Types of ultrasound access
Several echographic approaches are used in gynecological practice, the choice of which depends on the clinical task and the patient's anatomical features.
- Transvaginal US (Transvaginal US, TVUS). This is the preferred method with high anatomical detail due to the use of high-frequency transducers (5.0–7.5 MHz). The examination is performed with an empty urinary bladder, which minimizes the distance from the transducer to the organs being examined.
- Transabdominal US (Transabdominal US). Performed with transducers at a frequency of 3.5–5.0 MHz. A mandatory requirement is a tightly filled urinary bladder. It acts as an acoustic window and displaces gas-filled bowel loops that obstruct the view.
- Transrectal US. Used when the vaginal approach is difficult, and is also the most informative method for diagnosing rectosigmoid endometriosis.
- Doppler ultrasonography. Includes color, power, and spectral mapping. Provides crucial additional information on the blood supply (vascularization) patterns of pathological foci in the uterus and adnexa.
Main indications and diagnostic tasks
Ultrasound imaging is indicated for acute pelvic pain, enlarged uterus, postmenopausal bleeding, and for the initial characterization of ovarian masses.
The method is of particular importance in the diagnosis of endometriosis. Comprehensive scanning with a transvaginal transducer is recommended even when no pathology is detected during bimanual examination (level of evidence B). The method allows for the detection of endometriomas and deep infiltrating endometriosis involving the urinary bladder, ureters, and bowel. Typical locations of deep forms accessible for US evaluation include the uterosacral ligaments, rectovaginal septum, pouch of Douglas, and vaginal walls.
Additionally, echography serves as a reliable guidance tool for invasive procedures: aspiration, biopsy (tissue sampling), placement of pelvic drains, and brachytherapy devices (reduces the risk of incorrect applicator placement in cervical cancer).
Sonohysterography (Sonohysterography)
This is a specialized technique for evaluating the uterine cavity and fallopian tube patency. Under direct ultrasound guidance, a balloon catheter (size 5F) is inserted through the cervix, through which sterile saline or a special microbubble contrast agent is instilled.
Advantages of the method:
- Absence of ionizing radiation (unlike X-ray hysterosalpingography).
- Feasibility within a single visit alongside a standard gynecological ultrasound.
The technique is contraindicated during pregnancy and active pelvic infection.
The role of ultrasound in gynecological oncology: advantages and limitations
In oncology, a multimodal approach is used, where ultrasound acts as the first-line method. It is indispensable for the initial detection of adnexal masses (adnexal masses) and measurement of endometrial thickness.
Advantages:
- Wide availability and relative affordability.
- Multiplanarity (ability to obtain slices in different planes).
- No radiation exposure.
- Portability (devices can be used at the bedside or in the operating room).
Disadvantages:
- Subjectivity (results heavily depend on the operator's experience — operator dependent).
- Decreased image quality in patients with severe obesity (body habitus).
Important: Despite high spatial resolution, all types of ultrasound are less informative than CT or MRI when it comes to staging malignant tumors (assessing regional spread and searching for distant metastases).
The bladder rule: Abdominal — full (as an acoustic window), Vaginal — empty (so it does not obstruct the transducer).
Class and exam questions
What is the sensitivity of ultrasound in diagnosing endometriosis?
For uterine and adnexal pathologies, sensitivity reaches 91%. For deep infiltrative forms (involving the bowel, ligaments, or vagina), it is about 79%.
Why is ultrasound not used as the primary method for cancer staging?
Ultrasound excels at detecting the masses themselves, but does not reliably assess regional tumor spread or the presence of distant metastases. CT, MRI, and PET/CT are used for these purposes.
What is the advantage of sonohysterography over classical HSG?
Sonohysterography does not involve radiation exposure and can be performed right during a routine gynecological ultrasound within a single visit.
What else to study on this topic
- Magnetic resonance imaging (MRI) in the diagnosis of Müllerian duct anomalies
- Computed tomography (CT) in ovarian cancer staging
- Hysterosalpingography (HSG) and fallopian tube catheterization in infertility
- Multimodal approach in gynecological oncology: choosing between ultrasound, CT, MRI, and PET/CT
- Ultrasound diagnostics of deep infiltrating endometriosis
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