Emergency Ultrasound Diagnosis of a Pseudoaneurysm Associated With an Arteriovenous Fistula

Authors

  • Faizan H. Arshad MD,

  • Darrell Sutijono MD,

  • Christopher L. Moore MD


A 60-year-old woman with end-stage renal disease presented to the emergency department complaining of 5 days of progressively worsening swelling, redness, and pain in her left arm. The symptoms began after her left brachial-basilic arteriovenous (AV) fistula was accessed for hemodialysis. She had subsequently missed a dialysis appointment secondary to pain. The patient denied fevers, chills, chest pain, or shortness of breath. Physical examination revealed erythema, tenderness, and tense skin overlying the anterior aspect of her left forearm extending from the antecubital fossa to the hand. A bruit was audible and a thrill was palpable over the fistula site. The extremity was neurovascularly intact.

Bedside ultrasound (US) was performed by an emergency medicine resident using a high-frequency linear transducer (Model HD11XE, Philips, Andover, MA). Examination revealed a large fluid collection with noted swirling of blood flow (Video Clip S1). With color flow Doppler, the presence of a communicating neck to the collection was noted, which is diagnostic for a pseudoaneurysm1,2 (Figure 1 and Video Clip 1). Also observable with color flow Doppler is the classically described yin and yang sign1 (Figure 2), referring to the symbol of the Chinese concept of how seemingly opposing forces are interconnected and interdependent in the natural world, giving rise to each other in turn. This finding is caused by swirling motion of blood within the pseudoaneurysm cavity, with inflow and outflow of blood overlying opposite vessel walls. Another characteristic finding, the biphasic “to-and-fro,” is the pattern of blood flow at the communicating neck and is observable with spectral Doppler. During systole there is flow of blood into the cavity that causes it to expand, leading to recoil of the surrounding soft tissue during diastole and subsequent flow back into the artery1 (Figure 3). This harkens to the historic name of a pseudoaneurysm—a pulsatile hematoma.

Figure 1.

 Duplex scan revealing a large fluid collection with presence of a communicating neck.

Figure 2.

 (A) Duplex scan illustrating the yin and yang sign, caused by swirling motion of blood within the pseudoaneurysm cavity. Note the color scale to the right of the ultrasound image. Blue represents flow going toward the probe, and red represents flow going away from the probe. (B) Yin–yang symbol.

Figure 3.

 Triplex scan illustrating biphasic “to-and-fro” at the pseudoaneurysm neck. The grayscale with color Doppler image comprises the top half of the image, with the spectral Doppler sample gate located at the pseudoaneurysm neck. The spectral wave Doppler graph displays velocity (y-axis) over time (x-axis). Note that the velocity scale is inverted. The wave form above the x-axis illustrates flow away from the probe and into the pseudoaneurysm and that below the x-axis illustrates flow toward the probe and out of the pseudoaneurysm.

Hemodialysis patients are at increased risk for developing pseudoaneurysms, as they are exposed to recurrent cannulations of their AV fistulas with simultaneous heparinization,3 with most occurring in those with prosthetic grafts.2 Pseudoaneurysms are defects in the vessel wall allowing blood to flow in and out and are contained by the tissue around the artery rather than any layers of the arterial wall—hence the “pseudo” in pseudoaneurysm. Doppler US is the primary diagnostic modality, with a sensitivity of 94%.4 Traditional management of pseudoaneurysms involves surgical repair; however, two US-assisted techniques have been described. In US-guided compression (UGC), the US transducer is used to provide compression while concomitantly visualizing the communicating neck. If targeting the neck is not feasible, the pseudoaneurysm itself is compressed.5 The obstruction of blood flow into the pseudoaneurysm and subsequent stasis leads to coagulation and conversion of the pseudoaneurysm into a hematoma. This noninvasive technique is well established in treating iatrogenic femoral artery pseudoaneurysms, with a success rate of 63% to 88%,6 and has had reported effectiveness in treating AV fistula pseudoaneurysms.3 Generally performed by sonologists or radiologists, the procedure is time- and labor-intensive, as compression is held for periods of 10 minutes and repeated until successful or up to 60 minutes.7 Other limitations include patient discomfort during compression and a decreased success rate with concomitant anticoagulant use.5 Alternatively, thrombus formation may be stimulated by US-guided thrombin injection, with definitive results often occurring within seconds.5 Typically employed by interventional radiologists or vascular surgeons, this method has a reported success rate of 95% to 98% in treating iatrogenic femoral artery pseudoaneurysms.7 Embolic complications may occur if thrombin flows out of the pseudoaneurysm and continues into the involved artery.

While the treatment of pseudoaneurysms should involve consultation with a vascular surgeon, if definitive management is not immediately available, UGC may be utilized by the emergency physician and has been reportedly successful in achieving thrombosis in ruptured pseudoaneurysms.8 In this particular case, the patient was stable and the pseudoaneurysm was surgically managed. An extensive hematoma was evacuated, with noted thrombosis at the basilic vein transposition and a large proximal laceration, presumably secondary to cannulation for dialysis. Both ends of the AV fistula were ligated, and the patient had an uncomplicated hospital course after surgery.

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