Introduction
Structural defects of the uterus and vagina are associated with a host of gynecologic and obstetric clinical problems. The defects are caused by either a genetic error or exposure to a teratogen during embryonic development. The incidence of congenital uterine anomalies is not precisely known but reports suggest that defects occur in 2–4% of all women and in 10–15% of women with recurrent pregnancy losses. Advances in imaging techniques and development of less invasive surgical procedures have advanced the clinician’s ability to detect these abnormalities and provide more management options.
The three common developmental defects of the mullerian system are lateral fusion defects, vertical fusion defects, and agenesis. Lateral fusion defects are the most common mullerian developmental defects and septum is the most common fusion defect. Lateral fusion defects occur from failure of formation, fusion or absorption or abnormal migration of one or both of the mullerian ducts. An example of an asymmetric lateral fusion defect is the unicornuate uterus. The bicornuate or arcuate uterus results from a partial fusion defect whereas uterine didelphys occurs when the two mullerian ducts massively fail to fuse.
Vertical fusion defects result from either a failure of fusion between the caudal end of the mullerian duct and the urogenital sinus or a failure of proper vaginal canalization. Vertical fusion defects include cervical agenesis, cervical dysgenesis and vaginal septums and are often responsible for outflow obstruction problems.
Agenesis of the mullerian ducts may result in complete absence of the uterus and vagina known as Mayer Rokitansky Kuster Hauser syndrome, hemiuteri or uterine horns, uterus without a cervix or variable uterine development.
Uterine abnormalities
It is estimated that as many as 50–75% of congenital uterine abnormalities remain undiagnosed. In one study, 679 women with normal reproductive histories underwent a hysterosalpingogram. In this “normal” population, 3.2% were diagnosed with congenital anomalies, which included septate uterus (90%), bicornuate uterus (5%), and didelphys uterus (5%). It is important to consider the diagnosis of mullerian anomalies in all patients presenting with a history of recurrent miscarriage, premature delivery, abnormal fetal presentation or late abortion or for women presenting with primary amenorrhea, severe dysmenorrhea, dyspareunia or infertility. The clinician should be alerted to the possibility of a uterine anomaly in the clinical settings listed in Box 100.1.
Congenital uterine abnormalities are commonly associated with second-trimester loss because of limited intrauterine space and an associated incompetent cervix. An intrauterine septum may have poor blood supply to the septum, resulting in poor implantation, poor placental growth, and early or mid-trimester pregnancy loss. Premature labor and abnormal fetal presentation are also common problems associated with intrauterine anomalies that limit intrauterine space. Two-thirds of pregnancies in women with a uterine duplication are expected to reach term.
A noncommunicating rudimentary horn with functional endometrium may present as recurrent abdominal pain or hematometra. Many patients with mullerian system anomalies have cervical incompetence. Vaginal septums may present as dyspareunia or obstruct a normal vaginal delivery. Some patients with severe outflow obstruction present with hematocolpos.
Vaginal abnormalities
Abnormalities of the vagina can range from abnormalities of the hymen, transverse or longitudinal vaginal septum, hemivagina or vaginal agenesis. The imperforate hymen may be diagnosed at birth due to bulging mucocolpos or during adolescence when cyclic abdominal or pelvic pain, urinary problems or pain with defecation occur. Incomplete hymenal fenestration may cause partial obstruction, retention of blood or malodorous discharge or interfere with coitus or insertion of tampons.
Box 100.1 Conditions associated with uterovaginal anomalies
Obstetric problems
- high presenting part
- abnormal presentation, breech
- retained placenta
- premature birth
- dystocia
- stillbirth
- intrauterine growth retardation
- rupture
Gynecologic problems
- recurrent first-trimester loss
- second-trimester loss
- incompetent cervix
- dyspareunia, penetration problems
- difficult tampon insertion
- ectopic pregnancy
- primary amenorrhea
- cyclic abdominal, pelvic pain, endometriosis
- pelvic or vaginal mass
- foul or bloody discharge
Gynecologic examination findings
- broad uterus or fundal notch noted on examination
- presence of vaginal mass, septum
- cervical anomalies, two cervices
- two separate cornua on bimanual exam
- pelvic or vaginal mass
- blind pouch, shortened vagina
Ultrasound findings
- two-lobed contour of uterus with asymmetric shape of fundus
- hematocolpos, hematometra
- endometrial echo separated by longitudinal septum or wall
- off-center amniotic sac
Hysterosalpingogram findings
- oblong-shaped cavity instead of a normal triangular shape
- V-shaped endometrial cavity
- duplicated cavity
- septum
- prominent horns
Longitudinal septum may be associated with uterine anomalies and the patient may note dyspareunia or difficulty with inserting tampons. Transverse vaginal septa most often occur in the upper or middle vagina but 15–20% occur in the lower vagina. They may have a small perforation. The vagina is shortened and may be associated with a mucocolpos, hematocolpos or pyohematocolpos. There are a few reports of women with transverse vaginal septa having obstructed labor necessitating either cesarean section or incision during labor. Vaginal agenesis, also known as Mayer Rokitansky Kuster Hauser (MRKH) syndrome, occurs in women with normal female karyotype and a variable uterine remnant development. The patients often present with primary amenorrhea but have otherwise normal pubertal development.
Obstetric problems
Obstetric problems include miscarriage, intrauterine growth retardation, prematurity, postpartum bleeding, incompetent cervix, abnormal fetal presentation, and cesarean delivery. Increased risk of pregnancy-associated hypertension may be due to co-existing congenital renal anomalies. Pregnancy diagnosed in a rudimentary or obstructed uterine horn is dangerous as it can result in rupture.
Urinary tract abnormalities
The close embryologic development between the urinary and reproductive systems often means that abnormal development in one is commonly associated with abnormal development in the other system. The incidence of combined anomalies varies, but a diagnosis of unilateral absence or underdevelopment in one system is a strong signal to investigate the other. Up to 75% of patients with unicornuate uteri have unilateral renal agenesis. Analogously, 20% of patients with unilateral renal agenesis will have major reproductive tract anomalies. Women with significant uterine or upper vaginal anomalies should have either an intravenous pyelogram or ultrasound scanning of the kidneys.
Endometriosis
Retrograde menstruation appears to play a significant role in the development of endometriosis. The presence of patent tubes, a functioning endometrium, and an outflow obstruction is associated with a high incidence (up to 77%) of endometriosis.
Infertility
The presense of a bicornuate or unicornuate uterus or uterine didelphys does not appear to prevent implantation and may result in favorable pregnancy outcomes. Multiple studies report good pregnancy rates and term delivery rates in women with bicornuate or unicornuate uteri or uterine didelphys undergoing infertility treatment although pregnancy rates with in vitro fertilization (IVF) may be diminished due to mechanical difficulties associated with embryo transfer.
Other
Other associated problems include anomalies of the digestive tract, chiefly imperforate anus, cardiovascular system, eyes, ears, and musculoskeletal system, and increased risk of collagen vascular diseases. Vertebral abnormalities are common in true mullerian aplasia (MRKH syndrome).
Most uterine anomalies can be accurately defined with currently available imaging techniques including hysterosalpingography, ultrasonography, and MRI. Transvaginal ultrasound or hydrosonography is sensitive enough to distinguish the appearance of the endometrium during the proliferative and secretory phases of the menstrual cycle and can clearly assess the contours, cavity size and shape, structural changes, and overall size of the uterus. Transvaginal ultrasound can often distinguish between a bicornuate and septate or subseptate uterus, whereas on hysterosalpingography they often look similar. Transvaginal ultrasound can usually differentiate a small uterine horn from an ovarian mass. Ultrasound is useful in locating hematometra or hematocolpos and presence of ovaries, and for evaluating the presence of kidneys.
Hysterosalpingography and hysteroscopy are also useful techniques for the evaluation of uterine anomalies. On hysterosalpingography, the endometrial cavity of a unicornuate uterus appears as an oblong-shaped contour, instead of a normal triangular shape, and only one fallopian tube arises from the cavity. A uterine didelphys yields a duplicated endocervical canal and two oblong-shaped endometrial cavities. Incomplete fusion of the mullerian ducts results in a bicornuate, V-shaped endometrial cavity.
Magnetic resonance imaging is considered by many as the gold standard for diagnosing uterine anomalies. Accurate measurement of the uterine fundus diameter can distinguish a normal, bicornuate, didelphys or septate uterus. Uterine contours, presence of endometrial tissue in a uterine horn or diameter and length of a septum can be assessed.
Classification system and treatment options
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