Is a computed tomography (CT) scan with contrast necessary for diagnosing appendicitis?

From the Guidelines

A CT scan with contrast is not always necessary for diagnosing appendicitis, but it can be helpful in certain cases, as stated in the 2024 clinical practice guideline update by the Infectious Diseases Society of America 1. The initial evaluation often includes a non-contrast CT scan, which is usually sufficient to identify an inflamed appendix. However, contrast (typically intravenous) may be added when there's diagnostic uncertainty, suspicion of complications like abscess or perforation, or when alternative diagnoses need to be ruled out. Some key points to consider:

• Contrast helps better visualize blood vessels and tissue enhancement patterns, improving detection of inflammation and complications.
• In pregnant patients, ultrasound is typically tried first to avoid radiation exposure, with MRI as a second option.
• In children, ultrasound is also preferred initially to minimize radiation.
• The decision to use contrast should be individualized based on the clinical presentation, patient factors (like kidney function and allergy history), and the radiologist's preference.
• Most emergency departments have protocols in place to guide this decision-making process, as supported by the 2024 clinical practice guideline update by the Infectious Diseases Society of America 1. It's also important to note that CT without IV contrast also has high diagnostic accuracy in detecting acute appendicitis and may be appropriate, as mentioned in the guideline update 1. Additionally, reduced-dose CT has demonstrated similar diagnostic performance to that of standard-dose CT in both children and adults, and is a reasonable option to consider where available 1. Overall, the use of CT with or without contrast for diagnosing appendicitis should be guided by the clinical presentation and patient factors, and should be individualized based on the specific case.

From the Research

CT Scan for Appendicitis Diagnosis

• The use of computed tomography (CT) scans for diagnosing appendicitis has been extensively studied, with research indicating that CT scans can be an effective tool in diagnosing acute appendicitis 2, 3, 4, 5.
• Studies have compared the accuracy of contrast-enhanced CT scans versus non-contrast-enhanced CT scans, with some findings suggesting that contrast-enhanced CT scans may have higher sensitivity 2, 3.
• However, other studies have found that non-contrast-enhanced CT scans can be effective in diagnosing appendicitis, particularly in patients who may be at risk for adverse reactions to contrast media 3, 4.

Contrast Enhancement in CT Scans

• Research has investigated the use of different types of contrast enhancement in CT scans for appendicitis diagnosis, including intravenous contrast, rectal contrast, and oral contrast 2, 4, 5.
• Some studies have found that the use of rectal contrast can increase the accuracy of CT scans in diagnosing appendicitis, but this method can also be associated with patient discomfort and rare complications such as rectosigmoid perforation 4, 5.
• Other studies have suggested that non-contrast-enhanced CT scans or CT scans with oral contrast may be effective alternatives to contrast-enhanced CT scans 3, 4, 5.

Diagnostic Accuracy of CT Scans

• The diagnostic accuracy of CT scans for appendicitis has been reported to be high, with sensitivity and specificity ranging from 72% to 100% and 50% to 100%, respectively 2, 3, 4, 5.
• Studies have also investigated the use of CT scans in reducing negative appendectomy rates, with some findings suggesting that preoperative CT scans can help reduce the rate of unnecessary appendectomies 4.