What are the differential diagnoses and management plan for painless vaginal bleeding in women?

Painless Vaginal Bleeding: Differential Diagnosis and Management

Initial Diagnostic Approach

Begin with transabdominal ultrasound as the first-line imaging study to identify the source and guide all subsequent management decisions. 1

Pregnancy Status Determines the Differential

The most critical first step is determining pregnancy status, as this completely changes the differential diagnosis and management pathway:

If Pregnant (Second/Third Trimester):

Placenta previa and vasa previa are the primary life-threatening diagnoses that must be ruled out immediately with transabdominal ultrasound. 1, 2

Key differential diagnoses include:

• Placenta previa – painless bleeding is the hallmark presentation 1, 2
• Vasa previa – unprotected fetal vessels over the cervix causing fetal hemorrhage 2
• Low-lying placenta – placental margin near internal cervical os 1
• Bloody show from labor – benign cause in term pregnancy 2
• Cervical ectropion, polyps, or cervicitis – benign cervical causes 2

Critical management steps:

• Perform transabdominal ultrasound immediately to visualize placental location, identify the inferior placental margin, assess the cervix from external to internal os, and identify any vessels overlying the internal cervical os 1
• Never perform digital cervical examination if placenta previa is suspected or not yet ruled out 2
• Sterile speculum examination and transvaginal ultrasound are safe regardless of placental location 2
• Upgrade to transvaginal ultrasound when transabdominal imaging is inconclusive or inadequate, which is frequently necessary 1
• Measure the distance from the leading placental margin to the internal cervical os; if the placenta crosses the internal os by ≥15 mm in the second trimester, this predicts placenta previa at delivery 1
• Use color or power Doppler ultrasound to identify vessels overlying the internal cervical os, which indicates vasa previa 1

If Pregnant (First Trimester/Early Second Trimester):

Complications of pregnancy including threatened, incomplete, or missed abortion must be excluded first. 3

Key differential diagnoses include:

• Incomplete abortion – passage of tissue with retained products of conception 4, 3
• Threatened abortion – bleeding with closed cervix and viable pregnancy 3
• Missed abortion – nonviable pregnancy with retained tissue 3
• Ectopic pregnancy – can present with bleeding even without pain 3
• Trophoblastic disease – molar pregnancy 3

Critical management steps:

• Perform transvaginal ultrasound as the definitive imaging modality to assess the endometrial cavity, confirm retained products of conception, and evaluate cervical status from external to internal os 5, 4
• If retained products >15 mm or significant endometrial thickening is identified, consider uterine evacuation to prevent delayed hemorrhage or infection 5, 4
• Use Doppler flow within endometrial abnormalities to strongly support retained products of conception 4
• Assess for signs of infection including fever, foul discharge, or endometrial fluid collections on ultrasound, which indicate septic abortion 4

If Not Pregnant (Reproductive Age):

Structural abnormalities of the uterus and cervix are the primary organic causes, but dysfunctional uterine bleeding is diagnosed by exclusion. 6, 3

Key differential diagnoses include:

• Endometrial polyps 3
• Submucous uterine leiomyomas (fibroids) 3
• Cervical polyps or ectropion 3, 2
• Cervicitis or vaginal infections 3, 2
• Adenomyosis or endometriosis 3
• Malignancy (endometrial, cervical, vaginal) – must be excluded 3
• Iatrogenic causes – sex steroids, intrauterine devices, anticoagulants 3
• Coagulopathy – particularly von Willebrand disease in adolescents with menorrhagia 3
• Dysfunctional uterine bleeding – diagnosis of exclusion 3

Critical management steps:

• Perform transvaginal ultrasound as the initial imaging modality of choice to assess endometrial thickness and identify structural abnormalities 6
• Endometrial thickness in premenopausal women is less reliable than in postmenopausal women because it varies with menstrual cycle phase 6
• Consider hysterosonography for better delineation of the endometrium and focal abnormalities in the endometrial cavity 6
• Use color and pulsed Doppler to characterize focal endometrial abnormalities by demonstrating vascularity 6
• Screen for coagulopathy in adolescents with menorrhagia, women with high-risk factors, and those who fail medical or surgical therapy 3

If Not Pregnant (Perimenopausal/Postmenopausal):

Endometrial carcinoma must be excluded until proven otherwise in any woman of perimenopausal or postmenopausal age with vaginal bleeding. 3

Key differential diagnoses include:

• Endometrial carcinoma – the primary concern 3
• Endometrial hyperplasia 6
• Endometrial polyps 3
• Cervical carcinoma 3
• Atrophic vaginitis 6
• Hormone replacement therapy effects 6

Critical management steps:

• Perform transvaginal ultrasound to measure endometrial thickness, which is a well-established predictor of endometrial disease 6
• Endometrial thickness ≤4-5 mm reasonably excludes endometrial carcinoma in postmenopausal women with vaginal bleeding 6
• If endometrial thickness >4-5 mm, proceed to endometrial biopsy for definitive histologic diagnosis 6
• Use MRI as a problem-solving tool if the endometrium cannot be visualized on transvaginal ultrasound and hysterosonography is not possible 6
• CT is generally not warranted for evaluation of abnormal bleeding, but an abnormal endometrium incidentally detected on CT should be further evaluated with transvaginal ultrasound 6

Critical Pitfalls to Avoid

• Never perform digital cervical examination in pregnant patients with vaginal bleeding until placenta previa is ruled out by ultrasound 2
• Do not assume small amounts of blood loss are benign – this may be the initial symptom of emergent bleeding 2
• Do not rely solely on transabdominal ultrasound after pregnancy loss or in evaluating the endometrium, as it has limited sensitivity for detecting retained tissue and cervical abnormalities 1, 5
• Do not assume the absence of pain means no emergency – placenta previa and vasa previa present with painless bleeding but are life-threatening 1, 2
• Do not dismiss abnormal bleeding in perimenopausal/postmenopausal women without excluding malignancy 3
• Do not forget to screen for coagulopathy in adolescents with menorrhagia and women who fail standard therapy 3

Algorithmic Management Summary

1. Determine pregnancy status immediately 3
2. If pregnant: Perform transabdominal ultrasound to locate placenta and rule out placenta previa/vasa previa 1, 2
3. Upgrade to transvaginal ultrasound when transabdominal imaging is inadequate 1, 5
4. If postmenopausal: Measure endometrial thickness; if >4-5 mm, proceed to biopsy 6, 3
5. If reproductive age and not pregnant: Assess for structural abnormalities and screen for coagulopathy if indicated 6, 3
6. Ensure hemodynamic stability and monitor vital signs, as vaginal bleeding can cause significant volume loss 7, 8