Congenital Anomalies of the Uterus positive and negative predictive values for uterine polyps (233). Because of a smaller volume of distension media used, SIS is generally better tolerated than HSG or hysteroscopy (231,234). Another advantage of SIS is the ability to evaluate the myometrium and the adnexa for fibroids or adenomyosis. When combined with three-dimensional technology, SIS is particularly good at assessing the overall uterine contour and delineating congenital anomalies such as septate uteri (234). Standard SIS has somewhat lower sensitivity of 77.8% in detecting uterine congenital anomalies when compared to hysteroscopy, but this is higher than both two-dimensional transvaginal ultrasound and HSG. Hysterosalpingogram and SIS perform similarly for intrauterine adhesions, each having approximately 50% positive predictive value and greater than 90% negative predictive value (233).
Magnetic Resonance Imaging Although transvaginal ultrasound, HSG, SIS, and hysteroscopy may suggest congenital uterine anomalies, pelvic MRI is considered the gold standard for imaging and is particularly useful for diagnosing rudimentary uterine horns (235). Pelvic MRI has the best sensitivity and specificity for intramural and submucous myomas compared to pathologic examination and is especially useful for detecting large or multiple fibroids (236,237). MRI has been suggested as a tool to differentiate fibroids from adenomyosis, but routine substitution for ultrasound is not recommended (237,238).
Congenital uterine anomalies occur in 3% to 4% of women. This increases to 5% to 10% in women with early pregnancy loss and up to 25% in those with second and third trimester pregnancy losses (235). During female embryonic development, the paired paramesonephric or m¨ullerian ducts elongate toward each other and fuse in the midline. This is followed by resorption of the intervening septum to form the upper vagina, cervix, uterus, and fallopian tubes by week 20 of gestation. Failure of any of these steps leads to absent uterine development or development of unicornuate, bicornuate, arcuate, didelphic, or septate uteri. Because of the proximity of the paramesonephric ducts to the urinary system, renal anomalies often coexist with m¨ullerian anomalies. Appropriate urologic imaging should be performed whenever a m¨ullerian anomaly is diagnosed (235,239). Uterine anomalies are more closely associated with pregnancy wastage and poor obstetric outcomes than with infertility, as the prevalence of congenital uterine defects is generally similar among fertile and infertile women. The exception to this is m¨ullerian agenesis. Patients with m¨ullerian agenisis can have genetically related children only through the use of IVF and a gestational carrier. The arcuate uterus is the mildest congenital uterine anomaly and typically live birth rates are comparable to those in women with normal uteri (235). Surgical uterine repair to improve obstetric outcomes is controversial for most anomalies. However, rudimentary uterine horns require removal on diagnosis, and hysteroscopic metroplasty of the septate uteri significantly reduces the rates of pregnancy loss, but not infertility (235,240). The number of reproductive-age patients presenting with in utero exposure to DES is declining rapidly and will continue to decline in the future, because the substance was banned in 1971. Women whose mothers were exposed to DES have higher rates of uterine malformations (e.g., T-shaped uterus) and associated obstetric complications (235).
Acquired Abnormalities of the Uterus