What are the imaging phases of computed tomography enterography?

CT Enterography Imaging Phases

CT enterography is performed using either a single-phase protocol (enteric or portal venous phase at 50-70 seconds) or a multiphase protocol that includes arterial, enteric/portal venous, and optionally delayed phases to optimize detection of different pathologies. 1

Standard Phase Timing

The imaging phases of CT enterography follow a specific temporal sequence after intravenous contrast administration:

Single-Phase Protocol

• Enteric phase: 50 seconds after contrast injection
• Portal venous phase: 70 seconds after contrast injection
• Either timing is adequate for detecting inflammation and most masses 1

Multiphase Protocol

Multiphase examinations improve detection and characterization of vascular lesions and include 1:

• Late arterial phase: 35 seconds after contrast injection

  • Provides arterial opacification
  • Allows time for contrast extravasation to begin
  • Optimal for detecting Dieulafoy lesions and arterial bleeding sources

• Enteric phase: 50 seconds after contrast injection

  • Peak bowel wall enhancement
  • Best for visualizing inflammatory conditions
  • Optimal for detecting neuroendocrine tumors

• Portal venous phase: 60-70 seconds after contrast injection

  • Good bowel wall enhancement with solid organ evaluation
  • Improved detection of slow venous bleeding

• Delayed phase: 90+ seconds after contrast injection (optional)

  • Allows improved detection of slow venous bleeding
  • Best for detecting slowly bleeding angioectasias

Clinical Application

The choice between single-phase and multiphase depends on clinical indication 1:

• Single-phase is sufficient for suspected inflammatory bowel disease (Crohn's disease) or mass lesions
• Multiphase is superior when evaluating for gastrointestinal bleeding sources, particularly vascular lesions like angioectasias or arteriovenous malformations
• The visualization of abnormalities on multiple phases increases diagnostic confidence 1

Technical Considerations

All protocols require 1, 2:

• Neutral oral contrast: 1.5 L (approximately 900-1350 mL) ingested over 45-60 minutes before scanning to distend the small bowel
• Intravenous contrast: Required to visualize enhancing lesions
• No positive oral contrast: This would obscure hyperenhancing pathology against the bowel lumen

The enteric phase timing (50-70 seconds) represents the period between enteric and portal phases of enhancement, optimizing small bowel wall visualization 2. Research confirms no significant difference in diagnostic accuracy between 40-second and 70-second delays for Crohn's disease evaluation 3, supporting flexibility in phase timing based on institutional protocols.