What is the most appropriate initial investigation for a 41-year-old woman with abnormal uterine bleeding who is seeking contraception?

Transvaginal Ultrasound (Option C) is the Most Appropriate Investigation

Before prescribing contraception to a 41-year-old woman with abnormal uterine bleeding, transvaginal ultrasound (combined with transabdominal ultrasound) is the most appropriate initial investigation to identify structural causes such as polyps, adenomyosis, leiomyomas, and endometrial pathology that may influence contraceptive choice or require specific management. 1

Rationale for Ultrasound as First-Line Investigation

• The American College of Radiology assigns transvaginal ultrasound the highest appropriateness rating (7–9) for initial imaging work-up of abnormal uterine bleeding, classifying it as "usually appropriate" among all imaging modalities 1

• Combined transabdominal and transvaginal ultrasound with Doppler is specifically recommended as the most appropriate initial imaging study to identify structural causes of AUB before initiating contraceptive therapy 1

• Transvaginal ultrasound provides superior visualization of the endometrium and myometrium, with sensitivity of 90–99% for detecting uterine fibroids and 90% sensitivity with 98% specificity for submucosal fibroids 2

• This imaging modality reliably distinguishes structural etiologies (polyps, adenomyosis, leiomyoma, malignancy/hyperplasia) from non-structural causes (ovulatory dysfunction, coagulopathy, primary endometrial disorders) 1, 3

Why Other Options Are Less Appropriate

TSH (Option B) – Important but Secondary

• Thyroid-stimulating hormone should be checked as part of the standard diagnostic workup for AUB to evaluate ovulatory dysfunction, but this laboratory test does not take precedence over imaging when both contraception and structural evaluation are needed 1

• TSH is relevant for identifying endocrine causes of anovulatory bleeding but cannot detect structural pathology that may contraindicate certain contraceptive methods or require treatment before hormonal therapy 4, 5

FSH (Option A) – Not Routinely Indicated

• FSH is not routinely recommended in the initial workup of AUB in reproductive-age women requesting contraception 1

• FSH may be relevant for perimenopausal assessment but is not the priority investigation in a 41-year-old woman with AUB seeking contraception 1

Endometrial Biopsy (Option D) – Reserved for Specific Indications

• Endometrial biopsy should be performed in perimenopausal women with risk factors for endometrial cancer (obesity, diabetes, hypertension, unopposed estrogen exposure, Lynch syndrome), but is not the first-line investigation for all women with AUB requesting contraception 1, 6

• Women ≥45 years with abnormal uterine bleeding should undergo endometrial sampling regardless of ultrasound findings, but at age 41, imaging first allows risk stratification 6

• If ultrasound shows endometrial thickness ≥3–4 mm or focal lesions in a woman with risk factors, then endometrial biopsy becomes indicated 1, 6

Clinical Algorithm for This Patient

Step 1: Pregnancy Exclusion

• Perform β-hCG test first—mandatory in all reproductive-age women with AUB 1, 4

Step 2: Physical Examination

• Conduct speculum examination to exclude cervical or vaginal causes of bleeding 7
• Perform bimanual examination to assess uterine size and adnexal masses 1

Step 3: Transvaginal Ultrasound

• Order combined transvaginal and transabdominal ultrasound with Doppler as the primary imaging modality 1, 2
• Assess endometrial thickness, texture, echogenicity, and presence of focal lesions (polyps, fibroids) 1
• Evaluate for adenomyosis (sensitivity ~82.5%, specificity ~84.6%) and leiomyomas 1

Step 4: Risk Stratification for Endometrial Sampling

• Consider endometrial biopsy if ultrasound shows thickened endometrium (≥3–4 mm threshold adapted from postmenopausal guidelines) AND patient has risk factors: obesity, diabetes, hypertension, chronic anovulation, or family history of Lynch syndrome 1, 6
• If ultrasound is normal and patient has no risk factors, proceed with contraceptive counseling 1

Step 5: Advanced Imaging if Needed

• If initial ultrasound shows focal lesions or is inconclusive, perform saline infusion sonohysterography (96–100% sensitivity for endometrial pathology) 1, 4
• If ultrasound cannot adequately visualize the endometrium due to body habitus or interfering pathology, proceed directly to endometrial sampling rather than relying on incomplete imaging 1

Common Pitfalls to Avoid

• Do not prescribe hormonal contraception without imaging in a woman with AUB—structural causes like submucous fibroids or endometrial polyps may worsen with certain hormonal methods or require surgical management 1, 8

• Do not accept inadequate ultrasound visualization as reassuring—if the endometrium cannot be adequately assessed due to technical limitations, proceed to endometrial sampling or advanced imaging before initiating hormonal therapy 1

• Do not skip pregnancy testing—pregnancy complications are critical differential diagnoses in all reproductive-age women with abnormal bleeding 4, 9

• Do not order endometrial biopsy routinely in all women <45 years without risk factors—imaging-first approach allows appropriate risk stratification and avoids unnecessary invasive procedures 1, 6