What investigations are used to confirm Pelvic Inflammatory Disease (PID)?

Diagnostic Investigations for Pelvic Inflammatory Disease (PID)

The diagnosis of PID should be based on minimum clinical criteria including lower abdominal tenderness, bilateral adnexal tenderness, and cervical motion tenderness, with additional laboratory and imaging studies used to increase diagnostic certainty. 1

Minimum Clinical Criteria for PID Diagnosis

• Lower abdominal tenderness 1
• Bilateral adnexal tenderness 1
• Cervical motion tenderness 1

The CDC recommends empiric treatment for sexually active women at risk for STDs if they present with either uterine/adnexal tenderness or cervical motion tenderness when no other cause for the illness can be identified. 1, 2

Additional Diagnostic Criteria

Routine Investigations

• Oral temperature >38.3°C (101°F) 1, 2
• Abnormal cervical or vaginal discharge 1, 2
• Elevated erythrocyte sedimentation rate (ESR) and/or C-reactive protein (CRP) 1, 2, 3
• Presence of white blood cells (WBCs) on saline microscopy of vaginal secretions 2, 4
• Cervical cultures or non-culture tests for N. gonorrhoeae and C. trachomatis 1, 2

Advanced Investigations

• Transvaginal ultrasound - useful for detecting complications such as tubo-ovarian abscess or hydrosalpinx 5, 3
• Endometrial biopsy for histopathologic evidence 1
• Laparoscopy - considered the gold standard but not routinely recommended solely for diagnosis 1, 3, 6

Diagnostic Algorithm

1. Clinical Assessment:

   • Evaluate for minimum criteria (lower abdominal tenderness, adnexal tenderness, cervical motion tenderness) 1, 7
   • Check for additional signs (fever, abnormal discharge) 1, 2

2. Laboratory Testing:

   • Blood tests: Complete blood count, ESR, CRP 2, 3
   • Cervical cultures or nucleic acid amplification tests for N. gonorrhoeae and C. trachomatis 1
   • Wet mount microscopy of vaginal secretions to check for WBCs 2, 4

3. Imaging:

   • Transvaginal ultrasound if complications are suspected or diagnosis is uncertain 5, 3
   • Consider CT scan with contrast if differential diagnosis includes urinary or digestive conditions 3

4. Consider Advanced Testing:

   • Laparoscopy for definitive diagnosis in cases with severe symptoms or diagnostic uncertainty 1, 6
   • Endometrial biopsy in selected cases 1

Important Clinical Considerations

• No single historical, physical, or laboratory finding is both sensitive and specific for the diagnosis of PID 1, 6
• A "low threshold for diagnosis" is recommended due to the potential for reproductive damage even in mild cases 1
• Bacteriologic diagnosis is helpful for confirmation and guiding treatment of partners, but treatment should not be delayed while awaiting results 1
• The absence of hyperleukocytosis or normal CRP does not rule out the diagnosis of PID 3
• Transvaginal sonographic "cervical motion tenderness" may be useful in patients with equivocal physical examination findings 8

Diagnostic Pitfalls to Avoid

• Waiting for imaging studies should not delay the initiation of antibiotic therapy 3
• Highly sensitive diagnostic criteria may lead to overdiagnosis; carefully explain the uncertainty of diagnosis and value of empiric treatment 1
• If no clinical improvement occurs within 48-72 hours of treatment, reconsider alternative diagnoses (appendicitis, endometriosis, ruptured ovarian cyst, adnexal torsion) 1
• Do not withhold therapy from women with suspected PID due to failure to meet all minimum criteria 1
• Meta-analysis shows pelvic tenderness has moderate-to-high sensitivity (81%) but low specificity (40%) for PID diagnosis 7