What does an Appendicloth (Computed Tomography) CT scan mean?

CT Scan for Appendicitis: Diagnostic Interpretation

CT scans are highly accurate for diagnosing appendicitis, with sensitivity of 95% and specificity of 94%, making them the preferred imaging modality for adults with suspected appendicitis. 1

CT Findings in Appendicitis

A positive CT scan for appendicitis typically shows:

• Appendiceal enlargement: An appendix diameter >8.2mm is highly specific (93.4%) while maintaining good sensitivity (88.8%) 1
• Periappendiceal inflammation: Visible as fat stranding or haziness around the appendix, present in 68% of cases 2
• Appendicolith: Calcified fecal material within the appendix, seen in approximately 23% of cases 2
• Wall thickening and enhancement of the appendix when contrast is used 3
• Abscess formation: Present in more advanced cases (55% of cases) 2

Diagnostic Accuracy Based on CT Technique

The diagnostic accuracy varies based on the contrast used:

• IV contrast: 96% sensitivity, 93% specificity 1, 4
• Rectal contrast: 97% sensitivity, 95% specificity 1, 4
• IV and oral contrast: 96% sensitivity, 93-95% specificity 1, 4
• No contrast: 91% sensitivity, 94% specificity 1, 4

Clinical Implications of CT Results

• Positive CT: At the median prevalence of appendicitis (43%), a positive CT result indicates a 92% probability of having appendicitis 4
• Negative CT: A negative CT result reduces the probability of appendicitis to 4% 4
• CT helps identify complications such as perforation, abscess formation, peritonitis, and bowel obstruction 3

Limitations and Pitfalls

• Normal CT does not completely exclude appendicitis, particularly in early or mild forms without periappendiceal inflammation 2
• Unusual appendix locations (e.g., retrocecal) may be missed 5
• Tip appendicitis (inflammation limited to the distal appendix) may appear normal on CT 5
• Appendiceal stump inflammation in patients with prior appendectomy can be overlooked 5
• Perforated appendicitis may mimic other conditions like small bowel obstruction or gynecological disease 5

Imaging Protocol Considerations

• Low-dose CT protocols maintain similar diagnostic accuracy while reducing radiation exposure 1
• Focused CT from L2/L3 through the pubic symphysis is often sufficient to diagnose appendicitis and identify alternative diagnoses 6

Population-Specific Recommendations

• For children: Ultrasound is recommended as first-line imaging, with CT as a secondary study when ultrasound is equivocal 6, 1
• For pregnant patients: Ultrasound should be first-line, followed by MRI if ultrasound is equivocal 1
• For patients with contrast allergy: Non-contrast CT can be performed with slightly reduced sensitivity 1

CT scanning has revolutionized the diagnosis of appendicitis, significantly reducing negative appendectomy rates from 16.7% with clinical evaluation alone to 1.7-7.7% with preoperative CT 1. When clinical suspicion remains high despite negative or equivocal imaging, surgical consultation should be considered, as no imaging test is 100% sensitive.