To rule out appendicitis, does a CT scan of the abdomen and pelvis need to be done with contrast?

From the Guidelines

A CT scan of the abdomen and pelvis can effectively rule out appendicitis without contrast in many cases, as non-contrast CT scans are often sufficient for diagnosing appendicitis. According to the most recent study 1, IV contrast is usually appropriate whenever a CT is obtained in adults with suspected acute appendicitis; however, CT without IV contrast also has high diagnostic accuracy in detecting acute appendicitis and may be appropriate. The decision to use contrast should be based on the clinical scenario, patient factors (such as renal function and allergy history), and radiologist preference.

Some key points to consider:

• Non-contrast CT scans can show an enlarged appendix, surrounding inflammation, and potential appendicoliths (calcified deposits) 1.
• IV contrast can improve diagnostic accuracy in certain situations, particularly in thin patients, early appendicitis cases, or when there's diagnostic uncertainty 1.
• Oral contrast is generally not necessary and may delay diagnosis 1.
• Many emergency departments now routinely use non-contrast CT protocols for suspected appendicitis to expedite care while maintaining high diagnostic accuracy 1.
• The radiation exposure from a single CT scan is considered acceptable given the importance of accurate diagnosis, though ultrasound may be considered first in children and pregnant women to avoid radiation exposure 1.

It's worth noting that the most recent study 1 suggests that CT without IV contrast has high diagnostic accuracy, and the use of contrast should be determined on a case-by-case basis. Ultimately, the choice of whether to use contrast in a CT scan for suspected appendicitis should be made based on the individual patient's needs and the clinical scenario.

From the Research

CT Scan for Appendicitis Diagnosis

• To rule out appendicitis, a CT scan of the abdomen and pelvis can be used, but the question remains whether it needs to be done with contrast.
• Studies have shown that both contrast-enhanced and non-contrast-enhanced CT scans can be effective in diagnosing acute appendicitis 2, 3, 4.
• A study published in 2019 found that 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 3.
• Another study published in 2021 compared non-enhanced CT with contrast-enhanced CT for the diagnosis of acute appendicitis and found no significant difference in diagnostic accuracy between the two techniques 4.
• Focused appendiceal CT with IV and oral contrast has also been shown to be a suitable alternative to conventional CT-AP for diagnosing suspected acute appendicitis 5.
• A study published in 2006 found that IV-contrast-enhanced CT scans of the abdomen and pelvis without oral or rectal contrast had a sensitivity of 100% and specificity of 97% for diagnosing acute appendicitis 6.

Use of Contrast in CT Scans

• The use of contrast in CT scans for appendicitis diagnosis is not always necessary, as non-contrast-enhanced CT scans can also be effective 4.
• However, contrast-enhanced CT scans may have higher sensitivity and specificity than non-contrast-enhanced CT scans in some cases 3.
• The choice of whether to use contrast in a CT scan for appendicitis diagnosis should be made on a case-by-case basis, taking into account the individual patient's needs and medical history.