The appearance of levator ani muscle abnormalities in magnetic resonance images after vaginal delivery

Abstract

OBJECTIVE-To describe the appearance and occurrence of abnormalities in the levator ani muscle seen on magnetic resonance imaging (MRI) in nulliparous women and in women after their first vaginal birth.METHODS-Multiplanar proton density magnetic resonance images were obtained at 0.5-cm intervals from 80 nulliparous and 160 vaginally primiparous women. These had been previously obtained in a study of stress incontinence, and half the primiparas had stress incontinence. All scans were reviewed independently by at least two examiners blinded to parity and continence status. RESULTS-Nolevator ani defects were identified in nulliparous women. Thirty-two primiparous women (20%) had a visible defect in the levator ani muscle. Defects were identified in the pubovisceral portion of the levator ani in 29 women and in the iliococcygeal portion in three women. Within the pubovisceral muscle, both unilateral and bilateral defects were found. The extent of abnormality varied from one individual to the next. Of the 32 women with defects, 23 (71%) were in the stress incontinent group.CONCLUSION-Abnormalities in the levator ani muscle are present on MRI after a vaginal delivery but are not found in nulliparas.During a study of the role of vaginal birth in causing urinary incontinence we obtained magnetic resonance images of women with stress incontinence after their first vaginal birth and of normal continent nulliparous and primiparous controls. On evaluating these scans we found abnormalities in the levator ani muscles in both the continent and incontinent women. The abnormalities seemed to occur only in women who delivered vaginally, and not in nulliparas. These abnormalities involved both the pubovisceral and iliococcygeal portions of the muscle and were sometimes unilateral and sometimes bilateral. Here we describe these defects and evaluate whether or not they are associated with vaginal delivery. MATERIALS AND METHODSMagnetic resonance images of the pelvis were obtained from 240 women as part of an institutional review board-approved study concerning vaginal delivery and stress urinary incontinence. Multiplanar two-dimensional fast spin (echo time 15 ms, repetition time 4000 ms) proton density magnetic resonance images of all pelves were obtained by use of a 1.5-tesla superconducting magnet (Signa; General Electric Medical Systems, Milwaukee, WI) with version 5.4 software as previously described. 1 Images 5 mm apart were obtained in axial, coronal, and sagittal views.

Interrater reliability and physical examination of the pubovisceral portion of the levator ani muscle, validity comparisons using MR imaging

“…The structured examination used in this study focuses on detecting an absence of muscle substance in the pubovisceral portion of the levator ani muscle; the region we have found most often damaged by vaginal birth [DeLancey et al, 2003]. It is different than previously published techniques of examination [Brink et al, 1994;Sampselle et al, 1989;Worth et al, 1986].…”

“…Levator ani muscle damage is twice as common in women with new-onset stress incontinence after first birth [DeLancey 2003] and there is suggestion, for example, that damage to the levator ani muscle is associated with operative failure for prolapse [Koelbl et al, 1989;Hanzal et al, 1993], significant in light of the fact that 29% of women experience operative failure [Olsen et al, 1997]. If we knew definitely the obstetrical factors that place women at increased risk of significant injury we may be able to prevent levator ani injuries in the delivery room, but accurate determination of levator ani injury is a necessary precursor to these studies.…”

“…Note the loss of pubovisceral muscle bulk between the vagina and the internal obturator muscle in the axial and coronal scans. Determinations of muscle integrity were based on our previous experience with assessing normal muscle morphology [Strohbehn et al, 1996;Chou and DeLancey, 2001;DeLancey et al, 2003].…”

“…Defects in the levator ani muscle have long been recognized as a contributing cause of pelvic floor dysfunction [Halban and Tandler, 1907;Berglas and Rubin, 1953;Koelbl et al, 1989;Hanzal et al, 1993;DeLancey et al, 2003]. MR imaging has objectively demonstrated these defects in women with stress urinary incontinence and pelvic organ prolapse particularly in the region of the pubovisceral portion of the levator ani [Tunn et al, 1998;Hoyte et al, 2001].…”

Effect of Delivery and Episiotomy on the Emergence of Urinary Incontinence in Women: Review of Literature

“…Urinary incontinence in pregnancy increases the risk of later urinary incontinence, both postpartum and later in life 17,38 , but nevertheless it is not a predictor of benefi t from giving birth by cesarean section to protect against urine leakage 17,39 . Increase of urethral mobility in combination with lesions of the levator ani muscle is the probable mechanism of impairment during vaginal delivery 40 . Nevertheless, urethral hypermobility returns to pre-delivery rates after few months postpartum 41 .…”