False aneurysm

A false aneurysm (also known as a pseudoaneurysm), is when there is a breach in the vessel wall such that blood leaks through the wall but is contained by the adventitia or surrounding perivascular soft tissue. A direct communication of blood flow exists between the vessel lumen and the aneurysm lumen through the hole in the vessel wall. The risk of rupture is higher than that of a true aneurysm of comparable size due to poor support of the aneurysm wall and thus false aneurysms generally require treatment.

Pathology

Causes

• trauma (dissection or laceration)
• iatrogenic (dissection, laceration or puncture), e.g. arterial catheterisation (accounts for most cases in this category ⁴ ), biopsy, surgery
• spontaneous dissection
• fibromuscular dysplasia (dissection)
• mycotic aneurysm (inflammatory digestion of the vessel wall)
• myocardial infarction (left ventricular false aneurysm)
• regional inflammatory process
  • acute pancreatitis
  • chronic pancreatitis
• vessel injury / erosion due to a tumour : relatively uncommon
• vasculitides ⁴
  • Behcet syndrome
  • giant cell arteritis
  • Takayasu arteritis
  • systemic lupus erythematosus
  • polyarteritis nodosa
• penetrating atherosclerotic ulcer

Location

They can involve any arterial segment or even a cardiac chamber. Examples include

• femoral artery pseudoaneurysm : relatively common site due to femoral punctures
• carotid artery pseudoaneurysm
• visceral arterial pseudoaneurysm
• peripheral arterial (limb) pseudoaneurysm
• left ventricular pseudoaneurysm
• brachiocephalic artery pseudoaneurysm

Radiographic features

Some of the imaging features may be dependant on location

Ultrasound

Due to the turbulent forward and backward flow, a characteristic yin-yang sign may be seen on colour flow while a "to and fro" pattern may be seen with pulsed Doppler.