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Septate uterus

A septate uterus is a type of congenital uterine anomaly. It is classified as a class V Mullerian duct anomaly.

Epidemiology

It is considered the commonst uterine anomaly (accounts for ~ 55% of such anomalies) and is the most common anomaly associated with reproductive failure (in 67%.).

Pathology

It is considered a type of uterine duplicational anomaly and results from partial or complete failure of resorption of the uterovaginal septum after fusion of the para-mesonephric ducts. The septum is usually fibrous but can also have varying muscular components.

The external uterine contour may be convex, flat, or mildly (< 1cm) concave.

Subtypes

The septum, which arises in the midline fundus, is considered to be complete when it extends to the external cervical os.

Associations

As with other uterine anomalies, concurrent renal anomalies may be associated

Radiographic features  

General
  • convex/flat/minimally indented external fundal contour
  • acute angle of  < 75%  between uterine cavities
  • endometrial canals are completely separated by tissue iso-echoic to myometrium with extension into endocervical canal
Ultrasound

On ultrasound, the echogenic endometrial cavities are separated at the fundus by the intermediate echogenicity of the myometrium in all partial septa and within the fundal segments of complete septa. The external uterine contour must demonstrate a convex, flat, or mildly concave (ideally no more than 1cm) configuration and may best be appreciated on transverse images of the uterus. 

Colour Doppler

May show vascularity in the septum in 70% of cases; and if present may be associated with a higher rate of obstetric complications 8

Fluoroscopy - Hysterosalpingogram

Accuracy of alone is only 55% for differentiation of septate from bicornuate uteri. An angle of less than 75° between the uterine horns is suggestive of a septate uterus, and an angle of more than 105° is more consistent with bicornuate uteri. Unfortunately, the majority of angles of divergence between the horns fall within this range, and considerable overlap between the two anomalies is noted.

Pelvic MRI

MRI is considered the imaging modality choice in modern radiological practice.

On MR images, the septate uterus is generally normal in size and each endometrial cavity appears smaller than the configuration of a normal cavity. 

The septum may be composed of fibrous tissue (low T2 signal intensity), myometrium (intermediate signal) or both 2.

Complications

  • 90% miscarriage rate 
    • septate uterus is associated with the worst obstetric outcome of the Müllerian duct anomalies
    • patients with septate uteri usually do not have difficulty
      conceiving, but the pregnancies frequently end in abortion or premature birth

Treatment and prognosis

The distinction between septate uterus and bicornuate uterus has important management implications. In septate uterus, but not in bicornuate uterus, the septum can be shaved off during hysteroscopy (metroplasty) to form a single uterine cavity without perforating the uterus 4.

Reproductive outcome has been shown to improve after resection of the septum, with reported decreases in the spontaneous abortion rate from 88% to 5.9% after hysteroscopic metroplasty.

Differential diagnosis

Considerations a hysterosalpingogram include

  • bicornuate uterus: the configuration of the external uterine contour is crucial for the differentiation of a septate from a bicornuate uterus, because widely different clinical and interventional approaches are assigned to each anomaly.

On ultrasound images in the certain planes, also consider


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Abdominal and pelvic anatomy

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