What is the difference between a pseudoaneurysm and an aneurysm?

Difference Between Pseudoaneurysm and Aneurysm

A pseudoaneurysm (false aneurysm) is defined as a dilation of the aorta or other artery due to disruption of all wall layers, which is only contained by the periaortic connective tissue, while a true aneurysm contains all three layers of the vessel wall (intima, media, and adventitia). 1

Key Differences

Anatomical Structure

• True Aneurysm:

  • Contains all three layers of the vessel wall (intima, media, and adventitia)
  • Results from weakening and dilation of the arterial wall
  • Wall integrity is maintained, though stretched and thinned 2

• Pseudoaneurysm:

  • Disruption of all arterial wall layers
  • Blood flow is contained only by surrounding tissues (periarterial connective tissue)
  • Essentially a contained hematoma that communicates with the arterial lumen 1, 2

Etiology

• True Aneurysm:

  • Often related to degenerative processes
  • Associated with atherosclerosis, hypertension, genetic disorders
  • Develops gradually over time

• Pseudoaneurysm:

  • Usually traumatic or iatrogenic in origin
  • Common causes include:
    • Blunt trauma or penetrating injuries
    • Iatrogenic causes (catheter-based interventions, surgery)
    • Infections (mycotic aneurysms)
    • Penetrating ulcers 1

Risk of Rupture

• Pseudoaneurysm:

  • Generally higher risk of rupture
  • Fatal rupture occurs when pressure exceeds the maximally tolerated wall tension of surrounding tissue
  • Requires intervention regardless of size if feasible 1

• True Aneurysm:

  • Risk of rupture typically correlates with size
  • Management often depends on size, location, and growth rate

Clinical Implications

Management Approach

• Pseudoaneurysm:

  • Interventional or open surgical interventions are always indicated if feasible, regardless of size 1
  • In dialysis access, pseudoaneurysms should be treated by resection and insertion of an interposition graft if they:
    • Show rapid expansion
    • Exceed twice the diameter of the graft
    • Threaten viability of overlying skin
    • Are infected 1
  • Needle insertion into pseudoaneurysms should be avoided due to hemorrhage risk 1

• True Aneurysm:

  • Management often depends on size and location
  • In AV fistulae, true aneurysms require surgical intervention only when they involve the arterial anastomosis 1
  • Venipuncture should avoid aneurysmal areas due to difficult hemostasis 1

Diagnostic Approach

• Both conditions benefit from imaging with:
  • Duplex ultrasound (first-line for suspected pseudoaneurysm)
  • CT angiography (excellent for both conditions)
  • MRI (excellent for both conditions) 1

Special Considerations

Dialysis Access-Related Aneurysms/Pseudoaneurysms

• Should be checked at each dialysis session by knowledgeable care providers 1
• Patients should be educated on emergency procedures for aneurysm rupture 1
• Surgical assessment is needed when clinical findings suggest risk of complications (associated symptoms or skin breakdown) 1
• Emergent surgical assessment and treatment is required for complications such as erosion or hemorrhage 1

Treatment Options

• For pseudoaneurysms:

  • Small (<2.0 cm) asymptomatic pseudoaneurysms may be observed as 61% resolve spontaneously within 7-52 days 3
  • Ultrasound-guided thrombin injection has a high success rate (93%) for larger or symptomatic pseudoaneurysms 3
  • Surgical repair is indicated for persistent or recurrent pseudoaneurysms after non-surgical management 3

• For both conditions in vascular access:

  • Open surgical treatment is the definitive treatment for symptomatic cases 1
  • Covered intraluminal stents may be used as an alternative only in special circumstances 1

Complications

Pseudoaneurysms can lead to:

• Fatal rupture
• Fistula formation
• Compression or erosion of surrounding structures
• In dialysis access, they may expand and rupture, resulting in significant blood loss 1

Remember that proper diagnosis and timely intervention, especially for pseudoaneurysms, are crucial for preventing potentially life-threatening complications.