Should a CT abdomen and pelvis be done with or without contrast?

CT Abdomen and Pelvis With IV Contrast is Recommended Over Non-Contrast CT

CT abdomen and pelvis with IV contrast is the preferred imaging approach for most clinical scenarios due to its superior diagnostic accuracy and ability to detect a wider range of pathologies compared to non-contrast CT. 1

Rationale for Using IV Contrast

Enhanced Diagnostic Capability

• IV contrast significantly improves visualization of:
  • Vascular structures and active bleeding
  • Organ parenchymal abnormalities
  • Inflammatory changes
  • Neoplastic processes
  • Infection and abscess formation

Clinical Evidence Supporting IV Contrast

• The American College of Radiology recommends a single-pass venous phase acquisition with IV contrast for comprehensive evaluation 1
• Contrast-enhanced CT has superior detection rates (84.4%) compared to other modalities for conditions like complicated pyelonephritis 1
• IV contrast significantly improves conspicuity of findings such as interrupted mucosal enhancement and bowel wall hyperenhancement 1

Specific Clinical Scenarios

Trauma Assessment

• CT abdomen and pelvis with IV contrast is instrumental in decision making for penetrating trauma patients 2
• Allows for identification of solid organ injuries that are much more apparent with IV contrast 2

Cancer Evaluation

• Single-phase examination with IV contrast administered in the portal venous phase (typically 70 seconds after contrast administration) is recommended for comprehensive cancer staging 1

Acute Abdominal Pain

• In patients with acute abdominal pain, IV contrast-enhanced CT increases detection of urgent pathology compared to non-contrast CT (p=0.004) 3
• Adherence to ACR appropriateness criteria for IV contrast administration is associated with increased detection of urgent pathology 3

Specific Indications for Non-Contrast CT

While IV contrast is generally preferred, non-contrast CT is specifically indicated in certain scenarios:

1. Urolithiasis (Kidney Stones)

   • Non-contrast CT is the gold standard for detecting renal calculi 2
   • Virtually all renal calculi are radiopaque on CT, allowing for accurate detection even without contrast 2

2. Renal Impairment

   • For patients with acute kidney injury (AKI) or eGFR < 30 mL/min/1.73m², unenhanced CT is preferred 1

3. Contrast Allergy

   • Patients with severe allergic reactions to iodinated contrast media 1

4. Specific Clinical Scenarios

   • Suspected retroperitoneal hematoma
   • Common duct calculus
   • Abdominal aortic aneurysm assessment 4

Protocol Recommendations

• Contrast Type: Non-ionic iodinated contrast media (e.g., iohexol, ioversol)
• Volume: 100-150 mL (standard adult dose)
• Timing: Portal venous phase imaging at approximately 70 seconds post-injection 1
• Patient Position: Supine with arms above head (if possible)
• Breathing Instructions: Hold breath during acquisition

Common Pitfalls to Avoid

1. Unnecessary Repeat Imaging

   • Repeat CT within 72 hours is often of low diagnostic benefit if the first CT was performed with IV contrast 3

2. Inappropriate Non-Contrast Studies

   • Non-contrast CT may miss critical findings in many clinical scenarios
   • In a study of patients with surgical abdomen, IV contrast was necessary for accurate diagnosis of ischemic bowel disease (only 55.6% identified on non-contrast) 5

3. Delayed Scanning

   • Scanning too early may result in suboptimal venous enhancement
   • Excessive delay reduces vessel opacification 1

4. Overlooking Contraindications

   • Always check for history of severe contrast reactions and renal function 1

In summary, while non-contrast CT has specific indications, CT abdomen and pelvis with IV contrast provides superior diagnostic information in most clinical scenarios and should be the default choice when not contraindicated.