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.
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.)
