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Everything you need to know about Computed Tomography (CT) & CT Scanning

Oral Contrast

question1. Why do we use oral contrast?
question2. What kind of oral contrast do we use?
question3. When do we use positive agents and when do we use neutral agents?
question4. What are the advantages of oral LOCM (Omnipaque)?
question5. Is there any contraindication to the use of oral contrast?
question6. If a patient has had a prior reaction to IV contrast can we still use oral contrast?

7. Part 1: When does the patient get the oral contrast relative to the time the patients get the actual CT scan?

Part 2: Does this differ between inpatients and outpatients?


Part 1: This is both a simple and complicated question. The simple answer is that it depends on the clinical question to be answered (I.e. rule out pancreatitis, rule out diverticulitis, rule out appendicitis) where the time for contrast to reach a specific area will vary. In most cases waiting longer is often better but not always practical or possible. For example in the ER setting one might ideally wait 2-2.5 hours before doing an appendix study but this would not be acceptable to the ER docs who need faster throughput for their patients. Therefore we might wait but 30-40 minutes as long as IV contrast is also used.

Although wait time for oral contrast should not vary between inpatients and outpatients, it is often easier to have the longer wait times for inpatients. Good relationship between the CT staff and nursing is needed to coordinate patients getting contrast while on the floor and then being sent to CT at the appropriate time. At Hopkins this has taken a lot of work, but now works well.

In some outpatient centers patients can pick up the oral contrast either the day before (or days before) the study and drink it at home as instructed, or the contrast can be mailed to the patient.

Part 2: The absolute time delay between getting the oral contrast and the time of scanning should not differ between inpatients and outpatients. These days there is a push to decrease wait times in the ER setting and pressure in put on radiology to decrease wait times before doing a study.

"There is little evidence that ingestion of clear inert fluid prior to contrast enhanced CT is a cause of aspiration pneumonia; the length of fasting is variable in any country, being much longer in some hospitals than in others."

Preparative Fasting for Contrast-enhanced CT: Reconsideration
Lee BY et al.
Radiology 2012; 263:444-450

"Currently the length of preparatory solid food fasting is variable in different medical centers, ranging from 0 hours to overnight."

Preparative Fasting for Contrast-enhanced CT: Reconsideration
Lee BY et al.
Radiology 2012; 263:444-450

"Eliminating routine oral contrast use for AP CT in the ED may be successful in decreasing LOS and time from order to CT without demonstrated compromise in acute patient diagnosis."

Eliminating routine oral contrast use for CT in the emergency department: impact on patient throughput and diagnosis
Levenson RB et al.
Emerg Radiol (2012) 19:513-517


8. Are there any other oral contrasts that are used?

question9. Can you use a single bottle of Omnipaque -350 at multiple time points by drawing 10-20 cc at a time to use to mix oral contrast?
question10. What is VoLumen and when do you use it?


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