Obstetrics & Gynecology Email Alerts
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Obstetrics & Gynecology 2005;106:1259-1265
© 2005 by The American College of Obstetricians and Gynecologists
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Hsu, Y.
Right arrow Articles by DeLancey, J. O. L.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Hsu, Y.
Right arrow Articles by DeLancey, J. O. L.
Related Collections
Right arrow General gynecology
Right arrow Gynecologic surgery
Right arrow Imaging
Right arrow Urogynecology

ORIGINAL ARTICLES

Magnetic Resonance Imaging and 3-Dimensional Analysis of External Anal Sphincter Anatomy

Yvonne Hsu, MD1, Dee E. Fenner, MD1, William J. Weadock, MD2 and John O. L. DeLancey, MD1

From the 1Pelvic Floor Research Group and Division of Gynecology, Department of Obstetrics and Gynecology and 2Department of Radiology, University of Michigan, Ann Arbor, Michigan.

OBJECTIVE: To use magnetic resonance images of living women and 3-dimesional modeling software to identify the component parts and characteristic features of the external anal sphincter (EAS) that have visible separation or varying origins and insertions.

METHODS: Detailed structural analysis of anal sphincter anatomy was performed on 3 pelvic magnetic resonance imaging (MRI) data sets selected for image clarity from ongoing studies involving nulliparous women. The relationships of anal sphincter structures seen in axial, sagittal, and coronal planes were examined using the 3-D Slicer 2.1b1 software program. The following were requirements for sphincter elements to be considered separate: 1) a clear and consistently visible separation or 2) a different origin or insertion. The characteristic features identified in this way were then evaluated in images from an additional 50 nulliparas for the frequency of feature visibility.

RESULTS: There were 3 components of the EAS that met criteria as being "separate" structures. The main body (EAS-M) is separated from the subcutaneous external anal sphincter (SQ-EAS) by a clear division that could be observed in all (100%) of the MRI scans reviewed. The wing-shaped end (EAS-W) has fibers that do not cross the midline ventrally, but have lateral origins near the ischiopubic ramus. This EAS-W component was visible in 76% of the nulliparas reviewed.

CONCLUSION: Three distinct external anal sphincter components can be identified by MRI in the majority of nulliparous women.






HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 2005 by the American College of Obstetricians and Gynecologists.