When should I order a CT (Computed Tomography) abdomen for a patient with right-sided abdominal pain?

When to Order CT Abdomen for Right-Sided Abdominal Pain

CT abdomen and pelvis with IV contrast is the primary imaging modality for evaluating right-sided abdominal pain when the diagnosis is unclear, when appendicitis is suspected with classic presentation (fever, leukocytosis, RLQ pain), or when complications are suspected. 1

Clinical Scenarios Requiring CT

Suspected Appendicitis with Classic Presentation

• Order CT abdomen/pelvis with IV contrast (rated 8/9 "usually appropriate") when patients present with fever, leukocytosis, and classic RLQ pain. 1
• CT achieves sensitivity of 85.7-100% and specificity of 94.8-100% for appendicitis, with negative appendectomy rates dropping from 16.7% with clinical evaluation alone to 1.7-7.7% with preoperative CT. 1
• Oral or rectal contrast is not necessary and may delay diagnosis—IV contrast alone provides sensitivity of 90-100% and specificity of 94.8-100%. 1

Nonspecific Right-Sided Abdominal Pain

• CT is indicated when the clinical presentation is atypical or when multiple diagnoses are being considered beyond appendicitis. 1
• CT identifies the cause of RLQ pain in approximately 60% of cases, with common alternative diagnoses including right colonic diverticulitis (8%), bowel obstruction (3%), colitis, inflammatory bowel disease, and ureteral stones. 1, 2
• In patients with nonspecific abdominal pain, CT changed the leading diagnosis in 51% and altered admission decisions in 25% of cases. 1

When Complications Are Suspected

• Order CT when you suspect abscess, perforation, obstruction, or other complications that would alter surgical planning. 1
• CT provides critical information about disease extent and presence of complications that cannot be determined clinically. 1

Alternative Imaging Considerations

When to Start with Ultrasound Instead

• Consider ultrasound first (rated 6/9 "may be appropriate") in young women of reproductive age where gynecologic pathology is equally likely, or when radiation exposure is a primary concern. 1
• However, ultrasound has lower and more variable sensitivity for appendicitis, and results are highly operator-dependent. 1
• If ultrasound is nondiagnostic or negative but clinical suspicion remains high, proceed immediately to CT. 1

When CT Is NOT the Answer

• Do not order CT for right upper quadrant pain—ultrasound is first-line for suspected biliary pathology. 3, 4
• Plain radiography (rated 4/9) has limited utility except when specifically concerned about free air from perforation or bowel obstruction. 1

Critical Clinical Pitfalls

Pain Localization Is Unreliable

• Do not rely solely on pain location to exclude serious pathology—24% of appendicitis patients had no RLQ pain or tenderness, and pain localization by history or physical examination is insufficient to accurately diagnose intra-abdominal pathology. 5
• Right upper quadrant pain was negatively associated with abnormal CT findings, but this does not eliminate the need for imaging when clinical suspicion is high. 5

Radiation Concerns Should Not Prevent Appropriate Imaging

• While abdominal CT delivers approximately 10 mSv of radiation (compared to 3 mSv annual background), the diagnostic yield and impact on management far outweigh radiation risks in appropriate clinical scenarios. 1
• The morbidity and mortality from missed diagnoses (perforation, abscess, delayed surgery) significantly exceed radiation risks. 1

Timing and Protocol Matter

• Always order CT of both abdomen AND pelvis—limiting to pelvis-only "focused appendiceal CT" decreases sensitivity from 99% to 88% and misses 7% of patients with pathology outside the pelvis requiring surgery. 6
• Standard helical CT at 7-mm increments with IV contrast is sufficient; oral contrast delays diagnosis without improving accuracy. 1, 6

Bottom Line Algorithm

1. Classic appendicitis presentation (RLQ pain + fever + leukocytosis): CT abdomen/pelvis with IV contrast immediately 1

2. Atypical or nonspecific right-sided pain: CT abdomen/pelvis with IV contrast when diagnosis unclear or multiple etiologies considered 1

3. Young women with pelvic symptoms: Consider ultrasound first, but proceed to CT if nondiagnostic 1

4. Suspected complications: CT abdomen/pelvis with IV contrast 1

5. Right upper quadrant pain: Ultrasound first, NOT CT 3, 4