What is the appropriate workup for abnormal uterine bleeding in a woman presenting with missed, irregular periods and heavy bleeding?

Workup of Abnormal Uterine Bleeding

Start with transvaginal ultrasound (TVUS) combined with transabdominal ultrasound as your first-line imaging, obtain a complete blood count, pregnancy test, and thyroid function tests, then proceed to endometrial sampling based on age and risk factors 1.

Initial Clinical Assessment

Focus your history on these specific elements:

• Bleeding pattern: Distinguish between heavy menstrual bleeding (predictable, cyclical) versus intermenstrual bleeding (irregular, non-cyclical) 2
• Clot size: Clots ≥1 inch diameter predict heavy menstrual bleeding 3
• "Flooding": Changing pad/tampon more frequently than hourly 3
• Age: Critical for determining cancer risk and need for endometrial sampling
• Bleeding disorder history: Personal or family history of bleeding suggests coagulopathy and warrants hematology referral 3

Laboratory Workup

Order these tests systematically:

• Pregnancy test (β-hCG): Rule out pregnancy complications first—ectopic pregnancy is life-threatening 4
• Complete blood count: Assess for anemia; low ferritin predicts heavy menstrual bleeding 3
• Thyroid function tests: Thyroid dysfunction causes both anovulatory and ovulatory bleeding 5
• Coagulation studies: If flooding, prolonged menses, or bleeding history present—von Willebrand disease is the most common coagulopathy 3, 5
• Prolactin level: If oligomenorrhea or galactorrhea present 5

Imaging Strategy

TVUS is your primary imaging modality 1, 2:

• Combines transvaginal (high resolution) with transabdominal (large uterus overview) approaches 1
• Detects structural causes: fibroids, adenomyosis (82.5% sensitivity, 84.6% specificity), polyps 1
• Critical age-based thresholds:
  • Postmenopausal: Endometrial thickness ≥5 mm requires endometrial sampling (4 mm cutoff has nearly 100% negative predictive value for cancer) 1
  • Premenopausal: No validated thickness cutoff exists—abnormal echogenicity and texture matter more than thickness 1

Add sonohysterography if TVUS shows focal endometrial abnormality—saline infusion improves characterization of polyps and submucosal fibroids 1, 5.

Reserve MRI for when ultrasound is inconclusive or the uterus is incompletely visualized—MRI has 79% sensitivity and 89% specificity for endometrial cancer, and 100% sensitivity/specificity for leiomyosarcoma 1.

Endometrial Sampling Indications

Perform endometrial biopsy in these scenarios 5:

• Age ≥35 years with recurrent anovulation
• Age <35 years with endometrial cancer risk factors (obesity, chronic anovulation, PCOS)
• Excessive bleeding unresponsive to medical therapy
• Postmenopausal bleeding with endometrial thickness ≥5 mm 1

Common Pitfalls

Don't rely on endometrial thickness alone in premenopausal women—even thickness <5 mm can harbor polyps or pathology 1. The evidence clearly shows thickness is not an indicator of endometrial pathology in this population.

Don't skip pregnancy testing—complications of pregnancy (ectopic, trophoblastic disease) can be life-threatening and delay in diagnosis worsens prognosis 4.

Don't miss coagulopathies—if the patient reports flooding, prolonged menses, or has a bleeding history, refer to hematology early 3. Up to 90% of women with underlying bleeding disorders experience heavy menstrual bleeding.

Age-Specific Considerations

Reproductive age with irregular periods: Think anovulation first—check for PCOS, thyroid dysfunction, hyperprolactinemia 5. These patients need endometrial protection from unopposed estrogen.

Reproductive age with heavy regular bleeding: Consider structural causes (fibroids, adenomyosis) or coagulopathies 2, 3. TVUS will identify most structural pathology.

Perimenopausal/postmenopausal: Endometrial cancer risk increases—lower threshold for endometrial sampling 1, 5.