Transvaginal ultrasound (TVUS) is an imaging technique that uses sound waves to create detailed pictures of internal organs. This diagnostic tool is frequently employed to visualize the female reproductive system, including the uterus, ovaries, fallopian tubes, and cervix. This article explores how TVUS works and its applications in detecting gynecologic cancers.
Understanding Transvaginal Ultrasound
A transvaginal ultrasound involves inserting a small, wand-like transducer into the vagina. This transducer emits high-frequency sound waves that travel through pelvic tissues. These sound waves create echoes as they bounce off internal structures, converting them into real-time images on a monitor.
This method provides a more detailed view of the pelvic organs compared to an abdominal ultrasound. The transducer’s proximity allows for clearer and more precise imaging of the uterus, its lining (endometrium), ovaries, and fallopian tubes. The procedure typically takes 15 to 60 minutes, with the patient lying on an examination table, often with knees bent and feet in stirrups, similar to a pelvic exam.
Role in Detecting Gynecologic Cancers
Transvaginal ultrasound helps evaluate gynecologic cancers by identifying structural changes and abnormalities in the ovaries, uterus, and endometrium. For ovarian cancer, TVUS can reveal masses, irregularities, or free fluid in the abdomen, which may indicate advanced disease. Features like multilocular masses, papillary projections, solid areas, or pelvic nodules can suggest a higher risk of malignancy.
For endometrial cancer, TVUS measures endometrial thickness. An unusually thickened lining, especially in postmenopausal women with bleeding, can indicate endometrial cancer. Studies indicate that a cutoff of 5.15 mm for endometrial thickness can detect endometrial cancer with a sensitivity of around 80.5% and specificity of 86.2% in asymptomatic postmenopausal women. TVUS can also identify tumors or polyps within the uterus and assess cancer growth into the muscular layer. It can also help detect cervical abnormalities.
Limitations of Transvaginal Ultrasound
Transvaginal ultrasound has limitations in cancer detection. It cannot definitively distinguish between benign and malignant growths based solely on imaging. While certain features observed on TVUS may suggest malignancy, many masses are not cancerous, and further testing is always needed for a conclusive diagnosis. The size of a tumor alone does not reliably differentiate between benign and malignant lesions.
TVUS may not visualize all pelvic areas equally well, limiting its effectiveness in detecting very early-stage cancers without significant structural changes. Routine TVUS screening for ovarian cancer in average-risk women has not reduced mortality and can lead to unnecessary follow-up procedures.
Complementary Diagnostic Approaches
Due to its limitations, transvaginal ultrasound is often part of a broader diagnostic approach. If TVUS reveals suspicious findings, additional tests are performed. Biopsies, involving removal of a tissue sample for microscopic examination, are crucial to confirm cancer. This can include endometrial biopsies, which may be guided by hysteroscopy, a procedure using a small camera to visualize the uterine cavity.
Blood tests, such as tumor markers like CA-125, are also used, particularly for ovarian cancer evaluation. While elevated CA-125 can indicate cancer, it may also be raised by non-cancerous conditions. Other imaging techniques, such as MRI (magnetic resonance imaging) and CT (computed tomography) scans, provide different perspectives of the pelvic organs and can help assess the extent of any detected abnormalities or cancer spread. A comprehensive evaluation, combining these methods, offers a more accurate diagnosis and informs treatment.