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: No levator 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.

Figures

Figure 1

Axial and coronal images from a 45-year-old nulliparous woman. The urethra (U), vagina (V), rectum (R), arcuate pubic ligament (A), pubic bones (PB), and bladder (B) are shown. The arcuate pubic ligament is designated as zero for reference, and the distance from this reference plane is indicated in the lower left corner. Note the attachment of the levator muscle (arrows) to the pubic bone in axial +1.0, +1.5, and +2.0. Coronal images show the urethra, vagina, and muscles of levator ani and obturator internus (OI). (Reprinted with permission. © DeLancey 2002.) DeLancey. Levator Defects After Birth. Obstet Gynecol 2003.

Figure 2

Axial and coronal images from a 34-year-old incontinent primiparous woman showing a unilateral defect in the left pubovisceral portion of the levator ani muscle. The arcuate pubic ligament (A), urethra (U), vagina (V), rectum (R), and bladder (B) are shown. The location normally occupied by the pubovisceral muscle is indicated by the open arrowhead in axial and coronal images +1.0, +1.5, and +2.0. (Reprinted with permission. © DeLancey 2002.) DeLancey. Levator Defects After Birth. Obstet Gynecol 2003.

Figure 3

Axial and coronal images of a 38-year-old incontinent primiparous woman are shown. The area where the pubovisceral portion of the levator ani muscle is missing (open arrowhead) between the urethra (U), vagina (V), rectum (R), and obturator internus muscle (OI) is shown. The vagina protrudes laterally into the defects to lie close to the obturator internus muscle. A = arcuate pubic ligament. (Reprinted with permission. © DeLancey 2002.) DeLancey. Levator Defects After Birth. Obstet Gynecol 2003.

Figure 4

Levator ani defect in a 30-year-old incontinent primiparous woman with loss of muscle bulk but preservation of pelvic architecture. The area where the levator is absent in this woman is shown (open arrowhead) in the axial images and the coronal images +1.5 and +2.0. Note that in contrast to Figure 3, where the vagina lies close to the obturator internus (OI), it has a normal shape. The normal appearance of the levator ani muscle is seen in coronal images +2.0 and +2.5 (arrows). A = arcuate pubic ligament; U = urethra; V = vagina; R = rectum. (Reprinted with permission. © DeLancey 2002.) DeLancey. Levator Defects After Birth. Obstet Gynecol 2003.

Figure 5

Iliococcygeus muscle defect. Thinning of the iliococcygeus muscle is demonstrated (open arrowheads) on the patient’s left in axial images +3.0, +3.5, and +4.0 and coronal images +1.0 and +1.5. The urethra (U), vagina (V), bladder (B), rectum (R), and arcuate pubic ligament (A) are shown. (Reprinted with permission. © De-Lancey 2002.) DeLancey. Levator Defects After Birth. Obstet Gynecol 2003.