Key Facts

Uterine fibroids are benign monoclonal neoplasms arising from the smooth muscle of the myometrium. They are the most common pelvic tumour in women and a leading indication for hysterectomy.

Epidemiology

• Affect 20-40% of women of reproductive age; up to 70% by age 50 on histological examination
• Afro-Caribbean women: 3× more common, present earlier, larger, more numerous
• Peak incidence: 40-50 years
• Rare before menarche; usually regress after menopause

Aetiology

• Oestrogen and progesterone-dependent growth
• Genetic mutations (e.g. MED12 mutations found in 70% of fibroids)
• Risk factors: Afro-Caribbean ethnicity, nulliparity, early menarche, obesity (increased peripheral oestrogen conversion), family history, hypertension
• Protective factors: multiparity, combined oral contraceptive use, smoking (anti-oestrogenic effect)

Pathophysiology

• Monoclonal proliferation of smooth muscle cells with excessive extracellular matrix
• Growth is oestrogen and progesterone dependent
• Submucosal fibroids distort the endometrial cavity causing HMB
• Large fibroids cause pressure symptoms on bladder, bowel, and ureters
• During pregnancy: may enlarge (oestrogen-driven), red degeneration can cause acute pain

Heavy Menstrual Bleeding

• Most common symptom (especially submucosal fibroids)
• Regular cycles but heavy flow with clots
• Iron deficiency anaemia

Pressure Symptoms

• Urinary frequency and urgency (bladder compression)
• Constipation (rectal compression)
• Abdominal distension with large fibroids
• Ureteric obstruction (rare; hydronephrosis)

Reproductive Impact

• Subfertility (submucosal fibroids impair implantation)
• Recurrent miscarriage
• Pregnancy complications: malpresentation, preterm labour, red degeneration, obstructed labour

Red Flags

• Rapidly enlarging pelvic mass (exclude leiomyosarcoma)
• Postmenopausal growth of fibroids (exclude malignancy)
• Severe anaemia (Hb <70 g/L)
• Acute pain in pregnancy (red degeneration)

Bedside

• Abdominal examination: palpable pelvic mass arising from pelvis
• Bimanual examination: irregular, firm, non-tender enlarged uterus
• Speculum: cervical fibroid polyp may be visible

Bloods

• FBC (iron deficiency anaemia)
• Ferritin
• U&Es if suspecting ureteric obstruction
• TFTs if menstrual irregularity

Imaging

• Pelvic USS (TVS + TAS): first-line; well-circumscribed hypoechoic masses; can determine number, size, and location
• MRI pelvis: fibroid mapping pre-surgery; superior for surgical planning and distinguishing adenomyosis
• Saline infusion sonography: assess submucosal distortion of cavity
• Hysteroscopy: direct visualisation of submucosal fibroids

Special Tests

• Endometrial biopsy if age >45 or abnormal bleeding pattern
• Renal USS if large fibroids (exclude hydronephrosis)

Non-pharmacological

• Observation: small, asymptomatic fibroids need no treatment; review annually
• Iron supplementation for anaemia (ferrous sulphate 200mg BD-TDS)
• Weight management and lifestyle modification

Pharmacological

• First-line for HMB: Mirena IUS (NICE NG88); may not be suitable if cavity distorted
• Tranexamic acid 1g TDS during menses
• Mefenamic acid 500mg TDS during menses
• COC pill: reduces menstrual blood loss
• GnRH analogues (goserelin 3.6mg SC monthly): pre-operative to shrink fibroids (max 6 months; add-back HRT if >3 months); causes temporary menopause
• Ulipristal acetate 5mg OD: previously used pre-operatively but now restricted due to hepatotoxicity risk (EMA review)

Surgical/Interventional

• Hysteroscopic myomectomy: for submucosal fibroids; outpatient or day-case
• Laparoscopic/open myomectomy: for intramural/subserosal fibroids; fertility-preserving
• Uterine artery embolisation (UAE): interventional radiology; shrinks fibroids by 40-60%; preserves uterus but fertility implications uncertain
• MRI-guided focused ultrasound (MRgFUS): non-invasive thermal ablation; limited availability
• Hysterectomy: definitive treatment; abdominal, vaginal, or laparoscopic approach

Referral Criteria

• Palpable pelvic mass: gynaecology referral
• Failed medical management: gynaecology referral
• Rapid growth or postmenopausal enlargement: urgent referral (exclude malignancy)
• Subfertility with submucosal fibroids: reproductive medicine referral

• Fibroids typically regress after menopause due to oestrogen withdrawal
• Recurrence after myomectomy: 15-30% at 5 years
• UAE: 80-90% satisfaction; 15-20% require further intervention within 5 years
• Hysterectomy: 100% cure for fibroid-related symptoms
• Malignant transformation (leiomyosarcoma): extremely rare (<0.5%)
• Pregnancy after myomectomy: uterine rupture risk if full-thickness cavity breach (CS may be recommended)

FIGO Classification of Fibroids

Treatment Selection by Fibroid Type