Polycystic ovary syndrome (PCOS) is the most common endocrine disorder affecting 6-15% of reproductive-age women. Diagnosed by Rotterdam criteria (2 of 3): oligo/anovulation, clinical/biochemical hyperandrogenism, ultrasonographic polycystic ovarian morphology. Ultrasonographic diagnosis: ≥12 antral follicles (2-9 mm) in one ovary and/or ovarian volume >10 mL. Insulin resistance, obesity, infertility, metabolic syndrome, and type 2 diabetes risk are increased. 'String of pearls' pattern on imaging is characteristic.
Age Range
15-40
Peak Age
25
Gender
Female predominant
Prevalence
Common
PCOS is fundamentally based on dysregulation of the hypothalamic-pituitary-ovarian axis, insulin resistance, and hyperandrogenism. LH/FSH ratio is increased (usually >2:1) — elevated LH increases androgen production in theca cells, while low FSH prevents follicle maturation. Follicles cannot mature and small antral follicles (2-9 mm) accumulate in the peripheral cortex — creating the 'string of pearls' pattern on imaging. Stromal hypertrophy is the histological correlate of increased androgen production and appears as increased stromal echogenicity/volume on US. Ovarian capsule thickens (cortical fibrosis) creating mechanical barrier to ovulation. Increased ovarian volume results from both follicle accumulation and stromal hypertrophy, with >10 mL as diagnostic threshold.
Appearance of multiple small antral follicles (2-9 mm) aligned in the ovarian peripheral cortex like a string of pearls. Most characteristic ultrasonographic finding of PCOS. Follicles are anechoic, round, uniform in size, and aligned peripherally on the inner surface of the ovarian cortex — central stroma remains hyperechoic with increased volume. This pattern is the visual correlate of follicles failing to mature and arresting at small antral stage due to low FSH. Distinguished from normal cycle because normal ovary has scattered, size-variable follicles (dominant follicle >10 mm). New 2023 international consensus: ≥20 follicles (2-9 mm) per ovary or volume >10 mL is diagnostic (previous threshold was ≥12).
≥12 small antral follicles (2-9 mm) peripherally located in ovarian cortex show linear alignment — 'string of pearls' pattern. Follicles are anechoic, round, and uniform in size. Central stroma is hyperechoic with increased volume.
Report Sentence
Multiple small antral follicles (2-9 mm) with peripheral distribution are seen in both ovaries, demonstrating 'string of pearls' pattern consistent with polycystic ovarian morphology.
Ovarian volume >10 mL (ellipsoid formula: length x width x height x 0.523). Bilateral involvement typical. Increased volume results from both follicle accumulation and stromal hypertrophy.
Report Sentence
Both ovarian volumes are increased (right: ... mL, left: ... mL) exceeding the >10 mL threshold; consistent with polycystic ovarian morphology.
Central ovarian stroma shows increased echogenicity and volume. Stromal/total ovarian volume ratio is increased (>0.34). Stromal hypertrophy is the consequence of hyperandrogenism.
Report Sentence
Ovarian stromal echogenicity is increased, consistent with stromal hypertrophy.
Peripherally located high-signal follicles and central low-intermediate signal stroma on T2-weighted images. 'String of pearls' pattern also visible on MRI. Ovarian size increased.
Report Sentence
Multiple small peripherally located follicles and increased stromal volume are seen in both ovaries on MRI, consistent with polycystic ovarian morphology.
Increased vascularity in ovarian stroma. Stromal vessels are more prominent with lower resistance index. Stromal hypervascularity may correlate with degree of hyperandrogenism.
Report Sentence
Increased stromal vascularity is demonstrated on Doppler examination, a supportive finding consistent with PCOS.
Criteria
Hyperandrogenism + oligo/anovulation + polycystic ovarian morphology. All three Rotterdam criteria positive. Most common phenotype.
Distinct Features
Most prominent ultrasonographic findings. Bilateral large ovaries, numerous peripheral follicles, prominent stromal hypertrophy. Highest metabolic risk.
Criteria
Hyperandrogenism + oligo/anovulation, polycystic ovarian morphology ABSENT. Ultrasonographic criterion not met.
Distinct Features
Ovarian US may appear normal. Diagnosis relies on clinical and biochemical criteria. Metabolic profile similar to Phenotype A.
Criteria
Hyperandrogenism + polycystic ovarian morphology, regular ovulation. Oligo/anovulation ABSENT.
Distinct Features
Ultrasonographic PCOS morphology present but menstrual cycle regular. Fertility usually preserved. Milder metabolic profile.
Criteria
Oligo/anovulation + polycystic ovarian morphology, hyperandrogenism ABSENT. Androgen levels normal.
Distinct Features
Ultrasonographic PCOS morphology present, oligo/amenorrhea present, but no acne/hirsutism. Mildest phenotype. Lower metabolic risk.
Distinguishing Feature
Simple ovarian cyst is single, large (>3 cm), anechoic, thin-walled structure. PCOS is distinguished by multiple small follicles (2-9 mm), bilateral, increased ovarian volume and stromal hypertrophy. Ovarian volume is normal with simple cyst.
Distinguishing Feature
Hemorrhagic cyst is single, large, reticular pattern (fibrin strands), ovary locally enlarged. In PCOS, multiple small uniform follicles, peripheral alignment and bilateral involvement are prominent. Clinical context also distinguishes — hemorrhagic cyst with acute pain, PCOS with chronic oligo/amenorrhea.
Distinguishing Feature
Dermoid (mature cystic teratoma) has heterogeneous internal structure, fat-fluid level, calcification/teeth, 'tip of the iceberg' sign. Single lesion. PCOS has completely different morphology with multiple uniform small anechoic follicles, bilateral, stromal hypertrophy.
Urgency
routineManagement
medicalBiopsy
Not NeededFollow-up
annualPCOS is a chronic endocrine disorder requiring multidisciplinary management. Treatment is individualized based on clinical presentation: ovulation induction if infertility (letrozole first-line, clomiphene second-line); oral contraceptives + anti-androgens (spironolactone) for hyperandrogenism; metformin + lifestyle modification (diet, exercise, weight loss) for insulin resistance. Metabolic syndrome screening should be done annually (glucose, lipid profile, blood pressure). Endometrial hyperplasia risk is increased (unopposed estrogen from chronic anovulation) — at least one menstrual bleeding per year should be ensured or progesterone protection given. Long-term type 2 diabetes, cardiovascular disease, and endometrial cancer risk are increased. Ovarian drilling (laparoscopic) is an alternative in treatment-resistant cases.
PCOS is one of the most common causes of infertility. Risk of metabolic syndrome, type 2 diabetes, cardiovascular disease, and endometrial cancer is increased. Rotterdam criteria are used for diagnosis (2 of 3 criteria: oligoanovulation, hyperandrogenism, polycystic ovary morphology).