What is the differential diagnosis (DDX) of pain in the upper left quadrant?

Differential Diagnosis of Left Upper Quadrant Pain

CT abdomen and pelvis with IV contrast is the first-line imaging modality for evaluating left upper quadrant pain, as it provides comprehensive assessment of splenic, pancreatic, gastric, renal, and colonic pathologies with high diagnostic accuracy. 1

Common Causes of Left Upper Quadrant Pain

Splenic Pathology

• Splenic infarction, rupture, or abscess are primary splenic causes that CT with contrast readily identifies 1
• Splenomegaly from various etiologies can cause capsular stretching and pain 1

Pancreatic Disease

• Acute pancreatitis is a major cause of LUQ pain requiring contrast-enhanced CT for severity assessment and complication detection 1
• Pancreatic pseudocyst or abscess can present with LUQ pain 1

Gastric and Esophageal Pathology

• Gastritis, peptic ulcer disease, or gastric perforation should be considered 1
• Esophageal pathology including esophagitis or perforation may refer pain to the LUQ 1

Renal and Urologic Causes

• Pyelonephritis of the left kidney presents with LUQ pain and can be evaluated with high accuracy on CT 1
• Nephrolithiasis causing ureteral obstruction has near 100% sensitivity and specificity on unenhanced CT 1

Colonic Pathology

• Splenic flexure diverticulitis or colitis extending to the LUQ can mimic other pathologies 1
• Colonic perforation or obstruction at the splenic flexure 1

Atypical Presentations

• Appendicitis with intestinal malrotation can present as LUQ pain when the appendix is abnormally positioned 2, 3
• Internal hernias (such as through the foramen of Winslow) with incarcerated bowel or perforated appendix within the lesser sac 4

Cardiovascular Causes

• Acute coronary syndrome can present with LUQ pain, particularly in patients with cervical spinal cord injury who have altered pain perception 5
• Splenic artery aneurysm or dissection 1

Other Considerations

• Pneumonia of the left lower lobe with diaphragmatic irritation 1
• Musculoskeletal pain from rib fracture or costochondritis 1
• Herpes zoster before rash appearance 1

Diagnostic Approach

Initial Imaging Strategy

• CT abdomen and pelvis with IV contrast (rated 8/9 by ACR) is the preferred initial test, changing the leading diagnosis in up to 51% of patients and management in 25% of cases 1
• IV contrast enhancement is critical for detecting bowel wall pathology, pericolic abnormalities, vascular pathology, and intra-abdominal fluid collections 1

Alternative Imaging in Specific Populations

• Ultrasound is preferred for premenopausal women when gynecologic pathology is suspected 1
• Ultrasound is recommended for pregnant patients or young patients where radiation exposure is a concern 1
• Unenhanced CT is acceptable when IV contrast is contraindicated, though less accurate for detecting abscesses 1

Imaging Modalities to Avoid

• Plain radiography has limited utility for LUQ pain due to low sensitivity, though it may detect pneumoperitoneum or bowel obstruction 1
• MRI is not recommended for initial evaluation due to longer acquisition time, less sensitivity for extraluminal air, motion artifacts, and need for contraindication screening 1

Critical Clinical Pearls

When CT Shows Fatty Liver

• Fatty liver does not cause LUQ pain—other etiologies must be sought when fatty liver is incidentally discovered 6
• Complete evaluation for NAFLD should be performed separately from the LUQ pain workup 6

Red Flags Requiring Emergency Evaluation

• Fever with inability to pass gas or stool suggests complicated pathology 7
• Severe abdominal tenderness with guarding indicates possible perforation 7
• Signs of shock or progressively worsening pain over several days 7

Common Diagnostic Pitfalls

• Relying solely on plain radiographs which have poor sensitivity for most LUQ pain causes 1
• Failing to use contrast enhancement when evaluating for vascular pathologies or abscesses 1
• Missing atypical presentations such as malrotation with LUQ appendicitis or cardiac disease presenting as abdominal pain 2, 5
• Delaying imaging in elderly patients who may present with atypical symptoms and normal laboratory values 1

Sensitivity and Specificity Data

• CT for acute LUQ pain has 69% sensitivity and 100% specificity in the emergency setting 8
• Positive predictive value of CT is 100% when acute abnormality is identified 8
• Negative predictive value is 83%, meaning some pathologies may be undetectable on CT and require clinical correlation 8