Post-Puncture Pseudoaneurysm of the Femoral Artery: Ultrasound Diagnosis and Thrombin Guidance
Definition and Pathogenesis
A pseudoaneurysm (false aneurysm) often forms at the puncture site of the femoral artery. It is the persistent flow of blood into a cavity outside the walls of the carrying vessel, limited only by the adventitia or perivascular soft tissues (Diagnostic Ultrasound Vascular, 2025). After any endovascular intervention, inspection of the access site—usually the common femoral artery—is mandatory (Blagodir, 2026).
Ultrasound Signs
The typical appearance is a pulsating anechoic formation connected to the artery by a neck. On color mapping, a swirling 'yin-yang' flow is observed in the cavity and a characteristic bidirectional 'to-and-fro' flow in the neck (Blagodir, 2026). When guiding thrombin, the formation is described as a hypoechoic or heterogeneous structure adjacent to the artery with swirling internal flow on color Doppler imaging (Diagnostic Ultrasound Vascular, 2025).
Differential Diagnosis of the Access Site
| Finding | Ultrasound Signs |
|---|---|
| Pseudoaneurysm | 'Yin-yang' flow in the cavity + 'to-and-fro' in the neck |
| Arteriovenous Fistula | High-velocity low-resistance jet signal PSV >300 cm/s at the anastomosis site, arterialization of the adjacent vein |
| Hematoma | Confined collection outside the lumen without internal blood flow |
Pseudoaneurysm and arteriovenous fistula are the most common findings at the access site (Blagodir, 2026).
Ultrasound-Guided Thrombin Injection
The method involves percutaneous thrombin injection to treat persistent blood flow into a cavity outside the walls of the carrying vessel (Diagnostic Ultrasound Vascular, 2025). Before the procedure, it is necessary to:
• confirm the presence of a pseudoaneurysm as a hypoechoic/heterogeneous structure adjacent to the artery with swirling internal flow on color Doppler imaging;
• confirm the presence of a narrow neck between the pseudoaneurysm and the carrying vessel—a wide neck may exclude the possibility of thrombin injection (Diagnostic Ultrasound Vascular, 2025).
Extended indications for ultrasound-guided thrombin injection and the method itself are described in studies by Kang SS et al. (1998, 2000), cited in the AIUM Practice Parameter (2025 Revision). Recurrence of pseudoaneurysms after thrombin injection under ultrasound guidance is possible (Diagnostic Ultrasound Vascular, 2025).
Frequently asked questions
How to differentiate a pseudoaneurysm from a hematoma?
In a hematoma, there is no internal blood flow—it's a confined collection outside the lumen. A pseudoaneurysm has a swirling 'yin-yang' flow in the cavity and bidirectional flow in the neck (Blagodir, 2026).
What flow is characteristic of the neck of a pseudoaneurysm?
Bidirectional 'to-and-fro' flow on spectral Doppler; in the cavity, a swirling 'yin-yang' flow on color Doppler imaging (Blagodir, 2026).
What needs to be confirmed before thrombin injection?
The presence of the pseudoaneurysm (hypo-/heterogeneous structure with swirling flow) and a narrow neck between it and the carrying vessel. A wide neck may exclude thrombin injection (Diagnostic Ultrasound Vascular, 2025).
How to differentiate a pseudoaneurysm from an arteriovenous fistula at the access site?
A fistula is characterized by a high-velocity low-resistance jet signal PSV >300 cm/s at the anastomosis site and arterialization of the adjacent vein (Blagodir, 2026).
Is recurrence possible after thrombin injection?
Yes, recurrences of pseudoaneurysms after thrombin injection under ultrasound guidance have been described (Diagnostic Ultrasound Vascular, 2025; Esterson YB et al., 2017).