What laboratory tests are indicated for a patient presenting with abdominal pain?

Laboratory Tests for Abdominal Pain

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

Initial Laboratory Evaluation

• Complete blood count (CBC) to assess for leukocytosis, which may indicate infection or inflammation 2, 1
• Comprehensive metabolic panel including electrolytes, liver enzymes, and renal function tests 2, 1
• C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) as inflammatory biomarkers 2, 1
• Serum albumin and pre-albumin to assess nutritional status and degree of inflammation 2
• Urinalysis to evaluate for urinary tract infection or nephrolithiasis 1
• Serum lipase for suspected pancreatitis (more specific than amylase) 1
• Beta-human chorionic gonadotropin (β-hCG) testing in all women of reproductive age 1, 3

Laboratory Tests Based on Pain Location

Right Upper Quadrant Pain

• Liver function tests (AST, ALT, bilirubin, alkaline phosphatase) 1
• Hepatobiliary markers 1

Lower Quadrant Pain (Right or Left)

• CBC with differential to assess for appendicitis or diverticulitis 1
• CRP as an inflammatory marker 2

Diffuse Abdominal Pain

• Lactate and D-dimer if mesenteric ischemia is suspected 1, 3
• Blood cultures if sepsis is suspected 1

Special Considerations

Suspected Inflammatory Bowel Disease

• Fecal calprotectin when available 2
• Rule out infectious causes, especially Clostridium difficile and Cytomegalovirus 2

Suspected Bowel Obstruction

• CBC, electrolytes, and renal function tests 2
• Serum bicarbonate, arterial blood pH, and lactic acid levels to assess for intestinal ischemia 2
• Coagulation profile if emergency surgery is anticipated 2

Suspected Cyst Infection or Hemorrhage

• CBC to check for leukocytosis (>11,000/L) 2
• CRP to assess inflammation 2
• Blood cultures if infection is suspected 2

Common Pitfalls to Avoid

• Failing to obtain pregnancy testing in women of reproductive age before proceeding with imaging studies 1, 3
• Over-reliance on laboratory tests alone for diagnosis, as findings early in disease may be of limited value 1
• Neglecting to consider extra-abdominal causes of abdominal pain, which may require different laboratory tests 4
• Using plain abdominal radiography as the initial imaging modality, which has limited diagnostic value 5

When to Consider Additional Testing

• 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, 3
• CT with contrast is recommended for right lower quadrant, left lower quadrant, or generalized abdominal pain 3
• Ultrasonography is the initial imaging study of choice for right upper quadrant pain 3
• For suspected mesenteric ischemia, additional markers such as lactate and D-dimer should be obtained, though they lack specificity 1, 3

Laboratory testing for abdominal pain should be tailored to the clinical presentation and suspected diagnosis, with the understanding that no single test is definitive and the results must be interpreted in the context of the patient's history and physical examination findings 4, 6.