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E1874. Understanding the Appropriate Use of Oral Contrast in Abdominal CT Imaging
Authors
  1. Shripadh Chitta; VCU Health
  2. Neeraj Lalwani; VCU Health
Background
Computed tomography (CT) Abdomen is used in the emergency room (ER) to assess internal organs and bowel loops to accurately diagnose the cause of abdominal pain. Collapsed bowel loops and nearby pathology can be difficult to separate as they have similar attenuation, so oral contrast has a crucial role in delineating these two. However, oral contrast may need intensive preparation protocols, like bowel preps, that impact patient satisfaction. In the ER, oral contrast use increases length of stay while delaying the diagnosis. It may also cause increased costs and radiation dose while not significantly altering the final diagnosis. Therefore, the use of oral contrast remains controversial. Positive contrast (barium and iodinated water-soluble contrast) are useful to visualize abscesses, fistulae, leaks, extraluminal tumors or hematomas as well as in cancer staging and surveillance of peritoneal carcinomatosis. Nevertheless, they are generally contraindicated in active GI bleeds. Neutral contrast (water or water attenuation) aid in visualizing bowel wall inflammation and hyperemia, such as in monitoring Crohn’s disease or characterizing wall ischemia. Thus, neutral agents are used in CT enterography. Oral contrast is not used when patients are at high risk of aspiration, high suspicion of intraabdominal hemorrhaging, or when CT angiography is being performed. Oral contrast is not given after blunt abdominal trauma when doing CT imaging because several studies indicated omitting oral contrast had saved costs and time and reduced risk of aspiration in this high-risk population. There is a lack of universally accepted guidelines regarding the use of oral contrast. Decisions of whether to use positive or neutral contrast agents vary per institution and based on personal preferences.

Educational Goals / Teaching Points
• Types of oral contrasts. • Benefits of performing CT imaging without Oral Contrast. • Arguments in Favor of Routine Use of Oral Contrast • ACR Appropriateness Criteria – Guidelines on Oral Contrast Use • Describe indications for appropriate use of positive oral contrast agents and when their use is inappropriate. • Identify indications for appropriate use of neutral oral contrast agents and when their purpose is incompatible.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
• CT abdomen • Positive oral contrast identifies different imaging findings from neutral contrast agents • Pathophysiologic issues to be discussed include GI bleed, extraluminal tumors/hematomas, cancer staging, fistulae, abscesses, leaks, Crohn’s disease, blunt abdominal trauma

Conclusion
Routine use of oral contrast in abdominopelvic CT imaging has conventionally been advocated but remains contentious in the modern era. There is limited utility of using oral contrast in the setting of blunt trauma or acute non-traumatic abdominal pain. ACR appropriateness criteria can give acceptable guidelines to the clinician for when to order a CT with oral contrast. Nevertheless, use of oral contrast may increase diagnostic accuracy in certain circumstances. Radiologists should also be aware of indications where use of oral contrast can impact patient care and accurate diagnosis.