II. Indications

  1. Brisk Gastrointestinal Bleeding obscures source on Colonoscopy
  2. Gastrointestinal Bleeding with a patient too unstable for endoscopy
  3. Acute, high risk Lower Gastrointestinal Bleeding while awaiting preparation for endoscopy

III. Imaging: Three Stage CT (preferred)

  1. First: CT Abdomen and Pelvis WITHOUT IV Contrast (non-contrast CT)
    1. Identify any high density materials (e.g. calcium Antacids) that may be misinterpreted as contrast
  2. Second: CT Angiography WITHOUT Oral Contrast (arterial phase)
    1. Imaging correlates with arterial phase of contrast enhancement
      1. Imaging is performed 60 seconds after IV contrast injection
      2. Localizes active arterial Hemorrhage (contrast extravasation into bowel)
    2. Do not use high density oral or rectal contrast
      1. Oral Contrast obscures bleeding
      2. Oral Contrast not needed for other causes (e.g. Diverticulitis, Ischemic Bowel)
  3. Third: CT Abdomen and Pelvis (venous phase)
    1. CT is again performed 60 seconds after the arterial phase contrast CT
    2. No additional contrast is injected before scan
    3. Correlates with the portal venous phase of CT contrast enhancement
    4. May better characterize venous Hemorrhage that is missed or equivocal on the arterial phased scan

IV. Evaluation

  1. CTA may be test of choice in heavy Lower GI Bleeding in which endoscopy cannot be performed
  2. CTA may direct exploratory laparotomy (identifying source)
  3. PACS imaging density >90 Hounsfield Units (HU) is consistent with blood on CTA

V. Efficacy

  1. CTA can detect bleeding rates down to 0.3 ml/min
    1. False Negatives are more common in intermittent bleeding
  2. Test Sensitivity for Gastrointestinal Bleeding: >79% (contrast with 38% with RBC Scan)
    1. Test Sensitivity increases to 90% in Lower Gastrointestinal Bleeding
    2. He (2017) Eur J Radiol 93:40-5 [PubMed]
  3. CTA localizes the bleeding source in 53% (contrast with 30% for RBC Scan)
  4. CTA without bleeding predicts lower recurrent bleeding rate

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