From the Guidelines
For suspected appendicitis, a contrast-enhanced CT scan of the abdomen and pelvis without oral contrast is the recommended imaging test, as it provides high diagnostic accuracy with a sensitivity of 94-98% and specificity of 95-97% 1.
Key Considerations
- The use of intravenous (IV) contrast material is recommended to enhance visualization of the appendix and surrounding tissues.
- Thin-slice (3mm or less) technique should be used to maximize diagnostic accuracy.
- Oral contrast is generally not necessary and may delay diagnosis.
- The CT scan allows radiologists to identify an enlarged appendix (greater than 6mm in diameter), appendiceal wall thickening, periappendiceal fat stranding, and potential complications like perforation or abscess formation.
Diagnostic Performance
- A recent meta-analysis reported a summary sensitivity of 0.95 (95% CI: 0.93-0.96) and a summary specificity of 0.94 (95% CI: 0.92-0.95) for CT in the diagnosis of appendicitis 1.
- The diagnostic performance of CT is high, with a sensitivity of 90-100% and specificity of 94.8-100% for contrast-enhanced CT without enteral contrast 1.
Patient Considerations
- Patients should inform their healthcare provider about any allergies to contrast material, kidney problems, or pregnancy before undergoing the scan.
- While ultrasound may be used as an initial imaging test, particularly in children, pregnant women, and young adults, CT remains the gold standard for definitive diagnosis of appendicitis in most adult patients due to its superior diagnostic accuracy.
Evidence Summary
- The evidence supports the use of contrast-enhanced CT without oral contrast as the preferred imaging test for suspected appendicitis, due to its high diagnostic accuracy and ability to identify potential complications 1.
From the Research
Computed Tomography (CT) Scan for Diagnosing Appendicitis
- The type of CT scan indicated for diagnosing appendicitis is a topic of discussion among researchers, with some studies suggesting that low-dose unenhanced CT is equal to standard-dose CT with intravenous contrast agents in the detection of signs of acute appendicitis 2.
- A study published in 2019 found that the sensitivity and specificity of CT for diagnosing appendicitis in adults are high, with unenhanced standard-dose CT appearing to have lower sensitivity than standard-dose CT with intravenous, rectal, or oral and intravenous contrast enhancement 3.
- Another study published in 2021 compared nonenhanced CT (NECT) with contrast-enhanced CT (CECT) for the diagnosis of acute appendicitis and found that there was no significant difference in the diagnosis of acute appendicitis among the three techniques (NECT, CECT, and NECT + CECT) 4.
- A retrospective study published in 2009 suggested that enhanced CT should be primarily performed for diagnosing acute appendicitis in all patients to minimize the radiation exposure unless intravenous administration of contrast material is contraindicated 5.
CT Scan Techniques
- Low-dose unenhanced CT is considered a viable option for diagnosing appendicitis, especially in patients who are at risk of radiation exposure or have contraindications to contrast agents 2, 3.
- Contrast-enhanced CT is considered superior to nonenhanced CT in diagnosing appendicitis, especially in patients with atypical clinical presentation or suspected perforation 2, 5.
- The use of different types of contrast enhancement or no enhancement does not appear to affect specificity, but may affect sensitivity 3.
Patient Considerations
- Pregnant women and young adults may require special consideration when it comes to CT scans, with some studies suggesting that MRI or ultrasound may be preferred in these populations 6, 2.
- Patients with contraindications to contrast agents or increased risk of severe adverse reaction may benefit from nonenhanced CT scans 4.