Pseudoaneurysm: Causes, Symptoms, and Treatment Options

A pseudoaneurysm is not a true aneurysm but a contained leak of blood from a damaged artery. Where a true aneurysm involves a ballooning of all three layers of the blood vessel wall, a pseudoaneurysm forms when blood escapes through a hole in the artery and pools outside it, held in place only by the outer tissue and surrounding structures.¹ That distinction matters because a pseudoaneurysm is structurally weaker and more prone to rupture. The causes range from cardiac catheterization procedures and trauma to complications of diseases like pancreatitis, and treatment has shifted considerably over the past two decades from open surgery toward less invasive techniques.

How a Pseudoaneurysm Forms

To picture what happens, imagine a garden hose with a small puncture. Water sprays out and, if something presses against it, forms a bulging pocket. In an artery, a break in the vessel wall allows blood to push outward with each heartbeat, creating a pulsating blood-filled sac. The sac stays connected to the artery through a narrow channel, sometimes called the “neck.” Blood flows into the sac during each heartbeat and partially back into the artery between beats, producing a characteristic back-and-forth flow pattern that doctors use to identify the problem on ultrasound.²

The sac itself is not lined by normal artery tissue. It is essentially a walled-off blood clot and loose connective tissue surrounding a pocket of flowing blood. This is why pseudoaneurysms carry a real risk of rupture, especially as they grow: the “wall” is not engineered to contain arterial pressure the way a true artery is.

What Causes Them

The single most common cause is medical procedures that involve puncturing an artery, particularly cardiac catheterizations performed through the femoral artery in the groin. In one large study, pseudoaneurysms requiring surgical repair occurred in roughly 1% of diagnostic catheterizations and nearly 5% of interventional cardiac procedures.³ A separate high-volume center found an overall rate of about 0.4% across more than 22,000 patients, though the rate climbed to roughly 3% in patients undergoing transcatheter aortic valve procedures, which use larger access devices.⁴

Several patient factors increase the risk after catheterization:

High blood pressure: Hypertension has been independently linked to pseudoaneurysm formation in multiple studies, likely because sustained arterial pressure works against the puncture site’s ability to seal.³
Anticoagulation: Blood-thinning medications, particularly warfarin, impair clot formation at the puncture site. Warfarin use was a significant independent predictor of pseudoaneurysm development in patients undergoing atrial fibrillation ablation.⁵
Larger catheter size: Using sheaths of 7 French or greater more than doubled the odds of pseudoaneurysm compared with smaller devices.³
Higher body mass: Obesity makes it harder to apply effective pressure to the puncture site afterward, and patients with a BMI of 28 or above had roughly twice the odds of developing this complication.³
Blood counts and clotting markers: Low red blood cell counts and elevated INR (a measure of how slowly blood clots) were associated with higher pseudoaneurysm rates, and the interaction between these two factors was particularly strong.⁴

Beyond catheterization, trauma is another well-recognized cause. Blunt injuries account for the majority of traumatic pseudoaneurysms, with the splenic, pelvic, and liver arteries being the most commonly affected sites. In a series of 35 trauma patients treated with endovascular techniques, blunt trauma was responsible in about 89% of cases, and roughly three-quarters of the pseudoaneurysms were identified within 24 hours of injury.⁶ Penetrating wounds, stab injuries, and even bone abnormalities can also damage artery walls enough to produce a pseudoaneurysm.

Pseudoaneurysms Caused by Disease

Not all pseudoaneurysms trace back to a needle or a car accident. Pancreatitis, especially the severe necrotizing form, can erode into nearby arteries. Pancreatic enzymes that leak from the inflamed gland essentially digest the wall of any adjacent blood vessel, a process sometimes called “autodigestion.”⁷ The splenic artery is the most commonly affected, followed by the gastroduodenal artery.⁸

These visceral pseudoaneurysms are particularly dangerous. In one series of patients with necrotizing pancreatitis, about 4% developed a pseudoaneurysm, and the mortality rate attributable to bleeding from these lesions was 14%.⁸ Other reports put the overall mortality from ruptured pancreatitis-related pseudoaneurysms even higher, in the range of 34 to 52%, which is several times the rate seen in pseudoaneurysms from other causes.⁷ The warning signs can be subtle: worsening abdominal pain with a “crescendo” quality, or bleeding seen from surgical drains or the gastrointestinal tract.

The heart itself can also be affected. After a heart attack, the dead muscle tissue can rupture, and if the surrounding pericardium contains the breach, a left ventricular pseudoaneurysm forms. This is rare but carries an extremely high mortality rate if it goes undetected, because the thin pericardial wall is all that stands between the contained rupture and fatal hemorrhage.⁹

Symptoms and Diagnosis

Pseudoaneurysms in the arms or legs typically present as a painful, pulsating swelling near the site of a recent procedure or injury. In one review of extremity pseudoaneurysms, painful swelling was the most common physical finding, showing up in about half of cases.¹⁰ You might feel a rhythmic throbbing at the site, and the area can develop bruising or a visible lump. If the pseudoaneurysm presses on a nearby nerve, numbness, tingling, or weakness in the affected limb can follow.

In deeper locations, like the abdomen or the heart, symptoms are far less obvious. A visceral pseudoaneurysm may announce itself only through unexplained drops in blood counts, blood in the stool, or vague abdominal pain that gets progressively worse. Left ventricular pseudoaneurysms are notoriously difficult to diagnose clinically because their presentation overlaps with many other cardiac problems.⁹

Duplex ultrasound is typically the first-line diagnostic tool for suspected pseudoaneurysms in the limbs. The key finding is a “to-and-fro” waveform on Doppler, representing blood swirling into the sac during systole and back toward the artery during diastole. Ultrasound can also reveal how much of the sac has clotted, the size of the neck connecting it to the artery, and whether blood flow in the distal limb is compromised.² For pseudoaneurysms in deeper locations, CT angiography is the standard imaging method, offering a detailed map of the sac, its feeding vessel, and the surrounding anatomy.

When Treatment Can Wait

Small pseudoaneurysms sometimes close on their own. Blood clots gradually fill the sac, and the communication with the artery seals off. This is most likely when the pseudoaneurysm is small and the patient is not on blood thinners. One commonly used threshold for observation is a diameter under 2 cm: in a 10-year surgical series, pseudoaneurysms below that size were managed without surgery and followed with regular ultrasound.¹¹

The decision to intervene rather than watch depends on several factors. Indications for prompt treatment include a pseudoaneurysm larger than 3 cm, expansion on follow-up imaging, enlarging hematoma, severe pain, signs of nerve compression, infection at the site, limb ischemia, or the need for ongoing anticoagulation therapy.¹² If none of those flags are present, a period of close observation with serial ultrasound is reasonable for smaller lesions.

Ultrasound-Guided Thrombin Injection

For pseudoaneurysms that need treatment but are not surgical emergencies, ultrasound-guided thrombin injection has become the go-to approach. A doctor inserts a needle into the sac under real-time ultrasound guidance and injects a small amount of thrombin, a protein that triggers clot formation almost instantly. In an early landmark series of 70 patients, the technique succeeded in 94% of cases, with clotting occurring within seconds of injection.¹³ A larger study of 240 patients reported similar primary success rates, around 94% overall, and a secondary success rate of nearly 100% when a second injection was performed for initial failures.¹⁴

Compared with the older technique of ultrasound-guided compression, in which a probe is pressed firmly against the pseudoaneurysm neck for 20 to 60 minutes to force clotting, thrombin injection is faster and far more effective. A randomized trial found thrombin injection thrombosed 100% of pseudoaneurysms within 24 hours, versus only 13% for compression.¹⁵ Another comparative study reported a success rate of 96% for thrombin injection versus 74% for compression, with a mean thrombosis time of six seconds for thrombin compared with over 40 minutes for compression.¹⁶ Compression is also substantially more painful for the patient and requires sedation in many cases.

Thrombin injection is not without risks. The main concern is that thrombin can escape from the sac into the parent artery and cause downstream clotting. In one study of over 350 patients, micro-embolization occurred in about 15% of cases, though none of these resulted in significant limb-threatening blockage.¹⁷ The risk was highest when the channel connecting the sac to the artery was very short, less than about 2 mm, because there is less distance to buffer the thrombin from the bloodstream. Repeated injections also increased the risk. A narrow-necked pseudoaneurysm with a longer channel is the ideal candidate for this technique.

Even patients on anticoagulation, who were historically considered poor candidates for clotting-based treatments, can be treated successfully. One study found that anticoagulant use did not hinder thrombosis with thrombin injection.¹³ The technique has also been extended beyond the groin to pseudoaneurysms in other locations, with one series reporting successful treatment in all cases and no recurrences over an average follow-up of about five months.¹⁸

Endovascular Repair

When a pseudoaneurysm sits in a location where thrombin injection is impractical or too risky, or when the lesion is large and complex, endovascular techniques offer another minimally invasive option. These procedures are performed by threading a catheter through the arteries to the site of the pseudoaneurysm, usually from a groin or arm puncture site.

The specific technique depends on the anatomy of the pseudoaneurysm, particularly the width of its neck. Narrow-necked pseudoaneurysms can be treated by packing the sac with metal coils, which promote clotting within the sac while leaving the parent artery open. For wide-necked pseudoaneurysms, a covered stent can be placed across the neck, effectively patching the hole in the artery wall from the inside and restoring normal flow.¹⁹ In some cases, glue-like substances are used alongside or instead of coils to fill the sac.

These approaches work well in the visceral arteries. In a series of 40 patients with aneurysms and pseudoaneurysms of the abdominal arteries treated with covered stent-grafts, overall technical success was 96% and clinical success was 84%, with perfect outcomes in elective (non-emergency) cases.²⁰ Endovascular embolization has become the first-line treatment for pancreatitis-related pseudoaneurysms over the past two decades, with primary technical success around 93% in reported series and the ability to treat patients who are too sick for open surgery.²¹ In one institutional experience, 89% of pseudoaneurysms complicating necrotizing pancreatitis were handled with percutaneous embolization alone, with only a small minority requiring surgery afterward.⁸

Covered stents have also been used for giant or life-threatening pseudoaneurysms in locations where simply blocking the artery would cause organ damage. In one case of a large hepatic artery pseudoaneurysm, implanting two covered stents excluded the leak while keeping the liver’s blood supply intact, rapidly relieving the patient’s symptoms.²²

When Surgery Is Still Necessary

Open surgery used to be the default treatment for all pseudoaneurysms, but its role has narrowed as less invasive methods have proven effective. Surgery remains the right choice in several specific situations: when the pseudoaneurysm is infected, when there is active limb ischemia, when soft tissue around the sac is severely damaged, or when nerve compression is causing paralysis or significant weakness.²³ It is also warranted when less invasive treatments have failed, when the pseudoaneurysm is rapidly expanding, or when the patient needs another surgical procedure at the same time.¹²

The operation typically involves opening the area around the pseudoaneurysm, evacuating the collected blood, and directly repairing the hole in the artery. In a 10-year series, primary surgical repair was safe and effective for femoral pseudoaneurysms of 2 cm or larger.¹¹ Though recovery is longer and the complication rate is higher than with thrombin injection or endovascular repair, surgery offers the most definitive fix when the anatomy or clinical situation demands it.

Prevention After Catheterization

Since the majority of pseudoaneurysms arise from arterial catheterization, preventing them at the puncture site is a focus of ongoing research. After a catheter is removed, the standard approach has been to apply firm manual pressure to the groin for 15 to 30 minutes and then keep the patient lying flat for several hours. Vascular closure devices, which mechanically seal the puncture site, were developed partly to reduce this complication.

A Cochrane systematic review found that collagen-based closure devices modestly reduced pseudoaneurysm rates compared with manual compression, cutting the odds by about 26%. However, metal clip-based and suture-based closure devices did not show a statistically significant advantage over compression alone.²⁴ This means that while closure devices can help, they are not a guaranteed solution, and proper technique during the procedure itself, including accurate puncture of the common femoral artery and avoidance of the superficial or deep branches, remains the most important factor.

Other practical measures include using the smallest catheter size adequate for the procedure, managing blood pressure before and after catheterization, and being especially careful with anticoagulated patients. The finding that busy procedure rooms with high daily case volumes were associated with higher pseudoaneurysm rates suggests that time pressure and potentially less meticulous post-procedure compression also play a role.³

Pseudoaneurysms in Children

Pseudoaneurysms are uncommon in adults and rarer still in children, but they do occur, most often after an arterial line placement or catheterization procedure.²⁵ Diagnosis can be especially tricky in pediatric patients because the presentation may be substantially delayed after the initial injury, and the pseudoaneurysm may appear in an unexpected location.

Treatment in children mirrors the adult approach, with thrombin injection used successfully even in young patients. Case reports describe successful ultrasound-guided thrombin injection in children with femoral, epigastric, and tibial artery pseudoaneurysms.²⁶ For pseudoaneurysms in more complex locations, such as the neck arteries, endovascular techniques including stent grafts and parent vessel occlusion have been used with good results in small pediatric series.²⁷ The causes in children can be more varied, including infection and congenital bone conditions, in addition to the procedural injuries that dominate in adults.

The Radial Artery Shift and Changing Landscape

One significant development worth noting is the increasing use of the radial artery in the wrist, rather than the femoral artery in the groin, for cardiac catheterization. The radial artery is smaller, more superficial, and far easier to compress after a procedure. Pseudoaneurysm rates after radial access are a fraction of those seen with femoral access, which is one reason many interventional cardiologists have shifted their practice over the past decade. This trend has likely reduced the overall number of catheterization-related pseudoaneurysms, though femoral access remains necessary for certain procedures that require larger catheters or specific angles of approach.

For patients facing a catheterization procedure, it is worth asking whether radial access is an option. Not every procedure can be done from the wrist, and not every patient’s anatomy is suitable, but when it is feasible, the trade-off in vascular complications is clearly favorable. For those who do develop a groin pseudoaneurysm after femoral access, the reassuring news is that the condition is well-understood, detectable with a bedside ultrasound, and treatable in most cases without major surgery.

1
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PubMed Central. Visceral artery pseudoaneurysm in necrotizing pancreatitis: incidence and outcomes
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PubMed. Postcatheterization pseudoaneurysm: results of US-guided percutaneous thrombin injection in 240 patients
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21
PLoS ONE. Endovascular management of pancreatitis-related pseudoaneurysms: A review of techniques
22
PubMed Central. Endovascular repair with covered stent for a giant hepatic artery pseudoaneurysm: a case report and literature review
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PubMed Central. Iatrogenic Deep Femoral Artery Pseudoaneurysm Causing Quadriceps Paralysis: An Indication for Open Surgery in an Endovascular Era
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