Abnormal Uterine Bleeding (AUB) Diagnosis and Classification

Definition and Prevalence

• Abnormal uterine bleeding (AUB) is bleeding from the uterine corpus that is abnormal in regularity, volume, frequency, or duration and occurs in the absence of pregnancy, affecting at least one-third of women during their lifetime 1

Classification System

• The International Federation of Gynecology and Obstetrics (FIGO) established the PALM-COEIN classification system to categorize AUB causes into structural and nonstructural etiologies 1

Structural Causes

• Structural causes of AUB include polyps, adenomyosis, leiomyomas, and malignancy/hyperplasia, as defined by the PALM-COEIN classification system 1

Nonstructural Causes

• Nonstructural causes of AUB include coagulopathy, ovulatory dysfunction, endometrial disorders, iatrogenic causes, and not yet classified causes, as defined by the PALM-COEIN classification system 1

Age-Specific Considerations

• In premenopausal women, the most common structural causes of AUB are polyps, adenomyosis, and leiomyomas 1
• In postmenopausal women, endometrial cancer is the most serious etiology and becomes the primary focus of evaluation 1
• An endometrial thickness ≥5 mm on transvaginal ultrasound generally prompts endometrial tissue sampling in postmenopausal women, while thickness <4 mm has a nearly 100% negative predictive value for cancer 2

Adolescent Considerations

• Approximately 95% of AUB in adolescents is dysfunctional (anovulatory), though systematic evaluation is required to exclude underlying systemic or oncological diseases, and assessment should include evaluation for hyperandrogenism suggesting polycystic ovary syndrome 3