Clinical features

These are the six P's:

• Pain - sudden onset, continuous, variable intensity; often at the junction of perfused and ischaemic tissue, usually in one periphery.
  
  
• Paraesthesia - sudden onset, usually in one periphery; may be an altered or a complete absence of sensation.
  
  
• Pallor - periphery is white and may become blue with onset of necrosis. There is poor peripheral capillary return on pressure blanching and the skin may blister. Buerger's test is positive.
  
  
• Perishing cold
  
  
• Pulselessness - foot pulses are absent, and may be undetectable by Doppler ultrasound. Popliteal and femoral pulses may be absent depending on the level of occlusion.
  
  
• Paralysis - indicates extreme ischaemia. The movements of flexion and extension of the ankle and toes are eventually lost.

Involvement of both limbs implies occlusion at the aortic bifurcation.

Clinically, it is often difficult to identify the cause of the ischaemia. An embolus is more likely if the other limb has good peripheral pulses and a normal ankle systolic pressure, or if there is a history of risk factors such as a previous myocardial infarction. Thrombosis is more likely if there is a history of claudication.