What are the next steps for a female patient of reproductive age with concerns for endometriosis and polycystic ovarian syndrome (PCOS) who had a transvaginal ultrasound showing normal endometrial thickness, non-visualization of the right ovary due to overlying bowel gas, and otherwise unremarkable pelvic sonography?

Explaining Transvaginal Ultrasound Results and Next Steps

Direct Interpretation of Current Findings

Your ultrasound does not show evidence of polycystic ovarian syndrome (PCOS), but the incomplete visualization of your right ovary means we cannot definitively rule it out and need additional imaging. 1

The normal endometrial thickness is reassuring and does not suggest endometriosis on ultrasound, though it's important to understand that transvaginal ultrasound has limited ability to detect endometriosis unless it involves the ovaries (endometriomas) or deep infiltrating disease. 2

Immediate Next Steps for Imaging

You need repeat imaging to visualize the right ovary, which can be accomplished through one of the following approaches:

• Schedule a repeat transvaginal ultrasound with bowel preparation (fasting 4-6 hours, consider laxative the night before) to minimize bowel gas interference 1, 3
• Consider MRI pelvis without contrast if repeat ultrasound still cannot adequately visualize the ovaries, as this provides excellent visualization regardless of bowel gas 3

The right ovary must be evaluated because PCOS diagnosis requires assessing both ovaries for polycystic ovarian morphology (PCOM), defined as ≥20 follicles (2-9mm diameter) per ovary OR ovarian volume >10 mL. 1

Completing the PCOS Diagnostic Workup

PCOS diagnosis requires meeting at least 2 of 3 Rotterdam criteria after excluding other conditions: 1

1. Oligo- or anovulation (menstrual cycles >35 days apart or <8 cycles per year) 1
2. Clinical or biochemical hyperandrogenism 1
3. Polycystic ovarian morphology on ultrasound 1

Essential Laboratory Testing

Order the following blood tests (ideally in early follicular phase, days 2-5 of cycle, or any time if amenorrheic): 1, 3

• Total testosterone via LC-MS/MS (liquid chromatography-tandem mass spectrometry) - this is the single best initial marker with 74% sensitivity and 86% specificity 1
• Sex hormone-binding globulin (SHBG) to calculate free testosterone using the Vermeulen equation (89% sensitivity, 83% specificity) 1
• TSH and prolactin to exclude thyroid disease and hyperprolactinemia 1, 3
• 17-hydroxyprogesterone (early morning) to exclude non-classic congenital adrenal hyperplasia 1

Metabolic Screening (Required for All PCOS Patients)

All women with suspected or confirmed PCOS require metabolic evaluation: 1, 4

• 2-hour oral glucose tolerance test with 75g glucose load - rates of progression from normal glucose tolerance to impaired glucose tolerance and type 2 diabetes may be as high as 5-15% within 3 years in PCOS 4
• Fasting lipid profile - young lean PCOS women have lower HDL size and higher LDL particle numbers compared to controls 4

Clinical History Details to Document

Obtain specific information about: 1, 3

• Menstrual pattern: Exact cycle length, regularity, duration of irregularity (cycles >35 days suggest chronic anovulation) 1
• Hyperandrogenic symptoms: Onset and progression of hirsutism, acne, male-pattern hair loss (gradual onset suggests PCOS; rapid onset suggests androgen-secreting tumor requiring urgent evaluation) 1, 3
• Fertility concerns: Duration of attempting conception, if applicable 3
• Family history: Cardiovascular disease, type 2 diabetes, PCOS in first-degree relatives 1
• Medication review: Any exogenous androgens, hormonal contraceptives (must be off for accurate hormone testing) 1

Physical Examination Findings to Assess

Document the following clinical signs: 1, 3

• Modified Ferriman-Gallwey score for hirsutism (≥4-6 indicates clinical hyperandrogenism) 1
• BMI and waist-hip ratio - obesity is present in 60-70% of PCOS patients and is the most common co-factor 1, 5
• Acanthosis nigricans (velvety hyperpigmentation in skin folds indicating insulin resistance) 1
• Exclude Cushing's syndrome signs: Buffalo hump, moon facies, abdominal striae, hypertension 1

Addressing Endometriosis Concerns

Transvaginal ultrasound has limited sensitivity for endometriosis unless specific findings are present: 2

• Ultrasound can detect ovarian endometriomas (chocolate cysts) and deep infiltrating endometriosis involving the uterosacral ligaments, rectovaginal septum, or bowel 2
• Most endometriosis is not visible on ultrasound - the majority of pelvic pain symptoms do not differ significantly between women with and without sonographic evidence of endometriosis 2
• If endometriosis remains a strong clinical suspicion based on symptoms (severe dysmenorrhea, deep dyspareunia, dyschezia during menses), diagnostic laparoscopy remains the gold standard 2

Key Symptom Patterns for Endometriosis

The symptoms most associated with endometriosis are: 2

• Menstrual dyschezia (painful bowel movements during periods) 2
• Difficulty emptying the bladder 2
• Severe dysmenorrhea and deep dyspareunia (though these are less specific) 2

Important Clinical Pitfalls to Avoid

• Do not use ultrasound for PCOS diagnosis in adolescents (<8 years post-menarche or <20 years old) due to high false-positive rates from normal multifollicular ovaries 1
• Polycystic ovarian morphology alone is insufficient for diagnosis - up to one-third of reproductive-aged women without PCOS have PCOM on ultrasound 1
• Do not use AMH levels for PCOS diagnosis despite elevated levels in PCOS, as there is lack of standardization, no validated cut-offs, and significant overlap with normal women 1
• Hormonal contraceptives must be discontinued before biochemical testing, as they suppress the hypothalamic-pituitary-ovarian axis and make hormone levels unreliable 1
• Chronic anovulation increases endometrial cancer risk - any persistent abnormal bleeding requires endometrial evaluation with transvaginal ultrasound and endometrial biopsy 4, 5

When Ultrasound May Not Be Necessary

Recent evidence suggests that ultrasound is only required in approximately 30% of PCOS evaluations: 6

• If you already have both clinical/biochemical hyperandrogenism AND oligo-/anovulation, PCOS can be diagnosed without ultrasound 6
• Ultrasound is primarily needed when only one criterion is present (hyperandrogenism alone or ovulatory dysfunction alone) to identify PCOS phenotypes C and D 6