What is causing pelvic pain and chills?

Pelvic Pain and Chills: Differential Diagnosis and Evaluation

The combination of pelvic pain and chills strongly suggests pelvic inflammatory disease (PID) as the primary diagnosis, which requires immediate empiric antibiotic treatment without waiting for confirmatory testing. 1

Immediate Clinical Assessment

The presence of chills (indicating fever/systemic infection) alongside pelvic pain creates a clinical picture highly suspicious for infectious etiology, particularly PID. Begin empiric treatment immediately if the patient demonstrates any of the following minimum criteria on examination: 1

• Lower abdominal tenderness
• Adnexal tenderness
• Cervical motion tenderness

The CDC guidelines emphasize maintaining a low threshold for PID diagnosis because delayed treatment can result in tubo-ovarian abscess, chronic pelvic pain, infertility, and ectopic pregnancy. 1, 2

Additional Diagnostic Criteria Supporting PID

Routine criteria that increase diagnostic certainty include: 1

• Oral temperature >38.3°C (which correlates with the patient's chills)
• Abnormal cervical or vaginal discharge
• Elevated erythrocyte sedimentation rate or C-reactive protein
• Laboratory documentation of cervical infection with N. gonorrhoeae or C. trachomatis

Elaborate criteria for severe presentations include: 1

• Tubo-ovarian abscess on ultrasound (sensitivity 93%, specificity 98%) 1
• Histopathologic evidence of endometritis on endometrial biopsy
• Laparoscopic abnormalities consistent with PID

Imaging Approach

Transvaginal ultrasound is the first-line imaging modality for suspected gynecologic etiology. 1, 3 Specific ultrasound findings that support PID diagnosis include: 1

• Bilateral adnexal masses (2-3 cm diameter, solid or cystic with thick walls)
• Tubal wall thickness >5 mm
• Cogwheel sign (present in 86% of acute cases)
• Incomplete septa (present in 92% of tubal inflammatory disease)
• Cul-de-sac fluid

If ultrasound is nondiagnostic and nongynecologic etiology is suspected, CT abdomen and pelvis with IV contrast should be obtained (sensitivity 89% vs 70% for ultrasound in urgent diagnoses). 1

Immediate Treatment Protocol

Empiric broad-spectrum antibiotics must be initiated immediately without waiting for culture results. 1, 4, 2 The standard outpatient regimen includes: 2

• Single intramuscular dose of ceftriaxone (a recommended cephalosporin)
• Oral doxycycline for 14 days
• Metronidazole for 14 days if bacterial vaginosis, trichomoniasis, or recent uterine instrumentation is present

Hospitalization for parenteral antibiotics is indicated if: 1, 2

• The patient is pregnant
• Severe illness is present (which chills may indicate)
• Tubo-ovarian abscess is identified
• Surgical emergencies (appendicitis, ectopic pregnancy) cannot be excluded
• Outpatient treatment fails

Critical Differential Diagnoses to Exclude

Before finalizing PID diagnosis, exclude these life-threatening conditions: 3, 5, 6

• Ectopic pregnancy (must be excluded in all reproductive-age women with β-hCG testing) 3
• Appendicitis (CT sensitivity 95%, specificity 94%; most common surgical emergency) 1, 5
• Ovarian torsion (presents with enlarged ovary, absent arterial flow on Doppler) 1, 5
• Tubo-ovarian abscess (requires imaging confirmation and possible surgical intervention) 1

Age-Specific Considerations

In postmenopausal women with pelvic pain and chills, the differential broadens significantly: 1

• Ovarian cysts account for one-third of gynecologic pain cases
• Uterine fibroids are the second most common cause
• Pelvic infection accounts for 20% of cases (often related to recent instrumentation or surgery)
• Ovarian neoplasm must be considered (8% of cases)
• CT abdomen and pelvis with IV contrast is first-line imaging in this population 1

Common Pitfalls

Do not delay treatment waiting for culture results or imaging. The CDC explicitly states that empiric treatment should begin based on clinical criteria alone, as the long-term reproductive consequences of untreated PID are severe. 1, 2 Many PID cases are initially missed because providers fail to recognize mild or atypical presentations. 1

Reassess within 72 hours: If no clinical improvement occurs with outpatient antibiotics, hospitalization for parenteral therapy is required. 3, 2