What is the differential diagnosis for left upper quadrant abdominal pain?

Differential Diagnosis for Left Upper Quadrant Abdominal Pain

The differential diagnosis for LUQ pain includes splenic pathology (infarction, abscess, hematoma, rupture), pancreatic disorders (chronic pancreatitis being most common), gastric conditions, renal pathology (nephrolithiasis, pyelonephritis), colonic disorders (diverticulitis), and functional disorders. 1

Organ-Specific Differential Diagnosis

Splenic Pathology

• Splenic infarction, abscess, hematoma, or rupture should be considered, particularly in patients with trauma history or coagulopathy 1
• These conditions require urgent evaluation and may necessitate coagulation studies (PT/INR, PTT) if suspected 2

Pancreatic Disorders

• Chronic pancreatitis is the most common pancreatic cause of chronic LUQ pain 1
• Acute pancreatitis presents with elevated amylase and lipase (≥3× upper limit of normal) and requires two of three criteria: upper abdominal pain, elevated enzymes, or imaging findings 3
• Elevated pancreatic enzymes strongly suggest pancreatitis and warrant contrast-enhanced CT for severity assessment and complication detection 4, 3

Renal Pathology

• Nephrolithiasis can manifest as LUQ pain and is evaluated with unenhanced CT, which has sensitivity and specificity near 100% 1, 4
• Pyelonephritis should be considered, particularly with urinalysis abnormalities 4

Colonic Disorders

• Diverticulitis, though more common in the left lower quadrant, can extend to cause LUQ pain 1
• Colitis or other inflammatory bowel conditions may present with LUQ pain 4

Gastric Conditions

• Gastric pathology including ulcers or gastritis should be considered in the differential 1

Functional Disorders

• Functional disorders should only be diagnosed after organic pathology is confidently excluded 1, 5
• Once functional pain is established, repetitive testing is not recommended 1, 5

Initial Diagnostic Workup

Mandatory Laboratory Tests

Order these first-line tests for all patients with LUQ pain: 2

• Complete blood count (CBC) to assess for leukocytosis indicating infection or inflammation 2
• Comprehensive metabolic panel including liver enzymes (ALT, AST, alkaline phosphatase, GGT, bilirubin) 2
• Pancreatic enzymes (amylase and lipase) 2
• Renal function tests (BUN, creatinine) 2
• Pregnancy test for all women of reproductive age before any imaging 1, 2
• Urinalysis to evaluate for stones or infection 2

Conditional Laboratory Tests

• Lactate level if mesenteric ischemia is suspected 2
• Coagulation studies if splenic rupture or bleeding disorder is suspected 2

Imaging Strategy

First-Line Imaging

CT of the abdomen and pelvis with IV contrast is the first-line imaging modality for LUQ pain due to its high diagnostic accuracy and ability to detect a wide range of pathologies 4

• CT changes the leading diagnosis in up to 51% of patients and management decisions in 25% of cases 4
• CT with IV contrast improves detection of bowel wall pathology, vascular pathology, and intraabdominal fluid collections 4

Alternative Imaging Scenarios

• Ultrasonography should be used as initial imaging in pregnant patients, young patients where radiation is a concern, or when evaluating splenic, pancreatic, or renal pathology 1, 4
• Unenhanced CT is appropriate when IV contrast is contraindicated or for suspected urolithiasis 4
• In elderly patients (≥75 years), unenhanced CT has similar accuracy to contrast-enhanced CT 4

Imaging to Avoid

• Plain radiography has limited utility for LUQ pain due to low sensitivity, though it may detect pneumoperitoneum or bowel obstruction 6, 4
• MRI is not recommended for initial evaluation due to longer acquisition time, less sensitivity for extraluminal air, and motion artifacts 4

Critical Clinical Pearls

Laboratory Interpretation

• Elevated WBC with left shift suggests infection or inflammation (splenic abscess, pancreatitis, diverticulitis) 2
• Normal laboratory values do not exclude serious pathology—imaging may still be necessary based on clinical presentation 1, 2
• Elevated liver enzymes with cholestatic pattern may indicate biliary pathology extending to LUQ 2

High-Risk Features Requiring Urgent Evaluation

• Systolic blood pressure <100 mmHg (positive likelihood ratio 7.01) 7
• Shock index >0.85 7
• Signs of peritonitis or hemodynamic instability 7

Common Pitfalls to Avoid

• Failing to obtain pregnancy test in women of reproductive age before imaging leads to unnecessary radiation exposure and missed ectopic pregnancy 1, 2
• Relying solely on laboratory tests without appropriate imaging when clinical suspicion warrants further investigation 1, 2
• Using plain radiographs alone, which have poor sensitivity for most LUQ pain causes 4
• Failing to use contrast enhancement when evaluating for vascular pathologies or abscesses 4
• Delaying imaging in elderly patients who may present with atypical symptoms and normal laboratory values 4
• Repetitive testing once functional disorder is diagnosed—refer for psychological support instead 1, 5