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Evaluation of Infertility

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Fig. 20  Class IV: HSG shows widely splayed uterine horns with an intercornual angle >100° and with uterine fundi joined at the lower uterine segment indicating a bicornis unicollis subtype (a). HSG (b) and hysterosonography (c) in a different patient show uterine fundi joined at the level of the cervix suggesting a bicornis bicollis subtype

7.1.4\ Class IV: Bicornuate

Partial fusion of two müllerian ducts results in a bicornuate uterus with one cervix. The uterine horns are widely divergent, the uteri fundi joined either at the uterine corpus (bicornis unicollis subtype) (Fig. 20a) or lower uterine segment (bicornis

bicollis subtype) (Fig. 20b, c). In most cases there is a single cervix; however there may be two cervical openings, creating an appearance similar to septate uterus. Of all classes of MDAs, it is the bicornuate uterus that has the strongest association with cervical incompetence (Patton 1994). It is crucial to

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differentiate between a bicornuate and septate uterus because surgical correction of a bicornuate uterus is not generally warranted, since it is the cervical incompetence and not the cavity malformation that is the cause of the high spontaneous abortion rate with this anomaly. In addition, an abdominal metroplasty must be performed if surgical repair of a bicornuate uterus is undertaken, as opposed to hysteroscopic septoplasty which is performed for a septate uterus (Fielding 1996).

HSG of a bicornuate uterus will demonstrate separate uterine cavities with an intercornual angle that usually exceeds 105°. With this imaging modality, however, the outer uterine contour cannot be evaluated, and overlap with the appearance of a septate uterus can occur.

Sonographic diagnosis of a bicornuate uterus is made by both analysis of the outer fundal contour and visualization of a separate endometrial stripe in each horn. However, sonographic differentiation of a bicornuate uterus from a septate uterus may be difficult.

MRI diagnostic criteria are similar to those described for sonography. Imaging should be performed during the secretory phase to maximize contrast between the T2 signal of endometrium, the junctional zone, and the myometrium. On transaxial images, the intercornual distance exceeds 4 cm, and the tissue dividing the endometrial cavities is isointense with normal myometrium. On coronal images of the fundus, obtained in the plane of the tubal ostia, the serosal concavity exceeds 1 cm (Nicolini et al. 1987).

7.1.5\ Class V: Septate

Septate uterus results from failure of resorption of a septum after complete fusion of the müllerian ducts. In the majority of cases the midline septum is partial and extends for a variable distance from the fundus into the corpus or lower uterus segment (subseptate uterus). Less commonly the septum extends to the level of the cervix, forming a complete septate uterus. With a complete septate uterus, there may be two cervical openings, but this is owing to division of one canal, and not two separate cervices as occurs with a uterus didelphys (Fig. 21a–c).

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Fig. 21  Class V: complete septate uterus: on HSG one cervical opening was missed; only one uterine cavity was spilled with contrast media; a unicornuate uterus was supposed (a). Sonography (b) and coronal T2W MRI (c) clearly demonstrate the uterine cavity divided by a thick septum extending to the level of the cervix. The angle formed by the medial borders of the two uterine hemi-­cavities is <75°

Evaluation of Infertility

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Most patients evaluated for repeated abortions and found to have a uterine anomaly will have a septate uterus (Rock 1997). Avascular fibrous septa can be safely resected hysteroscopically whereas vascularized myometrial tissue within the septum requires metroplasty as a surgical procedure for treatment of this anomaly and may enhance fetal survival, with one report indicating that 95% of patients became pregnant, 73% carried to term, and 77% delivered a live-born baby (Rock and Jones 1977).

HSG of a septate uterus demonstrates two narrowly diverging cavities, yielding a V-shape configuration with relatively straight medial borders. The angle formed by the medial borders of the two uterine hemi-cavities is usually <75°. Diagnosis of a septate uterus is often not possible by HSG because the outer uterine contour cannot be imaged, and angle measurement may be difficult.

Sonography and MRI are each superior to HSG. The external uterine contour is normally convex, flat, or minimally indented by less than 1 cm (Nicolini et al. 1987), in contrast to that of a bicornuate uterus. Coronal MRI allows the characteristic fundal changes of a septate uterus to be identified.

In addition to fundal contour, a second sonographic feature of a septate uterus is splitting of the endometrial echo by a hypoechoic band, most easily seen in the fundus.

7.1.6\ Class VI: Arcuate

Formerly this MDA was classified as the mildest form of either a bicornuate or septate uterus. In 1988 the American Fertility Society issued a separate classification of arcuate uterus. Arcuate uterus should be considered a normal variant and it has no effect on fertility.

HSG of the arcuate uterus reveals a broad smooth indentation into the fundal cavity which causes a saddle-shaped appearance (Fig. 22). The indentation is approximately one-fifth the height of the uterus.

Both MRI and sonography reveal a smooth outer contour, associated with a subtle broad-­ based shallow indentation impressing the endometrial stripe.

Fig. 22  Class VI: minor indentation of the fundal uterine cavity indicating an arcuate uterus. Note major dextroposition of the uterine cavity with occlusion of the right fallopian tube at the level of the intramural portion

7.1.7\ Class VII: Diethylstilbestrol Related

These anomalies comprise sequelae of in utero DES exposure. DES was used to prevent miscarriage in the 1940s–1970s (Fielding 1996). Most likely as a result of DES disrupting vaginal plate development and stromal differentiation, structural anomalies occurred in the fetal vagina, cervix, uterus, and tubes. Because of the variability and overlap of features of associated cervical and vaginal malformations, these changes generally are not incorporated into the basic schematics and are reported as a subset of the primary uterine defect.

Structural anomalies encountered at physical examination are vaginal adenosis and the presence of an anterior cervical ridge or hood. Uterine cavity anomalies associated with DES exposure include hypoplasia, focal constrictions, bulbous dilatation of the lower uterine segment, and a T-shaped uterine configuration. These uterine anomalies are associated with an increased incidence of spontaneous abortion, preterm labor, and ectopic pregnancy (Patton 1994).

HSG is an excellent imaging modality for diagnosing DES-related uterine anomalies. Typical cavity contour changes seen include scalloping and constriction bands, while uterine shape abnor-