Ultrasound of the Month: Radial Pseudoaneurysm
/The Case
Figure 1: Clinical image of wrist swelling
An elderly patient presents to the emergency department (ED) for left wrist mass/swelling. The patient has a past medical history of coronary artery disease, diabetes (type 2) on metformin, and carotid stenosis s/p carotid endarterectomy. He underwent a right heart catheterization (RHC) 2 months prior to his first ED visit with placement of stents. His heart cath was accessed using his right radial artery. After his RHC, he was placed on Plavix. Over the preceding six weeks, he noted swelling of his left wrist which was tender to palpation without redness, warmth, or drainage.
On evaluation, the patient is hemodynamically stable with a 5 cm mass overlying the left palmar radial wrist (Figure 1). There is a pulsatility with palpation of the mass. No overlying erythema, warmth, or induration but there is mild fluctuance. No other abnormalities are noted on the remainder of his exam.
The patient's presentation raises concern for a pseudoaneurysm. Other differential diagnoses include hematoma, abscess, or cyst. Point of care ultrasound (POCUS) was used to evaluate the mass. The acquired images are shown in Figures 2-5.
Figure 2: Cystic structure
Figure 3. Color doppler image of cystic structure showing “yin-yang” sign
Figure 4. Swirling of blood in the pseudoaneurysm
Figure 5. Neck of the pseudoaneurysm visualized under color feeding the pseudoaneurysm. From the left radial artery
The findings led to concern for pseudoaneurysm formation. Vascular surgery was consulted for pseudoaneurysm management.
Pseudoaneurysm Pathophysiology
Pseudoaneurysms are tears in arterial walls leading to a sac communicating with the artery. As opposed to true aneurysms, pseudoaneurysms (i.e. false aneurysms) are not encapsulated by all 3 layers of the artery, but rather only by the media or adventitia. Pseudoaneurysms communicate with the artery via a channel or “neck” which allows blood to flow into a saccular space. Pseudoaneurysms can be seen in arteries (femoral being most common), viscera, and the aorta. Arterial pseudoaneurysms result from iatrogenic arterial cannulation for endovascular procedures, trauma, infection, or anastomotic failure (1). Iatrogenic pseudoaneurysms are a rare but concerning complication of procedures requiring arterial access. The large pulsatile sac may compress on neurovascular structures in proximity, cause thromboembolism, necrosis of overlying tissues, or rupture leading to life threatening bleeding (1, 2). Typical causes include multiple puncture attempts to achieve vascular access, inadequate post procedure compression, accidental arterial dilation during venous procedures, and failure of closure devices. Patients on anticoagulation are at increased risk of this complication. Radial artery pseudoaneurysms are an extremely rare complication of arterial cannulation occuring in <1% of arterial cannulations. In fact, the radial approach has been favored in recent years due to its low complication rate (including pseudoaneurysms rate) as well as being an area relatively easy to access and compress (3).
Imaging Recommendations
Given that pseudoaneurysms are fairly superficial and require visualizing fine details, a high frequency probe should be used. Imaging should show a saccular lesion with some pulsatility or movement. Images of the mass should be obtained in a longitudinal and transverse plane. Pseudoaneurysms may be anechoic in the absence of thrombi or partially hyperechoic if partially thrombosed. For diagnosis, images must show a communicating channel between the artery and the mass through which blood is flowing. Due to the different velocities of blood entering and exiting the pseudoaneurysm, swirling may be seen on grayscale ultrasonography. Increasing the gain may better visualize the swirling of blood in the sac. Using color doppler, one should see bidirectional, turbulent blood flow with red color flow towards the probe and blue color flow away from the probe (2). This creates the “yin-yang” sign characteristic of larger pseudoaneurysms as seen in Figure 3. Using color, one should also see the blood flowing through the communicating channel, or neck, of the pseudoaneurysms as seen in Figure 4. These findings separate pseudoaneurysms from hematomas and cysts (2).
Management
Prevention of pseudoaneurysms formation is noted in the literature as first line management. Post procedure, prolonged compression of the puncture site with limb rest is typically sufficient to prevent pseudoaneurysm formation (3,4,5). In anticoagulated patients, the length of compression is extended. If these measures fail, secondary treatment is needed. Historically, surgical management was the gold standard treatment for pseudoaneurysms. However, in recent years, less invasive treatments have been preferred by vascular surgeons with excellent clinical outcomes. For small pseudoaneurysms, compression of the mass typically resolves the pseudoaneurysm. In medium to large size pseudoaneurysms, direct visualization using ultrasound is used to create thrombosis inside the pseudoaneurysm (3,4). Ultrasound guided compression of the pseudoaneurysm neck until thrombosis of the pseudoaneurysm is considered the first line treatment. Alternatively, ultrasound guidance may be used for thrombin injections. In this procedure, ~300 IU of thrombin is injected under ultrasound guidance into the pseudoaneurysm until thrombosis of the pseudoaneurysm is achieved (6). Thrombin injections carry a small risk of embolization and are thus not attempted in very small pseudoaneurysms (1). Should these methods fail, open operative management is then pursued.
Case Resolution
Vascular surgery evaluated the patient and offered thrombin injection into the pseudoaneurysm which he accepted. The patient was taken to the vascular lab for an urgent thrombin injection. Post procedure, he was noted to be neurovascularly intact with minimal pain and good indices of perfusion. The patient was discharged after a brief period of observation.
AUTHORED BY KELLY TILLOTSON, MD
Dr. Tillotson (@kellytillotson2) is a PGY-3 in Emergency Medicine at the University of Cincinnati.
PEER REVIEW BY Lori Stolz, MD
Dr. Stolz (@sonostolz) is an Associate Professor of Emergency Medicine at the University of Cincinnati and Director of the Ultrasound Fellowship.
EDITING AND LAYOUT BY MARTINA DIAZ, MD
Dr. Diaz (@martina_diazb) is a PGY-3 in Emergency Medicine at the University of Cincinnati and the Resident Editor of Ultrasound of the Month.
References:
Rivera PA, Dattilo JB. Pseudoaneurysm. [Updated 2022 Mar 9]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK542244/
Chun EJ. Ultrasonographic evaluation of complications related to transfemoral arterial procedures. Ultrasonography. 2018 Apr;37(2):164-173. doi: 10.14366/usg.17047. Epub 2017 Aug 25. PMID: 29145350; PMCID: PMC5885482.
Cauchi MP, Robb PM, Zemple RP, Ball TC. Radial artery pseudoaneurysm: a simplified treatment method. J Ultrasound Med. 2014;33(8):1505-1509. doi:10.7863/ultra.33.8.1505
Kongunattan V, Ganesh N. Radial Artery Pseudoaneurysm following Cardiac Catheterization: A Nonsurgical Conservative Management Approach. Heart Views. 2018
