Abnormal Uterine Bleeding

Introduction

Abnormal uterine bleeding (AUB) describes any bleeding from the uterus that is abnormal in frequency, regularity, duration or volume, occurring outside pregnancy.¹ It is one of the most common reasons for gynaecological referral, affecting up to one in three women at some point in their reproductive life.

Heavy menstrual bleeding (HMB) has moved away from a fixed volume threshold (historically >80 mL per cycle) towards a functional definition: menstrual blood loss that has a negative impact on a woman's physical, social, emotional or material quality of life, either alone or combined with other symptoms.² This reflects the fact that women rarely measure their loss in millilitres, and that the impact on daily life is what actually drives the need for treatment.

Terminology has also shifted away from older Latin/Greek terms (menorrhagia, metrorrhagia) towards a descriptive system, and towards the FIGO PALM-COEIN classification for cause, which is now the internationally agreed framework and the one used throughout this article.¹

Describing bleeding as abnormal only means something against a defined normal, so it is worth knowing the reference ranges:

Classification: PALM-COEIN

PALM-COEIN splits causes into two groups: structural causes, which can usually be seen on imaging or histology, and non-structural causes, which usually cannot.¹

The structural causes (PALM) are covered in detail in their own articles - fibroids, adenomyosis and endometrial cancer - and this article focuses on the overall assessment framework and the non-structural (COEIN) causes.

Clinical features and history

A structured menstrual history establishes the pattern of bleeding and points towards likely causes.³

• Cycle length, regularity, and duration and heaviness of bleeding (number of pads/tampons, flooding, passing clots)
• Intermenstrual bleeding (suggests polyp, cervical pathology, or hormonal cause)
• Postcoital bleeding (suggests cervical ectropion, polyp, infection or cervical cancer until excluded)
• Pain - dysmenorrhoea (adenomyosis, fibroids) or pelvic pain (endometriosis, PID)
• Associated symptoms of anaemia - fatigue, breathlessness, palpitations
• Contraceptive and drug history (anticoagulants, copper IUD, hormonal methods)
• Bleeding since menarche and any bruising/epistaxis history (suggests an underlying coagulopathy)
• Cervical screening history
• For postmenopausal women: date of last period and any hormone replacement therapy

Examination

General examination looks for signs of anaemia (pallor, tachycardia) and for signs of an underlying endocrine cause (hirsutism and acne in PCOS, goitre in thyroid disease). Abdominal examination assesses for a palpable pelvic mass suggesting a large fibroid uterus or ovarian pathology.

Speculum examination visualises the cervix to look for polyps, ectropion, or a visible lesion, and allows cervical screening to be brought up to date if due. Bimanual examination assesses uterine size, shape and tenderness (a bulky, tender uterus suggests adenomyosis; an irregularly enlarged uterus suggests fibroids) and checks for adnexal masses or tenderness.

Investigations

Investigation is guided by age, risk factors for malignancy, and examination findings rather than applied uniformly to every woman.²

First-line for all women

• Full blood count - to identify iron-deficiency anaemia from chronic heavy loss
• Pregnancy test if there is any possibility of pregnancy

Pelvic ultrasound (transvaginal preferred)

Indicated if examination reveals an abnormality, symptoms suggest structural pathology, or first-line medical treatment fails. It identifies fibroids, polyps, adenomyosis and endometrial thickness.

Endometrial biopsy

Indicated to exclude endometrial hyperplasia or cancer in: persistent intermenstrual bleeding, women aged 45 or over with treatment failure or persistent symptoms, and any postmenopausal bleeding. Risk factors that lower the threshold for biopsy at a younger age include obesity, PCOS, tamoxifen use, and a family history of Lynch syndrome (which carries a high lifetime risk of endometrial cancer).⁴

Further tests

Coagulation screen and von Willebrand factor assay if a bleeding disorder is suspected (HMB since menarche, family history, or bruising/epistaxis); thyroid function tests if clinical features suggest thyroid disease; hysteroscopy with biopsy if ultrasound is inconclusive or a focal lesion (polyp, submucosal fibroid) needs direct visualisation and removal.

Management

Management addresses both the underlying cause where one is found, and the bleeding itself. For women with heavy menstrual bleeding and no identified structural or histological abnormality (or where definitive treatment of the cause is not appropriate), a stepwise approach is used based on whether contraception is also wanted.²

Medical management

Surgical management

Reserved for women who have failed medical treatment, have significant structural pathology, or have completed their family. Options include hysteroscopic resection of a polyp or submucosal fibroid, endometrial ablation (destroys the endometrial lining; not suitable if future fertility is wanted), uterine artery embolisation for fibroids, myomectomy, and hysterectomy as the definitive option when other treatments have failed or are not appropriate.

Postmenopausal bleeding

Postmenopausal bleeding is any vaginal bleeding occurring 12 months or more after the last menstrual period. It is regarded as endometrial cancer until proven otherwise and warrants urgent two-week-wait referral for investigation, even though the majority of cases turn out to be benign (endometrial or vaginal atrophy is the most common cause).⁴

First-line investigation is transvaginal ultrasound measuring endometrial thickness: a thickness of 4 mm or less has a high negative predictive value for cancer, while a thicker endometrium or ongoing bleeding despite a thin endometrium warrants endometrial biopsy, usually via outpatient hysteroscopy. Women taking tamoxifen are an exception - it causes a thickened, cystic-appearing endometrium on ultrasound that is difficult to interpret, so biopsy is usually needed regardless of the scan appearance.

Red flags

Prognosis

Most abnormal uterine bleeding is benign and responds well to medical management, particularly the LNG-IUS, which achieves outcomes comparable to surgery for many women while preserving fertility. The priority throughout assessment is correctly identifying the minority of women whose bleeding signals malignancy, since outcomes for endometrial cancer detected early through prompt investigation of postmenopausal or intermenstrual bleeding are excellent.