A 76-year-old man presented to the emergency room (ER) with acute onset of coolness, pain, and pallor of the left lower extremity. The patient had a history of hypertension and hypercholesterolemia as well as tobacco use in the past. He denied a history of claudication and had no symptoms related to the right leg. Motor and sensory functions of the left foot were mildly diminished. Femoral pulses were palpable bilaterally, but there were no palpable or Doppler signals distally on the left side, and a prominent right popliteal pulse was noted. The patient was suspected to have an acutely thrombosed left popliteal artery aneurysm.

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  Femoral and popliteal artery aneurysms are second only to aortic aneurysms in occurrence. Popliteal aneurysms account for over 70% of all peripheral aneurysms.

  
  
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  Incidence increases with advancing age and is higher in males.

  
  
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  Associated with arteriomegaly.

  
  
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  Up to 50% of patients will be found to have an abdominal aortic aneurysm (AAA).

  
  
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  Bilateral aneurysmal degeneration is common (Figure 33-1).

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  Pathogenesis of these aneurysms is believed to be primarily atherosclerotic.

  
  
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  Genetics and inflammation with enzymatic degradation of the elastin and collagen in the vessel wall are also believed to play a role.

  
  
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  Rarely popliteal artery entrapment syndrome can result in repetitive trauma and subsequent development of a popliteal artery aneurysm.

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  In an elderly patient, especially male, presenting to the ER with a sudden ischemic lower extremity, the diagnosis should be entertained; however, if the aneurysm is thrombosed a prominent popliteal pulse may not be appreciated on examination.

  
  
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  Aneurysms of the femoral artery usually affect the common femoral artery but can rarely be isolated to the superficial femoral or profunda femoral arteries. Typically, femoral artery aneurysms are asymptomatic. Large femoral artery aneurysms can result in femoral vein compression and leg edema and pain or paresthesias caused by nerve compression. Although rupture is rare, thrombus within the aneurysm can result in distal embolization or thrombosis.

  
  
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  With popliteal artery aneurysms, symptoms resulting from local compression and rupture are rare. Over 50% of patients with these aneurysms present with acute limb ischemia (Figure 33-2).^1,2

  
  
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  Occurrence of symptoms is correlated with size (>2 cm in diameter) and the presence of thrombus.

  
  
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  Asymptomatic patients may have already had distal emboli that can progressively occlude the outflow tibial vessels but not necessarily result in acute ischemia.

  
  
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  Symptoms of chronic ischemia include claudication and atheroemboli to the digits. Pain can occur from local nerve compression, rupture, or acute venous thrombosis, all of which are relatively rare.²