Can computed tomography (CT) enterography be performed with oral contrast?

CT Enterography with Oral Contrast: Technique and Recommendations

Yes, CT enterography should be performed with oral contrast, specifically neutral oral contrast agents, to optimize bowel distention and visualization of bowel wall pathology. 1, 2

Oral Contrast in CT Enterography: Key Points

• CT enterography requires neutral oral contrast (not positive contrast) to properly visualize bowel wall enhancement and inflammation 1
• Large volumes (1300-1800 cc) of neutral contrast are administered over a specific time period (30-60 minutes) with imaging conducted at 60 minutes 1
• Neutral contrast agents have attenuation values near that of water, which allows for better evaluation of mucosal enhancement 2

Why Neutral Oral Contrast is Essential

Neutral oral contrast agents are critical for CT enterography for several reasons:

• Improved visualization: Without adequate bowel distention from oral contrast, peristalsis or collapse can obscure or mimic disease 1
• Enhanced detection: Neutral contrast allows evaluation of mucosal enhancement by detecting subtle inflammation that would be obscured by positive contrast agents 1, 2
• Better diagnostic accuracy: When using neutral contrast, CT enterography has excellent diagnostic performance with sensitivity for Crohn's disease ranging from 75% to 90% and specificity >90% 1

Types of Neutral Oral Contrast Agents

Several neutral contrast agents can be used for CT enterography:

• Water (simplest option, but may be absorbed in the ileum) 1, 3
• 3.8% milk (superior to water for bowel distention, particularly in the jejunum, ileum, and terminal ileum) 3
• 0.1% gastrografin (dilute positive contrast) 3
• Other formulations designed to decrease absorption in the ileum 1

Technical Considerations

For optimal CT enterography results:

• Volume: 1300-1800 cc of neutral oral contrast 1
• Timing: Administered over 30-60 minutes before imaging 1
• Patient positioning: Supine or sitting positions during oral contrast administration provide better ileal distention than right decubitus position 4
• Additional techniques: Thin collimation, multiplanar reconstruction, and IV contrast administration maximize visualization of inflammatory changes 1

Clinical Applications

CT enterography with neutral oral contrast is particularly valuable for:

• Evaluation of inflammatory bowel disease, especially Crohn's disease 1, 5, 6
• Detection of small bowel bleeding 2
• Assessment of small bowel neoplasms 5, 6
• Evaluation of mesenteric ischemia 6
• Differentiation between active and fibrotic bowel strictures 6

Common Pitfalls to Avoid

• Using positive oral contrast (like full-strength barium or gastrografin) which can obscure mucosal enhancement 1, 2
• Insufficient volume of oral contrast leading to inadequate bowel distention 1
• Improper timing between contrast administration and imaging 1
• Not accounting for patient tolerance of large volumes of oral contrast 1

CT enterography with neutral oral contrast has become the preferred imaging modality for evaluating small bowel pathology, particularly in Crohn's disease, due to its ability to visualize the entire thickness of the bowel wall and detect extraenteric involvement 1, 6.