Polycystic Ovary Syndrome (PCOS) is a common hormonal condition affecting individuals of reproductive age. It can lead to a range of symptoms, including irregular menstrual cycles, excess androgen levels, and changes in ovarian morphology. An ultrasound examination plays a significant role as a diagnostic tool in identifying characteristic features associated with PCOS. This article clarifies the procedure and typical findings.
Understanding the Ultrasound Procedure
When evaluating for PCOS, healthcare providers commonly use two types of ultrasound: transabdominal and transvaginal. A transabdominal ultrasound involves placing a transducer on the lower abdomen, and it often requires a full bladder for optimal image clarity. This helps to push the bowel loops out of the way, providing a clearer view of the pelvic organs.
A transvaginal ultrasound involves gently inserting a slim transducer into the vagina. This method provides more detailed images of the ovaries and uterus due to the transducer’s proximity to the organs being examined. For a transvaginal scan, the bladder is usually emptied beforehand, as it is not needed for image transmission and improves comfort. Both procedures are quick, lasting approximately 15 to 30 minutes, and are well-tolerated.
Characteristic Ovarian Appearance
On an ultrasound, ovaries associated with PCOS often exhibit specific visual characteristics. One common finding is an increased ovarian volume, typically measuring greater than 10 milliliters (mL). While this enlargement can affect one or both ovaries, only one ovary meeting the criteria is sufficient for defining polycystic ovarian morphology. However, some individuals with PCOS may not show increased ovarian volume.
Another prominent feature is the presence of multiple small follicles, often described as having a “pearl necklace” or “string of pearls” appearance. These are not true cysts but rather numerous immature follicles, measuring between 2 to 9 millimeters (mm) in diameter. The Rotterdam criteria defines polycystic ovaries by the presence of 12 or more follicles per ovary. However, newer guidelines may suggest higher thresholds, such as 20 or 25 follicles. These follicles are arranged peripherally around the central ovarian tissue.
The central part of the ovary, known as the stroma, can also appear altered on ultrasound. In polycystic ovaries, the stroma can appear brighter or more echogenic, its ability to reflect sound waves. This subjective impression of increased brightness is partly due to the increased volume of the ovarian stroma itself and the contrast with the numerous small follicles surrounding it.
Other Relevant Ultrasound Findings
Beyond the ovaries, an ultrasound performed in the context of PCOS can reveal other findings. The thickness of the uterine lining, or endometrium, is one such finding. Due to the hormonal imbalances in PCOS, particularly the prolonged exposure to estrogen without sufficient progesterone, the endometrial lining can become thicker. This occurs because ovulation does not regularly take place, preventing the normal shedding of the uterine lining.
The ultrasound can also provide clues about ovulation patterns. In individuals with PCOS, the absence of a dominant follicle (a follicle that would mature and release an egg) or a corpus luteum (the structure forming after egg release) can indicate anovulation or irregular ovulation. This lack of a dominant follicle or corpus luteum, combined with the presence of many small, undeveloped follicles, supports the ovulatory dysfunction characteristic of PCOS.
Interpreting Your Ultrasound Results
While an ultrasound can provide valuable information about ovarian morphology, it is not sufficient for a standalone diagnosis of PCOS. Polycystic ovarian morphology can be present in individuals who do not have PCOS, and conversely, some individuals with PCOS may have ovaries that appear normal on ultrasound. The diagnosis of PCOS requires a comprehensive assessment that considers multiple factors.
The Rotterdam criteria, a diagnostic framework, specifies that a diagnosis of PCOS requires at least two out of three criteria: irregular or absent ovulation, clinical or biochemical signs of excess androgens, and polycystic ovaries on ultrasound. Therefore, ultrasound findings must be interpreted alongside clinical symptoms like irregular periods or excess hair growth, and blood tests measuring hormone levels. Healthcare professionals integrate this information to make an accurate diagnosis and develop an individualized management plan.