Classification of Abnormal Uterine Bleeding
The International Federation of Gynecology and Obstetrics (FIGO) PALM-COEIN classification system is the standard framework for categorizing abnormal uterine bleeding in women of reproductive age. 1
PALM-COEIN Classification System
The PALM-COEIN system divides causes of abnormal uterine bleeding into:
Structural Causes (PALM)
- Polyp: Endometrial polyps that can cause irregular or intermenstrual bleeding 1
- Adenomyosis: Growth of endometrial tissue into the myometrium 1
- Leiomyoma: Uterine fibroids, further subclassified as submucosal or other myomas 2, 1
- Malignancy and hyperplasia: Including endometrial cancer and precancerous conditions 1
Non-Structural Causes (COEIN)
- Coagulopathy: Bleeding disorders affecting clotting function 1
- Ovulatory dysfunction: Including anovulation and oligo-ovulation, often associated with heavy, irregular bleeding 2, 1
- Endometrial: Primary disorders of the endometrium 1
- Iatrogenic: Medication-related causes including hormonal contraceptives, anticoagulants, etc. 1
- Not yet classified: Causes that don't fit into other categories 2, 1
Clinical Application of the Classification
The PALM-COEIN classification system was developed to:
- Standardize terminology and improve communication among clinicians, educators, and researchers 3
- Guide the diagnostic approach to abnormal uterine bleeding 4
- Direct appropriate treatment based on the underlying cause 1
Diagnostic Approach Using PALM-COEIN
The evaluation process should be structured to identify the appropriate category:
- For structural causes (PALM): Imaging studies such as transvaginal ultrasound are the first-line approach 1, 5
- For non-structural causes (COEIN): Laboratory testing including pregnancy test, complete blood count, coagulation studies, thyroid function tests, and prolactin levels may be indicated 1, 6
- Endometrial sampling is necessary for patients ≥45 years or those with risk factors for endometrial cancer 1, 6
Important Clinical Considerations
- The PALM-COEIN system applies to non-pregnant women of reproductive age 3, 4
- Each potential cause can be linked with letter qualifiers specifying its etiologies 2
- When transvaginal ultrasound cannot completely evaluate the endometrium, additional imaging (MRI) or endometrial sampling should be considered 1
- This classification system has been endorsed by multiple national and international societies to improve worldwide communication 3
Evolution of the Classification System
- FIGO System 1 (2007): Standardized nomenclature and defined normal versus abnormal bleeding parameters 4
- FIGO System 2 (2011): Introduced the PALM-COEIN classification of AUB etiology 4
- Current practice uses both systems together for comprehensive evaluation and management 4
The PALM-COEIN classification provides a systematic framework that helps clinicians accurately diagnose and appropriately treat abnormal uterine bleeding, ultimately improving patient outcomes and quality of life 6, 4.