CT Abdomen and Pelvis Without Contrast for Bleeding Detection
No, CT abdomen and pelvis without IV contrast is NOT adequate to detect active bleeding and should not be used for this purpose. 1
Why Non-Contrast CT Fails for Active Bleeding Detection
The 2024 ACR Appropriateness Criteria explicitly state there is no significant literature supporting the use of CT abdomen and pelvis without IV contrast for detecting gastrointestinal or intra-abdominal bleeding. 1
What Non-Contrast CT Can and Cannot Do
Non-contrast CT is useful only for:
- Confirming the presence of hematoma (clotted blood) based on high attenuation (40-70 HU for clotted blood) 2, 3
- Identifying a "sentinel clot" that suggests a bleeding site 1
- Rapid exclusion or confirmation of hemorrhage in patients with renal compromise where contrast is contraindicated 1
Non-contrast CT cannot:
- Detect active arterial extravasation (the hallmark of ongoing bleeding) 1
- Distinguish between old and new bleeding sites 1
- Guide interventional therapy effectively 1
The Correct Imaging Study: CTA Without and With IV Contrast
For suspected active bleeding, you must order CT angiography (CTA) of the abdomen and pelvis without and with IV contrast using a multiphasic protocol. 4, 5
Critical Protocol Requirements
The multiphasic CTA protocol achieves 92% sensitivity for detecting GI bleeding and includes: 4
- Non-contrast phase: Identifies baseline high-attenuation material (sentinel clot) that could be mistaken for active bleeding 4, 5
- Arterial phase: Detects active arterial extravasation with sensitivity down to 0.3 mL/min bleeding rate 4, 5
- Portal venous/delayed phase: Captures slower or intermittent bleeding not visible on arterial phase alone 4, 5
Performance Characteristics
CTA demonstrates: 5
- Sensitivity: 79-85%
- Specificity: 92-95%
- Positive predictive value: 86%
- Negative predictive value: 92%
Active hemorrhage appears as extravasated contrast material with attenuation of 85-370 HU (mean 132 HU), significantly higher than clotted blood at 40-70 HU. 2
Common Pitfall to Avoid
Do NOT order "CT abdomen with IV contrast" - this is a standard diagnostic CT that is distinct from CTA and lacks the multiphasic arterial timing necessary to detect active bleeding. 4, 5 The ACR rates standard CT with contrast as "usually not appropriate" (rating 2-3) for bleeding detection. 5
Special Consideration for Epistaxis Context
While your question mentions epistaxis (nosebleed), CT imaging of the abdomen and pelvis is not indicated for epistaxis evaluation. 6, 7
For epistaxis patients on anticoagulants/antiplatelets:
- Coagulation studies are appropriate for patients with anticoagulant use history 6, 7
- Hypertension and anticoagulant therapy are risk factors for severe/recurrent epistaxis 6, 7
- Imaging is not part of routine epistaxis management unless there is concern for concurrent abdominal/pelvic bleeding 6, 7
Retroperitoneal Bleeding Exception
For suspected retroperitoneal hemorrhage specifically, non-contrast CT can be appropriate to expeditiously confirm or exclude bleeding, especially when renal function is compromised or additional contrast load is a concern before potential angiographic intervention. 1 However, CTA remains superior for localization and treatment planning. 1