How is a thrombin injection done? A Step-by-Step Medical Procedure

October 11, 2025 •

4 min read

Ultrasound-guided thrombin injections for femoral pseudoaneurysms have a high success rate, often exceeding 90%. This minimally invasive technique is considered a standard of care and is highly effective in promoting thrombosis. Here is how is a thrombin injection done as a treatment option.

Quick Summary

This procedure uses ultrasound to guide a needle into a pseudoaneurysm sac, where thrombin is injected to induce blood clotting, sealing the arterial leak. It is a quick and effective alternative to surgery for suitable cases.

Key Points

Ultrasound Guidance is Crucial: The procedure relies on real-time ultrasound imaging to ensure the accurate placement of the needle directly into the pseudoaneurysm sac.
Precise Injection Location: Thrombin is injected carefully and slowly into the sac, positioning the needle as far as possible from the neck to prevent leakage into the main artery.
Rapid Clot Formation: Thrombin triggers the conversion of fibrinogen to fibrin, leading to the rapid formation of a clot that thromboses the pseudoaneurysm within seconds.
Minimally Invasive: This percutaneous procedure is less painful, faster, and more effective than historical treatments like prolonged manual compression.
Post-procedure Monitoring: After injection, patients require a short period of bed rest and a follow-up ultrasound to confirm successful thrombosis and rule out complications.
Primary Use for Pseudoaneurysms: Thrombin injection is the standard treatment for iatrogenic pseudoaneurysms that are larger or fail to resolve spontaneously.

What is a thrombin injection?

A thrombin injection is a minimally invasive medical procedure used primarily to treat pseudoaneurysms, which are collections of blood leaking from an artery into surrounding tissue. This condition often occurs after a catheterization procedure, particularly in the femoral artery in the groin. The injection leverages thrombin's powerful role in the blood clotting cascade. When injected directly into the pseudoaneurysm sac, thrombin rapidly converts fibrinogen into a stable fibrin clot, effectively sealing the leak and promoting thrombosis.

Preparation for the procedure

Before undergoing the procedure, patients typically receive several key preparations to ensure safety and success. While no special preparation is typically required, medical staff will assess the patient's condition, including any anticoagulant or anti-platelet therapy. A complete duplex ultrasound study is performed to accurately map the pseudoaneurysm's anatomy, its size, and the relationship of the sac and neck to the underlying native artery.

Patient assessment: Reviewing the patient's medical history, current medications, and the results of recent imaging.
Site preparation: The injection site, usually in the groin, is cleaned with an antiseptic solution like povidone iodine to maintain a sterile field. Sterile drapes are placed around the area.
Equipment readiness: The ultrasound machine and probes are prepared with sterile covers. The thrombin solution, which is commercially available in freeze-dried form (e.g., THROMBIN-JMI) or human plasma derivatives, is reconstituted to the appropriate concentration.
Anesthesia: A local anesthetic may or may not be used, as the procedure itself is often fast and less painful than alternative treatments.

The ultrasound-guided thrombin injection procedure

The procedure is performed using continuous ultrasound guidance, which is crucial for precision and safety. The entire process typically takes less than 30 minutes.

Locating the pseudoaneurysm: The interventional cardiologist or vascular surgeon uses a high-frequency ultrasound transducer to pinpoint the pseudoaneurysm sac and its neck. Color Doppler is used to visualize the characteristic to-and-fro turbulent blood flow within the sac.
Needle insertion: A fine-gauge needle (e.g., 20 or 22-gauge) is carefully inserted percutaneously toward the pseudoaneurysm sac. The needle's position is continuously monitored on the ultrasound screen.
Confirming placement: Before injecting thrombin, a small amount of saline can be injected to confirm the needle's tip is correctly inside the sac, which is visible as a "color flash" on the ultrasound monitor.
Thrombin injection: A small syringe is used to slowly inject the reconstituted thrombin solution directly into the pseudoaneurysm cavity. The amount injected is typically sufficient to fill the sac. The injection is administered as far as possible from the neck of the pseudoaneurysm to prevent leakage into the main artery.
Observing thrombosis: As the thrombin is injected, the operator observes the ultrasound monitor for the telltale sign of clotting, which appears as a swirling, echogenic (brighter) pattern within the sac. The injection continues until the entire sac is thrombosed, and the abnormal color flow stops.
Final confirmation: A final color duplex ultrasound is performed to confirm complete occlusion of the pseudoaneurysm and verify that there is no residual blood flow or extravasation. The patency of the native artery is also re-checked.

Post-procedure care and recovery

Following the injection, patients are typically observed for a brief period in a recovery area to monitor for any immediate complications.

Bed rest: Patients are usually advised to remain on bed rest for a few hours (e.g., 2 to 6 hours) after the procedure to reduce the risk of rebleeding.
Monitoring: The patient's vital signs and distal pulses are monitored to ensure there are no signs of thromboembolic events or decreased circulation to the limb.
Follow-up imaging: A follow-up duplex ultrasound is typically scheduled within 24 to 48 hours to confirm sustained thrombosis of the pseudoaneurysm. For some, a follow-up is also done at 1 month to confirm the complete resolution of the lesion.

Potential complications and risks

While generally safe and effective, thrombin injections carry some risks, including:

Arterial thrombosis or embolism: This can happen if thrombin inadvertently leaks into the parent artery, potentially causing acute limb ischemia. This is the most serious risk.
Allergic reaction: Bovine-derived thrombin can trigger an anaphylactic or allergic reaction, especially with prior exposure. This risk is lower with human plasma or recombinant thrombin products.
Deep venous thrombosis (DVT): Rarely, compression from the pseudoaneurysm or the procedure itself can lead to DVT.
Infection or groin abscess: A localized infection at the puncture site is a rare but possible complication.


Feature	Thrombin Injection	Ultrasound-Guided Compression (UGC)	Surgical Repair
Success Rate	Very high (90%+), even in anticoagulated patients	Variable (55-95%), lower if patient is anticoagulated	High, but more invasive and risks associated with surgery
Pain Level	Minimally painful, often requires only local anesthesia	Can be very painful and difficult to tolerate for extended periods	Performed under general anesthesia, but with post-operative pain
Procedure Time	Quick, often less than 30 minutes	Time-consuming, average procedure can last 30-40 minutes	Longest procedure, requiring significant OR time
Risks	Low risk of embolism or allergy, rare DVT	Risk of incomplete closure, discomfort, and patient intolerance	Higher morbidity, including infection and nerve damage
Invasiveness	Minimally invasive, percutaneous needle injection	Non-invasive externally guided compression	Most invasive, requires open surgery

Conclusion

Ultrasound-guided thrombin injection has emerged as the preferred and standard method for treating uncomplicated pseudoaneurysms, particularly those in the femoral artery. The technique is valued for its high efficacy, minimal invasiveness, and excellent patient tolerance. By utilizing real-time ultrasound imaging, clinicians can precisely target the pseudoaneurysm sac and inject thrombin, causing immediate clotting and sealing the leak. Although potential complications exist, such as the low risk of distal embolization or allergic reaction, the overall safety profile is favorable, especially when compared to more traditional approaches like prolonged compression therapy or open surgery. The successful resolution of the pseudoaneurysm, as confirmed by follow-up imaging, allows for a rapid return to normal activity with minimal discomfort.

Frequently Asked Questions

A pseudoaneurysm is a hematoma (a collection of blood) that forms outside an artery following trauma or a puncture, such as during a catheterization procedure. A thrombin injection treats it by injecting the potent clotting enzyme, thrombin, directly into the blood sac to induce rapid clotting and seal the leak.

The procedure involves using ultrasound to guide a needle into the pseudoaneurysm. Saline is used to confirm placement, followed by a slow injection of thrombin into the sac. The physician watches for the immediate formation of a clot on the ultrasound screen.

The procedure is typically minimally painful. Some patients may feel mild discomfort, but it is generally well-tolerated and much less painful than alternatives like ultrasound compression.

After the injection, patients are monitored with ultrasound to ensure the pseudoaneurysm has thrombosed completely. Patients are advised to have a brief period of bed rest for a few hours, and a follow-up ultrasound is typically scheduled within 24 to 48 hours.

Potential risks include inadvertent injection of thrombin into the main artery, which can cause clotting and limb ischemia, and a rare allergic reaction, particularly to bovine-derived thrombin products. A rare risk of DVT and infection also exists.

No, it is not suitable for all cases. Some contraindications include pseudoaneurysms with a wide neck or local infection, or those involving an arteriovenous fistula. A physician evaluates each case using ultrasound to determine the best course of action.

Thrombin injection is often considered superior to ultrasound-guided compression because it is faster, less painful, and has a higher success rate. It is also less invasive than traditional surgical repair, which is often reserved for complex cases or failed injections.

The procedure is typically performed by specialists such as interventional cardiologists, vascular surgeons, or interventional radiologists who are experienced in performing ultrasound-guided vascular interventions.