- Author: Stephen A Metz, MD, PhD; Chief Editor: Richard Scott Lucidi, MD, FACOG more...
Traumatic disruption of the female perineum is not uncommon. Women are at risk during parturition; additionally, their increasing participation in sports activities increases the incidence of injury to this area. Tragically, women continue to be the victims of sexual abuse; however, many of these injuries involve only superficial structures and heal spontaneously with local care. When tissue disruption extends to deeper tissue planes or involves the vascular anatomy or structural integrity of the perineal support system, operative intervention is required.
Trauma to the female perineum can occur from many different circumstances. The most common setting, of course, is vaginal delivery secondary to acute distention of the vaginal canal during passage of the fetus or to instrumentation during operative delivery. Non-obstetric trauma can result from "straddle injuries" resulting from abrupt contact with a structure such as a bicycle crossbar, "penetration injuries" resulting from impalement by the end of a hard rod-like instrument, or "complex injuries" resulting from blunt trauma. The focus of this article is evaluation and management of injury to the female perineum resulting from nonobstetric trauma.
The incidence of trauma to the female perineum sufficiently damaging enough to require active medical intervention is unknown. One series from the University of North Carolina Hospitals reported 29 cases admitted for treatment between 1975 and 1991.
Perineal trauma, in general terms, occurs by one of the following mechanisms:
During parturition, as the fetal head passes through the birth canal and vaginal introitus
As the result of impact caused by acute deceleration injury (eg, straddle injury associated with falling on the crossbar of a bicycle)
Insertion injury (eg, from forceful coitus, insertion of foreign body during sexual assault, impaling injury secondary to a fall)
Penetrating injury, such as knife or gunshot
Complex injury from blunt trauma
Blunt trauma to the perineum (eg, straddle injury, deceleration injury) results in rapid stretching of involved tissues at such a rate and to such a degree that tissue elasticity is insufficient to accommodate expansion, and the tissue tears. The depth and extent of laceration are determined by the rate of stretching, the nature of the trauma incurred, the location of the trauma, and the inherent elasticity of the affected tissue. By and large, the depth of the injury is limited to the superfical tissue of the perineum, as the soft tissues of the perineum and bony structures of the pelvis offer protection to deeper structures.
The female perineum is highly vascular. Arterial blood supply is derived primarily from the terminal branches of the internal pudendal artery, which enters the perineum laterally near the ischial tuberosity, then divides into branches supplying the perianal and perivaginal tissue and the vestibular bulb. There are rich anastomoses with external arteries such as the posterior labial artery and the external pudendal artery. The perineum is drained by an extensive venous network, especially the erectile tissue of the labia majora and glans clitorus. These veins, which are not protected by valves, have multiple interconnections with the internal pelvic venous system. Even in the absence of epithelial laceration, blunt trauma to the perineum can result in significant tissue damage, such as hematoma formation, tissue crushing, and, possibly, devascularization because of compromise of local perfusion.
When evaluating a patient who presents with lower abdominal trauma or pelvic trauma (eg, vehicle accident injuries, penetrating trauma to the lower abdomen) consideration must be given to the possiblity of perineal or internal genitalia injury. Being alert to such a possibililty is especially true of children. Because of the nature of their activites, it is not uncommon for them to sustain complex perineal injuries resulting from forceful contact with toys, etc., but they may be reticent to report this because of embarrassment.
The possibility of remote trauma should be considered in the evaluation of a patient who presents with some form of perineal dysfunction, especially if there is some evidence of a remote history of trauma. For example, a woman who has sustained damage during forceful coitus may be too embarrassed to seek evaluation until she is compelled to by her perineal pain. Other presenting complaints may relate to competence of the structures that pass through the perineum (eg, anus, urethra) or to discomfort with coitus.
When confronted with a patient who may have sustained traumatic injury, attempt to ascertain the nature and degree of the trauma to identify the extent of collateral damage that may have occurred. Otherwise, occult injury may pass unnoticed and remain uncorrected. Adequate evaluation of the extent of the injury and appropriate reconstruction is not possible without a comprehensive knowledge of perineal structural and vascular anatomy.
The objective of the evaluation is to determine expeditiously the nature and extent of injuries so that appropriate restorative therapy can be instituted as promptly as possible.
History and physical examination are the most useful diagnostic tools for evaluating a patient who has sustained perineal trauma. A detailed history, if obtainable, provides information regarding the location and probable extent of the injury. This enables the examiner to direct special attention to aspects of the perineum and vagina that are at increased risk because of the nature of the trauma. For example, a history of a straddle injury should direct attention toward disruption of the perineal body, anus, and distal urethra, whereas penetration injury should prompt consideration of possible damage to the vaginal canal and pelvic viscera.
The first objective of the physical examination is to ensure that the patient is hemodynamically stable. As noted previously, the pelvis is richly perfused. Extensive occult hemorrhage can occur in the large potential spaces of the pelvis, such as the ischiorectal fossa. Moreover, as is true of obstetric trauma, intravaginal penetrating injuries can disrupt the retroperitoneal vasculature, with resultant retroperitoneal and intraperitoneal hemorrhage.
For women who sustain significant perineal trauma in association with more general injuries, for example, from motor vehicle accidents, the possibility of cervical spine instability must be evaluated prior to any definitive evaluation or management of non–life-threatening injuries.
Once the patient is deemed stable, a thorough visual examination is made of the vulva and vagina for lacerations, ecchymosis, and fluctuance, followed by a bimanual evaluation for intrapelvic masses. In the special case of a woman who has experienced a severe deceleration injury (eg, straddle injury), the bony pelvic girdle must be palpated for tenderness or crepitation. The symphysis pubis, particularly, must be evaluated for stability.
The importance of a meticulous examination, under anesthesia if necessary, cannot be overemphasized. The full extent of injuries can only be assessed by a comprehensive survey. Implicit in this statement is the realization that the surface disruption may signal the possibility of damage to deeper structures; therefore, the success of such an evaluation depends on an intimate and detailed understanding of pelvic anatomy.
Surgical repair of the vulva or vagina following trauma should be undertaken to obtain control of hemorrhage or to restore structural and functional integrity of lower genital tract structures.
The surface anatomy of the perineum and vulva is shown in the image below. Pertinent features are labeled. Surface features serve as useful landmarks for important deep structures. For example, the lateral segments of the hymeneal ring overlie the medial borders of the levator ani muscles. The labia majora are elevated by the bulbocavernosus muscles and vestibular bulbs. Surrounding the anus are radially directed superficial skin folds created by subcutaneous attachments of the extrinsic anal sphincter fibers. In the nulliparous female, the sagittal dimension of both the vaginal introitus and the perineum is approximately 2 cm. An increase introitus:perineum ration may indicate perineal body disruption, especially in the nulliparous patient.
The following image illustrates pertinent vulvar structures deep to the skin.
Take special note of the following features:
The perineum can be conveniently conceptualized as being composed of anterior and posterior triangles divided by a line connecting the 2 ischial tuberosities. Posterior to this line, which parallels the posterior borders of the transverse perineal muscles, are the ischiorectal fossae, which are fatty, tissue-filled spaces that communicate with the subcutaneous fat-pad of the back. Anterior to this line is the perineal membrane. This layer, which is pierced by the genital hiatus and the urethra, separates the anterior triangles into deep and superficial compartments.
On either side of the vaginal vestibule, immediately under the skin of the labium major, is a fingerlike extension of the superficial fatty layer (Camper fascia) of the lower abdominal wall. Through the medial aspect of this process passes a projection of the round ligament, which is surrounded by extensions of layers of the abdominal aponeurosis as it emerges from the external inguinal ring. Terminal processes of the round ligament insert in the fibers of the bulbocavernosus muscles.
The superficial anterior perineal compartment lies under the perineal fat pad on either side of the vaginal hiatus. This triangular compartment is bounded (1) medially by the bulbocavernosus (bulbospongiosus) muscles, which border the vaginal introitus; (2) laterally by the ischiocavernosus muscles, which lie along the ischiopubic rami; and (3) dorsally by transverse fibromuscular structures (the transverse perineal muscles), which span the gap between the ischial tuberosity and the central tendon of the perineum.
The anterior surface of the compartment is composed of condensation of areolar and adipose tissue, (ie, Colles fascia). This layer, which is a continuation of the Scarpa fascia of the anterior abdominal wall, extends from the lateral aspect of the bulbocavernosus muscle to the ischiopubic ramus. Anteriorly it inserts in the connective tissue of the inguinal ligament, and posteriorly it terminates as the fascia of the posterior margin of the anterior perineal triangle. The deep surface of the compartment is the perineal membrane.
The bulbocavernosus muscles originate at the deep surface of the inferior margin of the pubic arch, then course posteriorly along the lateral surfaces of the vaginal introitus to insert in the central tendon of the perineum (perineal body) between the posterior vaginal fourchette and the anus. Contraction of these muscles serves to close the distal portion of the vaginal hiatus. Each of these muscles overlies one of the paired vestibular bulbs, which are composed of highly vascular erectile tissue and venous plexus enmeshed in loose connective tissue. The vestibular bulbs become engorged during sexual arousal.
Midline perineal structures important to this topic include the clitoris, urethra, vagina, central tendon of the perineum, anal canal, and anal sphincter complex.
The urethral meatus penetrates the perineal membrane (urogenital diaphragm) immediately anterior to the vagina. At this level, the perineal membrane, compressor urethrae, and urethrovaginal sphincter muscle of the distal urethra intermingle to form a dense 3-diminsional mass of tissue. Anterior to the urethral meatus is the clitoris, which is suspended from the inferior arch of the pubic body by a suspensory ligament through which passes the clitoral vasculature.
The vagina is a hollow, muscle-walled viscous organ lined by nonkeratinizing squamous epithelium. Distal to the hymeneal ring, the vagina opens into the vestibule, which is bordered by the paired labia minora. The distal third of the vagina is densely adherent to the perineal membrane anteriorly and laterally, the medial borders of the levator ani laterally, and the perineal body posteriorly.
Above the levator ani, the muscular tube of the vagina is encased in loose connective tissue. The vagina is suspended in its position by the attachment of lateral condensations of this connective tissue (the paracolpos or fibers of Luschka) to the internal fascia of the levator ani and obturator internus muscles. Apical support of the vagina, together with the cervix and uterus, is provided by the cardinal and uterosacral ligaments.
The cardinal ligaments consist of condensations of loose areolar tissue, nerves, and blood vessels. These bundles sweep from the anterolateral aspects of the proximal anterior vagina and cervix to invest in the fascia of the ipsilateral coccygeus muscle proximal and medial to the ischial spines.
The uterosacral ligaments are similar complexes extending from the cervix and proximal posterior vaginal wall to invest along the lateral surfaces of the bodies of the second through fourth sacral vertebrae.
At the level of the perineal diaphragm, the urethra is so intimately related to the distal vagina that there is no natural cleavage plane between the two. Proximal to the levator fascia, the previously described vaginal adventitia separates the urethra and bladder from the vaginal muscularis.
Immediately posterior to the vaginal vestibule is the perineal body. From a functional standpoint, referring to the connective tissue elements of this structure as the central tendon of the perineum is more appropriate. Into this structure is inserted the paired bulbocavernosus muscles described above, the paired transverse perineal muscles, which originate at the ischial tuberosities, and fibers from the external anal sphincter. Into the deep portion of the perineal body, the fibers of the levator raphe and the rectovaginal fascia are inserted. This relationship is discussed in more detail later.
The importance of the central tendon of the perineum is evident from evaluation of the distribution and orientation of the fibers of the contributing muscle groups. If the perineal body is intact, coordinated contraction of these muscles, including the anal sphincter, results in cephalad motion of the central tendon and, consequently, elevation of the perineum.
Posterior to the perineal body is the anal canal. This, the terminus of the gastrointestinal tract, is composed of the same tissue layers as the more proximal components, ie, mucosa and submucosa surrounded by a lamina propria, an internal, circularly oriented smooth muscle layer, and an external longitudinal smooth muscle layer. The thickened circular smooth muscle layer of the proximal anal canal forms the internal anal sphincter, which provides 75-85% of the resting tone of the anal wall.
Caudad to the levator ani, the striated muscle fibers of the external anal sphincter surround the anal canal. This muscle is typically thought of as being composed of 3 components: the distal (subcutaneous) segment, the intermediate segment, and the proximal (deep) segment. The superficial segment is attached posteriorly to the tip of the coccyx, whereas the deep segment is intimately related to the puborectalis fibers that sweep posterior to the anal canal.
Anteriorly, fibers from the external sphincter insert into the central tendon of the perineum. The anal sphincter complex, composed of both internal and external anal sphincter components, averages almost 2 cm in thickness and extends for a distance of almost 3 cm caudad to the levator border. The internal anal sphincter, composed of smooth muscle, is innervated by the intrinsic autonomic system of the gastrointestinal system. The external anal sphincter receives innervation from the pudendal nerve.
Above the puborectalis raphe, the vagina is separated from the underlying distal rectum by a thin layer of connective tissue, the rectovaginal fascia or fascia of Denonvilliers, which is generally rudimentary in the female. Each lateral border of this sheet of tissue is fused with the inner fascia of the ipsilateral levator ani complex. This tissue sheet overlies the rectum, spanning the posterior pelvis from the level of the ischial spines distally to the levator raphe, into which it inserts.
Note that the most inferior recess of the peritoneal cavity (pouch of Douglas) is adjacent to that portion of the proximal posterior vaginal wall between the rectosigmoid junction and the posterior lip of the cervix.
Deep to the perineal membrane anteriorly, and forming the deep margin of the posterior compartment, are the levator ani muscles. These striated muscle groups originate along the posterior aspect of the pubic bone and the inferior margin of the obturator muscles (ie, arcus tendentious levator ani), and sweep posteriorly and medially to insert into the levator plate, a band of connective tissue extending from the coccyx to the posterior aspect of the rectum as it passes through the levator hiatus.
Fibers of the most medial of these bundles are intertwined with the deep portion of the perineal body between the vagina and the anal canal. The distal margin of the rectovaginal fascia is also fused with this complex. This layer of connective tissue, which separates the muscular walls of the vagina from the distal rectum, inserts into the anterior fascia of the levator ani on either side of the pelvis, along a line that extends from the ischial spine distally to the central perineal tendon between the anal canal and the vaginal fourchette.
The image below illustrates the vascular supply of the perineum.
The principal arterial supply to the perineum are the internal pudendal arteries. Each of these terminal branches of the internal iliac arteries passes medial to its ipsilateral ischial spine, then divides into a medially directed branch to the distal rectum (the inferior hemorrhoidal arteries) and a branch that courses anteromedially along the ischiopubic ramus to the pubic arch. Superficial and deep tributaries of this branch, in turn, course medially to supply the superficial structures, the central tendon of the perineum, the vestibular bulb, the distal urethra, and the clitoris. As is generally true of the pelvic region, there is an extensive anastomotic network of this vasculature with superficial branches of the ipsilateral femoral artery, most notably the external pudendal artery.
Arterial supply to the proximal vagina derives from several sources. Tributaries from the internal pudendal artery enter the superior aspect of the vagina via the uterosacral ligaments, then divide into lateral and medial branches along the posterior aspect of the vagina. Branches of the internal iliac and uterine arteries supply the anterior and anterolateral aspects of the vagina via the cardinal ligaments.
Innervation of the deep pelvis is provided by branches of the pudendal nerve. The superficial perineum derives sensory innervation primarily from the genital-femoral and ilioinguinal nerves, which originate in the upper lumbar portion of the spinal cord and pass through the inguinal canal to reach the perineum. The lateral femoral cutaneous and iliohypogastric nerves also provide sensory information.
Do not undertake restorative surgical management of a patient who has sustained perineal trauma, except as necessary to achieve control of hemorrhage, until the patient is sufficiently stable to tolerate general or regional anesthesia.
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