A pseudoaneurysm, or false aneurysm, is a serious complication involving an artery. It occurs when the wall of an artery is injured, causing blood to leak outside the vessel. The escaping blood collects in the adjacent soft tissue, forming a pulsating hematoma that remains connected to the main arterial flow. Unlike other vessel abnormalities, the wall of a pseudoaneurysm is composed entirely of clotted blood and surrounding fascia, not the structural layers of the original artery. This lack of a true vessel wall makes the sac inherently unstable, creating a risk for expansion or rupture.
Understanding the Pseudoaneurysm
The structure of a healthy artery is composed of three distinct layers: the tunica intima, tunica media, and tunica adventitia. The intima is the smooth inner lining, the media provides elasticity and structural support, and the adventitia anchors the vessel.
A true aneurysm involves a localized dilation where all three layers remain intact, though weakened. In contrast, a pseudoaneurysm results from a complete tear through all three arterial wall layers. This full-thickness defect allows blood to escape the high-pressure artery, contained only by the surrounding tissues or fascia. A pseudoaneurysm is essentially a contained hematoma that retains continuous communication with the arterial lumen through a narrow channel, or neck.
Primary Causes and Common Locations
Pseudoaneurysms are most frequently iatrogenic, meaning they are caused by a medical procedure. The primary cause is vascular access, particularly procedures like cardiac catheterization, angiography, or stent placement. If the puncture site, known as the arteriotomy, fails to seal completely, arterial blood leaks into the surrounding tissues and forms the false aneurysm.
The risk of this complication increases with the use of larger sheath sizes, inadequate compression after sheath removal, or when a patient is receiving anticoagulant medication. The most common location for this injury is the common femoral artery in the groin, due to its frequent use for access. Other sites include the brachial artery, the radial artery, and arteries in the neck. Trauma, such as penetrating injuries like stab or gunshot wounds, or blunt force trauma, is a less common cause.
Clinical Presentation and Diagnostic Methods
A patient presenting with a pseudoaneurysm often reports a localized, painful swelling at the site of a recent vascular procedure or injury. The mass is typically pulsatile, throbbing in rhythm with the heartbeat, which is a key physical sign of arterial connection. A healthcare provider listening over the mass may also hear an abnormal whooshing sound, called a bruit, caused by the turbulent blood flow within the sac.
The gold standard for confirming the condition is a Duplex Ultrasound, which uses sound waves to visualize blood flow. This specialized ultrasound accurately measures the size of the pseudoaneurysm and identifies the narrow channel, or neck, connecting the sac to the parent artery. Color Doppler imaging reveals a distinctive swirling pattern of blood flow within the sac, often called the “Yin-Yang sign.” A pulsed spectral Doppler tracing across the neck demonstrates a characteristic “to-and-fro” flow waveform, confirming the bidirectional movement of blood.
Treatment Strategies
Treatment for a pseudoaneurysm is determined by its size, location, and whether it is causing symptoms or expanding rapidly. Very small, stable pseudoaneurysms, particularly those under two centimeters, may be managed conservatively with observation and repeat ultrasound surveillance. These small lesions frequently clot and resolve spontaneously, especially in patients who are not taking blood-thinning medications.
For larger or symptomatic lesions, minimally invasive interventional techniques are the first-line treatment approach. One option is ultrasound-guided compression, where an ultrasound probe applies continuous, firm pressure to the neck of the pseudoaneurysm to encourage clotting. A more common method is ultrasound-guided thrombin injection, which involves precisely injecting the clotting agent thrombin directly into the sac. The thrombin rapidly causes the blood within the sac to clot, sealing the leak and disconnecting it from the artery.
Surgical repair is reserved for cases where minimally invasive treatments have failed, or for complicated lesions that are expanding quickly, infected, or causing pressure on nearby nerves. During surgical intervention, the artery is exposed, and the neck of the pseudoaneurysm is repaired directly, often through a patch repair or simple suture ligation. The goal of any treatment is to seal the arterial defect and prevent rupture.