Ovarian cancer is a serious health challenge, often detected at advanced stages due to subtle symptoms. Early, accurate detection improves treatment outcomes. Ultrasound serves as a primary, non-invasive imaging method for initial evaluation and identification of potential ovarian abnormalities. It allows medical professionals to visualize the ovaries and surrounding structures, guiding further diagnostic steps when concerns arise.
How Ultrasound Examines Ovaries
Ultrasound technology relies on high-frequency sound waves. A transducer, a small handheld device, emits these waves and captures the returning echoes. A computer processes these echoes to generate real-time images of internal organs, creating a sonogram. This method is considered safe because it does not use ionizing radiation.
Two main approaches are used for imaging the ovaries: transabdominal ultrasound (TAUS) and transvaginal ultrasound (TVUS). During a transabdominal ultrasound, a gel is applied to the lower abdomen, and the transducer is moved across the skin. Patients need a full bladder for this exam, which helps elevate the uterus and move bowel gas away for clearer images. While TAUS offers a broader view of the pelvic region, it may not provide the detailed images needed for ovarian assessment.
For a transvaginal ultrasound, a wand-shaped transducer is covered with a protective sheath and lubricating gel, then gently inserted into the vagina. This method allows the transducer to be positioned closer to the ovaries, providing a detailed view of these structures. Patients are asked to empty their bladder before a TVUS for improved image quality and comfort. Although some patients might experience slight discomfort or pressure during TVUS, it is not painful and is comparable to a Pap smear.
Identifying Ovarian Features on Ultrasound
A normal ovary on an ultrasound appears as an almond-shaped structure, located on either side of the uterus. Within a normal ovary, small, fluid-filled sacs called follicles may be visible, appearing as anechoic (black) rounded structures. These are part of the normal menstrual cycle.
Benign ovarian masses have distinct appearances on ultrasound. Simple cysts, which are common, show as anechoic, unilocular (single-compartment) lesions with thin, smooth walls and increased sound transmission behind them.
Dermoid cysts, also known as mature cystic teratomas, are benign tumors containing various tissues like hair, fat, or even teeth. On ultrasound, they can appear as complex masses with hyperechoic (bright) components that may cast shadows, or as areas with diffuse bright echoes. Specific features like thin, bright lines and dots (a “dot-dash pattern” or “dermoid mesh”) represent hair, while fat globules can appear as “floating balls” within the cyst.
Endometriomas, which are cysts formed from endometrial tissue outside the uterus, present as unilocular or multilocular cysts with homogeneous, low-level internal echoes, giving them a characteristic “ground-glass” appearance. These cysts have thin walls and may show minimal or no internal blood flow on Doppler imaging. Ovarian fibromas are benign solid tumors that appear as solid, hypoechoic (darker) masses with sound attenuation. Their appearance may resemble uterine fibroids.
In contrast, features raising suspicion for ovarian cancer on ultrasound involve more complex characteristics. Malignant masses may be large, often exceeding 10 cm, and can be solid or contain both cystic and solid components. The presence of solid growths or mural nodules (projections from the cyst wall) within a cyst is a concerning sign.
Thickened or irregular septations (internal divisions within a cyst) and papillary projections (finger-like growths) extending into the cyst cavity raise suspicion. Increased vascularity, indicating abnormal blood flow within the mass when evaluated with color Doppler, suggests malignancy. The presence of ascites, which is fluid accumulation in the abdominal cavity, is an indicator.
Beyond the Ultrasound Scan
An ultrasound examination serves as an initial assessment and screening tool for ovarian abnormalities but does not provide a definitive diagnosis of cancer. When suspicious features are identified during an ultrasound, further investigations are recommended to determine the nature of the mass.
One common follow-up involves blood tests, such as the CA-125 test. CA-125 is a protein that can be elevated in women with ovarian cancer, though it also can be high in various benign conditions like endometriosis, fibroids, or even during menstruation. Therefore, CA-125 levels alone are not sufficient for a definitive diagnosis, especially in early-stage disease where levels may not be significantly elevated.
Additional imaging modalities, such as Magnetic Resonance Imaging (MRI) or Computed Tomography (CT) scans, are employed to gain more detailed information about the mass and to assess for potential spread of disease. MRI offers high contrast resolution of soft tissues and can help differentiate between benign and malignant masses, while CT scans are used for staging to determine the extent of the disease, including any involvement of lymph nodes or other organs.
Ultimately, a definitive diagnosis of ovarian cancer requires a tissue biopsy, where a sample of the suspected tumor is removed for microscopic examination by a pathologist. This biopsy is performed during surgery, where the mass can be removed and surrounding tissues or lymph nodes sampled for spread. In some cases, a needle biopsy guided by ultrasound or CT scan may be performed, particularly if surgery is not immediately feasible. The multidisciplinary approach, combining imaging, blood tests, and pathology, is necessary for accurate diagnosis and subsequent treatment planning.