A 28-year-old nulliparous woman with PCOS presents with irregular, prolonged menstrual bleeding for 3 months. Pelvic examination is normal. Hemoglobin is 10.5 g/dL. Transvaginal ultrasound shows a normal uterus and ovaries with multiple small cysts. What is the most appropriate next investigation to exclude endometrial pathology before starting hormonal management?

Explanation

## Clinical Context This patient has **abnormal uterine bleeding (AUB) secondary to PCOS** with anovulation and unopposed estrogen exposure. Before initiating hormonal therapy (combined oral contraceptive or progestin), **endometrial safety** must be assessed to exclude hyperplasia or malignancy. ## Investigation of Choice **Key Point:** **Endometrial thickness measurement by transvaginal ultrasound** is the most appropriate **non-invasive screening test** to assess endometrial safety in anovulatory AUB. ### Rationale for Endometrial Thickness Assessment 1. **Non-invasive**, no anesthesia, cost-effective 2. **High negative predictive value (NPV)** when thickness ≤4 mm in postmenopausal women; in reproductive-age women with anovulation, a **normal thickness (<12 mm) essentially excludes significant pathology** 3. **First-line screening** before hormonal therapy in PCOS with AUB 4. **Safe cutoff:** Endometrial thickness **<12 mm** in reproductive-age women with anovulation is reassuring 5. **Avoids unnecessary invasive procedures** in low-risk patients ## Decision Tree for Endometrial Assessment in AUB ```mermaid flowchart TD A[AUB with anovulation<br/>PCOS/obesity/unopposed estrogen]:::outcome --> B[Measure endometrial thickness<br/>by TVS]:::action B --> C{Thickness?}:::decision C -->|< 12 mm| D[Reassuring<br/>Start hormonal therapy]:::action C -->|≥ 12 mm or<br/>abnormal echo| E[Endometrial biopsy<br/>or hysteroscopy]:::action C -->|Age > 45 or<br/>risk factors| F[Endometrial biopsy<br/>regardless of thickness]:::action ``` ## Comparison of Investigations | Investigation | Indication | Invasiveness | Cost | |---|---|---|---| | **Endometrial thickness (TVS)** | Screening in anovulatory AUB; normal thickness reassures | Non-invasive | Low | | Endometrial biopsy | Abnormal endometrial echo, thickness ≥12 mm, age >45, persistent AUB | Invasive; requires anesthesia | Moderate | | Diagnostic hysteroscopy | Intrauterine pathology (polyps, septum, adhesions); therapeutic option | Invasive; requires anesthesia | High | | Hysterosalpingography | Tubal patency assessment; not indicated for AUB evaluation | Invasive; radiation | Moderate | **High-Yield:** In **reproductive-age women with anovulatory AUB** (PCOS, obesity), **endometrial thickness <12 mm by TVS is reassuring** and excludes significant hyperplasia/malignancy in most cases. Biopsy is reserved for abnormal echo pattern or thickness ≥12 mm. ## Clinical Pearl This patient is **28 years old with PCOS** — a **low-risk** scenario for endometrial malignancy. Endometrial thickness measurement will likely be normal, allowing safe initiation of combined oral contraceptive or cyclic progestin therapy without invasive biopsy. [cite:Park 26e Ch 12]