Polycystic Ovary Syndrome (PCOS) is a common complex endocrine and metabolic disorder among women of reproductive age. It is characterized by chronic anovulation (disrupted or absent ovulation), hyperandrogenism (excess production of male hormones in women), and insulin resistance.

The pathogenesis of PCOS is currently not fully understood but is believed to be closely related to genetic and environmental factors, involving complex regulation of the neuroendocrine and immune systems. Its pathological features include bilateral enlarged ovaries with uneven surfaces, thickening of the ovarian capsule about 2 to 4 times thicker than normal, and rich vascular structures inside. Multiple follicles are arranged regularly beneath the ovarian capsule, ranging in diameter from 2 to 9mm, with some scattered within the cortical layer of the ovary.

The main clinical manifestations include oligomenorrhea (infrequent menstrual periods), amenorrhea (absence of menstruation), dysfunctional uterine bleeding, hirsutism (excessive body hair), infertility, and obesity, making it one of the most common endocrine disorders in women.

Patients with PCOS have a significantly increased risk of developing type 2 diabetes, hypertension, coronary heart disease, hyperlipidemia, endometrial cancer, and pregnancy-induced hypertension syndrome.

The incidence of PCOS in the population is around 5% to 10% among women of reproductive age, accounting for 30% to 60% of cases of anovulatory infertility. The number of PCOS patients seen in outpatient clinics is increasing annually. The clinical characteristics include ovulatory dysfunction or loss, oligomenorrhea or amenorrhea, infertility without contraception after marriage, excessive androgens in the body manifested as acne, hirsutism, masculinization of hair distribution, 40% to 60% of patients are overweight, often with central obesity. Some patients show ultrasound features of bilateral ovarian polycystic changes.

Laboratory tests show elevated serum androgens (androstenedione, testosterone) levels, sometimes tens of times higher than normal, elevated serum LH levels, often exceeding 2 standard deviations from the normal mean, and LH/FSH ratio greater than 2.5 to 3.

Ultrasound examination is a commonly used imaging method for gynecological diseases. Prior to the examination, hormone medications should be discontinued for at least one month. Ultrasound examination is performed on days 3 to 5 of the menstrual cycle (for those with regular menstrual cycles) or in the absence of a dominant follicle. For women with infrequent ovulation, if the follicle diameter is >10 mm or if a corpus luteum is present, a follow-up examination should be performed in subsequent cycles. Transabdominal or transvaginal ultrasound examination is of great clinical value in the diagnosis of PCOS. Transvaginal ultrasound examination has higher clarity and better results. Transabdominal ultrasound is prone to interference from factors such as abdominal wall thickness and fat attenuation. It should be noted that polycystic ovaries (PCO) are not unique to PCOS. PCO can be found in 20% to 30% of normal reproductive-aged women and may also occur after oral contraceptive use or in cases of amenorrhea.

Ultrasound manifestations of PCOS include:

Bilateral ovaries with uniform enlargement, volume exceeding 10cm3 (simplified calculation formula for ovarian volume: V=0.5x length x width x height).

Thickening of the ovarian capsule with enhanced echogenicity.

Multiple small follicles with diameters of about 2-9mm are visible within the ovaries, arranged regularly beneath the ovarian capsule, with a minimum of 12 follicles observed in the same ultrasound plane.

Enhanced echogenicity of the ovarian medulla.

Continuous ultrasound monitoring reveals no mature follicle development and absence of ovulation.

Transabdominal Ultrasound Image of Polycystic Ovarian Changes

Transvaginal Ultrasound Image of Polycystic Ovarian Changes

Color Doppler Ultrasound Image of Polycystic Ovarian Changes

Differential diagnosis:

It is necessary to differentiate from polycystic ovary syndrome, which is characterized by the presence of numerous medium-sized follicles in both ovaries. Serum hormone tests show elevated estrogen levels, and ultrasound shows bilateral ovarian enlargement with numerous follicles with diameters of about 4-10mm, typically around 6 follicles, without thickening of the ovarian capsule and with normal echogenicity.

Appendix: 2003 Rotterdam Consensus (ROT criteria) The 2003 Rotterdam Consensus reached an agreement that if two of the following three criteria are met, a diagnosis of PCOS can be made:

(1) Ultrasound shows polycystic ovarian changes;

(2) Oligo- or anovulation;

(3) Clinical manifestations of hyperandrogenism and biochemical evidence, with exclusion of conditions such as congenital adrenal hyperplasia, androgen-secreting tumors, and Cushing's syndrome that cause excess androgens.

When ultrasound reveals at least 12 small follicles with diameters of 2-9mm in each ovary or ovarian volume ≥10cm3, meeting criterion (1) of the ROT criteria, either criterion (2) or (3) is sufficient for a diagnosis of PCOS. If polycystic changes are present only in one ovary, it is also considered to meet criterion (1) of the ROT criteria.