A pseudoaneurysm, often called a false aneurysm, is a serious vascular condition that arises when an artery wall is breached, allowing blood to leak out under pressure. This escaping blood pools in the surrounding soft tissue, forming a contained sac connected to the main artery. Because this blood-filled pocket is not enclosed by the artery’s own structural layers, it is unstable and carries a risk of expansion or rupture. Prompt recognition and appropriate medical intervention are important for managing this condition and preventing severe complications.
Understanding the Pathology
A pseudoaneurysm is fundamentally different from a true aneurysm, which involves the dilation or bulging of an artery where all three layers of the vessel wall—the intima, media, and adventitia—remain intact. In contrast, a pseudoaneurysm occurs because of a full-thickness breach in the arterial wall, meaning the blood has escaped the vessel confines entirely.
The resulting blood collection is contained only by the surrounding perivascular tissues or a capsule of clotted blood and fibrin. This outer wall is significantly weaker than the robust, three-layered wall of an artery. The pocket of blood maintains a continuous connection, or “neck,” with the artery’s lumen, meaning it is constantly subjected to the high pressure of arterial blood flow. This direct communication distinguishes a pseudoaneurysm from a simple hematoma, a collection of clotted blood with no continuous flow from the vessel.
Why Pseudoaneurysms Form
The primary cause of a pseudoaneurysm is a disruption of the arterial wall integrity, most frequently due to trauma. The most common scenario is an iatrogenic injury, meaning it results from a medical procedure. Procedures requiring arterial access, such as cardiac catheterization, angiography, or other endovascular interventions, are frequently implicated.
During these procedures, a needle or catheter is inserted into an artery, most often the femoral artery in the groin. If the hole created by the access does not seal properly (typically due to insufficient compression afterward), blood can escape and form a pseudoaneurysm. Other medical causes include vascular surgery complications, where the repair or anastomosis site fails, and percutaneous biopsies.
Non-iatrogenic causes often involve blunt or penetrating trauma, such as from a fall, a stab wound, or a gunshot wound, which directly damages an artery. Additionally, certain infections (sometimes referred to as mycotic pseudoaneurysms) can weaken the arterial wall through inflammation and enzymatic digestion, leading to a breach. The risk of forming a pseudoaneurysm is higher in individuals taking anticoagulant medications, as these agents impair the body’s natural clotting mechanisms necessary to seal the puncture site.
Identifying Symptoms and Diagnosis
The clinical presentation often includes distinct, localized symptoms that develop shortly after the arterial injury. The most common finding is a pulsatile mass or lump noticeable beneath the skin near the site of the arterial breach. This mass may be painful or tender, and the area may show signs of swelling or bruising.
A physician may also detect a characteristic turbulent flow sound, known as a bruit, when listening to the mass with a stethoscope. If the expanding mass presses on nearby nerves, the patient might experience numbness or tingling in the limb supplied by the affected artery. Given the potential for rupture, any new pulsatile mass following a medical procedure or trauma warrants immediate medical evaluation.
Diagnosis relies heavily on imaging, with Duplex Ultrasound being the standard initial method because it is non-invasive and highly effective. This test uses sound waves to visualize the blood flow and clearly demonstrates the sac-like structure communicating with the artery. The ultrasound often reveals a distinctive “to-and-fro” or “yin-yang” flow pattern within the sac, confirming the turbulent arterial connection. For more complex cases, Computerized Tomography (CT) angiography or Magnetic Resonance Imaging (MRI) provides detailed anatomical information for surgical planning.
Management and Treatment Options
Treatment for a pseudoaneurysm is determined by its size, location, symptoms, and whether the patient is taking blood-thinning medication. Small, asymptomatic pseudoaneurysms (those less than two to three centimeters in diameter) are often managed with observation, as they may thrombose and resolve spontaneously. Regular ultrasound monitoring is performed to ensure the lesion is not growing.
For larger or symptomatic lesions, minimally invasive, percutaneous techniques are the preferred initial approach. Ultrasound-guided compression was historically an option, involving sustained pressure over the pseudoaneurysm’s neck to encourage clotting. However, it has largely been supplanted by percutaneous thrombin injection, which boasts a higher success rate and is less time-consuming and painful.
During a thrombin injection, the clotting agent thrombin is injected directly into the pseudoaneurysm sac under ultrasound guidance. This quickly causes the blood within the sac to clot, effectively sealing the leak from the artery. If these non-surgical methods fail, or if the pseudoaneurysm is large, rapidly expanding, or infected, surgical repair is necessary. Surgical intervention involves opening the sac and directly repairing the breach in the arterial wall, often using a patch or suture repair.