What is the differential diagnosis for left upper quadrant pain?

Differential Diagnosis for Left Upper Quadrant Pain

The differential diagnosis for left upper quadrant (LUQ) pain includes splenic pathology (infarction, abscess, hematoma, rupture), pancreatic disorders (chronic pancreatitis being most common), gastric conditions (including peptic ulcer disease and functional dyspepsia), renal pathology (nephrolithiasis), colonic disorders (diverticulitis), and life-threatening conditions such as myocardial infarction, perforated viscus, and ruptured abdominal aortic aneurysm that must be immediately excluded. 1

Life-Threatening Conditions to Rule Out First

Before considering other diagnoses, immediately assess for conditions requiring emergent intervention:

• Cardiovascular emergencies: Acute myocardial infarction can present with upper abdominal pain and must be excluded first 1
• Vascular catastrophes: Leaking or ruptured abdominal aortic aneurysm requires immediate recognition 1
• Perforated viscus: Look for signs of peritonitis, pneumoperitoneum, or shock 1
• Mesenteric ischemia: Consider in patients with atherosclerotic risk factors, especially if pain is postprandial with weight loss 2
• Ectopic pregnancy: Obtain pregnancy test in all women of reproductive age before any imaging to avoid missing this diagnosis 1

Organ-Specific Differential Diagnosis

Splenic Pathology

• Splenic infarction: Most commonly caused by cardiogenic emboli (62.5% of cases), particularly from atrial fibrillation 3
• Presents with LUQ or epigastric pain in 84% of cases, though associated symptoms like leukocytosis or elevated LDH occur inconsistently (only ~25% each) 3
• Can be the first manifestation of previously silent conditions like antiphospholipid syndrome or mitral valve disease 3
• Splenic abscess, hematoma, or rupture: Particularly consider in trauma or coagulopathy settings 1
• Splenic artery pseudoaneurysm: Rare but critical; presents with hemorrhagic shock, abdominal pain, and back pain; associated with pancreatitis, trauma, or can be idiopathic 4

Pancreatic Disorders

• Chronic pancreatitis: The most common pancreatic cause of chronic LUQ pain 1
• Acute pancreatitis: Can present with isolated left flank pain as the sole manifestation, though this is very rare 5
• Tail pancreatitis may extend fluid collections to the left perirenal space, mimicking renal pathology 5
• Postprandial pain with functional dyspepsia features may suggest pancreatic insufficiency 2

Gastric Conditions

• Peptic ulcer disease: Can cause LUQ pain and has been rarely associated with splenic artery pseudoaneurysm 4
• Functional dyspepsia: Most common cause of postprandial LUQ pain when structural abnormalities are excluded; characterized by pain/burning in upper abdomen, early satiety, or postprandial heaviness 2
• Gastric malignancy: Must be excluded with endoscopy if alarm features present (older age, family history of upper GI malignancy, weight loss, anemia) 2

Renal Pathology

• Nephrolithiasis: Can cause chronic LUQ pain 1
• Acute pyelonephritis: May present with left flank pain but can be confused with pancreatic pathology 5

Colonic Disorders

• Diverticulitis: Though more common in left lower quadrant, can extend to cause LUQ pain 1
• Requires CT with IV contrast for diagnosis (98% accuracy) 6

Atypical Presentations

• Appendicitis with intestinal malrotation: In rare cases of congenital malrotation, the appendix may be located in the LUQ, presenting as left-sided appendicitis 7
• Should be considered in patients with LUQ pain, especially if imaging reveals intestinal malrotation 7

Diagnostic Approach Algorithm

Step 1: Initial Laboratory Evaluation

Order these tests for all patients with chronic LUQ pain 1:

• Complete blood count
• Comprehensive metabolic panel
• Pancreatic enzymes (amylase and lipase)
• Urinalysis
• Pregnancy test (mandatory in all women of reproductive age before imaging) 1

Step 2: Imaging Strategy

• CT abdomen with contrast is the imaging modality of choice when diagnosis is unclear or alarm features present, with moderate sensitivity and excellent specificity 1
• CT changes the leading diagnosis in up to 51% of patients and management decisions in 25% of cases 1
• Ultrasonography can be initial imaging for evaluating splenic pathology, pancreatic conditions, and left kidney abnormalities, with the advantage of no radiation exposure 1
• MRI may be useful as second-line imaging if CT is non-diagnostic and symptoms persist, with sensitivity of 86-94% 1
• Plain radiography has limited utility due to low sensitivity, though may detect pneumoperitoneum or bowel obstruction 1

Step 3: Special Considerations for Postprandial Pain

If pain occurs specifically after eating 2:

• Test for H. pylori and treat if positive
• Consider chronic mesenteric ischemia if patient has weight loss and atherosclerotic risk factors; obtain CT angiography 2
• Perform endoscopy if alarm features present to exclude malignancy 2

Critical Pitfalls to Avoid

• Never skip pregnancy testing in women of reproductive age before imaging to avoid unnecessary radiation exposure and missing ectopic pregnancy 1
• Do not rely solely on laboratory tests without appropriate imaging when clinical suspicion warrants further investigation 1
• Normal laboratory values do not exclude serious pathology; imaging studies may still be necessary based on clinical presentation 1
• Do not assume typical presentations: Splenic infarction may present without leukocytosis or elevated LDH; acute pancreatitis can present solely as left flank pain 3, 5
• Avoid relying on clinical findings alone for pancreatitis diagnosis; biochemical confirmation is necessary 1
• Do not use CT as first-line in young patients; ultrasound is often more appropriate 1

Management Based on Findings

• Treat identified organic pathology according to specific diagnosis 1
• Consider functional disorder diagnosis only after organic pathology is confidently excluded 1
• Avoid repetitive testing once functional pain diagnosis is established 1
• For functional dyspepsia: Offer acid suppression with PPIs or H2-receptor antagonists; consider tricyclic antidepressants as second-line to modulate pain perception 2
• Refer to gastroenterology for refractory symptoms requiring endoscopy, advanced prokinetics, or behavioral interventions 2