From the Guidelines
For diagnosing appendicitis, a contrast-enhanced CT scan of the abdomen and pelvis with IV contrast is the best imaging option, as it provides optimal visualization of the appendix and surrounding inflammation, with a sensitivity of 90-95% and specificity of 95-97% for appendicitis 1. The use of CT scans in diagnosing appendicitis has become increasingly prevalent due to its high diagnostic yield, with studies showing that the sensitivity and specificity of CT scans range from 85.7% to 100% and 94.8% to 100%, respectively 1.
- The typical protocol involves administering intravenous contrast material followed by scanning the abdomen and pelvis with thin-slice (3-5mm) technique.
- Oral contrast is generally not necessary and may delay diagnosis, though some institutions still use it.
- CT is superior to ultrasound in adults due to better visualization regardless of body habitus, though ultrasound is often used first in children and pregnant women to avoid radiation exposure.
- The CT findings that suggest appendicitis include an enlarged appendix (>6mm diameter), appendiceal wall thickening, periappendiceal fat stranding, and sometimes an appendicolith (calcified deposit) 1. The high accuracy of contrast-enhanced CT helps reduce unnecessary surgeries and missed diagnoses, making it the gold standard imaging test for suspected appendicitis in most adult patients, as supported by recent guidelines 1.
- A recent update by the Infectious Diseases Society of America recommends the use of CT scans with IV contrast for diagnosing appendicitis in adults, with the option to use CT without IV contrast in certain cases 1.
- The guidelines also suggest that if initial imaging is inconclusive, CT or MRI may be obtained for subsequent imaging, highlighting the importance of CT scans in the diagnostic process 1.
From the Research
CT Scan Options for Appendicitis
- The sensitivity and specificity of CT for diagnosing appendicitis in adults are high, with summary sensitivity of 0.95 and summary specificity of 0.94 2
- Unenhanced standard-dose CT appears to have lower sensitivity than standard-dose CT with intravenous, rectal, or oral and intravenous contrast enhancement 2
- Low-dose CT has similar sensitivity and specificity to standard-dose CT 2, 3, 4
- Focused appendiceal CT with IV and oral contrast is a suitable alternative to conventional CT-AP for evaluating suspected appendicitis 5
- A reduced scan range CT protocol in young adults with high suspicion of appendicitis demonstrates similar diagnostic performance as a full-range abdominopelvic CT and imparts significantly less radiation dose 4
Contrast Enhancement Options
- CT with intravenous contrast has higher sensitivity than unenhanced CT 2
- CT with rectal contrast and CT with intravenous and oral contrast enhancement have similar sensitivity to CT with intravenous contrast 2
- Oral contrast enhancement has similar sensitivity to unenhanced CT 2