What imaging should be done next for a patient with pain in the lower left rib and upper left abdomen, with a normal chest X-ray and normal laboratory results?

CT Abdomen and Pelvis with IV Contrast is the Next Appropriate Imaging for Left Lower Rib and Upper Left Abdominal Pain

For a patient with pain in the lower left rib and upper left abdomen with normal chest X-ray and normal laboratory results, CT abdomen and pelvis with IV contrast is the most appropriate next imaging study.

Rationale for CT Abdomen and Pelvis with IV Contrast

• CT abdomen and pelvis with IV contrast is usually appropriate for the initial imaging of patients with acute abdominal pain, as it provides comprehensive evaluation of both abdominal and thoracic structures that may be causing the pain 1
• CT has high sensitivity and specificity (up to 98% accuracy) for diagnosing various causes of left-sided abdominal and lower chest pain 1
• IV contrast improves the characterization and detection of subtle bowel wall abnormalities and complications such as abscesses 1
• CT can identify alternative diagnoses that may present with similar clinical symptoms, avoiding misdiagnosis 1

Potential Diagnoses to Consider

• Diverticulitis - a common cause of left lower quadrant pain that may radiate to the left lower rib area 1
• Diaphragmatic hernia - can present with pain in the lower chest or upper abdomen 1
• Slipping rib syndrome - characterized by pain in the lower chest or upper abdomen with a tender spot on the costal margin 2, 3
• Other potential causes including:
  • Visceral pathology (splenic, gastric, pancreatic, or colonic issues) 1
  • Musculoskeletal disorders of the chest wall 3, 4

Advantages of CT Over Other Imaging Modalities

• Plain abdominal radiography has low sensitivity and accuracy for evaluating acute abdominal pain and should not be the next step 5
• Ultrasound may be useful for specific conditions but has limited value as the initial imaging for non-gynecologic left-sided abdominal pain 1
• MRI is not recommended for initial evaluation of acute abdominal pain as it:
  • Is less sensitive for extraluminal air and calculi
  • Is more time-consuming
  • Requires screening for metal
  • Is more subject to motion artifacts in symptomatic patients 1

Technical Considerations

• Low-dose CT techniques can achieve radiation dose reduction of 75-90% compared to standard-dose CT while maintaining similar sensitivity and specificity 1
• Administration of oral or colonic contrast may be helpful for bowel luminal visualization in addition to IV contrast 1
• Iodixanol injection (270 mg Iodine/mL or 320 mg Iodine/mL) is FDA-approved for CT imaging of the abdomen 6

Special Considerations

• If there is concern for diaphragmatic hernia, CT scan with contrast enhancement of the chest and abdomen is strongly recommended (1B evidence) 1
• For female patients of childbearing age, consider pelvic ultrasound first if gynecologic pathology is suspected 1
• In pregnant patients with suspected diaphragmatic hernia, ultrasonography is suggested as the first diagnostic study, followed by MRI 1
• In patients with renal insufficiency, CT without IV contrast may be considered, though this is less optimal 1

Potential Pitfalls to Avoid

• Relying solely on clinical assessment for diagnosis of abdominal pain can lead to misdiagnosis rates of 34-68% 1
• Overlooking diaphragmatic injuries, which can be missed on plain radiographs in up to 62% of cases 1
• Failing to consider slipping rib syndrome, which is often underdiagnosed despite being a common cause of lower chest/upper abdominal pain 2, 4
• Ordering unnecessary imaging studies before obtaining the definitive CT scan, which can delay diagnosis and increase healthcare costs 5, 7

By proceeding directly to CT abdomen and pelvis with IV contrast, you will obtain the most comprehensive evaluation for this patient's symptoms while minimizing delays in diagnosis and management.