II. Indications
- Brisk Gastrointestinal Bleeding obscures source on Colonoscopy
- Gastrointestinal Bleeding with a patient too unstable for endoscopy
- Acute, high risk Lower Gastrointestinal Bleeding while awaiting preparation for endoscopy
III. Imaging: Three Stage CT (preferred)
- First: CT Abdomen and Pelvis WITHOUT IV Contrast (non-contrast CT)
- Identify any high density materials (e.g. calcium Antacids) that may be misinterpreted as contrast
- Second: CT Angiography WITHOUT Oral Contrast (arterial phase)
- Imaging correlates with arterial phase of contrast enhancement
- Imaging is performed 60 seconds after IV contrast injection
- Localizes active arterial Hemorrhage (contrast extravasation into bowel)
- Do not use high density oral or rectal contrast
- Oral Contrast obscures bleeding
- Oral Contrast not needed for other causes (e.g. Diverticulitis, Ischemic Bowel)
- Imaging correlates with arterial phase of contrast enhancement
- Third: CT Abdomen and Pelvis (venous phase)
- CT is again performed 60 seconds after the arterial phase contrast CT
- No additional contrast is injected before scan
- Correlates with the portal venous phase of CT contrast enhancement
- May better characterize venous Hemorrhage that is missed or equivocal on the arterial phased scan
IV. Evaluation
- CTA may be test of choice in heavy Lower GI Bleeding in which endoscopy cannot be performed
- CTA may direct exploratory laparotomy (identifying source)
- PACS imaging density >90 Hounsfield Units (HU) is consistent with blood on CTA
V. Efficacy
- CTA can detect bleeding rates down to 0.3 ml/min
- False Negatives are more common in intermittent bleeding
- Test Sensitivity for Gastrointestinal Bleeding: >79% (contrast with 38% with RBC Scan)
- CTA localizes the bleeding source in 53% (contrast with 30% for RBC Scan)
- CTA without bleeding predicts lower recurrent bleeding rate
VI. References
- Broder (2022) Crit Dec Emerg Med 31(2): 14-5
- Broder (2024) Crit Dec Emerg Med 38(1): 21-3
- Chan (2015) Cardiovasc Intervent Radiol 28(2): 329-35 [PubMed]
- Feuerstein (2016) AJR Am J Roentgenol 207(3): 578-84 [PubMed]
- Karuppasamy (2021) J Am Coll Radiol 18(5S):S139-52 +PMID: 33958109 [PubMed]
- Kennedy (2010) J Vasc Interv Radiol 21(6):848-55 [PubMed]