Ultrasonography (US) and Computed Tomography (CT)
Ultrasonography, particularly transabdominal and transvaginal US (TVUS), is the primary imaging modality in gynecology.
Advantages of US:
- Absence of ionizing radiation.
- Availability, low cost.
- Multiplanar capability and no need for contrast agent administration.
Normally, on sagittal TVUS scans, the uterus is in an anteverted position (anteverted uterus) with a clearly visible endometrium. The ovaries are visualized containing follicles. The method is indicated for pelvic pain, postmenopausal bleeding, suspected mass lesions, and serves as an excellent navigation tool for drainage or biopsy.
As for computed tomography (CT), its role in benign gynecological conditions is now minimal and has been replaced by MRI. CT may be used only in cases of acute pelvic pain if US findings are inconclusive.
Magnetic resonance imaging (MRI)
MRI provides superior tissue resolution and is the modality of choice for complex diagnostic tasks, assessment of indeterminate adnexal masses, and Müllerian duct anomalies.
Normal zonal anatomy of the uterus on T2-weighted images (T2WI):
- Endometrium (endometrium) — central zone with a hyperintense (bright high) signal.
- Inner myometrium / junctional zone (junctional zone) — hypointense (dark) band directly beneath the endometrium.
- Outer myometrium layer — tissue with intermediate signal intensity.
Anterior to the uterus, the urinary bladder is normally visualized.
When scanning the pelvic organs, it is critically important to obtain slices oriented along the long axis of the uterus (coronal oblique and axial oblique) to compensate for its natural curve. Due to the high frequency of associated pathologies, abdominal MRI protocols must include targeted evaluation of the kidneys.
Uterine cavity and fallopian tube studies: HSG and sonohysterography
Specialized techniques are used to assess fallopian tube patency and diagnose causes of infertility:
- Hysterosalpingography (HSG). An X-ray procedure where contrast is introduced into the uterine cavity. Normally, contrast fills the uterus, fallopian tubes, and spills freely into the peritoneal cavity bilaterally (bilateral spill). The procedure is performed in the first 10 days of the cycle (outside of bleeding) and is contraindicated in pregnancy or acute infections.
- Fallopian tube catheterization. In case of occlusion in the interstitial (cornual) segment, a fine catheter and guidewire are introduced into the tubal ostium under fluoroscopic guidance. After mechanical disruption of the obstruction, patency is restored, resulting in pregnancy in approximately 60% of cases.
- Sonohysterography. An alternative to HSG under ultrasound guidance. Saline (or microbubble-containing fluid) is injected via a 5F balloon catheter. The method is ideal for visualizing intracavitary uterine lesions without ionizing radiation during a routine office visit.
Congenital anomalies of the female genital tract
Developmental anomalies occur in 1–15% of women and are associated with impaired formation or fusion of Müllerian ducts during embryogenesis. They frequently lead to infertility, cycle irregularities, and pregnancy complications.
Class I: Agenesis or hypoplasia (involvement of both ducts) The most frequent variant is Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome. Patients lack a uterus and the upper part of the vagina, but ovaries are normally developed (unlike gonadal dysgenesis). On ultrasound, uterine remnants are poorly visualized, so the diagnosis is established via T2WI MRI.
Class II: Unicornuate uterus (involvement of a single duct) This pathology is associated with a high risk of spontaneous abortion. It can be suspected on US or HSG, but MRI provides the exact picture: on axial oblique slices, the uterus acquires a characteristic "banana" shape — curved, with a narrowed fundus and deviated to one side, while maintaining its zonal structure.
Briefly: answers to topical questions
What classes of congenital Müllerian duct anomalies exist besides Class I and II?
Besides Class I and II, there are classes III, IV, V, and VI of congenital Müllerian duct anomalies.
- Uterine didelphys (Uterus Didelphys) — two separate uterine horns of normal size and two cervices are formed.
- Bicornuate uterus (Bicornuate Uterus) — results from incomplete fusion of the cranial portions of the uterovaginal horns.
- Septate uterus (Septate Uterus) — the result of incomplete resorption of the fibrous septum between the two horns.
- Arcuate uterus (Arcuate Uterus) — considered a normal variant, manifesting as a smooth, broad depression at the fundus of the uterine cavity.
How does Mayer-Rokitansky-Küster-Hauser syndrome differ from androgen insensitivity syndrome?
The main difference lies in the karyotype, the state of the gonads, and the need for hormone replacement therapy.
| Sign | Mayer-Rokitansky-Küster-Hauser syndrome | Androgen insensitivity syndrome |
|---|---|---|
| Karyotype | 46XX | 46XY |
| Gonads | Ovaries are normally developed, function is preserved | Dysgenetic gonads with a high risk of malignancy |
| Treatment | HRT is not indicated | Gonadectomy and estradiol HRT |
Both conditions are characterized by the absence of a uterus on ultrasound and require surgical creation of a neovagina.
To memorize the uterine layers on T2WI MRI, use the rule "Bright–Dark–Gray": Bright endometrium (hyperintense) -> Dark junctional zone (hypointense) -> Gray outer myometrium (intermediate signal).
Class and exam questions
Why is kidney imaging mandatory when suspected uterine developmental anomalies are present?
In 30–50% of cases, Müllerian duct anomalies are combined with renal malformations (such as agenesis or pelvic dystopia) due to their close embryological relationship.
What are the main advantages of sonohysterography over HSG?
Sonohysterography is entirely free of ionizing radiation and can be performed during the same visit as the baseline TVUS, providing excellent visualization of intracavitary uterine lesions.
How to differentiate Mayer-Rokitansky-Küster-Hauser syndrome from other syndromes accompanied by the absence of a uterus?
In MRKH syndrome, the patient's ovaries (and fallopian tubes) are fully preserved and function normally, which distinguishes this condition from androgen insensitivity syndrome or gonadal dysgenesis.
Which MRI projection is best suited for visualizing a unicornuate uterus?
Optimal visualization is achieved on axial oblique slices oriented perpendicularly to the long axis of the uterus. On these, the unicornuate uterus appears as a "banana"-shaped structure.
What else to study on this topic
- Embryogenesis of the Müllerian ducts and the pathogenesis of their fusion.
- Classifications of uterine anomalies (according to Buttram, Gibbons, and American Fertility Society criteria).
- Complications and risks of hysterosalpingography (HSG).
- Technique of fallopian tube cannulation in proximal occlusion.
- Differential diagnosis of acute pelvic pain using diagnostic imaging.
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Other topics in the section "Diagnostic Radiology of the Abdominal Organs"
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