Pelvic Floor



Pelvic Floor





33.1 Pelvic Floor Abnormalities


Description and Clinical Features

The pelvic floor is comprised of three compartments based on function and location, labeled anterior, middle, and posterior compartments. The anterior compartment encompasses the urethra, the middle includes the vagina, and the posterior has the rectum. The levator ani is the main muscle group that encircles and supports the pelvic inlet and pelvic floor. The muscles of the levator ani are the puborectalis, pubococcygeus, and iliococcygeus, which work together to counteract gravity and keep pelvic organs in position, while also facilitating defecation, urination, and childbirth. The external and internal anal sphincters, encased by the levator ani muscles, are the primary muscles responsible for maintaining fecal continence and defecation. Detrusor muscles in the wall of the bladder and the urethral sphincter muscles work together to maintain urinary continence and permit urination.

The major abnormalities of the pelvic floor result from damage or weakening of the sphincters and levator ani muscles and include urinary incontinence, fecal incontinence, and prolapse of the bladder, uterus, or rectum. Damage to the anal sphincter may result from childbirth or rectal surgery and can lead to fecal incontinence, often years afterward. Weakening of the levator ani muscles may also result from childbearing, but also occurs with advancing age, and can lead to urinary incontinence and bladder prolapse. Sonography has proven useful for assessing the degree of displacement of pelvic organs in patients with symptoms of recurrent urinary tract infections, urgency, frequency, urinary incontinence, pain, dysuria, voiding dysfunction, prolapse, vaginal pain, fecal incontinence, and dyspareunia.

Masses or cysts may arise in the walls of the urethra or vagina. These include urethral diverticula, Bartholin and Gartner duct cysts, vaginal endometriosis, and leiomyomata, among others. Sonography of the perineum and pelvic floor provides information about the origin, size, and composition of such lesions, to assist in making the diagnosis.


Sonography

Imaging the pelvic floor is best accomplished with 2D scanning at the introitus or using 3D volume reconstruction of views of the urethra, vagina, and rectum. The vaginal probe is placed on the perineum, not inside the vagina. The transverse plane demonstrates a cross section of the components of the pelvic floor, including the urethra, vagina, rectum, and surrounding muscles (Figure 33.1.1).

Evaluation of a patient with urinary incontinence, involves scanning longitudinally to image the urethra while the patient is relaxed and with Valsalva. When there is urinary incontinence and a cystocele, the bladder shifts caudally and rotates posteriorly into the vagina, findings that are exacerbated with Valsalva. The urethra becomes oriented perpendicular to the perineum (Figure 33.1.2). The urethra in women treated for incontinence surgically, such as with a urethral sling placed along the posterior length of the urethra, will be oriented more normally, supported by the sling (Figure 33.1.3).







Figure 33.1.1 Normal pelvic floor. A: Sagittal midline view of the pelvic floor with the probe on the introitus, at the entrance to the vagina, showing the urethra (U, arrows) anterior to the vagina (V, arrows), which is anterior to the rectum (R, arrows). B: Image from 3D volume, showing the three orthogonal planes at right angle to each other, sagittal, coronal, and axial, and an axial 3D slice showing the structures of the pelvic floor, the urethra (U), vagina (V, arrows), and rectum (R). The muscles (M) of the external anal sphincter and levator ani encase these structures laterally and posteriorly. C: Axial 3D slice showing the structures of the pelvic floor, the urethra (U), vagina (V, arrows), and rectum (R) en face, and the external anal sphincter and levator ani muscles (M).






Figure 33.1.2 Cystocele. A: Sagittal image of urethra (arrowheads) and bladder (BL) at rest, showing the bladder wall protruding slightly posteriorly (arrows) into the vagina (V). B: With Valsalva, most of the bladder (BL) prolapses (arrows) into the vagina (V). The urethra (arrowheads) is now oriented perpendicular to normal, preventing bladder emptying.







Figure 33.1.3 Cystocele repaired with urethral sling. A: Sagittal image showing normal orientation of urethra (arrowheads), held in place by surgical sling (arrows) (V, vagina; BL, bladder). B: 3D reconstructed view of the floor of the pelvis showing surgical sling (arrows) draped around the back of the urethra (U) and tethered on either side, providing support for the urethra (V, vagina; R, rectum).

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Feb 2, 2020 | Posted by in GYNECOLOGY | Comments Off on Pelvic Floor
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