An ovarian ultrasound is a non-invasive imaging technique that uses high-frequency sound waves to create images of the pelvic organs. The procedure may be performed transabdominally (transducer on the lower abdomen) or transvaginally (probe inserted into the vagina for higher resolution). This scan is routinely used to investigate pelvic pain or abnormal bleeding, characterize masses found on a physical exam, and monitor ovarian follicles during fertility treatments. The ability to visualize the ovaries helps determine if an abnormality is a normal physiological process or requires further investigation.
Understanding the Ultrasound Image
Interpreting an ultrasound image, also known as a sonogram, requires understanding how sound waves translate into shades of gray. The transducer emits sound pulses, and the returning echoes are processed to form a visual display. Different tissues reflect sound waves differently, a property called echogenicity, which determines a structure’s brightness on the screen.
Fluid-filled structures, like a simple cyst or the urinary bladder, do not reflect sound waves and therefore appear completely black; this is described as anechoic or echo-free. Conversely, dense structures such as fat or calcifications reflect most of the sound waves and appear bright white, a characteristic called hyperechoic. Tissues that share a similar gray shade with the surrounding structures are termed isoechoic.
The images are captured in specific orientations to map the three-dimensional anatomy of the pelvis. The sagittal view presents structures in a long-axis plane, running from the head to the feet. The transverse view shows a cross-sectional, short-axis plane, running from side to side. The operator constantly moves the transducer to sweep through the organs, ensuring the entire ovary and surrounding adnexal region are fully visualized.
Identifying Normal Ovarian Appearance
A healthy ovary in a reproductive-age person typically appears as a firm, ovoid or almond-shaped structure located on either side of the uterus. Its average volume is usually between 6 and 10 cubic centimeters. The ovary’s tissue texture is generally homogeneous, and it is distinctly divided into two regions: an inner medulla and an outer cortex.
The cortex is the functional layer, and its appearance changes throughout the menstrual cycle. During the follicular phase, the cortex is characterized by multiple small, round, anechoic (black) circles, which are the developing follicles. As the cycle progresses, one follicle becomes dominant, growing to a size between 17 and 27 millimeters just before ovulation. These fluid-filled structures are normal and indicate physiological function.
The appearance of the ovary changes significantly after menopause due to hormonal decline. Post-menopausal ovaries atrophy, becoming smaller and more homogeneous in texture. Their volume typically shrinks to less than 5 cubic centimeters, and they generally lack the multiple anechoic follicles seen in younger women.
Interpreting Common Ovarian Findings
Many ovarian findings are variations of normal physiological processes or common benign conditions. Functional cysts are the most frequently encountered finding and represent the natural result of ovulation. A follicular cyst is typically a simple, unilocular cyst that is anechoic with a thin, smooth wall. A corpus luteum cyst forms after ovulation and has a more complex appearance, often presenting with thick, crenulated inner walls and sometimes containing internal echoes due to hemorrhage. The presence of internal echoes within a functional cyst is a reassuring sign that the cyst is benign and involuting.
The ultrasound appearance of other common benign masses is often highly characteristic. An endometrioma, commonly called a chocolate cyst, is an ovarian lesion resulting from endometriosis. This type of cyst typically appears as a unilocular mass filled with homogeneous, low-level internal echoes, which gives the distinctive “ground glass” visual texture due to old, thick blood products. Dermoid cysts, or mature cystic teratomas, are composed of various tissues like hair, fat, and bone, giving them a highly heterogeneous appearance. They often contain a densely hyperechoic nodule, known as a Rokitansky nodule or dermoid plug, which frequently causes a shadow effect behind it, sometimes called the “tip of the iceberg” sign.
Certain features on a sonogram, however, may be visual red flags, indicating a need for closer scrutiny or further testing. Complex masses displaying thick septations, which are internal dividing walls measuring over 3 millimeters, or irregular solid components raise suspicion. The presence of irregular borders, or papillary projections—small, cauliflower-like growths extending from the cyst wall—are also concerning features. These complex findings suggest the need for additional imaging or specialist referral to rule out a malignant process.
Translating the Medical Report
The formal medical report is the radiologist’s interpretation, using standardized terminology to categorize the findings for the referring clinician. A common term encountered is adnexal mass, which is a broad, non-specific term referring to any mass originating in the area of the ovaries, fallopian tubes, or supporting ligaments. The report specifies the mass’s characteristics, including its size, often measured in three dimensions (length, width, and depth) to calculate an overall volume or maximum diameter. These measurements are important for monitoring, as a stable or decreasing size suggests a benign nature, while rapid growth is a cause of concern.
The report also details the results of Doppler flow imaging, which uses color to visualize blood flow within a mass. An absence of internal blood flow (Color Score 1) in a solid area is a positive indicator, while the presence of strong, disorganized flow (Color Score 4) within a solid component or a mural nodule is a feature often associated with malignancy. For a corpus luteum, the “ring of fire” pattern represents intense blood flow only in the cyst wall, which is a normal, expected finding.
To standardize risk assessment, radiologists use the Ovarian-Adnexal Reporting and Data System (O-RADS), which assigns a category from 0 (incomplete evaluation) to 5 (high risk of malignancy) to any non-physiologic finding. The O-RADS score is based on a structured analysis of the mass’s features, such as the presence of solid components, septations, and vascularity. This system helps ensure that patients with lesions classified as O-RADS 2 (almost certainly benign) can safely avoid unnecessary intervention, while those with O-RADS 4 or 5 lesions receive prompt referral to a gynecologic oncologist.