High-attenuation crescent sign

Radiological sign indicating aortic aneurysm rupture

High-attenuation crescent sign
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Synonyms	N/A
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Specialty	N/A
Symptoms
Complications	Aortic aneurysm rupture
Onset
Duration
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Causes
Risks
Diagnosis	Computed tomography
Differential diagnosis
Prevention	N/A
Treatment
Medication	N/A
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The high-attenuation crescent sign is a radiological finding observed on computed tomography (CT) scans, indicative of impending or active rupture of an aortic aneurysm. This sign is characterized by a crescent-shaped area of increased attenuation within the wall of the aneurysm, which represents acute hemorrhage into the aneurysmal wall.

Pathophysiology

The high-attenuation crescent sign occurs when there is bleeding into the wall of an aortic aneurysm. This bleeding is due to the rupture of the vasa vasorum, small blood vessels that supply the wall of the aorta. The presence of blood within the wall increases the attenuation on CT imaging, appearing as a crescent-shaped hyperdense area. This finding is critical as it suggests that the aneurysm is at high risk of rupture, which is a life-threatening emergency.

Clinical Significance

The detection of the high-attenuation crescent sign on a CT scan is a significant finding that requires urgent medical attention. It is often associated with symptoms such as sudden onset of severe abdominal or back pain, hypotension, and shock, which are indicative of aortic rupture. Early identification of this sign can lead to prompt surgical intervention, potentially saving the patient's life.

Diagnosis

The high-attenuation crescent sign is best visualized on non-contrast CT scans of the abdomen. It appears as a hyperdense crescent within the wall of the aneurysm, contrasting with the lower attenuation of the surrounding tissues. Radiologists play a crucial role in identifying this sign and alerting the clinical team to the potential for aneurysm rupture.

Management

Once the high-attenuation crescent sign is identified, the management typically involves urgent surgical consultation. The standard treatment for aortic aneurysm rupture is surgical repair, which may involve open surgery or endovascular aneurysm repair (EVAR), depending on the patient's condition and the location of the aneurysm.

Prognosis

The prognosis for patients with a high-attenuation crescent sign depends on the timeliness of diagnosis and intervention. Without treatment, the risk of rupture and subsequent mortality is high. However, with prompt surgical intervention, the outcomes can be significantly improved.

Also see

• Aortic aneurysm
• Aortic dissection
• Endovascular aneurysm repair
• Computed tomography