CT Abdomen with Contrast for Right-Sided Abdominal Pain
CT abdomen and pelvis with IV contrast is an excellent diagnostic imaging modality for evaluating right-sided abdominal pain, with 95% sensitivity and 94% specificity for appendicitis, while also identifying a broad range of alternative diagnoses that frequently require hospitalization or surgical intervention. 1
Primary Diagnostic Capabilities
CT with contrast excels at detecting the most common causes of right-sided abdominal pain:
Appendicitis and Gastrointestinal Pathology
- Acute appendicitis is diagnosed with 95% sensitivity (95% CI: 0.93-0.96) and 94% specificity (95% CI: 0.92-0.95) 1
- Right colonic diverticulitis is identified in 8% of patients presenting with right lower quadrant pain 1
- Bowel obstruction is detected in 3% of cases 1
- Infectious enterocolitis including typhlitis and inflammatory terminal ileitis 1
- Inflammatory bowel disease and colitis 1
- Bowel perforation with high sensitivity for detecting free intraperitoneal air and determining the cause 2
Non-Appendiceal Diagnoses
When appendicitis is excluded, CT identifies alternative diagnoses with 94.3% concordance with final clinical diagnosis (383/406 cases), including: 1
Genitourinary Pathology
Hepatobiliary Conditions
- Acute cholecystitis with 74-96% sensitivity and 90-94% specificity for biliary obstruction 4
- Gallstone disease (though sensitivity is only ~75% because 80% of gallstones are noncalcified) 4
- Biliary obstruction and choledocholithiasis 4
Other Critical Diagnoses
- Epiploic appendagitis 3
- Meckel's diverticulum torsion 3
- Gynecologic disorders 3
- Right lower lobe pneumonia 3
- Vascular disease including mesenteric ischemia 5
- Intra-abdominal malignancy 5
- Pancreatitis 5
Clinical Impact on Management
CT findings directly alter clinical management in the majority of cases:
- 41% of patients with non-appendiceal CT diagnoses require hospitalization 1
- 22% undergo surgical or image-guided intervention based on CT findings 1
- In contrast, only 14% of patients without a CT diagnosis are hospitalized, and only 4% require intervention 1
- CT scanning results in 96.8% diagnostic accuracy for acute abdominal pain 5
- 500 patients could be discharged immediately after CT excluded serious pathology in one large series 5
Important Clinical Caveats
When Contrast is Essential
Always use IV contrast unless there are specific contraindications, as noncontrast CT will miss critical diagnostic features including: 4
- Gallbladder wall enhancement and liver hyperemia in cholecystitis 4
- Vascular complications and bowel ischemia 2
- Distinguishing gangrenous from uncomplicated cholecystitis 6
Limitations to Recognize
- CT has only ~75% sensitivity for gallstone detection because most gallstones are noncalcified and isodense to bile 4
- For suspected biliary pathology, ultrasound should be the initial test, not CT 6, 4
- Noncontrast CT provides adequate diagnostic information in 90.7% of surgical abdomen cases, but contrast remains necessary for ischemic bowel disease (only 55.6% accuracy without contrast) 7
Alternative Imaging Considerations
- If biliary obstruction is the primary concern, proceed to MRCP after ultrasound, which has 85-100% sensitivity and 90% specificity for choledocholithiasis 6
- For suspected acute cholecystitis with equivocal ultrasound, consider HIDA scan (97% sensitivity, 90% specificity) rather than CT 4
- MRI is superior to CT for biliary tree evaluation but has longer acquisition times limiting use in unstable patients 6
Diagnostic Algorithm
For undifferentiated right-sided abdominal pain: 1
- If appendicitis or mixed gastrointestinal/genitourinary pathology is suspected → CT abdomen/pelvis with IV contrast is the primary imaging modality
- If right upper quadrant pain with suspected biliary disease → Start with ultrasound, then MRCP if needed 6, 4
- If acute flank pain with suspected urolithiasis → Consider noncontrast CT (stone protocol) 1
- If gynecologic pathology is primary concern → Refer to pelvic pain imaging guidelines 1