Diagnosing Pelvic Inflammatory Disease (PID)
The diagnosis of pelvic inflammatory disease relies primarily on clinical findings, including lower abdominal tenderness, bilateral adnexal tenderness, and cervical motion tenderness, as no single test is both sensitive and specific enough for definitive diagnosis. 1
Core Diagnostic Criteria
Minimum Criteria (All Required)
- Lower abdominal pain
- Adnexal tenderness on bimanual examination
- Cervical motion tenderness
Additional Criteria (Increase Diagnostic Specificity)
- Oral temperature >38.3°C (>101°F)
- Abnormal cervical or vaginal mucopurulent discharge
- Presence of white blood cells (WBCs) on saline microscopy of vaginal secretions
- Elevated erythrocyte sedimentation rate (ESR)
- Elevated C-reactive protein (CRP)
- Laboratory documentation of cervical infection with N. gonorrhoeae or C. trachomatis 1
Definitive Diagnostic Criteria
- Histopathologic evidence on endometrial biopsy
- Tubo-ovarian abscess on imaging
- Laparoscopic visualization (gold standard, but rarely needed) 1
Diagnostic Testing Algorithm
Essential Laboratory Tests (for all suspected cases):
- Cervical cultures for N. gonorrhoeae
- Cervical culture or non-culture test for C. trachomatis
- Pregnancy test (urine or serum β-hCG) in all reproductive-age women
- Complete blood count with differential
- Urinalysis 1
Imaging Studies:
- Transvaginal ultrasound: First-line imaging modality for evaluating acute lower pelvic/suprapubic pain 1
- CT scan: Reserved for cases with nonspecific presentation or when gynecologic and non-gynecologic causes cannot be distinguished (higher sensitivity than ultrasound: 89% vs 70%) 1
- MRI: Can provide additional detail in complex cases 2
Clinical Pearls and Pitfalls
Important Considerations
- Maintain a low threshold for diagnosis, as PID is often underdiagnosed due to mild or nonspecific symptoms 1
- Pelvic pain and fever are commonly absent in women with confirmed PID 3
- Consider milder symptoms such as abnormal vaginal discharge, metrorrhagia, postcoital bleeding, and urinary frequency as potential symptoms, particularly in women at risk of STIs 3
- Initiate treatment as soon as the presumptive diagnosis is made to prevent long-term sequelae 1
Common Diagnostic Pitfalls
- Waiting for laboratory confirmation before initiating treatment
- Overlooking PID in women with subtle or atypical symptoms
- Failure to recognize that PID can cause serious reproductive sequelae even in mild cases 1
- Not distinguishing PID from common mimics such as:
- Endometriosis
- Adnexal torsion
- Ruptured hemorrhagic ovarian cyst
- Adnexal neoplasms
- Appendicitis
- Diverticulitis 2
Risk Factors to Consider
- Young, sexually active women
- Multiple sexual partners
- Intrauterine contraceptive device use
- History of sexually transmitted infections 1
Follow-up Evaluation
- Evaluation within 48-72 hours is essential to assess clinical improvement
- Failure to improve clinically within this timeframe should prompt reconsideration of alternative diagnoses, such as ectopic pregnancy, acute appendicitis, or functional pain 1
By maintaining a high index of suspicion and following this diagnostic approach, clinicians can identify PID early and initiate appropriate treatment to prevent serious complications including infertility, ectopic pregnancy, chronic pelvic pain, and tubo-ovarian abscess 1, 4.