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Commonly Asked Questions About CT Contrast

By DuPage Medical Group Radiology

Learn the answers to commonly asked questions related to CT contrast.


What is the difference between oral and IV contrast?

IV contrast is injected into a vein and is used to highlight blood vessels and various organs such as the liver, kidneys and spleen. IV contrast causes these structures to "enhance" or light up white on CT images. This enhancement gives the radiologist a lot of information about the structure and function of these areas. IV contrast is filtered by the kidneys and is released from the body through the urine.

Oral contrast is given by mouth just prior to the scan. This type of contrast is used to highlight the stomach as well as the small and large intestines. There are several different types of oral contrast. Certain oral contrasts can be white and have a thicker consistency, others are thin and watery. The type of oral contrast given to the patient depends greatly on what the doctor is trying to evaluate. Oral contrast leaves the body through the stool and may cause loose stools in some people.

Patients receiving a scan of their abdomen may receive one or both types of contrast.

What will I feel when I receive the IV contrast?

Patients may feel a few or all of the following:

  • A warm or flushed sensation
  • A metallic taste in the mouth
  • Warmth in the back of the throat
  • Warmth in the chest
  • Warmth in the pelvic area
  • Occasionally a slight feeling of nausea
What should I expect after receiving contrast?

There are typically no lasting side effects from IV contrast. Be sure to stay hydrated for at least 48 hours following the test. This will help your body excrete the contrast. There are certain medications that need to be held for 48 hours after the exam. If you are on one of these medications, your technologist will let you know and he/she will give you the appropriate instructions. After the exam, you may eat and drink normally and resume your regular diet. It is not uncommon to experience stools that are looser than normal after receiving oral contrast.  

What are some possible reactions to the contrast?

Allergic reactions are not a common occurrence however, they can happen. When reactions occur, most commonly patients experience hives or itching. More severe reactions are extremely rare, and include symptoms such as swelling of the face and throat, tightness in the chest, or shortness of breath.  If any reaction occurs, physicians are onsite that can evaluate and treat the reaction as needed.

Topics and Subtopics: Diagnostic Testing & Radiology

Learn more about:
Radiology CT
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