Management of a 5-Year-Old with Abdominal Pain and WBC 17.2
Obtain CT abdomen/pelvis with IV and oral contrast immediately to identify surgical pathology, as this provides 95% sensitivity and 94% specificity for surgical causes and is the study of choice for acute abdominal pain with leukocytosis. 1
Immediate Diagnostic Workup
Laboratory Tests Required
- Complete blood count with differential (already shows WBC 17.2, but need neutrophil count, lymphocyte count, and eosinophil count) 2
- C-reactive protein (CRP) - CRP ≥5 mg/dL has high specificity for intra-abdominal pathology 1, 2
- Serum electrolytes, liver enzymes, and renal function 2
- Blood cultures if fever present before starting antibiotics 1
- Serum lactate if concerned about bowel ischemia or sepsis 2
The combination of neutrophilia >9.0 × 10⁹/L with lymphopenia (<1.4 × 10⁹/L) and eosinopenia (<0.04 × 10⁹/L) has 94.9% specificity for severe illness requiring surgical intervention, though sensitivity is only 27.5% 3. This leukocyte differential pattern is more predictive than WBC count alone 3.
Imaging Strategy
CT abdomen/pelvis with IV and oral contrast is mandatory - radiographs have limited value with only 25% sensitivity and show nonspecific findings that appear late when infarction has already occurred 2, 1. Plain films should only be used to screen for perforation or obstruction if CT is unavailable 2.
Critical Differential Diagnoses in This Age Group
Most Likely Surgical Causes
- Appendicitis (including perforated) - the only surgical problem occurring in >1% of pediatric abdominal pain cases 4
- WBC 17.2 suggests possible complicated disease, as WBC >23,000 indicates higher likelihood of perforation 1
- Guarding and abdominal tenderness are the two symptoms most strongly associated with surgical diagnosis in children 4
- In children with <24 hours of pain, WBC count is most useful; with 24-48 hours of pain, CRP is most useful 5
Important Medical Causes
- Mesenteric adenitis - presents with fever, right lower quadrant pain, and leukocytosis, mimicking appendicitis 6
- Infectious gastroenteritis - accounts for 12% of pediatric abdominal pain presentations 4
- Respiratory illness - surprisingly accounts for 12% of pediatric abdominal pain cases 4
Rule Out Infectious Causes
Obtain stool cultures for bacterial pathogens including Clostridium difficile toxin if any recent antibiotic exposure, as C. difficile can present as acute abdomen with leukocytosis and minimal diarrhea 2, 7.
Empiric Antibiotic Therapy
Start empiric broad-spectrum antibiotics immediately after obtaining blood cultures if any signs of sepsis (fever, hypotension, altered mental status) 1:
- Cefotaxime 2g IV every 8 hours (or weight-based dosing: 50 mg/kg/dose up to 2g) 2, 1
- Alternative: Ceftriaxone 1-2g IV daily (or 50-75 mg/kg/day in children) 1
- Add metronidazole if concerned about intra-abdominal abscess or C. difficile 1, 7
Monitoring and Follow-Up
- Clinical improvement should occur within 3-5 days - if not improving, repeat imaging to assess for abscess or inadequate source control 1
- Monitor CRP trends - rising CRP despite treatment suggests secondary peritonitis or abscess requiring surgical intervention 2, 1
- If adequately drained infection identified, 5 days of antibiotics is sufficient (not 10 days) 1
Common Pitfalls to Avoid
- Do not rely on normal CRP to rule out serious pathology - normal CRP does not exclude postoperative complications or early appendicitis 2, 1
- Do not skip CT in favor of ultrasound alone - while ultrasound can identify some pathology, CT is the definitive study with superior sensitivity and specificity 1
- Do not assume viral gastroenteritis without imaging when WBC is 17.2 - this degree of leukocytosis warrants exclusion of surgical pathology 1, 3
- Do not forget to check for recent antibiotic exposure - C. difficile can present as acute abdomen mimicking surgical disease 7