How to measure:
Formal angiogram considered gold standard
CTA as a diagnostic is near the level of formal angiography (96% sensitive, 95% specific)
US is sensitive for proximal extremity occlusions, but sensitivity markedly falls off distally and is operator dependent
Not useful for diagnosis, but essential for monitoring co-existing conditions and response to anticoagulant therapy. Should include:
CBC
BMP
PT/PTT
Creatine kinase
CBC
BMP
PT/PTT
Creatine kinase
Acute arterial ischemia
Peripheral artery disease
Venous gangrene
Vascular injury
Wet gangrene
Missile embolus
Atheroembolism 
Dry gangrene