Warping of the levator hiatus: how significant is it?
OBJECTIVE
The levator hiatus is the largest potential hernial portal in the human body. Excessive distensibility is associated with female pelvic organ prolapse (POP). Distension occurs not just laterally but also caudally, resulting in perineal descent and hiatal deformation or 'warping'. The aim of this study was to quantify the warping effect in symptomatic women, to validate the depth of the rendered volume used for the 'simplified method' of measuring hiatal dimensions and to determine predictors for the degree of warping.


METHODS
This was a retrospective study utilizing records of patients referred to a tertiary urogynecological service between November 2012 and March 2013. Patients underwent a standardized interview, clinical assessment using the POP quantification system of the International Continence Society and four-dimensional translabial ultrasound. The craniocaudal difference in the location of minimal distances in mid-sagittal and coronal planes was determined by offline analysis of ultrasound volumes, and provided a numerical measure of warping. We tested potential predictors, such as demographic factors, signs and symptoms of prolapse, levator avulsion and levator distensibility, for an association with warping.


RESULTS
Full datasets were available for 190 women. The mean craniocaudal difference in location of minimal distances in mid-sagittal and coronal planes was -1.26 mm (range, -6.7 to 4.6 mm; P < 0.001). This measure of warping was associated with hiatal area on Valsalva maneuver (r = - 0.284; P < 0.0001) and signs of significant prolapse on clinical and ultrasound examination (both P < 0.0001).


CONCLUSIONS
The plane of minimal dimensions of the levator ani hiatus is non-Euclidean, i.e. warped, and the degree of warping is associated with hiatal distension, or 'ballooning', and with POP. However, the degree of warping is minor, the largest difference we found in the location of the plane of minimal dimensions being 6.7 mm. Hence, our results support the determination of hiatal area in a rendered volume of 1-2 cm in depth. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.
Department of Obstetrics and Gynecology, Sydney Medical School Nepean, University of Sydney, Penrith, Australia.
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Dietz
Department of Obstetrics and Gynecology, Sydney Medical School Nepean, University of Sydney, Penrith, Australia.
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Severino
Department of Obstetrics and Gynecology, Sydney Medical School Nepean, University of Sydney, Penrith, Australia.|Universiti Kebangsaan Malaysia Medical Centre (UKMMC), Kuala Lumpur, Malaysia.
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Kamisan Atan
Department of Obstetrics and Gynecology, Sydney Medical School Nepean, University of Sydney, Penrith, Australia.|Department of Obstetrics and Gynecology, Liverpool Hospital, University of Western Sydney, Richmond, NSW, Australia.
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Shek
Departamento de Ginecología y Obstetricia, Facultad de Medicina, Clínica Alemana - Universidad del Desarrollo, Santiago, Chile.|Departamento de Ginecología y Obstetricia, Hospital Clínico de la Universidad de Chile, Santiago, Chile.
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Guzman Rojas
D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D056887:Pelvic Organ Prolapse / Q000000981:diagnostic imaging*; D010502:Perineum / Q000000981:diagnostic imaging*; D012189:Retrospective Studies; D062606:Tertiary Care Centers; D014463:Ultrasonography; D014636:Valsalva Maneuver; D055815:Young Adult
4D ultrasound; female pelvic organ prolapse; levator hiatus; measurement; translabial ultrasound