Polycystic Ovary Syndrome (PCOS) is a common endocrine disorder affecting women of reproductive age, characterized by hormonal imbalances that disrupt normal ovarian function. This condition is one of the most frequent hormonal abnormalities, impacting an estimated 6 to 12 percent of women globally. Healthcare providers rely on specific diagnostic tools to confirm the presence of the syndrome. Pelvic ultrasound imaging is a component of this process, providing a visual assessment of the ovaries to identify Polycystic Ovarian Morphology (PCOM).
The Purpose and Methods of PCOS Ultrasound
The goal of a pelvic ultrasound for PCOS is to visualize the ovaries and assess their internal structure and size. This imaging helps confirm structural changes associated with the syndrome and assists in ruling out other pelvic conditions. The visualization allows for the measurement of ovarian volume and the counting of small follicles, which are quantitative criteria for diagnosis.
Two main methods are used: transabdominal and transvaginal ultrasound. The transabdominal method is less invasive but offers lower resolution, making it less precise.
The transvaginal ultrasound (TVUS) is the preferred method for detailed evaluation. The probe is inserted into the vagina, allowing for closer proximity to the ovaries and resulting in higher-resolution images necessary for accurate measurement and follicle counting.
Interpreting the Polycystic Ovarian Morphology
When a polycystic ovary is viewed on an ultrasound image, it exhibits distinctive visual features. The most recognizable sign is the appearance of multiple small, fluid-filled sacs lining the periphery of the ovary. These sacs are immature follicles, measuring between 2 and 9 millimeters in diameter, that have failed to mature and ovulate.
This characteristic arrangement is frequently described as the “string of pearls” sign, where the small, dark circles are clustered just beneath the ovarian surface. This pattern alone does not confirm a PCOS diagnosis, as it can be seen in women without the syndrome.
Another visual clue is the appearance of the ovarian stroma, the central core of the ovary. In ovaries with PCOM, the stroma often appears enlarged and brighter than normal tissue, described as hyperechoic. This increased brightness reflects underlying hormonal activity, as the stroma contains cells responsible for androgen production.
Quantifying the Scan Results for Diagnosis
The visual evidence of PCOM must be translated into specific numerical measurements using the Rotterdam criteria. This framework requires at least one of two specific ultrasound findings.
Follicle Number per Ovary (FNPO)
The first criterion is the Follicle Number per Ovary (FNPO), which must show 12 or more follicles in a single ovary. These follicles must measure from 2 to 9 millimeters in diameter. Counting the follicles often requires high-resolution transvaginal imaging to ensure accuracy.
Ovarian Volume (OV)
The second quantitative criterion is an increased Ovarian Volume (OV), defined as a measurement greater than 10 milliliters in at least one ovary. The volume is calculated by measuring the ovary across its three dimensions, reflecting the overall enlargement caused by the multiple small follicles and the dense stroma.
Completing the Diagnosis Beyond Imaging
The finding of Polycystic Ovarian Morphology (PCOM) on an ultrasound is only one of three diagnostic pillars for Polycystic Ovary Syndrome. To receive a formal PCOS diagnosis, a patient must meet at least two of the three criteria established by the Rotterdam consensus. PCOM alone is not sufficient.
The other two necessary components are clinical or biochemical hyperandrogenism and oligo- or anovulation. Hyperandrogenism refers to signs of elevated male hormones, which can manifest clinically as hirsutism, severe acne, or male-pattern hair loss. Biochemical evidence is confirmed through blood tests that measure elevated levels of androgens. Oligo- or anovulation is identified by irregular or absent menstrual periods, indicating that ovulation is occurring infrequently or not at all. The definitive diagnosis requires a comprehensive evaluation integrating imaging results with a patient’s symptoms and hormonal blood work.