What is the best course of action for a 35-year-old patient with lower right quadrant (abdominal) pain and no bowel movements for 2 days, considering a computed tomography (CT) scan?

Management of Lower Right Quadrant Pain with Suspected Appendicitis

CT scan of the abdomen and pelvis with contrast media is the most appropriate next step for a 35-year-old patient presenting with lower right quadrant pain and constipation for 2 days. 1, 2

Rationale for CT Imaging

• CT abdomen and pelvis with contrast is rated 8/9 by the American College of Radiology (ACR) for suspected appendicitis, making it the first-line imaging modality 1, 2
• CT demonstrates excellent diagnostic accuracy with:
  • Sensitivity of 85.7-100%
  • Specificity of 94.8-100% 1, 2
• IV contrast enhances visualization of the appendix and surrounding inflammation 2
• CT can identify alternative diagnoses that may mimic appendicitis in patients with RLQ pain 1, 3

Clinical Considerations

• Lower right quadrant pain with constipation raises concern for appendicitis but could also indicate:
  • Right colonic diverticulitis (seen in 8% of RLQ pain cases)
  • Bowel obstruction (seen in 3% of RLQ pain cases)
  • Other conditions including typhlitis, inflammatory terminal ileitis, or ureteral stone 1
• Constipation for 2 days may be:
  • A symptom of appendicitis
  • A separate condition causing pain
  • A contributing factor to appendicitis through fecalith formation 1

CT Protocol Recommendations

• CT with IV contrast is preferred as it provides superior diagnostic accuracy 1, 2
• Oral contrast may not be necessary depending on institutional preference 1
• The summary sensitivity for CT with IV contrast (0.96) is higher than unenhanced CT (0.90) 1
• Single-phase IV contrast-enhanced examination is typically sufficient 1

Diagnostic Value of CT

• CT frequently alters diagnosis and management in patients with abdominal pain:
  • Changes diagnosis in 49-54% of cases
  • Increases physician diagnostic certainty from 70.5% to 92.2%
  • Changes management plan in 42% of patients 1
• CT can identify both appendicitis and alternative diagnoses including:
  • Colonic diverticulitis
  • Bowel obstruction
  • Inflammatory conditions
  • Urologic pathology 1, 3

Important Considerations

• While ultrasound could be considered as an initial imaging modality to avoid radiation, its sensitivity (76%) is lower than CT (94%) 2
• Plain abdominal radiographs have limited diagnostic value in this setting (rated only 4/9 by ACR) 1, 2
• CT of both abdomen and pelvis is necessary as limiting the scan to just the pelvis would decrease sensitivity from 99% to 88% 4
• Non-contrast CT is an option (rated 7/9 by ACR) if IV contrast is contraindicated 1

Pitfalls to Avoid

• Delaying imaging based on absence of fever (afebrile presentation does not rule out appendicitis) 2
• Starting antibiotics before confirming diagnosis (may mask findings) 2
• Using ultrasound as first-line in patients with higher BMI (significantly limited accuracy) 2
• Assuming normal white blood cell count rules out appendicitis 2
• Performing only limited CT of the pelvis (may miss pathology in the abdomen) 4

CT of the abdomen and pelvis with IV contrast represents the most appropriate next step in evaluating this patient with lower right quadrant pain and constipation, providing the highest diagnostic accuracy while enabling identification of appendicitis or alternative diagnoses.