MD Notes

creation date: 2025-07-27 18:54
tags: Pathologies

Abnormal Uterine Bleeding

Background

Definitions

Abnormal uterine bleeding (AUB) is a broad diagnosis that describes irregularities in the menstrual cycle, specifically in non-pregnancy patients.

A normal menstrual cycle is defined as:

  • Frequency of 24-38 days regularly
  • Lasts 2-7 days
  • Consist of 5-80 mL of blood loss
    and as such, AUB is characterized by variations of frequency, regularity, duration, and volume outside of normal parameters (5th and 95th percentiles).

A number of descriptive terms are used for specific variations (replaces former terms menorrhagia, metrorrhagia, and oligomenorrhea).

  • Heavy menstrual bleeding (HMB) is characterized by bleeding >80 mL or heavy enough to interfere with quality of life
  • Intermenstrual bleeding refers to cyclical or random spontaneous bleeding between menstrual periods
  • Breakthrough bleeding (BTB) refers to bleeding on hormone medication

AUB is also defined by acuity.

  • Acute AUB refers to excessive bleeding that requires immediate intervention to prevent further blood loss
  • Chronic AUB refers to menstrual irregularities for most of the previous 6 months

Etiology

Potential causes of AUB can be categorized into structural and nonstructural etiologies using the PALM-COEIN classification.

Structural etiologies
Polyp (P):

  • Endometrial or endocervical polyps - focal outgrowths of tissue
  • Can be asymptomatic or cause intermenstrual bleeding
  • Generally benign but can have malignancy risk
    Adenomyosis (A):
  • Presence of endometrial tissue within uterine muscle
  • Associated with heavy, painful, or prolonged menstruation
  • May result in uterine enlargement
    Leiomyoma (L):
  • Aka fibroids
  • Benign smooth muscle tumours
  • Can lead to heavy or prolonged menstrual bleeding, especially if large or submucosal; many are asymptomatic
    Malignancy and hyperplasia (M):
  • Includes hyperplasia and cancers
  • Presents with unpredictable bleeding
  • May be mediated by estrogen exposure without progesterone opposition

Nonstructural etiologies
Coagulopathy (C):

  • Systemic bleeding disorders resulting in heavy menstrual bleeding
    Ovulatory dysfunction (O):
  • Eg. PCOS, hypothalamic disorder, thyroid dysfunction
  • Leads to infrequent, irregular, heavy, or prolonged bleeding due to inconsistent ovulation
    Endometrial disorders (E):
  • Localized issues in endometrium resulting in inability to control bleeding
  • Eg. inflammation, infection, vasoconstriction abnormalities
    Iatrogenic (I):
  • Medications (eg. hormonal contraceptives, anticoagulants, tamoxifen)
  • Surgical injury
    Not otherwise classified (N):
  • Poorly understood causes
  • Eg. arteriovenous malformations, chronic endometritis, cesarean scar defects

Note that causes are not exclusive and may occur simultaneously to contribute.

Pathogenesis

The menstrual cycle involves an intricate interplay between endocrine, immune, and vascular system. Endometrial changes involve epithelial and stromal apoptosis, inflammatory mediator release, etc. Hemostasis also requires spiral arteriole constriction, clot formation, and tissue regeneration.

Any dysregulation of these processes may result in AUB. The exact mechanisms also differ based on the etiology. For example, ovulatory dysfunction results in disruptions to the hypothalamic-pituitary-ovarian axis while structural causes like fibroids can disrupt myometrial contractility, paracrine signalling, and vascular function.

Clinical Presentation

Signs & Symptoms

As mentioned by definition, AUB consist of abnormalities in one or more flow parameters:

  • Frequency - frequent (<24 days), normal (24-38 days), infrequent (>38 days), or absent
  • Regularity - absent, regular (variation ±2-7 days), or irregular (variation >20 days)
  • Duration - prolonged (>8 days) or normal ≤8 days)
  • Volume - heavy (>80 mL), normal (5-80 mL), or light (<5 mL); note, measurements may not be possible, approx. change of pad/tampon every 1-2 hours

Other findings that may be specific to an etiology include:

  • Intermenstrual and/or postcoital bleeding
  • Weight loss
  • Pain
  • Discharge
  • Bowel or bladder symptoms
  • Signs/symptoms of:
    • Anemia
    • Bleeding disorder
    • Endocrine disorder

History & Physical Exam

Hemodynamic stability should be assessed initially. Signs of instability (eg. tachycardia, hypotension, orthostatic) may require emergency department attention. This is discussed further below.

Outpatient history consist of gynecologic and obstetric history:

  • Recent or current pregnancy
  • Menstrual history including last menstrual period, frequency, regularity, duration, volume, intermenstrual bleeding, and associated symptoms such as cramping
  • Relation to sex (eg. deep penetration) or precipitating factor (eg. trauma, procedure)

Sexual history:

  • Possible pregnancy
  • Risk of sexually transmitted infections (eg. causing cervicitis and cervical bleeding)

Obstetric or gynecologic surgery:

  • C-sections
  • Myomectomy
  • Excisional cervical procedures

Contraceptive history:

  • Estrogen-progestin or progestin-only contraceptives (unscheduled, decreased, absent menstruation)
  • Copper IUD (increased menstrual flow)

Assessment of medical history:

  • Medications (eg. anticoagulants)
  • Bleeding disorders
  • Endocrine disorders
  • Risk factors for endometrial cancer
  • Other conditions (eg. diabetes, celiac disease, CKD, opioid use disorder)

Physical exam should examine for:

  • Systemic illness
  • Evidence of endocrine disorders

A complete pelvic exam should also be performed focusing on potential sites of bleeding, current bleeding (including presence of clots), size and contour of uterus, presence of mass or tenderness.

Risk factors

Risk factors vary based on the etiology. Generally:

  • Overweight or obesity
  • Medication (eg. blood thinners)
  • Contraceptive/IUD use
  • Past history of specific etiology (eg. fibroids)

Diagnosis

Criteria

Work-up

Beyond history and physical exam, patients should undergo:

  • Pregnancy testing - urine hCG; serum hCG should be considered if pregnancy is still suspected
  • Pelvic ultrasound - transvaginal generally sufficient, consider transabdominal if uterus cannot be assessed with transvaginal

Specific details of the workup depends on the history and physical.

Heavy menstrual bleeding
Imaging can assess for the following:

  • Uterine fibroids
  • Adenomyosis
  • Endometrial polyps
  • Uterine arteriovenous malformation (rare but may follow invasive procedure eg. D&C)

Laboratory tests should be done to assess for anemia:

  • CBC
  • Ferritin and serum iron
  • Consider TSH if suspect thyroid disease

Endometrial sampling can be performed if there are suspicions of uterine malignancy.

Intermenstrual bleeding
Imaging can assess for:

  • Endometrial polyps
  • Cesarean scar defect

Endometrial sampling is typically performed, especially if uterine malignancy or chronic endometritis is suspected.

Irregular bleeding
Irregular bleeding is most commonly associated with ovulatory dysfunction which occurs at the extremes of reproductive age. Further evaluation is not necessarily required but identifying the etiology may be beneficial for treatment.

Laboratory testing based on suspicion from history/physical:

  • TSH for thyroid disease
  • Prolactin levels
  • Androgen levels
  • FSH or LH
  • Estrogen levels

Endometrial sampling is typically performed if bleeding has been irregular for ≥6 months due to risk of endometrial hyperplasia/neoplasm.

Amenorrhea
Discussed separately as its own workup.

Suspicion of endometrial cancer
Patients with AUB and obesity or other risk factors should be evaluated with endometrial sampling. This is indicated for:

  • Age 45 - menopause if bleeding is frequent, heavy, prolonged, or occurs between cycles
  • Age <45 if bleeding is persistent for ≥6 months in the setting of history of unopposed estrogen exposure (eg. obesity, chronic ovulatory dysfunction), failed medical management of bleeding, or high risk of endometrial cancer

Differential

Differential diagnoses consist of bleeding from the genitourinary tract (or even gastrointestinal tract).

This could consist of benign growths, malignancy, STI, inflammation, and/or infection of the vulva, vagina, cervix, uterine tubes, ovaries, urinary tract, and GI tract.

Pregnancy and pregnancy-related complications can also result in bleeding:

  • Intrauterine pregnancy
  • Spontaneous abortion
  • Ectopic pregnancy
  • Placenta previa

Red Flags / Complications

Indication for emergency department:

  • Unstable
  • Tachycardia/hypotension
  • Flooding through >1 high protection product per hour consistently
  • Fever
  • Dizziness

A pregnancy test should always be done for new dysfunctional bleeding.

Complications of acute AUB are primarily due to severe blood loss:

  • Severe anemia
  • Hypotension
  • Renal dysfunction
  • Shock
  • Death

Complications of chronic AUB include:

  • Anemia
  • Infertility
  • Endometrial cancer

Management

Treatment of AUB depends on underlying cause, acuity of bleeding, fertility and contraceptive goals, comorbidities, and other medication considerations.

Treatment is indicated when AUB results in anemia or significantly impact the patient’s quality of life.

Acute Management

Intervention include mechanical control of bleeding using balloon, Foley catheter, or gauze packing. High-dose medical treatment can be:

Hormonal:

  • Conjugated estrogen 25 mg IV q4-6h for 24 hrs
  • Combined oral contraceptives TID for 7 days, then once daily tapered until bleeding cessation
    Nonhormonal:
  • Tranexamic acid 10 mg/kg IV up to 600 mg per dose, or 1.5 g PO q8h for 5 days
  • Adjunct with NSAID
    Adjunctive measures:
  • Antiemetic for hormonal therapy-induced nausea
  • Iron supplementation for anemia

Nonemergent Treatment

For hemodynamically stable patients, medical management is generally preferred, especially for patients looking to avoid surgery and preserve fertility.

Hormonal:

  • Levonorgestrel-releasing intrauterine system (LNG-IUD)
  • Estrogen-progestin oral contraceptive
  • Progestin-only therapy
    Nonhormonal:
  • Transexamic acid 1.5 g PO q8h for 5 days
  • Ibuprofen 600 mg q6h, or 800mg q8h (or another NSAID)

Surgical

Surgery may be considered for patients unresponsive to medical management or those desiring definitive treatment. A number of surgical options are available including:

  • Dilatation and curettage
  • Hysterectomy
  • Endometrial ablation
  • Hysteroscopic or laparoscopic myomectomy
  • Hysteroscopic polypectomy
  • Uterine artery embolization

Etiology-specific Management

It should be noted that depending on the underlying causes, there may be specific treatment options that are indicated. In most cases, treatment of underlying cause will also resolve AUB symptoms.

Briefly they are:

  • Polyps - surgical resection
  • Adenomyosis - hysterectomy
  • Leiomyomas - surgery (uterine artery embolization, endometrial ablation, hysterectomy) or medication
  • Malignancy - surgery or other, depending on stage
  • Coagulopathies - tranexamic acid or desmopressin
  • Ovulatory dysfunction - management of weight, correction of endocrine
  • Endometrial disorders - no specific treatment
  • Iatrogenic - Address offending medication with discontinuation, modification, or reassurance
  • Not otherwise classified causes - depends on condition

References

Tools / Guidelines

Additional Reading