Should a CT scan of the abdomen and pelvis be performed with or without IV contrast for a patient with right lower quadrant pain?

CT Abdomen and Pelvis With IV Contrast is the Optimal Imaging Choice for Right Lower Quadrant Pain

CT of the abdomen and pelvis with IV contrast is the most appropriate initial imaging modality for patients with right lower quadrant pain suspected to be appendicitis due to its superior diagnostic accuracy and ability to identify alternative diagnoses. 1

Rationale for IV Contrast in Right Lower Quadrant Pain

Diagnostic Performance

• CT with IV contrast demonstrates excellent diagnostic performance with sensitivity of 95-100% and specificity of 94-100% for appendicitis 1
• IV contrast significantly improves:
  • Characterization and detection of bowel wall pathology
  • Visualization of pericolic abnormalities
  • Identification of vascular pathology
  • Detection of intraabdominal fluid collections 2

Alternative Diagnoses

• CT frequently identifies causes of right lower quadrant pain beyond appendicitis, including:
  • Right colonic diverticulitis
  • Bowel obstruction
  • Benign adnexal masses
  • Inflammatory bowel disease
  • Infectious enterocolitis 1
• CT changes diagnosis in 49-54% of cases and increases physician diagnostic certainty from 70.5% to 92.2% 1
• Studies show CT identifies alternative diagnoses in 23.2-45.3% of patients presenting with classic appendicitis symptoms 2

Evidence Supporting IV Contrast

• The American College of Radiology (ACR) Appropriateness Criteria specifically recommends CT abdomen and pelvis with IV contrast as "usually appropriate" (rating 8/9) for patients with right lower quadrant pain with fever and leukocytosis 2
• Administration of IV contrast for the first CT abdomen and pelvis is associated with increased detection of urgent findings compared with non-contrast CT (p = 0.004) 3
• A 2019 study found that adherence to ACR appropriateness criteria for IV contrast administration was associated with increased detection of urgent pathology (p = 0.02) 3

Special Considerations

When Non-Contrast CT May Be Appropriate

• Non-contrast CT is an acceptable alternative (rated 7/9 by ACR) if IV contrast is contraindicated due to:
  • Severe contrast allergy
  • Renal insufficiency
  • Other contraindications to iodinated contrast 1
• Unenhanced CT still maintains reasonable diagnostic accuracy (sensitivity of 90% vs. 96% for contrast-enhanced) 1

Oral Contrast Considerations

• Many institutions no longer routinely use oral contrast because:
  • It delays scan acquisition and departmental throughput
  • Provides questionable diagnostic advantage 2
  • IV contrast alone is sufficient for most cases

Special Populations

• For pregnant patients:
  • Ultrasound should be first-line imaging
  • MRI without IV contrast is recommended if ultrasound is non-diagnostic 2
• For young, thin adults:
  • Ultrasound may be considered as initial imaging to avoid radiation exposure, but with awareness of its lower sensitivity (76% vs. 96% for CT) 1

Clinical Impact

• CT with IV contrast improves clinical decision-making:
  • Changes management plans in 42% of patients 1
  • Reduces negative appendectomy rates in reproductive-age women from 42% to 17% 4
  • Avoids unnecessary repeat imaging within 72 hours 3

Conclusion

For patients with right lower quadrant pain, CT abdomen and pelvis with IV contrast provides the optimal balance of diagnostic accuracy, ability to identify alternative diagnoses, and impact on clinical management. Non-contrast CT should be reserved for patients with contraindications to IV contrast.