Mullerian Anomaly Surgery - Double Uterus
Development of Mullerian Anomalies
As an early embryo, the fallopian tubes, uterus, cervix and upper vagina, develop from two separate tubes, known as mullerian or paramesonephric ducts. The mesonephric ducts develop into the internal male structures, but remnants can occur in the female and are known as paratubal cysts, or cysts that grow next to the fallopian tubes. Sometimes, they enlarge and have to be surgically removed. Developmental anomalies (abnormalities) of the mullerian duct system represent some of the most fascinating disorders in reproductive medicine.
The mullerian ducts differentiate to form the fallopian tubes, uterus, the uterine cervix, and the upper 1/3 of the vagina. The two mullerian tubes come together in the midline, the upper part of the two tubes spread apart to form each fallopian tube, the inner walls of the mid-portion of the tubes disintegrate, forming a hollow cavity or uterus, and the inner walls of the lower part of the mullerian ducts also disintegrate to form the cervix and upper vagina.
The lower 2/3 of the vagina develops from a completely different embryologic structure, known as the urogenital sinus. A wide variety of uterine malformations can occur when this morphogenesis (development) is disrupted. They range from uterine and vaginal agenesis (absence or failure to develop) to complete duplication of the uterus and vagina, to malformations of only the uterus, to minor uterine cavity abnormalities.
Since the renal (kidney) system and future parts of the axial skeletal system develop in close proximity to the uterine, or mullerian system, during embryonic development, mullerian malformations are frequently associated with abnormalities of the renal and skeletal system. Any patient that is found to have mullerian (uterine) anomalies should have a complete evaluation of their renal (kidney) system, including an intravenous pyelography (IVP) and renal sonography to exclude urinary tract anomalies.
Graphic representation of the two separate mullerian (paramesonephric) ducts that eventually develop into the fallopian tubes, uterus, cervix and upper vagina. Courtesy of fotosearch.com
Incidence of Mullerian Duct Anomalies
Mullerian duct anomalies (MDA) are associated with functioning ovaries and age-appropriate external genitalia. These abnormalities are often recognized after the onset of puberty, when a young woman fails to menstruate (agenesis or absence of the uterus) or has very painful periods (non-communicating functional uterus). In the reproductive years, it is found on routine ultra sound, or when she has difficulty with getting pregnant or has repeated pregnancy loss. In the prepubertal period, normal development of external genitalia and age-appropriate developmental sexual milestones (like breast and pubic hair) often mask abnormalities of the internal reproductive organs.
Graphic representation of the female reproductive tract development after normal mullerian duct development
The actual incidence and prevalence of all mullerian anomalies, both major and minor, in the general population are unknown, but is estimated at 1 in 300 (one reported range was 0.1 to 3.5%). Women with repeated pregnancy loss have a reported incidence of 5-10%, with the highest incidence of major mullerian defects occurring in patients having first trimester, late second or early third-trimester losses. The most commonly reported mullerian duct anomalies are as follows:
- Hypoplastic (underdeveloped uterus)
- Uterine Agenesis (absence of the uterus)
Diagnosis of Mullerian Duct Anomalies
There are a number of ways to make the diagnosis of a mullerian duct anomaly:
- High suspicion based on clinical history - no menstruation, extremely painful periods, late 2nd or early 3rd trimester loss
- Either routine or diagnostic ultrasound - seeing two uteruses instead of one
Ultrasound picture of a "double" uterus or bicornuate uterus
- Hysterosalpingogram or HSG - an x-ray of the uterus and tubes showing two or a "double" uterus, being either a septate or bicornuate
Hysterosalpingogram of a bicornuate uterus or "double uterus"
- Sonohysterogram or SHG - US of uterus with water injection
- MRI - gold standard to identify the type of mullerian duct malformation
Most Common Mullerian Duct Malformations
The most common mullerian duct malformations (defects) can separately involve the uterus, vagina, a combination of both, less so the cervix and rarely the fallopian tubes unless in conjunction with anomalies of other reproductive organs. The most common parts of mullerian duct defects are the following:
Slight indentation in the fundus or top of the uterus. Does not have any reproductive consequences and is a "normal" variation and does not require surgical repair.
Only one of the mullerian ducts develops, thus, the uterine cavity is half the size of a normal cavity. No surgery can be done and this malformation can increase the risk of late 2nd and early 3rd trimester loss because the uterus will "run out of room" and trigger premature labor.
Partial or complete lack of disintegration of the inner wall of the mullerian tubes. The remaining partial or complete mullerian duct becomes a septum or band of connective tissue down the middle of the uterine cavity. The outside top or fundus of the uterus is normal. This connective tissue has poor blood supply and when an embryo attaches to it, the uterus cannot supply adequate blood flow and nutrients resulting in a first trimester loss generally between 8-12 weeks pregnant. A septate uterus can be corrected with surgery, resulting in a unified uterine cavity, allowing the pregnancy to go close to term or full term.
Partial or complete lack of disintegration of the inner wall of each mullerian tube. The remaining partial or complete mullerian duct becomes a septum but has normal endometrial or uterine lining. The outside top or fundus of the uterus is indented or "heart-shaped". The difference between a septate and a bicornuate uterus is either made visually, at laparoscopy, or on MRI, where you can distinguish between a heart-shaped uterus and a normal shaped uterus. The embryo attaches and continues to develop because it has adequate blood flow but results in premature labor generally around 22-26 weeks because the pregnancy "runs out of room" to grow, because technically, it is only growing in "half a uterus". A bicornuate uterus can be corrected with surgery, resulting in a unified uterine cavity, with very god pregnancy outcomes.
Communicating and non-communicating horns
Underdevelopment of one side of the mullerian duct resulting in a much smaller but normal functioning uterus or "uterine horn"; that is either communicating with the other uterus, and hence no initial problems. There is an increased risk of prematurity and premature labor because it is basically a unicornuate uterus and a communicating very small "second uterus" or "uterine horn". Generally, if there is a history of pregnancy loss or the woman does not want to take the risk, the decision is to ablate or "burn" the endometrial lining or surgically removing the communicating horn because it is so small and cannot support a viable pregnancy, whereas the other side may be able to. A non-communicating horn poses a much greater problem because there is normal menstruation in that non-communicating "horn" but the menstrual blood has nowhere to go and continues to build up (hematometra or blood filled uterus), eventually causing considerable pain and the increased risk of endometriosis because of the back-flow of menstrual blood into the pelvic cavity (it has nowhere else to go). It will require surgery to remove the non-communicating horn.
Complete duplication of the entire reproductive system; with a fallopian tube on each side, a double uterus, a double cervix and a double vagina. This is due to the failure of any disintegration of either mullerian duct thus causing "duplication" all the way down the reproductive tract. Diagnosis is usually made on routine examination when either two vaginas or two cervices are found. Although, there is an increase in late 2nd and early 3rd trimester loss because the baby is "growing" in half of a uterus, statistically, surgical unification does not seem to improve pregnancy outcome.
Complete absence of the mullerian system (fallopian tubes, uterus, cervix and upper vagina) and the vaginal system (the lower 2/3 of the vagina). It presents in a young woman who has normal onset of secondary sexual characteristics but fails to begin menstruation. Pelvic examination only reveals a "dimple" where the vagina would normally be. Surgically this involves reconstructing a "new" vagina at the appropriate time so that the woman can have sexual intercourse. She will need to use a gestational carrier to achieve pregnancy. Psychological support and counseling are essential components of the pre-operative evaluation and care. In addition to not being able to have sexual intercourse, these young women will be infertile, resulting in possible psychological pain and self-esteem issues.
Absence of the fallopian tubes, uterus and upper vagina. First diagnosed in young woman who have normal development of secondary sexual characteristics but fail to begin menstruation. US and/or MRI shows the absence of the uterus and cervix and the vagina is shortened in ends in a blind pouch. No surgery is needed, the woman can have intercourse and pregnancy can be achieved by using a gestational carrier.
The shape of the uterine cavity is literally T-shaped. It is due to maternal exposure to DES, a drug used in the 50-60's to help prevent miscarriages. One consequence of maternal DES exposure was a T-shaped (or hypoplastic or underdeveloped) uterus in female offspring. This lead to an increased risk of miscarriages, because of the decreased uterine size, when these female offspring attempted pregnancy. It cannot be repaired by surgery and if a woman continues to have reproductive failure, she may have to consider a gestational carrier.
Hysterosalpingogram of a T-shaped uterus from DES exposure
Once the diagnosis is made, surgical correction depends on the underlying symptoms (extremely painful periods, no menstruation, cannot have intercourse), early diagnosis (have not attempted pregnancy but does not want to take the risk of pregnancy loss) or a history of either first or second trimester loss. Most mullerian tract malformations are initially seen by the young woman's primary care physician or by her gynecologist. Reproductive endocrinologists generally see women with mullerian tract defects because of a history of repeated pregnancy loss and/or premature labor in the late second trimester; however, reproductive medical specialists are occasionally the first to make the diagnosis of a mullerian abnormality because the young woman comes in with her parents. All mullerian tract malformation surgery requires a significant amount of experience and expertise in order to get the desired result and preserve uterine integrity and safe future childbearing potential. Arizona Center for Fertility Studies has a vast amount of experience in surgical correction of all types of mullerian malformations, except those requiring vaginal reconstruction, in which case, the woman is referred to a surgeon who does numerous sex change procedures.
Graphic representation of the most common types of mullerian abnormalities. A septate and bicornuate uterus. Intra-uterine adhesions or scarring, Asherman's syndrome, can sometimes present like a mullerian anomaly because it can distort the uterus
Mullerian Anomaly Surgery
Surgery can be accomplished by several different techniques, but the end result, is a unification procedure of the uterus or removal of a compromised horn.
- In the case of communicating or non-communicating uterine horns, the smaller uterus can be either removed by laparoscopy or laparotomy, depending on the difficulty of the surgery. In either case, the communicating or non-communicating horn is surgically removed, with care being taken to not effect the remaining "normal" uterus; which can be unicornuate size or larger, depending on the percent of the unequal mullerian defect. Sometimes, ablation, or cautery, can be done to the communicating horn, if you are able to get a hysteroscope into the horn. That is often difficult because of the small size of that horn.
- The majority of mullerian tract malformation surgeries done by Arizona Center for Fertility Studies are on either septate or bicornuate uteruses in women that have had a history of repeated reproductive failure in the first trimester (septate uterus) or in the mid to late second trimester (bicornuate uterus). In Arizona Center for Fertility Studies experience, the size of the septum, or width of tissue between the two uteruses, is the deciding factor as to the surgical approach. Either procedure is known as a metroplasty or repair of the uterus. If the septum is very thin in width, it can be removed hysteroscopically (see hysteroscopy link) or hysteroscopic metroplasty. This is done with concurrent laparoscopy to help reduce the risk of uterine perforation during the septum removal. On the other hand, if it a wide septum, Arizona Center for Fertility Studies believes it should not be done by hysteroscopy but by an open procedure or laparotomy, where the septum is wedged out of the uterus (with care being taken not to remove any normal uterine tissue) and then the two halves of the uterus are unified, creating one cavity. This is known as Tompkins metroplasty. The reason for this approach is that implantation occurs at the fundus of the uterus. If the septum is very wide and it is removed hysteroscopically, which is done with cautery, then when the final part of the septum is removed at the fundus with cautery, that entire area will be damaged from the cautery and will heal with scar tissue. Scar tissue has very poor blood supply and thus would make implantation impossible or be associated with early pregnancy loss. The advantage of a hysteroscopic metroplasty is that it avoids major surgery and the patient can attempt pregnancy in 6 weeks without any restrictions. With a Tompkins metroplasty, the entire uterus needs to be opened and the septum removed. As a result, the woman cannot attempt pregnancy for 3 months to allow the uterus to heal and has to deliver by cesarean section to avoid uterine rupture with labor. She will also need to be on estrogen therapy for three months to promote healing of the uterine incision by proliferation of the endometrium to grow over the incision. In Arizona Center for Fertility Studies opinion, it is a small price to pay to have a successful term pregnancy. Nobody will do a C/S on the woman "unless she is having a baby".
- If a "double" uterus is picked up on routine US or HSG/SHG, Arizona Center for Fertility Studies has changed its recommendation in recent years. Previously, the thinking was that the first pregnancy "stretched" out the uterus, so the next pregnancy would "make it further" and the woman would have a viable outcome. Also, not all women with a septate or bicornuate uterus would result in pregnancy loss. A certain percentage of these women will have a term or near term delivery. The problem is that you never know who "those few women are"; and statistically, without the surgery, these woman will definitely be at increased risk of pregnancy loss. Having seen too many woman lose 1-2 pregnancies (babies) in the 2nd trimester or have had 3-4 miscarriages before a metroplasty is considered, Arizona Center for Fertility Studies now discusses with each couple the option of having a metroplasty prior to attempting pregnancy, even before they have had a single 1st or 2nd trimester pregnancy loss. This way, they are aware of the pros and cons, risks and complications, of their decision, before they decide to attempt pregnancy. Most couples, if given a choice, will choose to do the metroplasty, rather than risk a first or second trimester pregnancy loss. There will probably be a few women who had surgery that did not need it, but that pales in the face of the woman who would have lost their babies without the surgery.