What are the indications for a pelvic ultrasound?

Indications for Pelvic Ultrasound

Pelvic ultrasound is indicated as the first-line imaging modality for evaluation of suspected gynecologic causes of pelvic pain, abnormal bleeding, and assessment of pelvic masses, with specific indications including suspected ectopic pregnancy, ovarian cysts, fibroids, tubo-ovarian abscess, and ovarian torsion. 1, 2

Primary Indications

Pregnancy-Related Indications

• Evaluation for intrauterine pregnancy when ectopic pregnancy is suspected 1

  • Should be performed regardless of β-hCG level in patients with abdominal pain and/or vaginal bleeding in early pregnancy
  • Helps minimize the likelihood of missing an ectopic pregnancy
  • Critical for time-sensitive diagnosis and management

• Suspected ectopic pregnancy 1

  • Identification of adnexal masses
  • Assessment of free fluid in the cul-de-sac (pouch of Douglas)
  • Echogenic fluid may indicate blood or pus

Gynecologic Indications

• Acute pelvic pain 1, 2

  • First-line imaging for suspected gynecologic causes
  • Evaluation of ovarian torsion (sensitivity 70-95%)
  • Assessment of pelvic inflammatory disease (PID)

• Evaluation of pelvic masses 1

  • Ovarian cysts (common in postmenopausal women)
  • Fibroids (uterine leiomyomas)
  • Adnexal masses
  • Tubo-ovarian abscess

• Abnormal uterine bleeding 1, 2

  • Assessment of endometrial thickness
  • Evaluation for structural abnormalities
  • Detection of fibroids or polyps

Technical Approach

Combined Ultrasound Approach

• Transabdominal ultrasound 1

  • Provides larger field of view
  • Visualizes uterus, adnexa, and remainder of pelvic contents
  • Assesses for free fluid

• Transvaginal ultrasound 1

  • Higher resolution images of pelvic structures
  • Better visualization of endometrium and adnexa
  • Should be performed in conjunction with transabdominal approach
  • May be limited by patient discomfort, particularly in postmenopausal women (26.8% report pain)

• Color and spectral Doppler 1

  • Standard component of pelvic ultrasound
  • Essential for evaluation of suspected ovarian torsion
  • Helps assess vascularity of masses

Specific Clinical Scenarios

Evaluation of Adnexal Structures

• Ovaries should be scanned in at least two planes (short and long axis) 1
• Complete evaluation through each ovary to identify:
  • Peripheral cysts
  • Adjacent masses
  • Signs of torsion (enlarged ovary, peripheralized follicles)

Uterine Assessment

• Examination in at least two planes (short and long axis) 1
• Evaluation for:
  • Fibroids (common cause of pain and bleeding)
  • Endometrial abnormalities
  • Structural anomalies

Cul-de-sac Evaluation

• Assessment for free fluid 1
  • Small to moderate amounts may be normal depending on menstrual cycle
  • Large amounts or echogenic fluid may indicate pathology
  • Significant fluid with suspected ectopic pregnancy raises concern for rupture

Limitations and Pitfalls

• Limited utility in certain scenarios 1

  • Infertility patients with risk factors for heterotopic pregnancy
  • Post vaginal-rectal surgery
  • Evaluation of fetal health beyond heart rate determination

• Diagnostic challenges 1

  • Ovarian torsion evaluation with ovarian/para-ovarian masses
  • Distinguishing malignant from benign ovarian masses
  • Interstitial ectopic pregnancy
  • Ovarian torsion in first trimester with intrauterine pregnancy

• Technical limitations 1, 2

  • Patient body habitus may limit transabdominal views
  • Bowel gas interference
  • Operator dependence

When to Consider Alternative Imaging

• When ultrasound is normal or inconclusive but clinical suspicion remains high 1, 2
• For suspected non-gynecologic causes of pelvic pain
• When better soft tissue characterization is needed (MRI)

Pelvic ultrasound should be performed promptly when clinically indicated, especially in time-sensitive conditions like suspected ectopic pregnancy, to minimize morbidity and mortality associated with delayed diagnosis 1.