What is the difference between Computed Tomography (CT) enterography and Computed Tomography (CT) angiography?

Difference Between CT Enterography and CT Angiography

CT enterography and CT angiography are fundamentally different imaging techniques: CT enterography requires oral contrast to distend the small bowel for evaluating bowel wall pathology, while CT angiography uses timed IV contrast with 3D vascular reconstruction to visualize blood vessels and detect active bleeding. 1

CT Angiography (CTA) Definition and Technical Requirements

CTA is defined by three essential elements that distinguish it from standard contrast CT: 1

• Timing: Thin-section CT acquisition timed to coincide with peak arterial or venous enhancement 1
• Reconstructions/reformats: Multiplanar reformations of the volumetric dataset 1
• 3D renderings: Three-dimensional vascular reconstructions (this is the required element that distinguishes CTA from standard contrast CT) 1

Clinical capabilities of CTA include: 1

• Detection of active bleeding at rates as slow as 0.3 mL/min 1
• Sensitivity of 81% in high-risk patients requiring significant transfusion, decreasing to 50% in slow bleeds 1
• Serves as a triage tool for identifying patients who may benefit from interventional procedures 1

CT Enterography Definition and Technical Requirements

CT enterography requires specific technical elements distinct from CTA: 1

• Oral contrast: Negative contrast material ingested in volumes sufficient to distend the small bowel 1
• IV contrast: Intravenous contrast is required 1
• Standard technique: Typically uses a uniphasic technique, though multiphasic techniques (mimicking CTA parameters) can be performed for gastrointestinal bleeding evaluation 1

Clinical applications of CT enterography include: 1, 2, 3

• Primary imaging for inflammatory bowel disease (particularly Crohn disease) 2
• Detection of small bowel neoplasms 2
• Evaluation of mesenteric ischemia 2
• Investigation of occult gastrointestinal bleeding in endoscopy-negative patients 1
• Differentiation between active and fibrotic bowel strictures 2

Key Clinical Distinctions

For acute gastrointestinal bleeding evaluation: 1

• CTA is preferred for detecting active bleeding because it can identify extravasation of contrast into the bowel lumen 1
• CT enterography has limited utility for acute bleeding detection due to dilution of blood by oral contrast material 1
• Studies show no significant clinical difference in accuracy between CTA and CT enterography for endoscopy-negative gastrointestinal bleeding 1

For small bowel pathology evaluation: 1, 2

• CT enterography provides superior visualization of bowel wall thickness, enhancement patterns, and luminal abnormalities 2
• CT enterography allows assessment of the entire bowel wall thickness and extraenteric involvement 2
• Sensitivity for occult bleeding etiology varies widely (25-88% depending on the study) compared to capsule endoscopy 1

Important Caveats

Limitations of CT enterography include: 4

• Cannot demonstrate isolated mucosal abnormalities such as aphthous ulcers 4
• Inadequate small bowel distention from poor oral contrast ingestion is the most common technical pitfall 4
• Opaque intraluminal debris can create interpretive challenges, especially during multiphasic protocols 4

Limitations of CTA include: 1

• Intermittent or slow bleeding can be missed, leading to false-negatives 1
• Requires active bleeding at the time of imaging for detection 1