What investigations are recommended for a patient presenting with acute abdominal pain and suspected pelvic pathology?

Recommended Investigations for Acute Abdominal Pain with Suspected Pelvic Pathology

Transvaginal ultrasound (TVUS) combined with transabdominal ultrasound should be the first-line imaging modality for patients presenting with acute abdominal pain and suspected pelvic pathology. 1, 2

Initial Diagnostic Approach

Laboratory Tests

• Serum or urine β-hCG test to rule out pregnancy-related conditions 2
• Complete blood count to assess for infection or inflammation 3
• Urinalysis to evaluate for urinary tract infection 2

Primary Imaging

• Transvaginal ultrasound (TVUS) - Provides excellent visualization of pelvic organs with high resolution 4
• Transabdominal ultrasound - Complements TVUS by providing wider field of view 2
• Color Doppler ultrasound - Essential component to evaluate blood flow, particularly useful in cases of suspected ovarian torsion or pelvic inflammatory disease 2

Imaging Selection Based on Clinical Scenario

For Suspected Gynecological Etiology (β-hCG Negative)

• TVUS has excellent diagnostic capabilities:
  • For tubo-ovarian abscess: 93% sensitivity and 98% specificity 2
  • For endometriosis: 98% sensitivity and 100% specificity for rectosigmoid involvement 2
  • For pelvic inflammatory disease: Specific findings include wall thickness >5mm, cogwheel sign, and incomplete septa 2

For Suspected Gynecological Etiology (β-hCG Positive)

• TVUS is the initial imaging of choice to evaluate for ectopic pregnancy 2
• Findings of adnexal mass without intrauterine pregnancy has a positive likelihood ratio of 111 for ectopic pregnancy 2

For Suspected Non-Gynecological Etiology

• CT abdomen and pelvis with IV contrast should be considered when:

  • Ultrasound findings are inconclusive 2
  • Urgent diagnosis is needed (e.g., appendicitis, diverticulitis) 2
  • Wider anatomical evaluation is required 2

• CT has higher sensitivity than ultrasound (89% versus 70%) for urgent diagnoses in adults with abdominopelvic pain 2

For Postmenopausal Women

• TVUS remains the first-line imaging modality 2
• Common causes of acute pelvic pain in this population include:
  • Ovarian cysts (one-third of cases) 2
  • Uterine fibroids 2
  • Pelvic infections (20% of cases) 2
  • Ovarian neoplasms (8% of cases) 2

Second-Line Investigations

MRI Abdomen and Pelvis

• Consider when ultrasound is inconclusive and CT is contraindicated 2
• Particularly useful for:
  • Characterizing complex adnexal masses 2
  • Evaluating endometriosis 2
  • Assessing pelvic floor dysfunction 2

Diagnostic Laparoscopy

• Gold standard for definitive diagnosis when imaging is inconclusive 5
• Particularly valuable in chronic pelvic pain evaluation 5
• Can identify conditions missed by clinical examination and imaging such as adhesions, endometriosis, and pelvic congestion syndrome 5

Common Pitfalls and Considerations

• Ultrasound sensitivity is limited in obese patients and those with significant bowel gas 1
• Normal Doppler findings do not exclude ovarian torsion; clinical suspicion should guide management 3
• CT with IV contrast is preferred over non-contrast CT for gynecologic pathology evaluation 2
• In complicated cases (diabetes, immunocompromise, advanced age), have lower threshold for CT imaging 2
• Pelvic examination should be performed in symptomatic patients but has low sensitivity (8.1%) compared to imaging 6, 5

By following this structured approach to investigation, clinicians can efficiently diagnose the cause of acute abdominal pain related to pelvic pathology, leading to appropriate and timely treatment.