Practice Essentials
Genital tract outflow is important for the expulsion of normal secretions from the cervix and vagina. Outflow is also critical for menstrual efflux. [1] Outflow obstruction may occur at different levels, with resultant variations in clinical presentation and treatment.
The majority of obstructions are congenital and therefore are present at birth; however, they usually go undiagnosed until puberty. [1] This is because very few symptoms are present before the start of menstruation. Occasionally, outflow obstruction can be found earlier on physical examination or in newborns who form a mucocele from obstructed vaginal secretions. There have been some case reports of acquired obstruction from labial adhesions secondary to radiation or lichen sclerosis.
The treatment for all obstructions is surgical intervention, carried out by a skilled surgeon who is comfortable with navigating the pelvic anatomy and has a thorough understanding of embryologic development. Often, surgical treatment will take place during early adolescence, in which case referral to a pediatric and adolescent gynecologist may be preferred. [1]
With appropriate treatment, the prognosis is excellent, and full recovery is typical. Occasionally, outflow obstruction is found in conjunction with more complicated anomalies (eg, exstrophy or cloacal anomalies) that may also involve the urologic and digestive tracts, making treatment and recovery much more complicated.
Pathophysiology
Embryologically, the reproductive system develops from all three germinal layers, starting at approximately 6 weeks' gestation and reaching completion by 14 weeks. [2] The ovaries are derived from endoderm, the internal reproductive structures from mesoderm, and the external reproductive structures from ectoderm. [3] Because the greater part of the obstructive pathology develops during embryology, it is important to understand the steps that occur.
The female internal reproductive structures include the fallopian tubes, the uterus, the cervix, and the upper two thirds of the vagina. Before differentiation into male and female, all embryos have paired mesonephric (or wolffian) ducts that connect the kidneys to the cloaca, as well as paired paramesonephric (or müllerian) ducts. [4] Female development is the default occurrence in the absence of the SRY gene from the Y chromosome. Without SRY, the mesonephric ducts degenerate, and the paramesonephric ducts develops further into the internal reproductive structures. [3]
Failure of vertical fusion or canalization of the paired ducts in utero may result in rudimentary uterine horns, bicornuate uterus, uterus didelphys, or a longitudinal vaginal septum. [4] Often time such müllerian anomalies occur in conjunction with renal anomalies due the metanephric duct developing into the kidneys and ureters around the same time. [5]
The female external reproductive structures include the lower third of the vagina, the external genitalia, and parts of the bladder. These develop as the urogenital sinus involutes cephalad and differentiates into the sinovaginal bulb. The sinovaginal bulb ultimately meets and fuses with the vaginal plate from the distal portion of the müllerian ducts forming the hymen. [4] Normally, the hymen then perforates during embryogenesis, but if it does not, the result is an imperforate hymen. Incomplete vertical fusion of the two systems can lead to cervical atresia, transverse vaginal septa, or distal vaginal atresia. [4]
Etiology
The exact etiology of such genital tract anomalies is unclear. Any defect in the normal organogenesis involving the urogenital sinus or the müllerian duct can result in genital tract anomalies. No single gene mutation has been found to be responsible for such anomalies. Mice studies have shown a variety of genes involved in normal development of the reproductive system [1] ; specifically, WNT and HOX have been found to be involved with Mayer-Rokitansky-Küster-Hauser syndrome (MRKH). [5]
Acquired outflow obstructions have also been described. They can develop in patients who have posttransplant graft-versus-host reactions, undergo radiation therapy, or have lichen sclerosis lesions that cause scarring of the vagina and vaginal agglutination.
Epidemiology
Female genital malformations occur in 5-7% of the general population. [1] The most common of these is imperforate hymen, with an estimated incidence of 1:1000-2000. [1] Müllerian agenesis (also referred to as müllerian aplasia, MRKH, or vaginal agenesis) has an incidence of 1 per 4500-5000 females. [6] It is caused by embryologic underdevelopment of the müllerian duct, with resultant agenesis or atresia of the vagina, uterus, or both. As many as 53% of such malformations are associated with other anomalies as well, particularly anomalies of the kidneys and the skeleton. [6]
Prognosis
After surgery, these patients' quality of life usually improves immediately; only very rarely do any further complications arise. [7] The extent of the surgical procedure required depends on the type of anomaly found. For the most common anomalies (eg, imperforate hymen), the procedure is performed via a vaginal approach and is relatively low-risk. For some of the more complex anomalies, especially those in which with other systems are affected, an abdominal approach may be necessary, and other specialists (eg, urology) should be involved. [8]
In selected patients, menstrual suppression may be attempted as a means of delaying surgery. [8] However, complete suppression is not always achievable, and it is a therapy that would have to be maintained until menopause. Infertility rates among patients after treatment are consistent with those among the general population, aside from the unique situation of cervical agenesis that neessitates hysterectomy for treatment. [3]
If outflow obstruction is left untreated, menstrual blood will continue to accumulate just above the anomaly. Some of the blood does begin to be reabsorbed, but not rapidly enough for reabsorption to be completed before trapped menstrual blood accumulates with the next period. Once the volume of trapped blood is large enough, it can become very painful to the patient and can even lead to urinary retention and constipation. [9] These patients also have higher rates of endometriosis, which is theorized to be due to retrograde menstruation occurring as a consequence of the obstruction. [10] In most patients, the endometriosis seems to resolve after the obstruction is relieved. [11]
Patient Education
For patient education resources, see the NASPAG and Female Sexual Problems.
