What is abnormal uterine bleeding?

Abnormal Uterine Bleeding Definition and Classification

Abnormal uterine bleeding (AUB) is defined as bleeding from the uterus that is abnormal in regularity, volume, frequency, or duration and occurs in the absence of pregnancy. 1, 2

Definition and Prevalence

• AUB affects approximately one-third of women during their lifetime, making it a common gynecological complaint 1, 3
• AUB encompasses both predictable cyclical heavy menstrual bleeding (HMB) and irregular non-cyclical intermenstrual bleeding (IMB) 3
• To be classified as AUB, the abnormal bleeding pattern should persist for at least 6 months in reproductive-aged women beyond menarche 4

Classification System: PALM-COEIN

The International Federation of Gynecology and Obstetrics (FIGO) developed the PALM-COEIN classification system to categorize causes of AUB:

Structural Causes (PALM):

• Polyps - endometrial growths that can cause irregular bleeding 1, 2
• Adenomyosis - presence of endometrial tissue within the myometrium 1, 2
• Leiomyoma (fibroids) - benign smooth muscle tumors that can be submucosal or intramural 1, 2
• Malignancy and hyperplasia - including endometrial cancer and precancerous conditions 1, 2

Non-structural Causes (COEIN):

• Coagulopathy - bleeding disorders affecting clotting mechanisms 1, 2
• Ovulatory dysfunction - hormonal imbalances leading to anovulation 1, 2
• Endometrial disorders - primary dysfunction of the endometrium 1, 2
• Iatrogenic - medication-induced bleeding (e.g., hormonal contraceptives, anticoagulants) 1, 2
• Not yet classified - causes that don't fit into other categories 1, 2

Age-Specific Considerations

• Reproductive-age women: Common causes include structural abnormalities (polyps, adenomyosis, leiomyomas) and ovulatory dysfunction 1, 2
• Perimenopausal women: Often experience AUB due to anovulation, but structural causes must be ruled out 2, 5
• Postmenopausal women: Endometrial cancer is the most serious concern and should be the main focus of evaluation 1, 2

Clinical Presentations

• Heavy menstrual bleeding: Excessive blood loss during regular menstruation, often associated with fibroids and adenomyosis 3, 6
• Irregular menstrual bleeding: Unpredictable timing and duration of bleeding 6
• Intermenstrual bleeding: Bleeding between regular menstrual periods, commonly caused by polyps, ovulatory dysfunction, or intrauterine devices 3, 7

Diagnostic Approach

• Initial evaluation includes a thorough history, physical examination, and laboratory tests (pregnancy test, thyroid-stimulating hormone, prolactin levels) 1, 2
• Transvaginal ultrasound (TVUS) is the first-line imaging modality for evaluating structural causes of AUB 2, 3
• Saline infusion sonohysterography provides enhanced visualization of intracavitary lesions like polyps and submucous fibroids 1, 6
• Hysteroscopy with biopsy remains the reference standard for definitive diagnosis of intrauterine pathology 6
• MRI may be indicated when TVUS cannot adequately evaluate the endometrium, particularly in the presence of leiomyomas or adenomyosis 1, 2

Important Considerations and Pitfalls

• Endometrial sampling is necessary in patients with risk factors for endometrial cancer, especially in postmenopausal women with bleeding 2, 5
• TVUS has limitations in certain situations (uterine position, patient body habitus, presence of leiomyomas or adenomyosis) that may necessitate additional imaging or sampling 1
• Transabdominal ultrasound is less sensitive for endometrial assessment but may help evaluate other structural abnormalities 1
• Endometrial biopsy is preferred over dilation and curettage for diagnosing endometrial hyperplasia or cancer due to its lower invasiveness, greater safety, and lower cost 1