What lab tests are recommended for patients presenting with abdominal pain?

Laboratory Tests for Patients with Abdominal Pain

For patients presenting with abdominal pain, a comprehensive laboratory workup should include complete blood count, comprehensive metabolic panel, urinalysis, serum lipase, and pregnancy testing in women of reproductive age. 1

Initial Laboratory Evaluation

• Complete blood count (CBC) is essential to assess for leukocytosis, which may indicate infection or inflammation 1, 2
• Comprehensive metabolic panel (CMP) including liver function tests should be ordered to evaluate hepatobiliary pathology and assess organ function 1, 2
• Urinalysis is recommended to evaluate for urinary tract infection or nephrolithiasis 1
• Serum lipase is more specific than amylase for diagnosing pancreatitis and should be included in the initial workup 1, 2
• Beta-human chorionic gonadotropin (β-hCG) testing is mandatory in all women of reproductive age to rule out pregnancy-related conditions including ectopic pregnancy 1, 2
• C-reactive protein (CRP) is useful to assess inflammatory response and can help differentiate between inflammatory and non-inflammatory causes 2

Laboratory Tests Based on Pain Location

• Right Upper Quadrant Pain:

  • Liver function tests (ALT, AST, alkaline phosphatase, bilirubin) and hepatobiliary markers are particularly important 1
  • Ultrasonography is the initial imaging test of choice for patients with right upper quadrant pain 3

• Lower Quadrant Pain (Right or Left):

  • Complete blood count with differential is recommended to assess for appendicitis or diverticulitis 1
  • Computed tomography (CT) is recommended for evaluating right or left lower quadrant pain 3

• Diffuse Abdominal Pain:

  • Lactate and D-dimer may be helpful if mesenteric ischemia is suspected 1
  • CT with intravenous contrast is often the preferred imaging option for generalized abdominal pain 3

Special Considerations

• In patients with fever and abdominal pain, blood cultures should be considered, especially if sepsis is suspected 1
• For immunocompromised patients with abdominal pain, a more extensive workup may be necessary 1
• In patients with suspected pancreatitis, consider using elevated cutoff levels for pancreatic enzymes to improve diagnostic accuracy 1
• For patients with chronic abdominal pain, diagnostic investigations should be limited and adapted according to clinical features, alarm symptoms, and symptom severity 4

Common Pitfalls to Avoid

• Failing to obtain pregnancy testing in women of reproductive age before proceeding with imaging studies can lead to delayed diagnosis of pregnancy-related conditions 1
• Over-reliance on laboratory tests alone for diagnosis can lead to missed diagnoses, as laboratory findings early in the course of disease may be of limited value 1, 5
• Conventional radiography has limited diagnostic value in the assessment of most patients with abdominal pain and should not be routinely ordered 3
• Repeated testing is not recommended once a diagnosis of functional pain is established 4

When to Consider Additional Testing or Imaging

• If initial laboratory workup is inconclusive but clinical suspicion remains high for serious pathology, imaging studies should be considered based on the location of pain 1
• The American College of Radiology has developed clinical guidelines (Appropriateness Criteria) based on the location of abdominal pain to help physicians choose the most appropriate imaging study 3
• For suspected mesenteric ischemia, additional markers such as lactate and D-dimer may be helpful, though they lack specificity 1
• In pregnant patients with inconclusive ultrasonography results, magnetic resonance imaging is preferred over computed tomography when available 2