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Pseudoaneurysm

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Authors

Diego Riveros, MD
Sports Medicine Fellow
West Virginia University

Brenden Balcik, MD
Attending Physician
West Virginia University

Summary

  • Pseudoaneurysms, or “false-aneurysms,” develop after injury to the arterial wall, causing blood to accumulate between the middle and outer layer (tunica media & tunica adventitia) of the vessel.
  • Pseudoaneurysms can be easily diagnosed with point-of-care ultrasound in the emergency department.
Color doppler of a pseudoaneruysm.

Introduction

  • Pseudoaneurysms, or “false aneurysm,” occurs when there is an injury to an arterial vessel wall, causing blood to accumulate between the tunica media and tunica adventitia layers of the artery. This is in contrast to true aneurysms which is a dilation of the artery involving all three layers (tunica intima, tunica media, and tunica adventitia) [1]Rivera PA, Dattilo JB. Pseudoaneurysm. In: StatPearls. StatPearls Publishing; 2021..
  • Pseudoaneurysms can occur at any arterial site but are most commonly found after iatrogenic injury at the femoral artery or radial artery. 3.5% – 5.5% of all interventional procedures involving the femoral artery have this disease complication [2]Kronzon I. Diagnosis and treatment of iatrogenic femoral artery pseudoaneurysm: a review. J Am Soc Echocardiogr. 1997;10(3):236-245..
aneurysm vs pseudoaneurysm
Illustration of aneurysm and pseudoaneurysm
  • Large pseudoaneurysms are higher risk to either spontaneously rupture or enlarge causing mass effect injury to nearby structures including compression of veins (causing thrombosis) and nerve damage.
  • After iatrogenic cause, penetrating trauma and IV drug use are among the most common causes.
  • Ultrasound remains a vital tool in the diagnosis and management of pseudoaneurysms. It’s accessibility, lack of radiation, and ease of use makes it the initial imaging modality of choice. Ultrasonography has been estimated to be 94% sensitive and 97% specific in diagnosing post catherization pseudoaneurysm [3]Mahmoud MZ, Al-Saadi M, Abuderman A, et al. “To-and-fro” waveform in the diagnosis of arterial pseudoaneurysms. World J Radiol. 2015;7(5):89-99..
  • Point of care ultrasound (POCUS) can be used to make a quick diagnosis and expedite the management of this disease process that can have serious adverse complications. Evaluation of deeper arterial pseudoaneurysms such those in deep visceral arteries (such as celiac, superior, or inferior mesenteric) is more challenging; fortunately this group of pseudoaneurysm is rare [4]Barrionuevo P, Malas MB, Nejim B, et al. A systematic review and meta-analysis of the management of visceral artery aneurysms. J Vasc Surg. 2020;72(1S):40S-45S..

Risk Factors

  • Recent arterial invasive procedure (e.g. cardiac catheterization, arterial pressure monitor catheter)
    • Large sheath size
    • Insufficient manual compression time (< 5 minutes)
  • IV drug use
  • Penetrating trauma
  • Anticoagulation/Antiplatelet medications

Patient Presentation

  • Classically, patients present with a painful, pulsatile mass after an interventional procedure such as cardiac catherization. Bruit is often present during auscultation.
  • Large pseudoaneurysm may start to put pressure on overlying skin causing discoloration, pain, and ultimately, ischemia, necrosis, and hemorrhage[5]Rivera PA, Dattilo JB. Pseudoaneurysm. In: StatPearls. StatPearls Publishing; 2021..

Ultrasound Transducer and Settings

  • Given most pseudoaneurysms are located in the extremities, a high frequency linear transducer is optimal.
  • A curvilinear transducer may be used for deeper pseudoaneurysms such as those in the mesenteric system or to evaluate the femoral artery in patients with large  body habitus.
  • Proper positioning of the patient depends on what anatomical region is being evaluated. For femoral pseudoaneurysms, the patient should be in supine position with the hip externally rotated and abducted with knee flexed to about 30 degrees. [6]Hwang JY. Doppler ultrasonography of the lower extremity arteries: anatomy and scanning guidelines. Ultrasonography. 2017;36(2):111-119.
  • For radial pseudoaneurysms, the arm should be placed in a comfortable position with the forearm supinated. A ‘bump’ beneath the wrist may be utilized to help extend the wrist and expose the region in question.

Anatomy

  • Anatomical considerations depend on the location of the pseudoaneurysm.
  • When evaluating for femoral pseudoaneurysm, special consideration should be placed on the relationship between the femoral artery and the femoral nerve and vein, as these structures can be implicated as well.
Lower Limb Arteries Anterior and Posterior
Upper Limb Arteries
Arterial anatomy of upper and lower extremities (click to enlarge)

Ultrasound Protocol

  • In general, the arterial system of the anatomical region of interest should be evaluated in its entirety to ensure no portion of the pseudoaneurysm is missed. Long and short axis views should be obtained to determine the size of the lesion.
  • When evaluating the femoral artery, the transducer should initially be placed on the common femoral artery, typically at the inguinal crease. Throughout the examination, the artery should be imaged in multiple planes with special attention placed on the ‘NAVeL’ structures (femoral nerve, femoral artery, femoral vein, and lymphatics from lateral to medial).
ying yang sign
Yin -Yang Sign[7]Thomassen, Irene, et al. “Treatment of temporal artery pseudoaneurysms.” Vascular 22.4 (2014): 274-279.
  • As the transducer is glided caudally, the examiner will identify the bifurcation of the common femoral artery into the deep femoral artery and the superficial femoral artery (SFA), along with the femoral vein. The SFA is then scrutinized on top of the femoral vein as the transducer is moved distally and the vessels dive more posterior approaching the knee.
  • At the knee, the popliteal artery and vein are evaluated in the popliteal fossa with the popliteal vein appearing on top of the artery. [8]Hwang JY. Doppler ultrasonography of the lower extremity arteries: anatomy and scanning guidelines. Ultrasonography. 2017;36(2):111-119..
  • Gray scale, or ‘B-mode,’ should be utilized first to assess the area of concern with special attention to any round or ovoid anechoic collections. Pseudoaneurysms, seromas, hematomas, or cysts/abscesses can all have this appearance.[9]Mahmoud MZ, Al-Saadi M, Abuderman A, et al. “To-and-fro” waveform in the diagnosis of arterial pseudoaneurysms. World J Radiol. 2015;7(5):89-99. The overall size of the pseudoaneurysm in long and short axis should be measured.
  • Color Doppler can then be used to look for flow in the anechoic collections. Seromas and cysts should not have internal flow whereas pseudoaneurysms and pulsating hematomas may. Thrombus in the pseudoaneurysm can also be evaluated with color doppler as areas of mixed echogenicity without flow.
Pseudoaneurysm with clot formation[10]Mouawad NJ, Haurani MJ, Mason T, Satiani B. Delayed presentation and management of blunt traumatic inferior gluteal artery pseudoaneurysm with associated arteriovenous fistula. Vasc Endovascular … Continue reading
  • Heavy turbulence should be seen in pseudoaneurysms with intermixing of the red and blue colors, representing a ‘yin and yang’ pattern.[11]Mahmoud MZ, Al-Saadi M, Abuderman A, et al. “To-and-fro” waveform in the diagnosis of arterial pseudoaneurysms. World J Radiol. 2015;7(5):89-99.[12]Lupattelli T. The yin-yang sign. Radiology. 2006;238(3):1070-1071.
  • Spectral waveform analysis is also very useful in differentiating pseudoaneurysm from other pathology. Analysis at the neck of the pseudoaneurysm should reveal a ‘to-and-fro’ waveform. This represents the change in flow from blood entering the sac during systole (high pressure) and blood leaving the sac during diastole (low pressure).

     

to and fro waveform
‘To and fro’ waveform[13]Mahmoud MZ. “ To-and-fro” waveform in the diagnosis of arterial pseudoaneurysms. World journal of radiology. 2015;7. 5:89.

Management

  • Vascular surgery and/or interventional radiology should be consulted for all pseudoaneurysms.
  • If pseudoaneurysm is large, expanding, or the patient is showing signs of instability, ensure the patient is type and crossed anticipating the patient will need resuscitation.
  • Small aneurysms (<2 cm) may be observed with expected spontaneous thrombosis.
  • Other therapeutic options include ultrasound-guided compression, ultrasound-guided thrombin injection, and surgical repair.

Pearls and Pitfalls

  • The examiner should evaluate proximal and distal on the particular arterial system to avoid missing portions of the pseudoaneurysm.
  • To differentiate pseudoaneurysm from other pathology, find the neck of the pseudoaneurysm using color doppler and evaluate for the ‘yin-and-yang’ swirl sign and the ‘to-and-fro’ waveform on color doppler.
  • Avoid focusing only on the obvious pseudoaneurysm finding. You may miss other important pathology such as a thrombosed vein or signs of nerve compression/damage.
  • Common femoral arterial pseudoaneurysms may extend into the retroperitoneum and rupture in this space. Look for any free fluid in the abdomen or pelvis using the curvilinear probe when evaluating a femoral pseudoaneurysm, especially in unstable patients.
  • Be ready for acute resuscitation if the pseudoaneurysm is showing signs of expansion or instability.

     

With special thanks to Drs. Nicolas Denne and Joseph Minardi for their visual contributions

References

References[+]