Gynecology For The Colon And Rectal Surgeon
Susan C. Parker, MD, MS
Surgeons, whether in the field of colon and rectal surgery, urology, or gynecology, tend to view pelvic structures from their own vantage point and focus on the viscera of their expertise. Historically, these specialties did not overlap with the exception of operations such pelvic exenterations for malignancy. A national focus on female pelvic floor disorders endorsed by the NIH, the development of techniques such as sacral nerve stimulation that apply to disorders of multiple specialties, and the emergence of joined specialties (urogynecology) and combined specialty meetings are a few examples of an emerging appreciation of the shared functionality and importance of pelvic structures. The colon and rectal surgeon should recognize the effect posterior pelvic operations have on anterior viscera so that patients can be appropriately counseled or offered the option of combined operations to simultaneously treat pelvic disorders. An appreciation of the anatomical aspects of anterior pelvic support and various reconstructive procedures for urinary incontinence and genital prolapse may help our understanding of posterior prolapse and provide us with a better appreciation for the complexities of pelvic surgery.
Pelvic Support Structures
Injuries to pelvic support structures commonly occur during parturition leading to disorders such as vaginal prolapse, urinary incontinence, cystoceles, and rectoceles. 50% of parous women have some degree of genital prolapse while only 2% of nulliparous women have symptomatic prolapse. Increasing parity has a strong association with pelvic organ prolapse resulting in a 11-fold increase in risk in women with greater than 3 deliveries compared to nulliparous women. Pelvic floor injuries are the result of defects in anatomic support such as fascial tears, or denervation of pelvic floor muscles.
The muscular elements of the pelvic floor, the levator ani muscle, pubococcygeus, and ileococcygeus muscles form the inferior support of the urethra, vagina and rectum. The levator ani is commonly described as providing support like a hammock but it also has complex anterior fascial connections that provide additional support, define anatomical spaces, and, when ruptured, lead to prolapse disorders. When there is a loss of muscular support from the levator ani muscles due to denervation or loss of muscular tone, support of the pelvic viscera becomes more dependent on the connective tissue. This is typically illustrated by the concept of a boat (viscera) in water (levator muscle) steadied with mooring lines (connective tissue). If the water is drained, support of the boat is dependent on the mooring lines that are now under great stress and more likely to break. Those mooring lines are known as the endopelvic fascia.
The endopelvic fascia is one continuum of fibromuscular connective tissue covering the levator ani muscle that condenses into tough fibrous bands that provide support to pelvic structures. The anterior pelvic structures, urethra, and bladder are separated from the posterior pelvic structures (anus and rectum) by the vagina and uterus supported by endopelvic fascia. It spans ventral to dorsal from pubic bone to sacrum and laterally along the vaginal wall arcing backwards into large butterfly-wing expanses called the uterosacral cardinal ligament complexes. Laterally this fascia attaches to the sides of the pelvis along the arcus tendineus fascia pelvis (obturator fascia) that extends from the pubic symphysis to the ischial spine. Posterior, between the rectum and vagina, this fascia is known as Denonvilliers’ fascia or the rectovaginal septum. It has been further described as providing three levels of support to the vagina (DeLancey levels I – III). Whatever name is used, (Denonvilliers, rectovaginal, endopelvic, levator) this fascia has histologic differences when compared to abdominal wall fascia, fascia lata, and other muscular fascial coverings. Endopelvic fascia has the typical collagen and elastin fibers seen in other fascias, but it also has strands of smooth muscle fibers that are particularly thick and abundant in the rectovaginal septum. The purpose or innervation of these smooth muscle fibers is unknown.
Vaginal Support
In the normal patient the vagina has a distinct curvature, lying at a 45-degree angle to a vertical line distally and curving horizontally as it crosses the levator plate. This angulation reflects the integrity of the levator plate and any loss of muscular tone can result in a loss of angulation and a more vertical lying vagina. Normally, an increase in intraabdominal pressure compresses the vagina against the levator plate. Patients with pelvic floor injury exhibit changes such as a larger vaginal introtus and a vertical vagina that lacks the protective mechanism of angulation and can evert or prolapse in response to increased intraabdominal pressure. The cervix, which does not implant onto the apex of the vagina but into the anterior vaginal wall, is supported, along with the uterus, by its attachment to the uterosacral cardinal ligament complex.
Posterior Vaginal Support, Rectoceles and Enteroceles
Rectoceles are common, seen in up to 80% of nulliparous, asymptomatic women undergoing defecography. While most rectoceles are small in size and do not require surgical correction, large rectoceles are common in women with pelvic prolapse and can contribute significantly to evacuation difficulties. The structural changes that result in rectocele formation are poorly understood but excellent anatomical work has shed some light on this perplexing problem. DeLancey describes three levels of the support of the vagina. The disruption of vaginal support at different levels can result in rectocele formation or prolapse. The distal level of support (Level III) is a thick layer of connective tissue, the perineal body that is the midline of the urogenital diaphragm or perineal membrane. The perineal membrane stretches from ischiopubic rami to ischiopubic rami with a central condensation, the perineal body. The layer extends up the rectovaginal space 2 – 3 centimeters above the hymenal ring becoming progressively thinner. A break in this membrane allows the rectum to displace downwards. Proximally, the endopelvic fascia or rectovaginal septum extends between the vaginal wall and the inner surface of the pelvic diaphragm (Level II). These fibers attach to the posterior lateral vaginal wall and a few fibers stretch horizontally between rectum and vagina. Cutting these fibers in the midline causes little displacement of the vagina but cutting lateral fibers does result in destabilization of the vagina. The cardinal/uterosacral ligament complex (Level I) supports the upper vagina.
The levator ani muscles are attached to the upper surface of the perineal membrane. A break in this membrane allows the muscle to pull apart. Another important aspect of levator ani muscle anatomy is the lack of a midline connection between the vagina and rectum. Levatoroplasty artificially creates a midline connection of muscle fibers between the rectum and vagina. In some cases, this artificially increased levator tone can result in dysparunia, pelvic pain, or paradoxical relaxation.
Enteroceles occur when the peritoneum lies in contact with the vaginal mucosa without the intervening endopelvic fascia. Enteroceles can be anterior to the vagina, apical, or posterior. Anterior enteroceles are more common in patients who have undergone surgery, particularly operations for vaginal prolapse that alter the horizontal angulation of the vagina opening the space between the vagina and bladder. An apical enterocele is seen after hysterectomy and almost always associated with a degree of vaginal eversion or prolapse. Posterior enteroceles are more common if the uterus is in place and accompany cystoceles, uterine prolapse or rectoceles. Enteroceles of this type can be difficult to detect on physical exam, particularly if the patient has a large rectocele. A rectal enterocele occurs when the anterior wall of the rectum is pushed out through the anus by the enterocele sac. It can be distinguished from true rectal prolapse by the lack of circumferential prolapse and with the use of imaging techniques.
Increasing use of defecography and peritoneography has led to more frequent diagnosis of enteroceles; their prevalence is now estimated at 18-37%, and upwards of 55% of patients with an enterocele have other concomitant pelvic floor disorders. However, little is known of the actual impact enteroceles may have on rectal emptying. Halligan and colleagues prospectively studied 50 consecutive patients with constipation, and compared their results with 31 controls undergoing peritoneography for groin pain. While a majority of constipated patients (77% versus 10% in the control group) had deep rectogenital pouches, only 58% filled with small bowel contents during the study. Moreover, those with an enterocele evacuated more rapidly and completely than either the constipated patients with a deep pouch or those without. Therefore, when is the diagnosis of an enterocele relevant? Among the 11% of US women who will have a pelvic floor repair by age 80 years, preoperative identification and repair of an enterocele (incorporated into the previously planned repair) may help to prevent persistent symptoms or presumed early recurrence of obstruction. Nonetheless, among minimally symptomatic or asymptomatic patients, or among those in whom a repair is not otherwise warranted, the prudent surgeon must not over-construe the importance of an incidentally identified enterocele.
Surgery for Vaginal Prolapse
There are three treatment options for vaginal prolapse; watchful waiting, pessary, and surgery. Quality of life issues are the main reasons to consider surgery. Symptoms of vaginal or uterine prolapse than may prompt surgery include an uncomfortable vaginal bulge, defecation difficulties, the need to splint for defecation or voiding, ulceration, back pain, urinary retention, and hydronephrosis. A pessary is a good temporizing measure but may not work for all patients. Uterine prolapse is corrected with hysterectomy, either vaginal or abdominal, along with resuspension of the vaginal apex to the uterosacral ligaments. Additionally, a sacrocolpopexy, suspension of the vaginal apex to the anterior sacrum using fascia or mesh, or to the sacrospinous ligament using suture will provide additional support. A less invasive option is a Le Fort colpocleisis that is an obliterative procedure and appropriate for elderly, infirm or non-sexually active patients.
Anterior vaginal wall fascial defects are repaired by anterior colporrhaphy using graft materials such as fascia or mesh. Paravaginal fascial defects are repaired using a vaginal or abdominal approach. The abdominal method typically accompanies other reconstructive surgery such as a Burch colposuspension.
Posterior vaginal wall defects often result in a combination of vaginal prolapse, enterocele, and rectocele. In extreme cases, the rectosigmoid colon may detach from the anterior sacrum and prolapse anteriorly into the vagina. Correction of the vaginal prolapse alone, without attention to the rectosigmoid detachment, can lead to a later presentation of rectal prolapse.
Normal Continence
Stress urinary incontinence is a common problem. The factors influencing continence can be described using the anocronym UCLA which stands for Urethral changes occurring during stress, Closing function of the urethra, Length of the urethra, and Anatomy.
Urethral changes during stress are the valvular effect of the bladder neck, the underlying support of the urethra, and the contraction of the pelvic musculature. The closing function of the urethra refers to a seal-proof closure that provides continence during activities such as walking or straining. This is due to a complex urethral sphincter somewhat analogous to the complex anal canal – specifically an inner mucosal layer with vascular cushions, a middle smooth muscle, and an outer skeletal muscle sphincter. The urethral mucosa covers a rich vascular cushion that deforms with external pressure but can also form a watertight seal around a catheter. Factors that can adversely affect this mucosal "seal" include estrogen losses, radiation, and atherosclerosis. The middle layer is a fibromuscular envelope with smooth muscle and slow-twitch skeletal muscle. Autonomic nerves from sacral nerves S2 – S4 innervate the smooth muscle. The outer component is a fast-twitch skeletal muscle innervated by S2-S4 with both voluntary and involuntary reflexes. Involuntary reflexes increase muscle tone in response to increased abdominal pressure to prevent leakage of urine. A general loss of pelvic floor tone can also mean a loss of the urethral skeletal muscular tone leading to stress urinary incontinence.
Urethral length refers to the distance between the bladder neck and the external urethral meatus. Again analogous to the high-pressure zone of the anal canal, the functional urethral length refers to the length of the urethral with pressures above intravesical (bladder) pressures. Patients with stress incontinence have a shorter functional length due to incompetence of the proximal portion of the urethra. Incompetence of the proximal portion means the midportion of the urethral is more important for continence as the distal urethra does not supple any support and is just a conduit for urine. The midportion of the urethra lies on the pubourethral ligament that provides a "backboard" of support. An increase in intraabdominal pressure compresses the midportion of the urethra against this "backboard" occluding it and preventing the egress of urine.
Normal anatomic support of the bladder neck and urethral allows intraabdominal pressure to be transmitted in a way that increases continence. Loss of bladder neck and urethral support may not result in incontinence if other components of continence do not fail. Analogous to obstetric sphincter injury and subsequent fecal incontinence occurring at a much later age, anatomic defects affecting the bladder or urethral support also occur during childbirth but incontinence is more frequently seen after menopause suggesting a similar failure of compensatory mechanisms in patients with underlying anatomic defects.
Surgical Correction of Urinary Incontinence
Operations for the correction of urinary incontinence repair the anatomical support of the bladder neck and urethra (Burch procedure), provide support to the midurethra (slings), or augment the mucosal seal (collagen injection). Additional fascial defects are often identified (midline and lateral) as defects affecting bladder support are rarely isolated and usually occur with defects involving vaginal support. Placing stitches lateral to the urethra in the endopelvic fascia and then suspending it from Cooper’s ligament to stabilize the urethra proving "backboard" support constitutes the Burch procedure. This requires an intraabdominal approach and is easily combined with a paravaginal repair of lateral fascial defects. Sub-urethral slings (tension free vaginal tape, autologous fascia, allograft fascia) are also aimed at providing support to a hypermobile urethra but can be done as an outpatient procedure under minimal sedation. Tension free vaginal tape was first introduced in 1995 in Sweden and has quickly become a common minimally invasive approach to stress urinary incontinence. It consists of a 1 X 40 cm strip of polypropylene mesh (Prolene, Ethicon, Inc.) covered by a plastic sheath and attached to two reusable stainless steel needles. An incision is made in the anterior vaginal wall 1 cm proximal to the external urethral meatus. A small periurethral tunnel is developed. The needles are advanced up through the vaginal incision exiting out skin incisions made on either side of the midline just below the symphysis pubis after passing through the endopelvic fascia below the symphysis pubis and the retropubic space. The plastic sheath covering the polypropylene mesh is removed leaving the sling in place. The patient is then instructed to cough and the tape tension is adjusted to achieve continence during stress while avoiding overcorrection and urinary retention. In a recent multicenter study, 3% of patients experienced complications such as urinary retention, hemorrhage, bladder perforation, and infection. With an increase in intraabdominal pressure (cough, laugh, sneeze stress incontinence) the urethra is compressed against the new "backboard" or sling allowing compression and closure of the urethra. Only early data is available for TVT, but success rates of 74 – 84%are comparable to open sling procedures. Injectables such as silicone or collagen are used to bolster the mucosal seal. In selected patients, a combination of techniques, i.e. a sling and injectable, may be needed to restore continence.
Combined Operations
Given the shared functionality of pelvic structures, when should colon and rectal surgeons consider combined operations with other specialties for the pelvic prolapse patient? Operations can be combined for patient convenience, to avoid the emergence of new symptoms, and to avoid a second abdominal procedure.
For convenience, an operation such as an overlapping sphincteroplasty for fecal incontinence can be combined with a sling procedure for urinary incontinence. The widely used tension-free vaginal tape procedure is usually done as an outpatient procedure but can be performed after an overlapping sphincteroplasty. It requires placing the patient in lithotomy position.
Urinary incontinence can emerge as a new problem after pelvic floor operations. Large rectoceles and enteroceles can provide support to the anterior vaginal wall leading to a degree of obstruction that may mask underlying urethral defects. Once the rectocele or enterocele is reduced, the patient can be rendered profoundly incontinent of urine. In extreme cases, the risk of urinary incontinence may outweigh the perceived benefit of a rectocele or enterocele repair. The simple maneuver of reducing the rectocele or enterocele bulge when the patient is standing with a full bladder may reveal this problem.
The multidisciplinary approach to the patient with pelvic floor disorders is best applied to the patient with multiple lifestyle altering symptoms of urinary, genital, and defecatory dysfunction, especially if an abdominal approach is being considered. While the ideal situation allows evaluation of all systems in a single setting, i.e., a pelvic floor center, the same can be accomplished by good communication and coordination between specialties.
Selected References
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Smith AR, Hosker GL, Warrell DW. The role of partial denervation of the pelvic floor in the etiology of genitourinary prolapse and stress urinary incontinence of urine: a neurophysiological study. Br J Obstet Gynaecol 1989;96:24-8
Dupont MC, Albo ME, Raz S. Diagnosis of stress urinary incontience. An overview.
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Ulmsten U, Johnson,P, Rezapour M. A three-year followup of tension free vaginal tape for surgical treatment of female stress urinary incontinence. Br J Ob Gyn 1999; 106:345-350.
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