Postmenopausal Bleeding (PMB) — Investigation Algorithm

Epidemiology & Risk

• ~10% of women with PMB have endometrial or cervical malignancy
• 90% of endometrial cancers present with PMB — so PMB must always be taken seriously
• Endometrial cancer rates are rising; Black women have disproportionately higher incidence and mortality

• Obesity (BMI ≥30), diabetes, hypertension ("Corpus cancer triad")
• Nulliparity, late menopause
• Unopposed oestrogen (including tamoxifen use)
• Hereditary syndromes (Lynch syndrome)

Causes of PMB (Common → Less Common)

Investigation Algorithm

Step 1 — History & Clinical Assessment

• Characterise bleeding (amount, duration, frequency, recurrence)
• Full gynaecological history: LMP, parity, HRT use, tamoxifen, anticoagulants
• Risk factor assessment (BMI, diabetes, family history of Lynch syndrome)
• Red flags: recurrent bleeding, persistent bleeding, high-risk background

Step 2 — Examination

• Speculum examination — inspect vulva, vagina, cervix for:
  • Atrophic changes
  • Cervical polyps, ectropion, visible lesions
• Bimanual pelvic examination — uterine size/tenderness, adnexal masses

Step 3 — First-Line Investigations

⚠️ ACOG 2026 update (major change): ACOG now recommends both TVUS and endometrial tissue sampling as part of the initial evaluation for most patients — replacing the prior approach of using TVUS alone when ET ≤4 mm. This shift was driven by evidence that 5–12% of cancers may be missed using ultrasound alone as the triage tool. The combination approach is especially important for Black women.

TVUS Endometrial Thickness (ET) Interpretation

• 3 mm cut-off: sensitivity 97.9%, specificity 35.4%
• 4 mm cut-off: sensitivity 94.8%, specificity 46.7%
• 5 mm cut-off: sensitivity 90.3%, specificity 54%

TVUS Decision Pathway

PMB
  │
  ▼
Pelvic examination + Cervical cytology
  │
  ▼
Transvaginal Ultrasound (TVUS)
  │
  ├── ET ≤ 4 mm ──────────────────────────────┐
  │   (and uniform, no polyp/mass)             │
  │                                            ▼
  │                               No biopsy required
  │                               UNLESS: recurrent PMB / risk factors
  │                               → then proceed to hysteroscopy
  │
  ├── ET > 4 mm ──────────────────────────────┐
  │   (or irregular outline / polyp)           │
  │                                            ▼
  │                          Endometrial biopsy (Pipelle)
  │                          ± Hysteroscopy
  │
  └── ET not visualised ──────────────────────┐
                                              ▼
                                    Proceed to Hysteroscopy

Special Situations

HRT Users

Tamoxifen Users

• ET correlation is poor (subendometrial changes cause artifactual thickening)
• Any PMB on tamoxifen warrants full evaluation with hysteroscopy, regardless of ET

Recurrent PMB

• Investigate regardless of ET; hysteroscopy is often required even with thin endometrium

Uterine Fluid (Hydrometra / Haematometra)

• If ET >4 mm within the fluid, or fluid is echogenic → proceed to biopsy
• Thin ET within fluid (<4 mm): reassure if no other concerns, but monitor

Anticoagulant Users

• Procedures carry low risk; anticoagulation does not need to be stopped for Pipelle biopsy or outpatient hysteroscopy

Asymptomatic Thickened Endometrium (Incidental Finding)

• ET ≥11 mm: investigate regardless of symptoms
• ET 5–10 mm with risk factors: offer investigation

Step 4 — Hysteroscopy

• ET >4 mm (especially if irregular outline or focal lesion)
• Inadequate/failed Pipelle biopsy
• Recurrent PMB despite previous negative workup
• Tamoxifen use
• Suspected polyp / submucosal fibroid on USS
• Unable to visualise ET on TVUS

• Outpatient hysteroscopy — preferred; direct visualisation + targeted biopsy
• Inpatient hysteroscopy + D&C — for patients unable to tolerate outpatient procedure or where pathology is complex

Endometrial Biopsy Interpretation

Additional Investigations (Second Line / Targeted)

Referral Criteria (Urgent / Two-Week Wait)

• Any PMB requires urgent gynaecological assessment
• Visible cervical lesion → urgent colposcopy referral
• Confirmed or suspected malignancy → gynaecological oncology MDT

Key Sources

• Berek & Novak's Gynecology — Diagnosis & Management of Postmenopausal Abnormal Bleeding, Ch. 10
• ACOG Clinical Practice Update (April 2026) — recommends combined TVUS + biopsy for most patients with PMB
• NHS Lanarkshire / SIGN 61 guideline (2025) — ET ≤4 mm threshold; full guideline PDF
• RCOG Patient Information (2025) — RCOG PMB poster