Initial Laboratory Workup for Ongoing Abdominal Pain in an 8-Year-Old
For an 8-year-old with ongoing abdominal pain, obtain a complete blood count (CBC) with differential, urinalysis, C-reactive protein (CRP), and comprehensive metabolic panel as your initial laboratory evaluation. 1
Core Laboratory Tests
The initial lab workup should include:
- Complete blood count (CBC) to assess for leukocytosis (suggesting infection/inflammation) or anemia (suggesting chronic blood loss or inflammatory conditions) 1
- Urinalysis to rule out urinary tract infection, which is a common cause of abdominal pain in children and can present with abdominal symptoms 2
- C-reactive protein (CRP) as a marker of inflammation, particularly useful in pediatric patients with suspected inflammatory conditions 1
- Comprehensive metabolic panel to evaluate for metabolic abnormalities and assess organ function 1
Additional Tests Based on Clinical Presentation
If Appendicitis is Suspected
When physical examination reveals right lower quadrant tenderness, guarding, or other concerning signs (decreased bowel sounds, psoas sign, obturator sign, Rovsing sign, rebound tenderness), the laboratory evaluation becomes more focused 2:
- White blood cell count with differential is particularly important, as leukocytosis supports the diagnosis of appendicitis 3
- Lactate level if there are signs of systemic illness or potential perforation 2
If Gastrointestinal Infection is Suspected
For patients presenting with diarrhea, fever, or bloody/mucoid stools 1:
- Stool testing for bacterial pathogens (Salmonella, Shigella, Campylobacter, Yersinia) 1
- Stool testing for ova and parasites if there is relevant travel history or endemic area exposure 1
- C. difficile testing if there has been recent antibiotic use within the past 8-12 weeks 1
If Inflammatory Bowel Disease is Considered
For chronic or recurrent abdominal pain with concerning features 1:
- Fecal calprotectin as a marker of intestinal inflammation 1
- Erythrocyte sedimentation rate (ESR) in addition to CRP to assess inflammatory activity 1
- Stool Hemoccult testing to screen for occult gastrointestinal bleeding 1
Critical Considerations
Important caveat: Laboratory findings early in the disease course may be normal or nonspecific, particularly in conditions like mesenteric ischemia or early appendicitis 4. The absence of abnormal labs does not exclude serious pathology 2.
Red Flag Symptoms Requiring Urgent Evaluation
Even with normal initial labs, immediate surgical consultation is warranted if the child has 2:
- Severe, localized pain that increases in intensity
- Pain preceding vomiting
- Bilious vomiting
- Hematochezia (bloody stools)
- Abdominal guarding or rigidity
- Signs of peritonitis
Age-Specific Considerations
In the 8-year-old age group (5-12 years), the most common causes of acute abdominal pain requiring laboratory evaluation include acute appendicitis, gastroenteritis, constipation, urinary tract infection, and mesenteric adenitis 5. The laboratory workup should be tailored to distinguish between these entities based on clinical presentation 2.
Role of Imaging After Laboratory Evaluation
Ultrasonography is the preferred initial imaging modality in children with abdominal pain due to lack of ionizing radiation, low cost, and ease of use 2. Laboratory results help guide whether and what type of imaging is needed, but imaging decisions should not be delayed if there is high clinical suspicion for surgical pathology 2, 3.