What does the PALM‑COEIN classification system for abnormal uterine bleeding represent, and what conditions are included in each category?

PALM-COEIN Classification System for Abnormal Uterine Bleeding

The PALM-COEIN classification system is a standardized framework developed by FIGO (International Federation of Gynecology and Obstetrics) that categorizes causes of abnormal uterine bleeding into structural causes (PALM) and non-structural causes (COEIN), replacing outdated terms like menorrhagia, metrorrhagia, and dysfunctional uterine bleeding. 1, 2

Structural Causes (PALM)

The "PALM" component encompasses anatomic abnormalities that can be visualized through imaging or histopathology:

P - Polyp

• Endometrial polyps are benign growths arising from the endometrial lining 1
• Can prolapse through the cervical os, appearing as smooth, elongated masses 3
• Saline infusion sonohysterography distinguishes polyps from other lesions with 97% accuracy 3

A - Adenomyosis

• Presence of endometrial glands and stroma within the myometrium 1
• Frequently coexists with fibroids and presents with heavy menstrual bleeding, dysmenorrhea, and dyspareunia, commonly affecting women in their 40s 1
• Typically causes uniformly enlarged, boggy uterus on examination, distinguishing it from the irregular contour seen with fibroids 4

L - Leiomyoma (Fibroids)

• Benign smooth muscle tumors of the uterus 1, 4
• One of the three most common structural causes of AUB in premenopausal women alongside polyps and adenomyosis 4
• An enlarged, irregular uterus on palpation is pathognomonic for fibroids, as the irregular contour reflects multiple fibroid nodules distorting normal uterine architecture 4
• Submucosal fibroids can become pedunculated and prolapse through the cervix 3

M - Malignancy and Hyperplasia

• Includes endometrial hyperplasia and endometrial cancer 1
• Endometrial cancer is the most serious etiology and becomes the primary focus of evaluation in postmenopausal women with AUB 3
• Endometrial thickness ≥5 mm on transvaginal ultrasound generally prompts endometrial tissue sampling in postmenopausal women 3

Non-Structural Causes (COEIN)

The "COEIN" component encompasses causes without anatomic substrate:

C - Coagulopathy

• Systemic disorders of hemostasis including inherited bleeding disorders (von Willebrand disease, platelet function disorders) and acquired coagulopathies 1, 2
• Oral anticoagulant therapy significantly increases odds of AUB, with rivaroxaban conferring the highest risk 5

O - Ovulatory Dysfunction

• Anovulation or oligo-ovulation leading to irregular, unpredictable bleeding patterns 1, 2
• Combined hormonal contraceptives are effective for ovulatory dysfunction bleeding 1
• When prescribing progestogen therapy, ovulation may still occur in up to 20% of patients despite treatment 1

E - Endometrial

• Primary disorders of the endometrium in ovulatory women, including local hemostatic abnormalities and inflammatory conditions 2, 6
• Distinct from structural lesions or systemic coagulopathy 7

I - Iatrogenic

• Bleeding related to medications or medical interventions 1, 2
• Hormonal contraceptives—particularly progestin-only methods (pills, depot medroxyprogesterone acetate, implants) and combined hormonal contraceptives—most frequently result in shortened menstrual bleeding (<4 days) by thinning the endometrial lining 1
• Anticoagulant therapy is a major iatrogenic cause, with women younger than 50 years experiencing greater relative increase in AUB (19.7% vs 9.2%) compared with women 50 years or older 5

N - Not Yet Classified

• Reserved for entities that are rare, poorly defined, or not yet adequately characterized 2, 6
• Includes conditions that don't fit into other categories until further research clarifies their classification 8

Clinical Application

The American Academy of Family Physicians recommends using the PALM-COEIN classification system to categorize the bleeding cause in all patients presenting with AUB. 1

• This system replaced confusing and imprecisely applied terms such as menorrhagia, menometrorrhagia, metrorrhagia, dysfunctional uterine bleeding, polymenorrhea, and oligomenorrhea 9
• Using FIGO System 1 (which defines bleeding pattern using frequency, duration, regularity, and flow volume) as a gateway to FIGO System 2 (PALM-COEIN) streamlines the investigation of reproductive-aged women and girls with AUB 2
• Multiple causes may coexist in a given individual, requiring comprehensive evaluation 8

Diagnostic Pitfalls

• The presence of an enlarged, irregular uterus on exam definitively indicates structural pathology, making dysfunctional uterine bleeding (DUB) incompatible with this presentation 4
• Endometrial biopsy alone should not be used to rule out focal lesions, as it has variable sensitivity 1
• If bleeding persists despite initial medical therapy, further investigation with imaging or hysteroscopy is indicated to diagnose focal lesions possibly missed by endometrial sampling 1