What imaging modalities are used to evaluate pelvic pain?

Imaging Modalities for Evaluating Pelvic Pain

Ultrasound, including both transvaginal and transabdominal approaches, is the first-line imaging modality for evaluating pelvic pain, particularly when gynecologic causes are suspected. 1

Initial Imaging Selection Algorithm

Step 1: Determine Pregnancy Status

• Obtain serum β-hCG test for all women of reproductive age with pelvic pain
• Positive β-hCG requires immediate evaluation for potential ectopic pregnancy 2

Step 2: Select Primary Imaging Modality Based on Clinical Suspicion

For Suspected Gynecologic Etiology:

• First-line: Pelvic ultrasound (transvaginal + transabdominal)
  • Provides complementary information with high spatial resolution
  • Should include color and spectral Doppler evaluation as standard components 2, 1
  • Excellent for evaluating:
    • Ovarian cysts, torsion, masses
    • Uterine pathology (fibroids, adenomyosis)
    • Tubo-ovarian abscess
    • Free fluid in cul-de-sac
    • Ectopic pregnancy

For Suspected Non-gynecologic Etiology:

• First-line: CT abdomen and pelvis with IV contrast
  • Higher sensitivity (89% vs 70%) than ultrasound for urgent diagnoses 1
  • Superior for evaluating:
    • Appendicitis (sensitivity 94%, specificity 94%) 2
    • Diverticulitis
    • Bowel obstruction
    • Urolithiasis (use non-contrast "stone protocol") 2

Step 3: Secondary Imaging Based on Initial Findings

• If ultrasound is normal/inconclusive but symptoms persist:

  • Proceed to CT abdomen/pelvis with IV contrast 1

• For pregnant patients or when radiation exposure is a concern:

  • MRI pelvis without contrast is preferred over CT 2, 1

• For suspected pelvic venous disorders:

  • MRI with time-resolved postcontrast T1-weighted imaging 2

Specific Clinical Scenarios

Acute Pelvic Pain with Positive β-hCG:

• Transvaginal ultrasound is mandatory regardless of β-hCG level 1
• CT should be avoided due to radiation exposure unless absolutely necessary 2

Suspected Appendicitis:

• CT abdomen/pelvis with IV contrast (sensitivity 94%, specificity 94%) 2
• Low-dose CT protocols are non-inferior to standard-dose CT 2
• In pregnant patients, MRI or ultrasound should be considered first 2

Suspected Urolithiasis:

• Non-contrast CT "stone protocol" (sensitivity 92-99%, specificity 86-93%) 2
• Low-dose CT is comparable to standard-dose for stones >2mm 2

Chronic Pelvic Pain:

• Begin with transvaginal and transabdominal ultrasound 2
• If ultrasound is negative but symptoms persist, consider MRI pelvis 2
• MRI is superior for evaluating:
  • Endometriosis
  • Adhesive disease
  • Pelvic floor dysfunction
  • Soft tissue abnormalities 2

Important Considerations

• Ultrasound has limitations including patient body habitus, bowel gas interference, and operator dependence 1
• Diagnostic laparoscopy may be considered when imaging is inconclusive but clinical suspicion remains high 3
• MRI has emerged as a problem-solving tool when ultrasound findings are equivocal 2
• For suspected pelvic inflammatory disease, contrast-enhanced MRI with diffusion-weighted imaging provides better characterization 2

By following this algorithmic approach to imaging selection based on clinical presentation and pregnancy status, clinicians can optimize diagnostic accuracy while minimizing unnecessary radiation exposure and improving patient outcomes.