What does pseudoaneurysm look like?

What Does a Pseudoaneurysm Look Like?

A pseudoaneurysm, sometimes called a "false aneurysm," doesn't look much like a normal artery bulge—because it’s not. Unlike a true aneurysm, where all three layers of the arterial wall stretch outward together, a pseudoaneurysm forms when there’s a crack or tear in the inner layers. Blood leaks out slowly, only to be contained by the outermost layer—the tunica adventitia. This creates a sac-like structure that pulses with blood, connected to the artery by a narrow opening.

On imaging, such as an ultrasound or CT scan, a pseudoaneurysm often appears as a round or oval swelling near an artery, usually close to a site of prior trauma, surgery, or catheterization—commonly in the femoral artery after a heart procedure. The blood inside may swirl in a characteristic “to-and-fro” pattern, visible on Doppler ultrasound, which helps doctors confirm the diagnosis.

While it might look similar to a regular aneurysm from the outside, the structural weakness of a pseudoaneurysm makes it more prone to rupture or continued expansion. That’s why it’s considered dangerous if left untreated. The wall of a pseudoaneurysm lacks the strength of a normal vessel wall since it's missing the muscular and elastic layers—the body, in a way, is patching a leak with whatever is left.

Patients may notice a pulsating lump, feel pain, or even develop swelling in the area. Sometimes, there are no symptoms at all. Early detection and treatment—whether through ultrasound-guided compression, thrombin injection, or surgery—can prevent complications. Understanding what a pseudoaneurysm looks like, both inside the body and on scans, is key to catching it before it causes serious harm.