What is the differential diagnosis and management plan for a sexually active adult of reproductive age presenting with 2 days of lower abdominal pain, unprotected sex, urinary frequency, lower suprapubic tenderness, and positive McBurney and Rovsing signs?

Differential Diagnosis and Management Plan

Immediate Clinical Assessment

This presentation requires urgent consideration of both pelvic inflammatory disease (PID) and acute appendicitis, with PID being the most critical diagnosis to rule in or out given the history of unprotected sex and potential for irreversible reproductive damage if treatment is delayed. 1, 2

The positive McBurney and Rovsing signs strongly suggest appendicitis, but these findings can overlap with PID, creating a diagnostic challenge that requires systematic evaluation. 3

Differential Diagnosis

Primary Considerations

1. Pelvic Inflammatory Disease (PID)

• The combination of unprotected sex, lower abdominal pain, urinary frequency, and suprapubic tenderness meets minimum criteria for empiric PID treatment 1
• Urinary frequency may represent bladder irritation from adjacent pelvic inflammation 2
• Critical point: Positive McBurney and Rovsing signs do NOT exclude PID, as pelvic inflammation can cause right lower quadrant peritoneal signs that mimic appendicitis 3
• Delayed treatment increases risk of tubal infertility (12% after one episode), ectopic pregnancy, and chronic pelvic pain 4

2. Acute Appendicitis

• Positive McBurney sign (tenderness at McBurney's point) and positive Rovsing sign (right lower quadrant pain with left lower quadrant palpation) are highly specific for appendicitis in adults 5
• However, appendicitis in women of reproductive age must be differentiated from gynecologic pathology 3
• Duration of symptoms (2 days) and presence/absence of nausea and vomiting are key differentiating features 3

3. Complicated Urinary Tract Infection/Pyelonephritis

• Urinary frequency with suprapubic tenderness suggests possible cystitis or ascending infection 6
• However, this would not typically cause positive McBurney and Rovsing signs 6

4. Ectopic Pregnancy

• Must be excluded in any woman of reproductive age with lower abdominal pain and sexual activity history 2, 7
• Can be life-threatening if ruptured 2

5. Ovarian Pathology

• Ruptured ovarian cyst or ovarian torsion can cause acute lower abdominal pain 2, 6
• Less likely given the specific location of tenderness and positive appendiceal signs 6

Diagnostic Algorithm

Step 1: Immediate Laboratory Testing

• Urine pregnancy test (beta-hCG) - mandatory first step to rule out ectopic pregnancy before pursuing other diagnoses 2, 7, 6
• Complete blood count with differential (elevated WBC supports infection) 1, 5
• Urinalysis and urine culture (to evaluate for UTI/pyelonephritis) 6
• Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) - elevated in both PID and appendicitis 1

Step 2: Pelvic Examination

Perform bimanual pelvic examination looking specifically for: 1

• Cervical motion tenderness (chandelier sign) - highly suggestive of PID 1
• Uterine tenderness - supports PID diagnosis 1
• Adnexal tenderness - present in both PID and appendicitis, but bilateral suggests PID 1, 3
• Cervical discharge - obtain specimen for wet mount microscopy looking for white blood cells 1
• Cervical cultures for N. gonorrhoeae and C. trachomatis (do not delay treatment for results) 1, 2, 4

Critical pitfall: If cervical discharge appears normal and no white blood cells are found on wet prep, PID is unlikely and alternative causes should be investigated 1

Step 3: Imaging

• Transvaginal ultrasonography - first-line imaging for women of reproductive age with lower abdominal pain 7, 6
  • Can identify ectopic pregnancy, tubo-ovarian abscess, ovarian cysts, and free fluid 1
  • May show thickened, fluid-filled tubes in PID 1
• Computed tomography - if ultrasonography is nondiagnostic or if appendicitis remains high on differential 7, 6, 5
  • CT has 74-95% sensitivity for appendicitis 2

Management Plan

If PID is Diagnosed or Strongly Suspected

Initiate empiric broad-spectrum antibiotics immediately without waiting for culture results: 1, 4, 8

Outpatient Regimen (Preferred for mild-to-moderate disease): 8

• Ceftriaxone 250 mg IM single dose 8
• PLUS Doxycycline 100 mg orally twice daily for 14 days 8, 9
• PLUS Metronidazole 500 mg orally twice daily for 14 days 8, 10

This regimen provides coverage for N. gonorrhoeae, C. trachomatis, anaerobes, gram-negative facultative bacteria, and streptococci 1, 8

Alternative Outpatient Regimen (if fluoroquinolone resistance is low): 8

• Levofloxacin 500 mg orally once daily for 14 days 8
• WITH Metronidazole 500 mg orally twice daily for 14 days 8, 10

Hospitalization Criteria (requires parenteral therapy): 8

• Diagnosis uncertain and surgical emergencies (appendicitis) cannot be excluded 8
• Pelvic abscess suspected 8
• Severe illness, nausea, or vomiting 8
• Pregnancy 8
• Failed to respond to outpatient therapy within 72 hours 4, 8

Inpatient Regimen A (Preferred): 8

• Clindamycin 900 mg IV every 8 hours 8
• PLUS Gentamicin loading dose 2 mg/kg IV/IM, then 1.5 mg/kg every 8 hours 8
• Switch to Doxycycline 100 mg orally twice daily when clinically improved to complete 10-14 days total 8

If Appendicitis is Diagnosed or Cannot Be Excluded

• Immediate surgical consultation 5
• NPO status and IV fluid resuscitation 5
• Pain control with opioids, NSAIDs, or acetaminophen (does not delay diagnosis) 5
• Appendectomy via laparoscopy or open laparotomy is standard treatment 5
• Intravenous antibiotics may be considered first-line in selected patients with uncomplicated appendicitis 5

Critical Management Points

Mandatory 72-hour follow-up: 4, 8

• All patients treated for PID as outpatients must be reassessed within 72 hours 4, 8
• Should demonstrate substantial clinical improvement including defervescence, reduction in abdominal tenderness, and decreased uterine/adnexal/cervical motion tenderness 4
• If no improvement within 72 hours, hospitalize for parenteral antibiotics and consider surgical intervention for possible tubo-ovarian abscess 4, 8

Partner management: 4, 8

• All male sex partners with contact within 60 days preceding symptom onset must be examined and treated empirically for N. gonorrhoeae and C. trachomatis regardless of symptoms 4, 8
• Patient must abstain from sexual intercourse until both partners complete therapy 4, 8

Rescreening: 4, 8

• Test-of-cure with repeat C. trachomatis and N. gonorrhoeae testing 4-6 weeks after therapy completion in women with documented infection 4, 8

Common Pitfalls to Avoid

• Failing to obtain pregnancy testing before imaging can lead to delayed diagnosis of life-threatening ectopic pregnancy 2
• Assuming normal-appearing cervical discharge rules out PID - must check for white blood cells on wet prep 1
• Delaying antibiotic treatment for PID while awaiting culture results increases risk of tubal infertility and chronic pelvic pain 1, 4
• Dismissing the diagnosis of PID because of positive appendiceal signs - the two conditions can coexist or mimic each other 3
• Requiring multiple criteria before treating PID - CDC guidelines emphasize maintaining a low threshold for diagnosis given the serious reproductive consequences of delayed treatment 1

Algorithmic Approach Summary

1. Obtain urine pregnancy test immediately 2, 7, 6
2. Perform pelvic examination with cervical cultures 1, 2
3. If cervical motion tenderness, uterine tenderness, or adnexal tenderness present → initiate empiric PID treatment immediately 1, 8
4. If appendiceal signs predominate and pelvic examination is negative → obtain imaging (ultrasound first, then CT if needed) 7, 6
5. If diagnosis remains uncertain → hospitalize for observation, parenteral antibiotics covering both PID and surgical pathology, and surgical consultation 8
6. Reassess at 72 hours - if no improvement, escalate care 4, 8