What is Abnormal Uterine Bleeding?
Abnormal uterine bleeding (AUB) is bleeding from the uterine corpus that deviates from normal menstruation in regularity, volume, frequency, or duration, occurring in the absence of pregnancy. 1
Definition and Scope
AUB affects approximately one-third of women during their lifetime and represents one of the most common gynecologic complaints. 2, 3 The condition encompasses:
- Heavy menstrual bleeding (HMB): Predictable cyclical bleeding that is excessive in volume or duration (>8 days). 2, 3
- Intermenstrual bleeding (IMB): Irregular, non-cyclical bleeding between periods. 2, 3
- Any combination of abnormal bleeding patterns that persist for at least 6 months. 4
This modern terminology replaces outdated and ambiguous terms such as "dysfunctional uterine bleeding," "menorrhagia," and "irregular menstrual bleeding." 3, 5
Classification: The PALM-COEIN System
The International Federation of Gynecology and Obstetrics (FIGO) PALM-COEIN classification is the standardized framework for categorizing AUB causes. 6, 7, 1
Structural Causes (PALM)
- Polyp: Endometrial polyps causing irregular or heavy bleeding. 1, 3
- Adenomyosis: Endometrial tissue within the myometrium, commonly presenting with heavy menstrual bleeding, dysmenorrhea, and dyspareunia in women in their 40s. 7, 1
- Leiomyoma: Uterine fibroids, the most common structural cause of HMB. 1, 2
- Malignancy and hyperplasia: Endometrial cancer or precancerous changes, particularly critical in postmenopausal and high-risk patients. 1, 3
Non-Structural Causes (COEIN)
- Coagulopathy: Inherited or acquired bleeding disorders. 1, 3
- Ovulatory dysfunction: The most common cause in reproductive-aged women, including PCOS and anovulatory cycles. 6, 2, 3
- Endometrial: Primary endometrial disorders. 1, 3
- Iatrogenic: Medication-related (e.g., anticoagulants, IUDs, hormonal therapies). 1, 3
- Not yet classified: Causes not fitting other categories. 1, 3
Initial Work-Up
Mandatory First Steps
Pregnancy test (β-hCG) in all reproductive-aged women before any further evaluation. 6, 7
Assess hemodynamic stability: Urgent evaluation is required if bleeding saturates a large pad/tampon hourly for ≥4 hours. 6
Laboratory evaluation:
Imaging
Combined transabdominal and transvaginal ultrasound with Doppler is the first-line imaging study to identify structural causes such as fibroids, polyps, and adenomyosis. 6, 1, 2
- Saline infusion sonohysterography has 96-100% sensitivity and 97% accuracy in distinguishing leiomyomas from polyps. 6
- MRI should be considered when ultrasound incompletely visualizes the uterus or findings are indeterminate. 6, 1
Endometrial Sampling
Endometrial biopsy is mandatory in the following high-risk groups: 6, 5
- Age >45 years
- Postmenopausal status (any bleeding requires evaluation)
- Obesity, diabetes, hypertension
- Chronic anovulation with obesity and diabetes (even if <35 years old due to synergistic cancer risk from unopposed estrogen)
- Unopposed estrogen exposure, tamoxifen use, Lynch syndrome
Common pitfall: Endometrial biopsy alone has variable sensitivity for focal lesions; saline infusion sonohysterography or hysteroscopy should be used when structural pathology is suspected despite negative biopsy. 7
First-Line Management
Medical Therapy (Preferred Initial Approach)
Medical therapy is first-line treatment for AUB unless contraindicated or structural pathology requires surgery. 6, 7
Hormonal Options (in order of efficacy):
Levonorgestrel-releasing intrauterine device (LNG-IUD): Most effective medical treatment, reducing menstrual blood loss by 71-95% with efficacy comparable to endometrial ablation. 7, 1 Preferred in patients with cardiovascular disease where NSAIDs and tranexamic acid are contraindicated. 7
Combined oral contraceptives (COCs): First-line for anovulatory AUB, providing cycle regulation and reducing bleeding. 6, 7 Particularly appropriate for younger women desiring contraception. 1
Cyclic progestins: Administered for 21 days per month, effective for women with cyclic heavy bleeding, especially when estrogen is contraindicated. 6, 7
Non-Hormonal Options:
Tranexamic acid: Reduces menstrual blood loss by 20-60%, highly effective non-hormonal alternative. 6, 7, 1 Avoid in patients with cardiovascular disease or post-SCAD due to thrombosis risk. 7
NSAIDs: Most effective for ovulatory menorrhagia, reducing bleeding by 20-50%. 6, 1 Avoid in cardiovascular disease due to MI risk. 7
Surgical Management
Reserved for failed medical management, contraindications to medical therapy, or patient preference after completing childbearing:
Endometrial ablation: Uterus-sparing option with efficacy comparable to LNG-IUD. 7, 1 Important caveat: Long-term complications include postablation Asherman syndrome, synechiae, cervical stenosis, and potential delayed endometrial cancer diagnosis; thorough informed consent is essential. 7
Hysterectomy: Provides definitive resolution of all symptoms with significantly better health-related quality of life compared to other therapies. 6, 1 Choose the least invasive surgical route (vaginal > laparoscopic/robotic > abdominal) based on uterine size and surgical expertise. 6, 1
Age-Specific Considerations
Perimenopausal women: Higher risk for endometrial hyperplasia/cancer; lower threshold for endometrial sampling even with anovulation as the suspected cause. 6, 1
Postmenopausal women: Any bleeding requires evaluation for endometrial cancer, which is the primary concern in this population. 6, 1
Reproductive-aged women with chronic anovulation, obesity, and diabetes: Require endometrial sampling even if younger than 35 years due to markedly elevated risk of endometrial hyperplasia and cancer from persistent unopposed estrogen. 6
Referral Indications
Refer to gynecology when: 6
- Medical management fails
- Endometrial sampling shows hyperplasia or malignancy
- Postmenopausal bleeding with endometrial thickness ≥4 mm
- Persistent bleeding despite treatment warrants hysteroscopy to diagnose focal lesions potentially missed by endometrial sampling 7