CTA GI Bleed (Active Gastrointestinal Hemorrhage)

Indications

• Overt GI bleeding (hematochezia, melena) — localize active hemorrhage
• Hemodynamically significant lower GI bleeding before embolization or surgery
• Obscure GI bleeding after negative or non-localizing endoscopy
• Suspected small bowel bleeding source

Patient prep

• NO oral contrast — positive oral contrast obscures intraluminal extravasation
• Large-bore IV (18 G preferred) for high flow rate
• Do not delay for renal function in hemodynamically significant bleeding; resuscitate concurrently
• Supine, arms up

Contrast

Technique

• Supine, arms up; coverage diaphragm through symphysis pubis, identical range all phases
• Non-contrast first — identifies pre-existing intraluminal hyperdense material (pills, clips, prior contrast) that mimics bleeding
• Late arterial phase for active extravasation; delayed phase confirms (extravasated contrast pools/changes shape)
• 120 kV (100 kV thin patients); thin 1-1.25 mm recon; coronal reformats and thin-slab MIPs
• No oral or rectal contrast

Series / Sequences

Key points

• Active bleeding = intraluminal contrast on arterial phase that is absent on non-contrast and changes/increases on delayed phase — all three phases matter
• CTA detects bleeding rates as low as ~0.3-0.5 mL/min and localizes for targeted angiography/embolization
• Never give positive oral contrast — it makes extravasation undetectable
• A negative CTA during a bleeding pause is common; consider repeat when bleeding recurs, or nuclear tagged-RBC scan for slower intermittent bleeding (see GI Bleed Tagged RBC protocol)

References