blinded against other data. RESULTS: A test-retest series showed good repeatability (intraclass correlation coefficients, 0.619-0.849) of all parameters. The mean age of the women (n = 111) was 30.9 (range, 18.8-40.5) years. None reported anal incontinence. On tomographic imaging, none showed anal sphincter defects. The mean EAS length was 17.5 (range, 8.4-34.8) mm, being shorter dorsally at 16.4 (range, 7.0-32.7) mm versus 18.7 (range, 7.5-36.9) mm ventrally (P < .001). The ventral EAS reached farther cranially by 0.8 ± 2.5 (range, -4.8-5.1) mm on average. The mean EAS thickness was 3.4 (range, 2.0-5.8) mm, being thicker dorsally than ventrally (P < .001). CONCLUSIONS: Anal sphincter biometry can be assessed with good repeatability by TLUS. The EAS seems longer ventrally. Asymmetry of the EAS could result in a false-positive diagnosis of defects in women in whom the ventral EAS terminates more caudally than its dorsal aspect, which seems uncommon. Hence, the likelihood of a false-positive diagnosis of substantial defects of the EAS using the published method seems low.

KW - 3-/4-dimensional ultrasound

KW - anal sphincter

KW - anal sphincter biometry

KW - exoanal ultrasound

KW - obstetric anal sphincter injury

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