What is the initial workup for a patient presenting with left upper quadrant abdominal pain?

Initial Workup for Left Upper Quadrant Abdominal Pain

CT of the abdomen and pelvis with IV contrast is the first-line imaging study for patients presenting with left upper quadrant (LUQ) pain, as it provides the highest diagnostic accuracy and can detect the wide range of pathologies that cause LUQ pain. 1

Clinical Assessment

Before imaging, obtain:

• Complete blood count with differential - elevated WBC suggests infectious or inflammatory process 2
• C-reactive protein - CRP >50 mg/L significantly increases likelihood of inflammatory pathology; CRP >170 mg/L suggests severe disease 2
• Lipase - to evaluate for pancreatitis 1
• Urinalysis - to assess for renal pathology 1
• Focused physical examination - assess for peritoneal signs, Murphy's sign if pain extends to right upper quadrant, and localization of maximal tenderness 2

Imaging Algorithm

First-Line Imaging: CT Abdomen/Pelvis with IV Contrast

• CT changes the leading diagnosis in 51% of patients and alters management in 25-42% of cases with abdominal pain 1
• Provides superior diagnostic yield with sensitivity of 69% and specificity of 100% for acute LUQ pathology 3
• Evaluates for pancreatitis, renal pathology (pyelonephritis, nephrolithiasis), splenic pathology, colitis, and diverticulitis 1
• IV contrast enhancement is critical for detecting bowel wall pathology, vascular abnormalities, and abscesses 1

Alternative Imaging in Specific Populations

Use ultrasound as initial study when:

• Premenopausal women with suspected gynecologic pathology - transvaginal ultrasound has high sensitivity/specificity for gynecologic causes 2, 1
• Pregnant patients - to avoid radiation exposure 1
• Young patients where radiation is a concern 1
• Suspected gallbladder pathology (if pain extends to right upper quadrant) - ultrasound has 81% sensitivity and 83% specificity for cholecystitis 2, 1

Use unenhanced CT when:

• IV contrast is contraindicated (severe renal dysfunction, contrast allergy) 1
• Suspected urolithiasis - unenhanced CT has near 100% sensitivity and specificity 1
• Elderly patients (≥75 years) - unenhanced CT has similar accuracy to contrast-enhanced CT 1

Common Pathologies to Consider

• Pancreatitis - requires contrast-enhanced CT for severity assessment and complication detection 1
• Renal pathology - pyelonephritis, nephrolithiasis, renal infarction 1
• Splenic pathology - infarction, abscess, rupture 1
• Colonic pathology - colitis, diverticulitis extending to LUQ 1, 4
• Gastric pathology - gastritis, perforation 3
• Herpes zoster - consider if pain precedes vesicular rash 5
• Atypical appendicitis - rare but possible with intestinal malrotation 6

Imaging Modalities to Avoid

• Plain radiography - has poor sensitivity for most LUQ pathology; only useful for detecting pneumoperitoneum or bowel obstruction 1
• MRI - not recommended for initial acute evaluation due to longer acquisition time, reduced sensitivity for extraluminal air, motion artifacts in symptomatic patients, and need for contraindication screening 2, 1
• Fluoroscopic contrast enema - not useful for initial LUQ pain workup 2

Critical Pitfalls to Avoid

• Do not rely solely on clinical assessment - misdiagnosis rates of 34-68% occur with clinical evaluation alone for conditions like diverticulitis 2, 7
• Do not wait for classic symptom triads - only 25% of diverticulitis patients present with pain, fever, and leukocytosis 2, 7
• Do not use plain radiographs as definitive imaging - they miss most acute pathology 1
• Do not omit contrast when evaluating for vascular pathology or abscesses - contrast is essential for these diagnoses 1
• Do not delay imaging in elderly patients - they often present with atypical symptoms and normal laboratory values despite serious pathology 1
• Consider atypical presentations - appendicitis can present in LUQ with intestinal malrotation 6