Corpus luteum on ultrasound

Normal ultrasound anatomy of the female reproductive organs

Transvaginal ultrasound allows for a detailed examination of the pelvic organ structure. In the sagittal view, the uterus is normally visualized in an anteverted position (anteverted uterus). Inside the uterus, a normal endometrium (normal endometrium) is clearly defined.

During scanning in the sagittal and axial planes, the physician assesses the adnexa. A normal ovary (normal ovary) is visualized, within the structure of which a follicle (follicle) is identified.

Differential diagnosis: When mass lesions are detected in the adnexa or uterus, a thorough differentiation must be performed. The structures that need to be ruled out or confirmed on the sonogram include:

• Corpus luteum;
• Regular follicle;
• Cyst;
• Myoma node (in an atypical location).

Magnetic resonance imaging (MRI) in gynecology

When ultrasound data are insufficient, MRI is used. The optimal sequence for assessing the zonal anatomy of the uterus is sagittal T2-weighted MRI (Sagittal T2-weighted MRI).

On tomograms, the uterus has a clear layered structure:

1. Endometrium (endometrium): appears as a central stripe producing a hyperintense (high) MR signal.
2. Inner myometrium (junctional zone, junctional zone): lies directly beneath the endometrium and presents as a band with a hypointense (low) signal.
3. Outer myometrium layer: characterized by intermediate signal intensity.

Anterior to the uterus, the urinary bladder (bladder) is always visualized on the images, serving as an important anatomical landmark.

Fallopian tube assessment: HSG and catheterization

Hysterosalpingography (HSG) is used to assess the condition of the fallopian tubes (fallopian tubes) and the uterine cavity (uterine cavity). The normal picture and main sign of patency is a bilateral spill (bilateral spill) of radiopaque contrast agent directly into the peritoneal cavity (peritoneal cavity).

In case of pathology detection, such as bilateral occlusion in the area of the uterotubal junctions (bilateral corneal occlusion), catheterization may be used. The procedure includes the following stages:

• Diagnostics: confirmation of obstruction using the initial HSG.
• Instrument insertion: a special catheter is inserted into the right uterine cornu (right cornu), after which the guidewire (guidewire) is carefully advanced to the site of obstruction.
• Treatment: the guidewire successfully overcomes the occlusion site, through which tubal patency (tubal patency) is fully restored.

Ultrasound diagnosis of lesions: urogenital tract and scrotum

The principles of differential diagnosis on ultrasound are universal, yet serious difficulties arise in a number of cases. For example, when examining the scrotal contents, it is difficult to distinguish testicular infarction, epididymal tumors, organized hematomas, and epididymo-orchitis.

Golden rule of oncological vigilance: any intratesticular (intratesticular) mass must be considered malignant until proven otherwise surgically.

Normally, the head, tail, and appendix (appendix) of the epididymis are visualized on ultrasound. If an indeterminate mass is detected, alternative methods are used: percutaneous ultrasound-guided biopsy or sonoelastography to assess the "stiffness" of the lesion.

Multiparametric MRI is used as a second-line method (the protocol includes T1, T2, diffusion-weighted imaging [DWI], and dynamic contrast-enhanced [DCE] MRI). This allows for precise characterization of tumors, assessment of trauma and acute scrotum syndrome.

Malignant pathologies and their sonographic patterns

Malignant testicular neoplasms account for about 1% of all malignant tumors in men (incidence 3:100,000 per year, peak age 15–45 years). The main risk factor is cryptorchidism (cryptorchidism), which is associated with 10% of primary cancers and retains risks even after orchiopexy. The risk of developing cancer in the contralateral testis after treatment of the primary tumor increases 500–700 fold.

Clinically, the pathology most often presents as a painless unilateral mass, though 10% of patients experience acute pain due to hemorrhage into the tumor. The negative predictive value (NPV) of ultrasound for ruling out cancer approaches ~100%.

Tumors are divided into germ cell tumors (95%, originating from germ cells) and sex cord-stromal tumors (5%).

Ultrasound differentiation of histological types:

• Seminomas (seminomas): the most common type (peak incidence in the 4th and 5th decades). On ultrasound, they appear as hypoechoic (hyporeflective) compared to normal parenchyma, well-circumscribed, and homogeneous masses. They often replace almost the entire testis, may contain microcalcifications, and can be multifocal. They are extremely radiosensitive and associated with high hCG (hCG) levels.
• Embryonal cell tumors: less homogeneous, but also well-circumscribed.
• Teratomas (teratomas): characterized by mixed echogenicity (mixed reflectivity), often containing cystic spaces and calcifications. They respond well to chemotherapy and are associated with elevated AFP (AFP) and hCG.

Computed tomography (CT) is the mainstay for staging tumors that spread in a predictable pathway, whereas MRI and PET-CT are used in specific clinical situations.

Class and exam questions

What else to study on this topic

• The role of sonoelastography in assessing the stiffness of focal lesions
• Multiparametric MRI: DWI and DCE protocols
• Histological classification of germ cell tumors
• Technique of fallopian tube catheterization in bilateral occlusion
• Risk factors and screening for testicular microlithiasis

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.