Femoral Pseudoaneurysm with Overnight Re-expansion After Initial Improvement
What Is Happening
You are observing the classic behavior of a femoral artery pseudoaneurysm that is actively communicating with the arterial system—the overnight re-expansion from 1.5 cm back to 3 cm indicates ongoing arterial flow into the pseudoaneurysm cavity, and the temporary reduction with manual pressure confirms that this is a compressible, blood-filled structure connected to the femoral artery through a persistent neck defect. 1, 2
Pathophysiology of the Re-expansion
The pseudoaneurysm forms when the arterial puncture site from catheterization fails to seal completely, creating a persistent communication (neck) between the femoral artery and a cavity in the surrounding soft tissue that fills with pulsatile blood. 3, 4
The "to-and-fro" Doppler flow pattern on ultrasound confirms that blood flows out of the artery into the pseudoaneurysm during systole and partially back through the neck during diastole—this continuous communication explains why the mass refills after compression is released. 1, 4
The overnight increase in size from 1.5 cm to 3 cm indicates that the neck remains patent and the pseudoaneurysm is actively enlarging; all untreated pseudoaneurysms inevitably enlarge over time, increasing rupture risk as they expand. 2
The very hard consistency you describe likely represents a combination of fresh clot formation within the cavity mixed with ongoing liquid blood flow—the pseudoaneurysm contains both flowing blood and layers of thrombus. 4
Immediate Risk Assessment at Day 9
Critical Risks Requiring Urgent Action
At 3 cm diameter, this pseudoaneurysm has crossed the threshold for mandatory definitive treatment—observation is inappropriate for lesions ≥ 2.0 cm, and your patient's lesion is now 3 cm with documented re-expansion. 2, 5
Untreated pseudoaneurysms carry high risk of rupture with active hemorrhage, venous compression leading to deep vein thrombosis, arterial compression causing limb ischemia, nerve compression producing neuropathy, and progressive enlargement. 2
The overnight re-expansion is particularly concerning because it demonstrates that manual pressure alone cannot achieve durable closure—the neck remains widely patent and the pseudoaneurysm is under active arterial pressure. 2, 4
Skin erosion over the pseudoaneurysm signals impending rupture and requires urgent surgical intervention; examine the overlying skin carefully for any thinning, discoloration, or breakdown. 2
Definitive Management Algorithm
Immediate Treatment (Do Not Delay)
Ultrasound-guided thrombin injection is the first-line definitive therapy for this 3 cm femoral pseudoaneurysm, achieving approximately 93% technical success even in patients on antithrombotic medications. 1, 2, 6
Thrombin injection (typically 100–1000 international units under ultrasound guidance) induces immediate thrombosis of the pseudoaneurysm cavity while preserving flow in the native femoral artery. 1, 6
The procedure is performed by placing a 20-gauge needle into the pseudoaneurysm cavity away from the neck under ultrasound visualization, then slowly injecting thrombin while monitoring for complete thrombosis with color Doppler. 6
Success is confirmed when color flow disappears from the pseudoaneurysm cavity and the "to-and-fro" Doppler signal in the neck ceases; duplex ultrasound must be repeated at 24 hours to confirm closure and at 1 month to verify persistent thrombosis. 2, 6
Distal arterial thromboembolism occurs in less than 2% of cases—this low complication rate makes thrombin injection safer than prolonged observation of a 3 cm lesion. 1, 2
When to Proceed Directly to Surgical Repair
- Open surgical repair is indicated when:
- Thrombin injection or compression therapy has failed or the pseudoaneurysm has recurred 2
- Clinical signs of rupture, active bleeding, or skin erosion are present 2
- Venous thrombosis or painful neuropathy secondary to compression exists 2
- The patient has limb ischemia from arterial compression or distal embolization 2
Why Conservative Management Is Not Appropriate Here
Conservative observation with activity restriction is reserved only for asymptomatic pseudoaneurysms smaller than 2.0 cm; your patient's 3 cm lesion with documented re-expansion does not meet these criteria. 2, 4, 5
Approximately 61% of small (<2 cm) pseudoaneurysms close spontaneously within 7–52 days in patients not receiving antithrombotic therapy, but this favorable natural history does not apply to lesions ≥ 2 cm. 2, 4
The re-expansion overnight demonstrates that this pseudoaneurysm is not spontaneously thrombosing—continued observation would expose the patient to unacceptable rupture risk. 2, 5
Critical Pitfalls to Avoid
Do not rely on the temporary size reduction after manual pressure as evidence of improvement—the fact that the pseudoaneurysm refills immediately after pressure is released confirms ongoing arterial communication and mandates definitive treatment. 2, 4
Do not adopt a "watch-and-wait" approach for a 3 cm pseudoaneurysm; the size threshold for mandatory intervention is 2.0 cm, and your patient is well above this cutoff. 2, 5
Physical examination alone misses more than 60% of pseudoaneurysms—the CT and ultrasound confirmation in your case was essential, and repeat imaging after any intervention is mandatory. 1, 2
If the patient is on anticoagulation or dual antiplatelet therapy, spontaneous closure rates drop markedly, making definitive treatment even more urgent. 2, 7
Post-Treatment Monitoring
After successful thrombin injection, duplex ultrasound must be performed at 24 hours to confirm complete thrombosis of the pseudoaneurysm cavity. 2
Mandatory follow-up ultrasound at 1 month is required to verify persistent thrombosis and rule out recurrence. 2
Approximately 5% of pseudoaneurysms recur after initial thrombin injection, but recurrent lesions can be safely re-injected with high success rates. 1
Activity restriction (no heavy lifting, straining, or vigorous activity) should continue for at least 1–2 weeks after successful treatment until follow-up imaging confirms durable closure. 2