Can a computed tomography (CT) scan without intravenous (IV) contrast rule out acute appendicitis in pregnant women?

From the Guidelines

A CT scan without IV contrast can be used to rule out appendicitis in pregnant women, with high diagnostic accuracy, as reported in a 2024 clinical practice guideline update by the Infectious Diseases Society of America 1. The use of non-contrast CT scans in pregnant women is preferred due to the avoidance of radiation exposure to the fetus from iodinated contrast. According to a meta-analysis of 7 studies with 1,060 patients, non-contrast CT has a pooled sensitivity and specificity of 92.7% and 96.1%, respectively, for the diagnosis of acute appendicitis 1. Some key points to consider when using CT scans without IV contrast in pregnant women include:

• Ultrasound is typically the first imaging choice for pregnant women with suspected appendicitis due to its lack of radiation, though it may be limited by factors like maternal body habitus or fetal position.
• If ultrasound is inconclusive and appendicitis remains a concern, a low-dose non-contrast CT scan may be performed as a reasonable alternative.
• MRI without contrast offers another radiation-free option with high sensitivity and specificity for appendicitis during pregnancy, though availability and timing constraints may exist. The decision about imaging should balance diagnostic accuracy with radiation concerns, considering the patient's trimester, clinical presentation, and available imaging resources, as suggested by the American College of Radiology 1. Early diagnosis remains crucial as untreated appendicitis poses significant risks to both mother and fetus. In adults with suspected appendicitis, if initial imaging is inconclusive, CT without IV contrast also has high diagnostic accuracy in detecting acute appendicitis and may be appropriate, as stated in the 2024 clinical practice guideline update by the Infectious Diseases Society of America 1.

From the Research

CT Scan without IV Contrast for Pregnant Women

• The use of CT scans without IV contrast for diagnosing appendicitis in pregnant women is a topic of discussion in the medical community 2, 3, 4.
• According to a study published in 2014, low-dose unenhanced CT is equal to standard-dose CT with intravenous contrast agents in the detection of signs of acute appendicitis 2.
• A 2019 study found that non-intravenously enhanced low-dose computed tomography with oral contrast (LDCT) can be used to assess pregnant women with right lower quadrant pain when MRI is not immediately available 3.
• The study also found that an algorithm integrating US and low-dose CT is highly sensitive and specific for appendicitis in pregnant women 3.

Alternative Imaging Modalities

• Ultrasonography (US) is recommended as the first-line imaging test for suspected appendicitis in pregnant women 2, 4, 5.
• MRI is also considered a suitable alternative for pregnant women, especially when US is inconclusive 2, 3, 4, 5.
• The use of CT scans with IV contrast is generally discouraged in pregnant women due to the potential risks associated with radiation and contrast agents 4, 5.

Diagnostic Accuracy

• The diagnostic accuracy of CT scans without IV contrast for appendicitis in pregnant women is not well established, and more research is needed to determine its effectiveness 3, 6.
• A study published in 2015 found that the combination of US and CT scan can improve the diagnostic accuracy for appendicitis, but the use of CT scans without IV contrast was not specifically evaluated 6.