Uterine Anomalies: Bicornuate, Septate, and Unicornuate Uterus

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Chapter 120 Uterine Anomalies: Bicornuate, Septate, and Unicornuate Uterus

INTRODUCTION

Description: Uterine abnormalities are characterized by incomplete formation of the uterus resulting in one or two separate halves or horns or a single uterus with a central septum. (The central septum may divide the uterine cavity either partially or completely. The two resulting halves may be of unequal size or volume.) In its most extensive form, duplication of the cervix and vaginal canal also may occur. These abnormalities are associated with renal agenesis and blind vaginal pouches that may become filled with menstrual fluid after puberty, resulting in a painful mass.
Prevalence: Estimated to be 0.1% of female births. Septate or arcuate uterine anomalies may be present in up to 3% of women.
Predominant Age: Congenital.
Genetics: May be transmitted by polygenic or multifactorial pattern.

ETIOLOGY AND PATHOGENESIS

Causes: Failure of the fusion of the Müllerian ducts, which normally takes place near the beginning of the 10th week of gestation. This may vary from septation of the uterus to complete duplication of the uterus, cervix, and vaginal canal. Most septations are due to a failure of the normal processes of development of the Müllerian system between the 10th and 13th week of gestation when the lower portion of the median septum of the uterus is resorbed, or between the 13th and 20th week when the upper septum (in the uterine body) is resorbed. In utero exposure to diethylstilbestrol has been associated with a T-shaped uterine cavity similar to the arcuate form of a septate uterus. A unicornuate uterus may result from a failure of the normal formation or the destruction of one the Müllerian ducts. This may occur if there is a lack of development of the mesonephric system on the affected side resulting in a failure of the associated Müllerian system. (In these patients, the ipsilateral kidney and ureter are usually absent.)
Risk Factors: None known.

CLINICAL CHARACTERISTICS

Signs and Symptoms

• Asymptomatic
• Recurrent abortion (15% to 25% of patients with recurrent abortions have uterine abnormalities; there is a 50% risk of pregnancy loss when the uterus is unicornuate)
• Premature labor (20% risk for unicornuate uterus)
• Uterine pain or rupture in early pregnancy
• Abnormal presentation in labor (breech or transverse position)
• Inability to stop menstrual flow using tampons (when there is duplication of the vagina as well)
• When outflow is obstructed—hematometra
• Dysmenorrhea, abdominal pain, pelvic mass, abrupt blood discharge

DIAGNOSTIC APPROACH

Differential Diagnosis

• Leiomyomata
• Adnexal mass
• Endometriosis
• Chromosomal abnormality resulting in recurrent abortion

Associated Conditions: Endometriosis (75% when outflow obstruction is present), pelvic adhesions, recurrent abortion, infertility, dysmenorrhea, dyspareunia, hematocolpos, and renal anomalies (contralateral pelvic, horseshoe, or absent kidney).

Workup and Evaluation

Laboratory: No evaluation indicated.
Imaging: Hysterosalpingography, ultrasonography, or sonohysterography. Magnetic resonance imaging may be used, but expense and availability limit its utility.
Special Tests: Hysteroscopy or laparoscopy may be required to complete the evaluation.
Diagnostic Procedures: Physical examination, imaging, and direct observation by hysteroscopy, laparoscopy, or both. Differentiation between septate and bicornuate uterine anomalies requires visualization of the uterine fundus.

Pathologic Findings

In patients with an unicornuate uterus, a normal ovary and tube are generally present. A normal ovary may be present on the opposite side as well. The septate uterus is characterized by the presence of a fibrous septum of variable length with poor vascularization.

MANAGEMENT AND THERAPY

Nonpharmacologic

General Measures: Evaluation and education.
Specific Measures: Patients with nonobstructive abnormalities require no therapy. Patients with recurrent fetal wastage may be considered for uterine reunification (metroplasty) procedures or the excision of any septum, usually by operative hysteroscopy. Patients with a unicornuate deformity and recurrent fetal wastage should be counseled about adoption or the possibilities of in vitro fertilization with implantation into a host uterus.
Diet: No specific dietary changes indicated.

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Activity: No restriction.
Patient Education: Reassurance; American College of Obstetricians and Gynecologists Patient Education Pamphlet AP079 (If Your Baby Is Breech), AP100 (Repeated Miscarriage), AP090 (Early Pregnancy Loss: Miscarriage and Molar Pregnancy), AP143 (Hysterosalpingography).

Drug(s) of Choice

None. (Estrogen therapy is often given for 1 to 2 months after resection of a uterine septum, although the need for this is still debated.)

FOLLOW-UP

Patient Monitoring: Normal health maintenance.
Prevention/Avoidance: None.
Possible Complications: Obstruction of the outflow of menstrual blood is associated with a 75% chance of endometriosis with resultant pelvic scarring and infertility. There is an increased risk of ectopic pregnancy and early pregnancy loss (33% to 35%).
Expected Outcome: Normal reproduction is frequently possible without intervention (25% of cases) for patients with a bicornuate uterus; metroplasty is associated with an increased likelihood of success when pregnancy failures have occurred (80% to 90%). When the only abnormality is a uterine septum, normal reproduction is generally possible without intervention (85% success). For patients with a unicornuate uterus, a live birth rate of 40% may be expected; outcomes are not statistically different from those experienced by women with didelphic uteri.

MISCELLANEOUS

Pregnancy Considerations: Increased risk of pregnancy loss, premature delivery, or fetal malpresentation. The risk of ectopic pregnancy is increased for patients with a unicornuate uterus.
ICD-9-CM Codes: 752.2 (Unicornuate or bicornuate uterus), 752.3 (Septate uterus).

REFERENCES

Level II

Lin PC. Reproductive outcomes in women with uterine anomalies. J Womens Health (Larchmt). 2004;13:33.

Moutos DM, Damewood MD, Schlaff WD, Rock JA. A comparison of the reproductive outcome between women with a unicornuate uterus and women with a didelphic uterus. Fertil Steril. 1992;58:88.

Reinhold C, Hricak H, Forstner R, et al. Primary amenorrhea: evaluation with MR imaging. Radiology. 1997;203:383.

Rock JA, Jones HJ. The double uterus associated with an obstructed hemivagina and ipsilateral renal agenesis. Am J Obstet Gynecol. 1980;138:339.

Toaff ME, Lev-Toaff AS, Toaff R. Communicating uteri: review and classification with introduction of two previously unrecorded types. Fertil Steril. 1984;41:661.

Level III

Buttram VC. Müllerian anomalies and their management. Fertil Steril. 1983;40:159.

Doyle MB. Magnetic resonance imaging in mullerian fusion defects. J Reprod Med. 1992;37:33.

Golan A, Langer R, Bukovsky I, Caspi E. Congenital anomalies of the mullerian system. Fertil Steril. 1989;51:747.

Grimbizis GF, Camus M, Tarlatzis BC, et al. Clinical implications of uterine malformations and hysteroscopic treatment results. Hum Reprod Update. 2001;7:161.

Hay D. Uterus unicornis and its relationship to pregnancy. J Obstet Gynecol Br Emp. 1961;68:371.

Jayasinghe Y, Rane A, Stalewski H, Grover S. The presentation and early diagnosis of the rudimentary uterine horn. Obstet Gynecol. 2005;105:1456.

Jones HW. Reproductive impairment and the malformed uterus. Fertil Steril. 1981;36:137.

Katz VL, Lentz GM. Congenital abnormalities of the female reproductive tract. In: Katz VL, Lentz GM, Lobo RA, Gershenson DM, editors. Comprehensive Gynecology. 5th ed. Philadelphia: Mosby/Elsevier; 2007:250.

Markham SM, Waterhouse TB. Structural anomalies of the reproductive tract. Curr Opin Obstet Gynecol. 1992;4:867.

Mayo-Smith WW, Lee MJ. MR imaging of the female pelvis. Clin Radiol. 1995;50:667.

Nahum GG. Uterine anomalies. How common are they, and what is their distribution among subtypes? J Reprod Med. 1998;43:877.

Pinsonneault O, Goldstein DP. Obstructing malformations of the uterus and vagina. Fertil Steril. 1985;44:241.

Woodward PJ, Sohaey R, Wagner BJ. Congenital uterine malformations. Curr Probl Diagn Radiol. 1995;24:178.

Woodward PJ, Wagner BJ, Farley TE. MR imaging in the evaluation of female infertility. Radiographics. 1993;13:293.

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