Acute Limb Ischaemia

  • Acute limb ischaemia (ALI) defines the suddenness of onset, not severity
  • The severity of ischaemia may be absolute (no blood flow – a white, bloodless limb) or relative (acutely reduced blood flow but some colour, feeling and movement in the foot)
  • The symptoms and signs reflect the underlying cause and dictate the urgency of referral
  • ALI may be primarily due to:
    • Embolus into normal arteries (usually absolute ischaemia)
    • Thrombosis of a popliteal aneurysm (usually absolute ischaemia)
    • Thrombosis of existing disease (usually relative ischaemia)


Signs and Symptoms

  • Pain of sudden onset at rest or walking short distances (calf, thigh or entire limb)
  • Always affects the foot (calf pain with no symptoms in the foot is not typical of ischaemia)
  • Interferes with sleep/ Worse with elevation of the limb / Better with limb dependent

History and Examination


Relating to embolus:

  • Sudden onset of severe limb pain, numbness and paralysis
  • Underlying cause (eg. AF without anticoagulation; limb trauma)

Relating to thrombosis ("thrombosis-in-situ" or "acute on chronic ischaemia"):

  • Known arteriopath / vascular risk factors
  • Pre-existing symptoms of peripheral arterial disease (intermittent claudication)
  • Sudden deterioration in claudication distance / rest pain
  • Known lower limb aneurysm (femoral or popliteal)

Absolute ischaemia

  • The "six P's": Pale (bloodless limb), Painful, Pulseless, Perishing cold, Paraesthaesia, Paralysis
  • Absent pulses on affected side with normal pulses on the other side suggest embolism
  • Atrial fibrillation – commonest cause of embolism
  • Loss of sensation, paralysis and muscle tenderness are signs of advanced ischaemia and need for emergency intervention

Relative ischaemia

  • Symptoms without the features of absolute ischaemia
  • Abnormal pulses in both legs
  • Doppler examination – absent or abnormal flow signals at ankle/foot

Differential Diagnoses

  • Many other causes of leg pain – the symptoms bulleted above are the key to diagnosis
  • DVT causes leg swelling and sometimes blue discoloration, but hand-held Doppler examination shows good arterial flow signals at the foot/ankle

Red Flags

  • Bloodless limb
  • Rest pain and altered sensation


  • Absolute ischaemia: None – Emergency referral
  • Acute onset of relative ischaemia: None – Emergency referral


Absolute ischaemia:

  • Emergency referral to the vascular service
  • Analgesia

Relative ischaemia

  • Risk factors modification:
    • Smoking advice
    • Diabetic review
    • Statin therapy
    • Blood pressure control
    • Antiplatelet therapy
  • Urgent outpatient referral to the vascular service


Referral Criteria

  • Absolute or relative ischaemia of acute onset

Referral Instructions

Absolute ischaemia
  • Immediate via ED or on call general surgical registrar
  • For discussion with a consultant ring switchboard and ask for vascular surgeon of the week
Relative ischaemia
  • Urgent referral to vascular specialist for outpatient appointment
  • e-Referral Service
    • Specialty: Surgery - Vascular
    • Clinic Type: Not otherwise specified
    • Service: DRSS-South Devon & Torbay-Surgery Vascular- Devon CCG -15N

Referral Forms

DRSS referral form

Torbay and South Devon seeking advice form

Supporting Information

Pathway Group

This guideline has been signed off by Alex Rowe for South Devon and Torbay CCG.

Publication date: June 2015


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