CT Findings of Appendicitis

Primary Diagnostic Features

The American College of Radiology recommends a maximum outer diameter (MOD) >8.2 mm as the optimal cutoff for diagnosing appendicitis, yielding sensitivity 88.8%, specificity 93.4%, and accuracy 91.7% in patients with suspected appendicitis 1, 2
A diameter with compression (MOD minus compressible contents) >6.6 mm provides the best overall performance with sensitivity 93.8%, specificity 94.9%, and accuracy 94.4% in patients with suspected appendicitis 1, 2
Wall thickness >3 mm is significantly associated with perforation (OR 3.2, p=0.02) in patients with appendicitis 1, 3

Extraluminal appendicolith is highly specific for perforation (OR 28.9, p=0.02) but has low sensitivity in patients with appendicitis 1, 3
Appendicoliths predict perforation with OR 2.47-2.67 (p=0.015) in patients with appendicitis 3, 4
Periappendiceal fluid with severity grade ≥2.5 has 22% sensitivity but 100% specificity for appendicitis in patients with suspected appendicitis 1, 2
Absence of intraluminal gas is present in 67.6% of appendicitis versus 48.9% without (p=0.024) in patients with suspected appendicitis 1, 2

Extraluminal gas is the strongest predictor (OR 28.9, p=0.02) with 96% specificity but only 38% sensitivity for perforation in patients with appendicitis 1, 3
Focal wall enhancement defect has the highest specificity at 98.8% for perforation in patients with appendicitis 3, 4
Circumferential periappendiceal inflammatory changes predict perforation with OR 5.63 (p<0.001) in patients with appendicitis 3, 4
Appendiceal diameter ≥11 mm has the greatest sensitivity (62.7%) for perforation in patients with appendicitis 3, 4

Contrast-enhanced CT has superior sensitivity (96%, 95% CI: 0.92-0.98) compared to unenhanced CT (90%, 95% CI: 0.87-0.93) for diagnosing appendicitis in patients with suspected appendicitis 1, 5
CT with IV and oral contrast shows sensitivity 96% (95% CI: 0.93-0.98) for diagnosing appendicitis in patients with suspected appendicitis 1, 5
Rectal contrast provides the highest sensitivity (97%, 95% CI: 0.93-0.99) and specificity (95%, 95% CI: 0.90-0.98) for diagnosing appendicitis in patients with suspected appendicitis 1, 5