What is the best initial imaging study for a patient presenting with stabbing left upper quadrant (LUQ) pain?

Best Initial Imaging Study for Left Upper Quadrant Pain

CT of the abdomen and pelvis with contrast is the recommended first-line imaging modality for patients presenting with stabbing left upper quadrant (LUQ) pain due to its high diagnostic accuracy and ability to detect a wide range of pathologies. 1

Rationale for CT as First-Line Imaging

• CT provides superior diagnostic yield compared to plain radiography for detecting sources of abdominal pain, with the ability to change the leading diagnosis in up to 51% of patients and management decisions in 25% of patients 1
• CT has excellent specificity (100%) for detecting acute abdominal pathology causing LUQ pain, though sensitivity is moderate (69%) 2
• CT can effectively identify common causes of LUQ pain including splenic pathology, pancreatitis, renal conditions, and intestinal disorders that may refer pain to this region 1
• CT with IV contrast significantly improves detection of bowel wall pathology, pericolic abnormalities, vascular pathology, and intraabdominal fluid collections 1

Special Populations and Considerations

• For pregnant patients or young patients where radiation exposure is a concern, ultrasound is recommended as the initial imaging modality 1
• In premenopausal women when gynecologic pathology is suspected as a cause of LUQ pain, ultrasound is the preferred initial imaging study 1
• When IV contrast is contraindicated (e.g., severe renal impairment, contrast allergy), unenhanced CT is recommended, though it has lower sensitivity for certain conditions 1
• In elderly patients (≥75 years), unenhanced CT has similar accuracy to contrast-enhanced CT for acute abdominal pain 1

Imaging Modalities to Avoid as Initial Studies

• Plain radiography has limited utility for LUQ pain due to low sensitivity, though it may detect pneumoperitoneum or bowel obstruction 1
• Fluoroscopic contrast studies are not recommended as initial imaging for LUQ pain 1
• MRI is not recommended for initial evaluation of acute LUQ pain due to longer acquisition time, less sensitivity for extraluminal air, motion artifacts in symptomatic patients, and need for screening for contraindications 1

Clinical Pearls and Pitfalls

• Consider the patient's age, sex, and clinical presentation when selecting imaging modality 1
• Don't rely solely on plain radiographs which have poor sensitivity for most causes of LUQ pain 1
• Avoid delaying appropriate imaging in elderly patients who may present with atypical symptoms and normal laboratory values 1
• Be aware that atypical presentations of common conditions (like appendicitis) can occur in patients with congenital anomalies such as intestinal malrotation, potentially causing LUQ pain 3
• Splenic infarction is an uncommon but important cause of LUQ pain that can be detected by CT 4

Diagnostic Algorithm

1. For most adult patients with acute LUQ pain: CT abdomen/pelvis with IV contrast 1
2. For pregnant patients or young patients: Start with ultrasound 1
3. For patients with contraindication to IV contrast: Non-contrast CT 1
4. For premenopausal women with suspected gynecologic cause: Pelvic ultrasound 1
5. For suspected urolithiasis: Non-contrast CT (sensitivity and specificity near 100%) 1