What is Abnormal Uterine Bleeding (AUB)?
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. 1
Definition and Scope
AUB affects at least one-third of women during their lifetime and represents a significant clinical problem across all reproductive age groups. 1 The condition encompasses:
- Heavy menstrual bleeding (HMB): Predictable cyclical excessive bleeding 2
- Irregular menstrual bleeding: Non-cyclical bleeding patterns 2
- Intermenstrual bleeding (IMB): Bleeding between regular cycles 2
Classification System: PALM-COEIN
The International Federation of Gynecology and Obstetrics (FIGO) established the PALM-COEIN classification system to categorize AUB causes into structural and nonstructural etiologies. 1, 3
Structural Causes (PALM):
- Polyp: Endometrial polyps 1
- Adenomyosis: Endometrial tissue within the myometrium 1
- Leiomyoma: Uterine fibroids 1
- Malignancy/hyperplasia: Endometrial cancer or hyperplasia 1
Nonstructural Causes (COEIN):
- Coagulopathy: Bleeding disorders 1
- Ovulatory dysfunction: Hormonal imbalances, PCOS 1
- Endometrial: Primary endometrial disorders affecting hemostasis 1
- Iatrogenic: Exogenous hormones, intrauterine devices 1
- Not yet classified: Other unclassified causes 1
Age-Specific Considerations
Premenopausal Women:
The most common structural causes are polyps, adenomyosis, and leiomyomas. 1 Endometrial thickness varies with menstrual cycle phase and is not a reliable indicator of pathology in this population. 1
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, while thickness <4 mm has a nearly 100% negative predictive value for cancer. 1
Adolescents:
Approximately 95% of AUB in adolescents is dysfunctional (anovulatory), though systematic evaluation is required to exclude underlying systemic or oncological diseases. 4 Assessment should include evaluation for hyperandrogenism suggesting polycystic ovary syndrome. 5
Clinical Impact
AUB significantly impacts women's quality of life and overall well-being. 6 The condition can lead to anemia, anxiety, and may necessitate hysterectomy if diagnosis and treatment are delayed. 6