What labs should be ordered for a patient presenting with acute left upper quadrant pain?

Laboratory Tests for Acute Left Upper Quadrant Pain

For patients presenting with acute left upper quadrant pain, a comprehensive laboratory panel should include complete blood count, liver function tests, pancreatic enzymes, and renal function tests to evaluate for splenic, pancreatic, gastric, or renal pathology. 1

Initial Laboratory Workup

• Complete blood count (CBC) to assess for leukocytosis, which may indicate infection or inflammation 1
• Liver function tests (LFTs), including ALT, AST, alkaline phosphatase, GGT, and bilirubin to evaluate for hepatobiliary disease 1, 2
• Pancreatic enzymes (amylase and lipase) to rule out pancreatitis 1, 2
• Renal function tests (BUN, creatinine) to assess kidney function 1
• Pregnancy test for all women of reproductive age to rule out ectopic pregnancy or other pregnancy-related conditions 1, 2

Additional Tests Based on Clinical Suspicion

• Coagulation studies (PT/INR, PTT) if splenic rupture or hematoma is suspected 1
• Cardiac enzymes (troponin) if cardiac pathology is suspected, as coronary artery disease can sometimes present with left upper quadrant pain 3
• Lactate level if mesenteric ischemia is suspected 1
• Urinalysis to evaluate for renal stones or infection 1

Laboratory Testing Algorithm

1. First-line tests (order for all patients with acute LUQ pain):

   • CBC with differential
   • Comprehensive metabolic panel (including liver enzymes)
   • Amylase and lipase
   • Pregnancy test (for women of reproductive age) 1, 2

2. Second-line tests (based on clinical suspicion):

   • Cardiac biomarkers if cardiac pathology is suspected 3
   • Lactate if ischemia or severe infection is suspected 1
   • Coagulation studies if bleeding disorder or splenic pathology is suspected 1

Clinical Pearls

• Elevated white blood cell count with left shift suggests infection or inflammation, which may indicate splenic abscess, pancreatitis, or diverticulitis 1
• Elevated liver enzymes with a cholestatic pattern (elevated alkaline phosphatase and bilirubin) may indicate biliary pathology extending to the left upper quadrant 2, 4
• Elevated amylase and lipase strongly suggest pancreatitis, a common cause of left upper quadrant pain 1, 5
• Normal laboratory values do not exclude serious pathology; imaging studies may still be necessary based on clinical presentation 1

Common Pitfalls

• Failing to order a pregnancy test in women of reproductive age, potentially missing ectopic pregnancy 1, 2
• Overlooking cardiac causes of left upper quadrant pain, especially in patients with risk factors for coronary artery disease 3
• Relying solely on laboratory tests without appropriate imaging studies when indicated 1
• Not considering viral etiologies (like EBV) which can present with abdominal pain and abnormal liver function tests 6

Remember that laboratory tests should be interpreted in conjunction with clinical findings and appropriate imaging studies to establish a definitive diagnosis for left upper quadrant pain 1.