From the Guidelines
The primary difference between a CT abdomen with contrast and without contrast lies in the use of an intravenous contrast agent, which enhances the visibility of blood vessels, organs, and abnormalities in the contrast-enhanced scan. The main difference between these two types of scans is that contrast-enhanced scans utilize an intravenous contrast agent, typically iodine-based, to highlight blood vessels, organs, and abnormalities, whereas non-contrast scans do not use this agent 1.
- Contrast-enhanced CT scans are better suited for detecting vascular issues, tumors, infections, and inflammatory conditions because the contrast material makes these abnormalities more visible by enhancing their appearance relative to surrounding tissues.
- Non-contrast CT scans are preferred for evaluating kidney stones, calcifications, and in patients who have contraindications to contrast, such as severe kidney disease or allergies to contrast material. According to the 2024 clinical practice guideline update by the infectious diseases society of america, IV contrast is usually appropriate whenever a CT is obtained and can be helpful to characterize and detect subtle bowel wall abnormalities and complications of diverticulitis 1. However, CT without IV contrast may be appropriate in certain situations, as noted in the same guideline update 1. In some cases, both types of scans are performed in the same session, known as a dual-phase study, starting with the non-contrast scan followed by the contrast-enhanced scan, which allows radiologists to compare the images and better characterize abnormalities. The contrast agent is typically administered through an IV, and patients may experience a warm sensation or metallic taste during injection, as mentioned in the context of CT abdomen scans 1. Patients scheduled for contrast CT should usually fast for 4-6 hours beforehand and may need kidney function tests to ensure the contrast can be safely administered. It's worth noting that the use of IV contrast significantly improves the conspicuity of findings such as interrupted mucosal enhancement and bowel wall hyperenhancement, making the CT examination more sensitive in diagnosis, as highlighted in the acr appropriateness criteria® epigastric pain study 1.
From the Research
CT Abdomen with Contrast vs Without Contrast
- The main difference between a CT abdomen with contrast and without contrast lies in the ability to detect and characterize lesions, particularly in the liver 2.
- A CT abdomen with contrast can better detect urgent and non-urgent pathology, including liver lesions, compared to a non-contrast CT 2.
- The use of intravenous contrast in CT abdomen and pelvis examinations can improve the detection of urgent findings and better characterize both urgent and non-urgent findings 2.
Detection of Liver Lesions
- Contrast-enhanced CT can provide valuable information in the evaluation of focal liver lesions, including hypervascular hepatic focal lesions 3.
- Texture analysis of arterial phase scans on dynamic contrast-enhanced CT can aid in the differential diagnosis of hypervascular solid focal hepatic lesions, particularly between benign and malignant lesions 3.
- Contrast-enhanced ultrasound (CEUS) can also provide added diagnostic value in characterizing incidental focal liver lesions that are indeterminate on contrast-enhanced CT or MR imaging 4.
Contrast Agents
- Different contrast agents, such as iodinated contrast material (ICM), carbon dioxide, gadolinium, and microbubble contrast agents, have their own unique features and limitations 5, 4.
- The choice of contrast agent depends on the clinical situation and the question to be answered, such as the evaluation of chronic liver disease or focal liver lesions 6.