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Background
CTA is the preferred imaging test for the evaluation of patients suspected to have limb threatening emergency. The widespread use of 64-row multidetector CT technology offers considerable benefits including the ability to generate isotropic data sets of long vascular territories. By demonstrating the extent, location, and type of the disease, CTA aids to determine the appropriate management for patients inflicted by these entities.

Educational Goals / Teaching Points
This exhibit discusses the integration of extremity CTA into the clinical management of acute nontraumatic limb threatening emergencies.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
According to the type of the disease, nontraumatic acute limb threatening conditions can be described as occlusive thromboembolic disease, or nonocclusive infectious limb emergencies. A cute arterial occlusive thromboembolic disease includes thrombosis as the most common cause of acute limb ischemia followed by emboli. Thrombotic occlusions occur in an already diseased artery. Emboli in the other hand occurs in an otherwise normal artery usually due to migration of an embolus from the heart. Acute limb ischemia is an emergency as cell death begins after 4 hrs of total ischemia. Urgent revascularization is therefore necessary to salvage the limb. Extensive deep venous thrombosis can result in limb-threatening emergency as in patients with phlegmasia Cerulea Dolens. When venous gangrene involves the muscular compartment, it may result in increased compartment pressures and a pulse deficit. Emergent thrombectomy is usually required. Infectious limb-threatening emergencies include the dreadful entity of necrotizing fasciitis (NF). Necrotizing fasciitis is a severe acterial disease of sudden onset that spreads rapidly. The most affected areas are the limbs and perineum. Aggressive antibiotics and surgical debridement are usually required. Mycotic aneurysm is another cause of limb threatening emergency where aneurysmal degeneration of the arterial wall results from local infection or a septic embolus. Treatment consists of antibiotic therapy combined with aggressive surgical debridement and vascular reconstruction, as needed.

Conclusion
The importance of radiological imaging in diagnosis of acute, nontraumatic limb threatening emergencies increases continuously. Because of its speed and accuracy, extremity CTA is a useful triage tool that has replaced conventional angiography as the diagnostic tool of choice for these disease entities.