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MRI of Pelvic Floor Dysfunction - An Overview

Faiq Shaikh, M.D. is a dual fellowship-trained nuclear medicine physician & Informaticist, with a focus on translational research in the domains of Cancer imaging, Radiomics, Genomics, Informatics and Machine learning applications in Medicine. He has written more than 35 scientific articles and abstracts and 3 book chapters on related topics.

Introduction

Modern 3T MRI System

Pelvic floor weakening is a common (occuring in half of women 50+) condition that leads to descent of the urinary bladder, uterovaginal vault, and rectum in the females, leading to urinary and fecal incontinence, and in extreme cases, pelvic organ prolapse.

Causes

Pelvic floor weakness is caused by a variety of factors, most of which increase the intra-abdominal pressure, such as pregnancy, multiparity, advanced age, menopause, obesity, connective tissue disorders, smoking, chronic obstructive pulmonary disease, etc. All these conditions lead to weakness of the pelvic musculature, ligaments, and fascia support result in descent of the pelvic floor organs.

Anatomy

The pelvic floor is divided into three compartments:

  • Anterior compartment: contains the urinary bladder and urethra
  • Middle compartment: contains the uterus, cervix, and vagina
  • Posterior compartment: contains the rectum.

The structures in these compartments are supported by muscles, fascia, and ligaments anchoring them to the bony pelvis.

The endopelvic fascia is the most superior layer and covers the levator ani muscles and the pelvic viscera. Laterally, it forms the arcus tendineus. It attaches the cervix and vagina to the pelvic side wall as the parametrium and paracolpium. Posteriorly, the endopelvic fascia forms the rectovaginal fascia between the posterior vaginal wall and the rectum.

These fascial condensations are not well visualized on conventional MRI but their defects may be seen indirectly through secondary findings. These ligaments are not visualized on conventional MRI but may be visualized with an endovaginal coil which allows higher resolution and signal-to-noise ratio.

The levator ani muscles lie deep in relation to the endopelvic fascia and comprise of the puborectalis and the iliococcygeus muscles. Posteriorly and in the midline, the iliococcygeus condenses to form the levator plate. These are all well visualized on MRI. The perineal membrane lies inferior to the levator ani muscles and separates the vagina and rectum, which may be damaged during vaginal delivery when episiotomy is performed.

Pathophysiology

Pelvic floor relaxation is the weakness of the supporting muscles, fascia, and ligaments. This weakness progresses with age and may be related to hypoestrogenic states, such as menopause.

  • occurs when the urinary bladder prolapses into the anterior vaginal wall, which may cause urinary incontinence.
  • occurs due to weakness of the rectovaginal fascia, prolapsing rectum into the posterior vaginal wall, which may cause fecal incontinence.
  • The parametrium and paracolpium weakness causes prolapse of the cervix and uterus.
  • occurs when the small bowel prolapses through the rectovaginal fascia.

Accurate assessment of all compartments of the pelvic floor is necessary for surgical planning in order to minimize the risk of recurrence.

Diagnostics

Methods for the assessment of pelvic floor weakness include urodynamics, voiding cystourethrography, ultrasonography of the bladder neck and anal sphincter, fluoroscopic cystocolpodefecography, and MRI - which m is now the standard-of-care for preoperative planning for pelvic floor dysfunction, although it’s still not used for routine assessment.

Magnetic resonance imaging

MRI visualizes all three compartments of the pelvic floor and the pelvic support muscles and organs. We perform dynamic MRI of the pelvic floor with the patient in the supine or lateral decubitus positions. Conversely, MRI defecography or fluoroscopic cystocolpodefecography are performed in the sitting position, which is closer to the physiologic state. MR defecography is not superior to dynamic supine MRI for depiction of clinically relevant bladder descent and rectoceles. Overall, MRI accurately detects enteroceles and its contents when compared with fluoroscopic cystodefecography.

The preferred MRI pelvis protocols include: Ultrafast, large-field-of-view, T2-weighted sequences such as single-shot fast spin-echo (SSFSE), and half-Fourier acquisition turbo spin-echo (HASTE). After the dynamic examination is completed, small-field-of-view (20–24 cm) T2-weighted axial fast spin-echo (FSE) or axial turbo spin-echo (TSE) sequences are acquired to obtain high-resolution images of the muscles and fascia of the pelvic floor. The entire examination is typically completed in 20 minutes. This exam is performed with a torso phased-array coil wrapped around the pelvis. Endovaginal coil may be used to improve the spatial resolution of the pelvic ligaments, but it is invasive and can be uncomfortable.

MRI visualizes the uterus, cervix, and rectovaginal space. Ultrasonic gel may be administered into the vagina and rectum for better visualization. Also, incompletely voiding the urinary bladder improves visualization of the bladder and anterior vaginal wall prolapse.

For patients with a rectocele, patient is imaged after having evacuated the rectal contents. Chronic constipation and perineal hernias show as ballooning of the iliococcygeus muscle. The level of the pelvic floor is demarcated radiologically on the midsagittal image using the pubococcygeal line (from the most inferior portion of the pubic symphysis to the last horizontal sacrococcygeal joint). The levator plate should be parallel to the pubococcygeal line in normal cases.
The H line (5 cm) extends from the inferior symphysis pubis to the posterior anorectal junction on the midsagittal image and depicts the levator hiatus. The M line (2 cm) goes perpendicular from the pubococcygeal line to the most distal aspect of the H line and depicts the descent of the levator hiatus from the pubococcygeal line. Pelvic floor prolapse causes sloping of the levator plate and increasing length of the H and M lines, indicating widening and descent of the levator hiatus.

The T2-weighted axial images of the pelvic floor should be analyzed for signal intensity, symmetry, thickness, and fraying of the pelvic floor muscles. Bladder neck at strain should be less than 1 cm away from the pubococcygeal line. Descent of the bladder neck below the pubococcygeal line depicts the prolapse of the urinary bladder through the anterior vaginal wall resulting in a cystocele. Descent of the bladder neck during strain results in clockwise rotational descent of the bladder neck and proximal urethra. Distortion of the periurethral and paraurethral ligaments is seen in stress urinary incontinence. The normal butterfly shape of the vagina may also be altered by weakening of the paravaginal ligaments as it is displaced posteriorly. Prolapse of the middle compartment is associated with the vaginal apical prolapse and damage to the paracolpium seen in post-hysterectomy patients.  On midsagittal MR images, descent of the uterus, cervix and vagina usually suggests disruption of the uterosacral or cardinal ligaments and elongated H and M lines. Pelvic organ prolapse increases the urogenital hiatus in the levator muscles. Caudal angle of more than 10° between the levator plate and the pubococcygeal line on midsagittal image is a sign of pelvic floor weakness.

On the midsagittal image, rectocele is identified by a rectal bulge of more than 3 cm (from anal canal and the tip of the rectocele). Contrast-enhanced MR shows hyperintense T2 signal in peritoneal fat contents in peritoneoceles, the hyperintense fluid-filled small-bowel loops in enteroceles, and the hyperintense gel-filled rectum/sigmoid colon in rectoceles/sigmoidoceles. Intussusception of the rectum on MR is seen as rectum invaginating distally toward the anal canal (MR defecography is superior to dynamic supine MR for this indication).

Performing MRI for pelvic floor dysfunction when indicated for surgical planning and the assessment if the extent of disease may reduce the risk of surgical failure.
This information is extremely useful to urogynecologists and surgeons.


MRI of pelvic floor dysfunction: review. Law YM, Fielding JR. AJR Am J Roentgenol. 2008.

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Perineal Massage for Childbirth

Perineal massage involves pelvic floor muscle stretching by application of an external pressure to muscle and connective tissue in the perineal region. It is performed 4 to 6 weeks before childbirth to help the soft tissue in that region to withstand stretching during labor. This helps to prevent perineum during birth by decreasing the need for an episiotomy or an instrument-assisted delivery. Lengthening of skeletal muscles is known to modify the viscoelastic properties of the muscle-tendon unit, which decreases the tension peak of the musculature and therefore, chances of injury.

Pelvic floor muscle stretching is performed via widening of the hiatus in the axial plane. Perineal massage is a simple technique has been found to be associated with a decrease in the incidence of perineal tears requiring suture or an episiotomy. It has also been reported to reduce postpartum pain.

Instrument-assisted stretching is performed with the help of an inflatable silicon balloon that can be pumped to gradually stretch the vagina and perineum. However, the evidence to support its benefit is lacking. In fact, there is some concern that pelvic floor muscle stretching may cause a decrease in muscle strength. Some have argued that such exercise neither improve or worsen pelvic function (Labrecque M, et al., Medi-dan, et al.). While a meta-analysis by Aquino, et al. concluded that perineal massage during labor significantly lowered risk of severe perineal trauma, such as third and fourth degree lacerations (Aquino, et al.).

A recent major study done by deFreitas, et al., perineal massage and instrument-assisted stretching were found to improve perineal muscle extensibility when performed in multiple sessions on primiparous women beginning at 34th week of gestation, which is very helpful in preventing child trauma in labor; however, there was no increase in muscle strength.

The technique of performing the manual perineal massage (as exemplified in the aforementioned study) may involve two sessions per week for a month by an OBGYN-focused physiotherapist. The patients are rested in dorsal decubitus position with the inferior limbs semi-flexed and the lower limbs and feet supported on the examination table. Coconut oil can be used for the perineal massage - which starts off with circular movements in the external area of the vulva, around the vagina and in the central tendon of the perineum, followed by the index and middle fingers inserted approximately 4 cm in the vaginal introitus for an internal massage of the lateral walls of the vagina ending toward the anus, repeated four times on each side, with the whole process lasting approximately 10 minutes.

Instrument-assisted procedure may include inserting the instrument (Epi-No) covered with a condom and lubricated with a water-based gel, inflated at the vaginal introitus so that 2 cm of the balloon is visible, making sure the patient can tolerate the stretching, and are advised to keep the pelvic floor relaxed as the instrument is slowly expelled during expiration. Physiotherapist supervision is necessary in order to maintain the correct positioning of the balloon as it lengthens the muscles. He/she will also ensure proper expulsion of the equipment during expiration.

Overall, perineal massage techniques (with or without instrumentation) are beneficial in terms of preventing trauma during labor. There are many studies that support the efficacy of these techniques in doing so (Leon-Larios, et al.). But it is also important to appreciate the limitations and use it judiciously.


Randomized trial of perineal massage during pregnancy: perineal symptoms three months after delivery. Labrecque M, et al. Am J Obstet Gynecol. 2000.
Perineal massage during pregnancy: a prospective controlled trial. Mei-dan E, et al. Isr Med Assoc J. 2008.
Perineal massage during labor: a systematic review and meta-analysis of randomized controlled trials. Aquino CI, et al. J Matern Fetal Neonatal Med. 2018.
Effects of perineal preparation techniques on tissue extensibility and muscle strength: a pilot study. de Freitas SS, et al. Int Urogynecol J. 2018.
Influence of a pelvic floor training programme to prevent perineal trauma: A quasi-randomised controlled trial. Leon-Larios F, et al. Midwifery. 2017.

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Post-prostatectomy Penile Rehabilitation

Erectile dysfunction (ED) is a debilitation complication of radical prostatectomy, which is a treatment for prostate cancer. ED is caused by a variety of causes, diabetic vasculopathy, smoking, high blood pressure, high cholesterol, psychological issues, peripheral vascular disease and medication; we will focus on post-prostatectomy ED and the role of penile rehabilitation in its management.

Post-prostatectomy-related Erectile dysfunction

Radical prostatectomy can result in nerve injury to the penis. Moreover, significant fibrotic changes take place in the corpus cavernosum of the penis postoperatively. It takes approximately 1-2 years for erectile function to return after radical prostatectomy. This is a period of “neuropraxia,” during which there is transient cavernosal nerve dysfunction. However, a prolonged “flaccid state” might lead to irreversible damage to the cavernous tissue 1.

Research on penile hemodynamics in these patients have shown that venous leakage is also implicated in its pathophysiology. An injury to the neurovascular bundles likely leads to smooth muscle cell death, which then leads to irreversible veno-occlusive disease.

There is a potential role of hypoxia in stimulating growth factors (TGF-beta) that stimulate collagen synthesis in cavernosal smooth muscle. Prostaglandin E1 (PGE1) was found to suppress the effect of TGF-β1 on collagen synthesis.

Role of Penile Rehabilitation

The goal of Penile Rehabilitation is to limit and reverse ED in post-prostatectomy patients. The idea is to minimize fibrotic changes during the period of “penile quiescence” after nerve-sparing radical prostatectomy. Several approaches have been tried, including PGE1 injection, vacuum devices, and phosphodiesterase type 5 (PDE-5) inhibitors.

Mulhall and coworkers followed 132 patients through an 18-month period after they were placed in “rehabilitation” or “no rehabilitation” groups after radical prostatectomy, and 52% of those undergoing rehabilitation (sildenafil + alprostadil) reported spontaneous functional erections, compared with 19% of the men in the no-rehabilitation group 2.

Prostaglandin E1 (PGE1)

Alprostadil is a vasodilatory prostaglandin E1 that can be injected into the penis or placement in the urethra in order to treat ED. Montorsi, et al. studied the use of intracorporeal injections of alprostadil starting at 1 month after bilateral nerve-sparing radical prostatectomy and reported a higher rate of spontaneous erections after 6 months compared with no treatment 3. Gontero, et al. investigated alprostadil injections at various time points after non–nerve-sparing radical prostatectomy and found that 70% of patients receiving injections within the first 3 months were able to achieve erections sufficient for intercourse, compared with 40% of patients receiving injections after the first 3 months 4.

Vacuum constriction device (VCD)

VCD is an external pump that is used to get and maintain an erection. Raina, et al evaluated the daily use of a VCD beginning within two months after radical prostatectomy, and reported that after 9 months of treatment, 17% of patients using the device had return of natural erections sufficient for intercourse, compared with 11% of patients in the nontreatment group 4.

PDE-5 Inhibitors

PDE-5 inhibitors (such as Sildenafil) are the first-line treatment for ED of many etiologies. Several studies have shown that the use of PDE-5 inhibitors might lead to an overall improvement in endothelial cell function in the corpus cavernosum. Chronic use of oral PDE-5 inhibitors suggest a beneficial effect on endothelial cell function. Desouza, et al. concluded that daily sildenafil improves overall vascular endothelial cell function. However, Zagaja, et al. found that men taking oral sildenafil within the first 9 months of a nerve-sparing procedure did not have any erectogenic response 4.

Overall, accumulating scientific literature is suggesting that penile rehabilitation therapies have a positive impact on the sexual function outcome in post-prostatectomy patients. It must be noted that these methods do not cure ED and should be used with caution.


1Penson DF, McLerran D, Feng Z, et al. 5-year urinary and sexual outcomes after radical prostatectomy: results from the prostate cancer outcomes study. J Urol. 2005;173:1701-1705.
2Mulhall J, Land S, Parker M, et al. The use of an erectogenic pharmacotherapy regimen following radical prostatectomy improves recovery of spontaneous erectile function. J Sex Med. 2005; 2:532-540.
3Montorsi F, Guazzoni G, Strambi LF, et al. Recovery of spontaneous erectile function after nerve-sparing radical retropubic prostatectomy with and without early intracavernous injections of alprostadil: results of a prospective, randomised trial. J Urol. 1997;158:1408-1410.
4Gontero P, Fontana F, Bagnasacco A, et al. Is there an optimal time for intracavernous prostaglandin E1 rehabilitation following non- nerve sparing radical prostatectomy? Results from a hemodynamic prospective study. J Urol. 2003;169:2166-2169.

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