DOI: 10.1148/rg.25si055503
RadioGraphics 2005;25:S173-S189
© RSNA, 2005
Pseudoaneurysms and the Role of Minimally Invasive Techniques in Their Management1
Nael E. A. Saad, MB, BCh,
Wael E. A. Saad, MB, BCh,
Mark G. Davies, MD, PhD,
David L. Waldman, MD, PhD,
Patrick J. Fultz, MD and
Deborah J. Rubens, MD
1 From the Departments of Radiology (N.E.A.S., W.E.A.S., D.L.W., P.J.F., D.J.R.) and Vascular Surgery (M.G.D.), University of Rochester Medical Center, 601 Elmwood Ave, Box 648, Rochester, NY 14642. Presented as an education exhibit at the 2004 RSNA Annual Meeting. Received February 1, 2005; revision requested March 22 and received April 28; accepted May 17. All authors have no financial relationships to disclose.
Address correspondence to N.E.A.S. (e-mail: nael{at}mindless.com).
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Abstract
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Pseudoaneurysms are common vascular abnormalities that represent a disruption in arterial wall continuity. Some complications associated with pseudoaneurysms develop unpredictably and carry high morbidity and mortality rates. The advent of new radiologic techniques with a greater sensitivity for asymptomatic disease has allowed more frequent diagnosis of pseudoaneurysms. Conventional angiography remains the standard of reference for diagnosis but is an invasive procedure, and noninvasive diagnostic modalities (eg, ultrasonography [US], computed tomographic angiography, magnetic resonance angiography) should be included in the initial work-up if possible. A complete work-up will help in determining the cause, location, morphologic features, rupture risk, and clinical setting of the pseudoaneurysm; identifying any patient comorbidities; and evaluating surrounding structures and relevant vascular anatomy, information that is essential for treatment planning. Therapeutic options have evolved in recent years from the traditional surgical option toward a less invasive approach and include radiologic procedures such as US-guided compression, US-guided percutaneous thrombin injection, and endovascular management (embolization, stent-graft placement). The use of noninvasive treatment has led to a marked decrease in the morbidity and mortality rates for pseudoaneurysms.
© RSNA, 2005
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LEARNING OBJECTIVES
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After reading this article and taking the test, the reader will be able to:
- Describe the causes and natural history of pseudoaneurysms.
- Identify the diagnostic features of pseudoaneurysms at various imaging modalities.
- Discuss the triage of patients with pseudoaneurysms to appropriate treatment.
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Introduction
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Pseudoaneurysms arise from a disruption in arterial wall continuity resulting from inflammation, trauma, or iatrogenic causes such as surgical procedures (1), percutaneous biopsy, or drainage. Under the influence of sustained arterial pressure, blood dissects into the tissues around the damaged artery and forms a perfused sac that communicates with the arterial lumen (1–3). The perfused sac is contained by the media or adventitia or simply by soft-tissue structures surrounding the injured vessel. With the introduction of modern imaging modalities, the diagnosis of pseudoaneurysms has become more common (4), which allows early detection and therapeutic intervention before the pseudoaneurysm manifests clinically, sometimes with catastrophic results. Although conventional angiography remains the diagnostic standard of reference (5), other modalities such as duplex Doppler ultrasonography (US), magnetic resonance (MR) angiography, and helical computed tomographic (CT) angiography are useful in the noninvasive detection and diagnosis of pseudoaneurysms, albeit with variable results (6,7). Therapeutic options have also evolved over the past few years from surgical management toward a less invasive approach, dramatically decreasing the morbidity and mortality rates for pseudoaneurysms.
In this article, we review the natural history and clinical features of pseudoaneurysms. We also discuss and illustrate the imaging features of these lesions at US, MR angiography, CT angiography, and conventional angiography. In addition, we discuss various treatment options (surgery, US-guided compression, US-guided percutaneous thrombin injection) as well as endoluminal management.
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Natural History
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Pseudoaneurysms have a variety of causes, including inflammation, trauma, and various iatrogenic causes (eg, surgery [1], percutaneous biopsy, drainage). Any affected vessel is susceptible to the development of a pseudoaneurysm. Although modern imaging modalities have made the diagnosis of pseudoaneurysms more common, the increase in the number of surgical and arteriographic procedures performed has led to a real increase in the prevalence of pseudoaneurysms (8). Surgery can cause pseudoaneurysms through direct injury to the vessel or the introduction of infection. A wide array of procedures lead to pseudoaneurysm formation, including minimally invasive procedures such as catheterization, in which the prevalence of pseudoaneurysm formation is as high as 7.7% with the use of large-bore sheaths and periprocedural anticoagulation and antiplatelet therapy (9,10). Pseudoaneurysms are also recognized complications of liver transplantation (11,12), heart transplantation (13), obstetric procedures such as dilatation and curettage and cesarean section (14), and endovascular stent-graft implantation for aortic aneurysms (15), in addition to percutaneous biopsy or drainage. Blunt and penetrating trauma may also cause pseudoaneurysms of the involved artery. Affected arteries include the carotid (5), extremity (6,16), splenic (17,18), and hepatic (19) arteries. Inflammatory conditions such as pancreatitis or infection (20) may also lead to pseudoaneurysm formation. Pseudoaneurysms may undergo spontaneous thrombosis (7,21) or may progress with development of complications such as infection, development of local compression on neurovascular structures, or rupture (10).
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Clinical Features
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Pseudoaneurysms may be asymptomatic and detected only incidentally during radiologic investigation of other conditions or during surgery (22). Symptomatic pseudoaneurysms manifest with local or systemic signs and symptoms. Local effects of a pseudoaneurysm (whether it is infected or not) are secondary to mass effect on adjacent structures causing compromise of function. This condition may manifest as a palpable thrill, audible bruit, or pulsatile mass. Ischemia of the surrounding tissues due to vascular compromise may lead to necrosis of the overlying skin and subcutaneous tissue. Neurologic symptoms may develop secondary to nerve compression or ischemia. Compression of adjacent veins may lead to edema and deep venous thrombosis. Thromboembolism is also a potential complication. In addition, the pseudoaneurysm may rupture, leading to hemorrhage with its potential clinical sequela of life-threatening shock (7,10,21,23).
Rupture is the most serious cause of morbidity from pseudoaneurysms; rupture of splenic artery pseudoaneurysms, for example, has a mortality rate approaching 100% (24). Pseudoaneurysms can communicate with and rupture into the gut; the biliary system; and the thoracic, peritoneal, pelvic, and retroperitoneal spaces (25). Hemorrhage from these ruptures may manifest as sentinel bleeding from a drain or percutaneous trans-hepatic biliary drain, or as hematemesis, melena (23), splenic rupture, or subcapsular hepatic hematoma (26).
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Imaging Features
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Ultrasonography
Gray-scale US demonstrates a hypoechoic cystic structure adjacent to a supplying artery (8,12,14). The size of the pseudoaneurysmal sac, the number of compartments (lobes) in the sac, the connection of the sac to the artery, and the length and width of the pseudoaneurysmal neck can be assessed with gray-scale US (Fig 1a) (9). Pseudoaneurysms may be simple (one lobe) or complex (two or more lobes separated by a patent tract with a diameter smaller than the minimal dimension of the smallest lobe) (9). Septa within the lobe or lobes of a pseudoaneurysm may also be seen. In addition, concentric layers of hematoma are occasionally seen within the pseudoaneurysm (Fig 2). However, gray-scale US is not diagnostic, since these findings are seen in a number of conditions, the most common being simple and complex cysts and hematomas.
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Figure 1a. (a) Duplex Doppler US image depicts a pseudoaneurysm (PsA) with bidirectional flow within the neck (N). The donor artery supplying the pseudoaneurysm can also be seen (A). (b) Color Doppler US image of the pseudoaneurysm clearly depicts the pseudoaneurysmal neck (N) and the yin-yang (red-blue) Doppler US appearance of the pseudoaneurysmal sac (PsA).
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Figure 1b. (a) Duplex Doppler US image depicts a pseudoaneurysm (PsA) with bidirectional flow within the neck (N). The donor artery supplying the pseudoaneurysm can also be seen (A). (b) Color Doppler US image of the pseudoaneurysm clearly depicts the pseudoaneurysmal neck (N) and the yin-yang (red-blue) Doppler US appearance of the pseudoaneurysmal sac (PsA).
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Figure 2a. (a) Transvaginal gray-scale US image depicts a pseudoaneurysm of the left internal iliac artery (arrowhead) and concentric layers of mural thrombosis (arrow). (b) Transvaginal color Doppler US image of the pseudoaneurysm demonstrates characteristic yin-yang (red-blue) flow in the sac (arrowhead). (c) Trans-vaginal color Doppler flow US image demonstrates to-and-fro (bidirectional) flow.
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Figure 2b. (a) Transvaginal gray-scale US image depicts a pseudoaneurysm of the left internal iliac artery (arrowhead) and concentric layers of mural thrombosis (arrow). (b) Transvaginal color Doppler US image of the pseudoaneurysm demonstrates characteristic yin-yang (red-blue) flow in the sac (arrowhead). (c) Trans-vaginal color Doppler flow US image demonstrates to-and-fro (bidirectional) flow.
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Figure 2c. (a) Transvaginal gray-scale US image depicts a pseudoaneurysm of the left internal iliac artery (arrowhead) and concentric layers of mural thrombosis (arrow). (b) Transvaginal color Doppler US image of the pseudoaneurysm demonstrates characteristic yin-yang (red-blue) flow in the sac (arrowhead). (c) Trans-vaginal color Doppler flow US image demonstrates to-and-fro (bidirectional) flow.
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Doppler US helps establish the diagnosis. Blood flow within a cystic structure is characterized by a typical swirling motion called the "yin-yang sign" (Figs 1b, 2b). However, this pattern of flow may also be seen in saccular aneurysms, so that a diagnosis made on the basis of this finding alone may prove to be inaccurate. The hallmark of the diagnosis is the demonstration of a communicating channel (neck) between the sac and the feeding artery with a "to-and-fro" waveform at duplex Doppler US. The "to" component represents blood entering the pseudoaneurysm in systole; the "fro" component represents blood exiting the pseudoaneurysm during diastole (Fig 2c) (26). In addition, placing the imaging findings in the clinical context (ie, the history of the cause of the pseudoaneurysm) allows the diagnosis of a pseudoaneurysm versus a saccular true aneurysm.
US is a valuable diagnostic tool for the detection of pseudoaneurysms. This modality is portable, readily available, inexpensive, and fast, involves no ionizing radiation or renal toxic contrast material, and is noninvasive (11,27,28). US has been reported to have a sensitivity of 94% and a specificity of 97% in the detection of postcatheterization pseudoaneurysms (10). However, the usefulness of US in the evaluation of deep (visceral) arteries is limited, with reports of low sensitivity (29). Moreover, US is operator dependent, and the evaluation of vessels in trauma patients with fractures or hematomas may be difficult (6).
CT Angiography
CT angiography, especially with the advent of multi–detector row helical CT scanners, is a valuable diagnostic tool. Unenhanced CT scans may demonstrate a low-attenuation rounded structure arising from the donor artery. Intermediate or high attenuation (hemorrhage) adjacent to the pseudoaneurysm indicates pseudoaneurysmal rupture (Fig 3a), which may vary in attenuation depending on whether it is chronic or acute. The wall of the pseudoaneurysm is usually smooth and well delineated except in a mycotic pseudoaneurysm, whose wall is thickened, irregular, or ill defined. Contrast-enhanced CT may demonstrate a contrast material–filled sac (Fig 3a ) (13). However, the entire pseudoaneurysm may not fill with contrast material; a low-attenuation area will remain within the pseudoaneurysm, a finding that indicates partial thrombosis (Fig 3b). The donor artery is adjacent to the pseudoaneurysm and can usually be seen communicating with it (Fig 3).
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Figure 3a. Pseudoaneurysmal rupture in a 77-year-old woman who presented to the emergency department with acute onset of abdominal pain. (a) Axial contrast material–enhanced CT angiogram demonstrates a ruptured splenic artery pseudoaneurysm (PsA) with adjacent hemorrhage (arrowheads). The pseudoaneurysm is completely filled with contrast material, and the afferent (AA) and efferent (EA) splenic artery loops are clearly depicted. (b) Axial contrast-enhanced CT scan shows intrasac thrombosis of the pseudoaneurysm (arrow) and communication with the donor artery (arrowhead).
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Figure 3b. Pseudoaneurysmal rupture in a 77-year-old woman who presented to the emergency department with acute onset of abdominal pain. (a) Axial contrast material–enhanced CT angiogram demonstrates a ruptured splenic artery pseudoaneurysm (PsA) with adjacent hemorrhage (arrowheads). The pseudoaneurysm is completely filled with contrast material, and the afferent (AA) and efferent (EA) splenic artery loops are clearly depicted. (b) Axial contrast-enhanced CT scan shows intrasac thrombosis of the pseudoaneurysm (arrow) and communication with the donor artery (arrowhead).
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CT angiography has advantages over other imaging modalities including US, MR imaging, and angiography. Although US and MR imaging are also noninvasive, CT angiography is not as operator dependent and has a shorter acquisition time (
1 minute). Postprocessing of the raw data to generate three-dimensional (3D) images may be time consuming; however, diagnostic information sufficient for surgical planning can be obtained from the axial images. Furthermore, CT can help detect associated injuries or other associated disease entities such as pancreatitis that may not be detected with other modalities (eg, angiography, which is limited to evaluation of the vascular structures) (5). Three-dimensional CT angiography allows visualization of the lesion from all angles, which is not possible with angiography (16). In addition, CT provides a global perspective on the entire vasculature, including adjacent vascular beds; angiography is limited to selected vascular territories, which can lead to overlooking synchronous pseudoaneurysms or other vascular diseases. CT angiography has a high sensitivity and specificity for detecting arterial injuries. For example, in a study by Soto et al (6), CT angiography had a sensitivity and specificity of 95.1% and 98.7%, respectively, in detecting pseudoaneurysms in the proximal extremities.
The usefulness of CT angiography is still limited by imaging artifacts caused by bullet fragments or other metallic objects. The spatial resolution of CT angiography is inferior to that of conventional angiography, leading to limited detectability of subtle abnormalities. In addition, it may be difficult to distinguish between pseudoaneurysms and true aneurysms in small visceral arteries at CT. In general, more contrast material is needed for CT angiography than for angiography. In addition, endovascular therapy cannot be performed at the time of diagnosis (5).
CT virtual endoscopy is an additional feature that multi–detector row helical CT scanners provide but requires a dedicated workstation for image creation and interpretation (30).
MR Angiography
MR imaging techniques are numerous, and a comprehensive discussion of the use of these techniques for vascular imaging is beyond the scope of this article; we will make reference only to certain sequences and the advantages they offer. Three-dimensional gadolinium-enhanced MR angiography allows visualization of a lesion in any projection (Fig 4). Furthermore, much like with 3D CT angiography, no iodinated contrast material or ionizing radiation is necessary (31), making 3D contrast-enhanced MR angiography a valuable tool in the imaging of pseudoaneurysms in patients with impaired renal function and allergies to CT contrast material (32). Axial spoiled gradient-echo or spin-echo T1-weighted MR imaging allows visualization of intraluminal thrombus and the assessment of pseudoaneurysmal sac size (Fig 4b) (31).
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Figure 4a. Pseudoaneurysm in a 37-year-old woman who had undergone posterior lumbar fusion. (a) Axial gradient-echo T1-weighted MR angiogram demonstrates flow void in a pseudoaneurysm (arrowhead) due to turbulent flow. (b, c) Coronal spoiled gradient-echo (b) and conventional (c) T1-weighted MR images demonstrate a pseudoaneurysm of the right internal iliac artery (arrowhead). IVC = inferior vena cava.
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Figure 4b. Pseudoaneurysm in a 37-year-old woman who had undergone posterior lumbar fusion. (a) Axial gradient-echo T1-weighted MR angiogram demonstrates flow void in a pseudoaneurysm (arrowhead) due to turbulent flow. (b, c) Coronal spoiled gradient-echo (b) and conventional (c) T1-weighted MR images demonstrate a pseudoaneurysm of the right internal iliac artery (arrowhead). IVC = inferior vena cava.
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Figure 4c. Pseudoaneurysm in a 37-year-old woman who had undergone posterior lumbar fusion. (a) Axial gradient-echo T1-weighted MR angiogram demonstrates flow void in a pseudoaneurysm (arrowhead) due to turbulent flow. (b, c) Coronal spoiled gradient-echo (b) and conventional (c) T1-weighted MR images demonstrate a pseudoaneurysm of the right internal iliac artery (arrowhead). IVC = inferior vena cava.
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MR angiography remains time consuming compared with US or CT. It is not practical in the trauma setting because (a) it has limited availability, (b) proper monitoring of the patient in the magnet may be difficult, and (c) patients are often connected to imaging-incompatible medical equipment (6). The usefulness of MR angiography may also be limited due to (a) artifacts caused by patient motion, (b) metallic artifacts due to surgical clips or orthopedic hardware, (c) vessel tortuosity, (d) turbulent flow, or (e) pulsatility (33).
Conventional Angiography
Angiography remains the standard of reference for the diagnosis of pseudoaneurysms despite the advent of new imaging technologies such as CT angiography and MR angiography (5,16,32). A significant advantage of angiography is its capacity for real-time hemodynamic assessment of a particular vascular bed, which includes identifying collateral vessels to assess the expendability of the donor artery. Such assessment is important in treatment planning (discussed later). Other pseudoaneurysms not seen at US, CT, or MR imaging of the vascular bed in question may also be identified at angiography. The donor artery can be accurately identified and selective angiography performed to identify the characteristics of the pseudoaneurysm, including the size of its neck (4). Lesions that may have a similar appearance at CT (eg, pseudoaneurysms, arteriovenous fistulas, vascular malformations) are better differentiated with angiography (18). In addition, angiography provides a diagnostic tool with concomitant therapeutic potential if indicated (5,6).
The principal disadvantage of angiography as a diagnostic modality is its invasive nature and the increased risk of procedure-related complications (5,16,32). The risk of developing a pseudoaneurysm at the puncture site is as low as 1% in diagnostic procedures. However, this risk increases to 3.2%–7.7% in therapeutic procedures (9). The overall prevalence of a major vascular complication from angiography is reported to be 0.02%–9%. These complications include the development of pseudoaneurysms, hematomas, arteriovenous fistulas, distal embolization, arterial spasm, ischemia, intimal dissection, and vessel thrombosis (5,30). Furthermore, angiography makes use of ionizing radiation and iodinated contrast material, each with its own risks and complications (32).
Another limitation of angiography is that it does not help accurately assess the size of a pseudoaneurysm that contains a thrombus (Fig 5). In addition, vascular lesions, including other pseudoaneurysms, can be overlooked if particular vascular beds are not evaluated during catheter-directed angiography. As a result, angiography should be used as a focused diagnostic modality to complement and to compensate for pitfalls of other diagnostic modalities such as CT angiography and as a prelude to endoluminal treatment of pseudoaneurysms.
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Figure 5a. Thrombotic pseudoaneurysm in a 58-year-old man who presented with abdominal pain. The patient had fallen 10 days earlier. (a) Selective digital subtraction angiogram of the phrenic artery shows contained contrast material extravasation (arrowhead). (b) Contrast-enhanced CT scan shows a large pseudoaneurysm of the phrenic artery (arrow) that is nearly completely thrombosed. A small area of contrast enhancement is seen (arrowhead), a finding that corresponds to the extravasation seen in a. Clearly, the full extent of the pseudoaneurysm was underestimated at angiography.
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Figure 5b. Thrombotic pseudoaneurysm in a 58-year-old man who presented with abdominal pain. The patient had fallen 10 days earlier. (a) Selective digital subtraction angiogram of the phrenic artery shows contained contrast material extravasation (arrowhead). (b) Contrast-enhanced CT scan shows a large pseudoaneurysm of the phrenic artery (arrow) that is nearly completely thrombosed. A small area of contrast enhancement is seen (arrowhead), a finding that corresponds to the extravasation seen in a. Clearly, the full extent of the pseudoaneurysm was underestimated at angiography.
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Treatment
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Symptomatic pseudoaneurysms (intermittent or continuous bleeding) should be treated. However, the decision to treat asymptomatic pseudoaneurysms is controversial due to the unclear and variable natural history of pseudoaneurysms, particularly when factoring in the anatomic locations of various pseudoaneurysms, the clinical setting, and patient comorbidities. As mentioned earlier, pseudoaneurysms may undergo spontaneous thrombosis (20,34), and some investigators have advocated observation for small, asymptomatic pseudoaneurysms. However, there is currently no way to predict which pseudoaneurysms will undergo spontaneous thrombosis (21,35).
The controversy in the literature over spontaneous thrombosis of pseudoaneurysms mostly concerns postcatheterization extremity pseudoaneurysms and posttraumatic visceral (hepatic and splenic) pseudoaneurysms (20,21,34,35). We recommend observing small, asymptomatic pseudoaneurysms and treating them only if they enlarge, do not resolve, or become symptomatic. However, the risk of spontaneous rupture of extraorganic visceral pseudoaneurysms is very high regardless of their size, and the mortality rate for such ruptures in morbid postsurgical patients has been reported to approach 100% (23,24,26). Therefore, some authors believe that definitive treatment should be administered in all such cases (24,27).
Traditionally, pseudoaneurysms have been treated with surgical repair (9,10,21,24); however, traditional surgical treatment is invasive and is often associated with significantly higher morbidity and mortality rates (9,21,34). Over the past few years, minimally invasive radiologic treatments have been developed as alternatives to surgery, including US-guided compression, direct percutaneous management (including US-guided thrombin injection), and endoluminal management (36–41).
The therapeutic options (including observation) for the treatment of pseudoaneurysms should be tailored to the site, rupture risk, and clinical setting of the pseudoaneurysm as well as to patient comorbidities. A detailed discussion of the management of pseudoaneurysms relative to their location, morphologic features, and clinical setting is beyond the scope of this article. However, in the following paragraphs we provide an overview of the various therapeutic approaches and their respective merits, drawbacks, and indications.
Surgery
In general, surgical management of pseudoaneurysms varies widely and includes resection with a bypass procedure, arterial ligation, and partial or complete organ removal (42). The latter obviously involves intraorganic visceral pseudoaneurysms, which include renal pseudoaneurysms (partial or complete nephrectomy), hepatic pseudoaneurysms (segmentectomy), and splenic pseudoaneurysms (splenectomy). Surgical treatment of pseudoaneurysms involving vital arteries includes pseudoaneurysm resection with patch repair of the vital donor artery and arterial ligation with a bypass procedure. Surgical treatment of pseudoaneurysms involving expendable arteries may consist of arterial ligation alone. The definitions and examples of vital versus expendable donor arteries are discussed later (see "Endoluminal Management").
Surgery is the traditional treatment of choice. However, surgery has associated complications including anesthesia-related risks, bleeding, wound infection, lymphocele formation, radiculopathy, prolonged recovery time, perioperative myocardial infarction, and death (21,34). As a result of technologic advances in US-guided and endoluminal management of pseudoaneurysms, there is an ongoing paradigm shift toward minimally invasive management of pseudoaneurysms. However, surgery still plays a role in certain situations.
Surgical repair was the treatment of choice for superficial extremity pseudoaneurysms until 1991, when US-guided compression was introduced (10,21,43). The technique used for surgical repair depends on the presence or absence of concomitant infection. In noninfected pseudoaneurysms, primary repair of the artery is performed if possible, with the use of bypass grafts (autologous vein or synthetic graft prostheses) reserved for more damaged vessels. In the presence of infection, efforts are directed toward control of the infection with antibiotic therapy and drainage of abscesses or debridement of infected tissues. Surgical repair of the artery is then performed, preferably with vein bypass grafts rather than synthetic grafts and with positioning of the grafts in an extraanatomic location far from the infected tissues (10). Despite the growing popularity of imaging-guided compression and endoluminal management of catheter-related pseudoaneurysms, surgical management still plays an important role in (a) pseudoaneurysms with local mass effect complications such as ischemia and neuropathy (in an attempt to rapidly reduce this mass effect), (b) infected pseudoaneurysms, and (c) cases in which therapy with minimally invasive techniques has failed (10).
US-guided Compression
Since first being described by Fellmeth et al (43) in 1991, US-guided compression of pseudoaneurysms has rapidly replaced surgery in the treatment of postcatheterization pseudoaneurysms (10,21). Compression is performed with the US transducer itself, a procedure that permits direct and continuous visualization of the vessels (38). Pressure is applied to pseudoaneurysms in various locations depending on lesion accessibility. Typical protocol includes an initial 10–20-minute compression of the pseudoaneurysmal neck; if this is not feasible, the pseudoaneurysm itself is compressed (10,35,44). Compression should eliminate flow within the pseudoaneurysm but permit arterial perfusion to the extremity (10). Cycles are repeated for up to 1 hour. Anticoagulation therapy decreases the success rate; therefore, anticoagulants should be discontinued prior to the procedure if possible (10).
US-guided compression is limited by patient and operator discomfort due to the long compression time required. Compression is painful to the patient, necessitating the administration of analgesics (10,45). Only fairly superficial pseudoaneurysms can be treated with this method, such as those affecting the femoral, axillary, and brachial arteries (10). In obese patients, this therapeutic application can be hindered even at these sites. Other factors affecting the success of this method include anticoagulation status, pseudoaneurysm size, whether the pseudoaneurysm is simple or complex, age of the pseudoaneurysm, and the length and width of the pseudoaneurysmal neck (10). Rare complications such as venous thrombosis, skin necrosis, and pseudoaneurysmal rupture have been reported (45). Local arterial thrombosis and distal embolization due to occlusion of the underlying artery caused by the pressure required to compress the pseudoaneurysm have also been reported (40). The failure rate of this technique has been reported to be as high as 15%–38%, with a recurrence rate after initial success as high as 20%–30% in patients who have received anticoagulants (10,21,45,46).
US-guided Percutaneous Thrombin Injection
At many institutions, US-guided percutaneous thrombin injection has replaced US-guided compression as the therapeutic method of choice for treatment of postcatheterization pseudoaneurysms (21,40,46). Thrombin converts inactive fibrinogen into fibrin, leading to thrombus formation (10). Percutaneous thrombin injection was first reported in 1986 by Cope and Zeit, who performed the procedure under fluoroscopic guidance. However, this method was not fully embraced until the work of Kang et al was published in 2000 (38).
Thrombin preparation consists of adding sterile normal saline solution to the commercially available sterile thrombin powder (10). Most investigators use a concentration of 1000 IU/mL (10,21,37,40,45). However, some authors advocate the use of a lower concentration of 100 IU/mL (47).
After complete US evaluation of the pseudoaneurysm is performed, thrombin is injected into the sac under US guidance with a sterile technique. The needle is positioned in the center of the sac, and thrombin is injected at a constant rate while flow within the sac is monitored with Doppler US. The thrombin is continuously injected until flow within the sac ceases, usually within seconds (Fig 6) (10,21,45). The volume of injected thrombin ranges from 0.5 to 1.0 mL (37,47).
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Figure 6a. Pseudoaneurysm in a patient who had undergone cardiac catheterization. (a) Color Doppler US image shows a pseudoaneurysm of the left common femoral artery (PsA). (b) On a color Doppler US image obtained after percutaneous injection of 1 mL of thrombin (concentration of 1000 IU/mL) through an 18-gauge needle, no flow is seen in the pseudoaneurysm (PsA).
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Figure 6b. Pseudoaneurysm in a patient who had undergone cardiac catheterization. (a) Color Doppler US image shows a pseudoaneurysm of the left common femoral artery (PsA). (b) On a color Doppler US image obtained after percutaneous injection of 1 mL of thrombin (concentration of 1000 IU/mL) through an 18-gauge needle, no flow is seen in the pseudoaneurysm (PsA).
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Technical success rates with this method in the setting of postcatheterization pseudoaneurysms are greater than 90% (10,21,48), even in patients undergoing anticoagulation or antiplatelet therapy (37,40,45,46,48,49), making this method superior to US-guided compression (37,44,46, 47,49). US-guided percutaneous thrombin injection is not limited to use in superficial arteries; pseudoaneurysms in deep visceral arteries may also be treated with this method (37,39), especially when the donor artery is endoluminally inaccessible and its occlusion is not a viable option (4). Arteries above the inguinal ligament can also be treated with this method, which is contraindicated in US-guided compression due to the potential risk of rupture (44).
Complication rates as low as 4% have been reported (48). Complications include thromboembolic events due to thrombin flowing beyond the clot into the arterial system, rather than clot embolization (9,10,21,37,39,40,45,47–49). For this reason, it has been proposed that a lower concentration of thrombin (100 IU/mL) be used (47). Some authors advocate the use of balloon occlusion of the pseudoaneurysmal neck prior to thrombin injection. However, such occlusion makes the procedure more invasive, and the related complications outweigh the theoretic potential benefit (10,39). Postprocedural monitoring of peripheral pulses and the ankle-brachial index allows early detection of peripheral thromboembolism downstream from the injection site (37). In the event of downstream thrombosis, intraarterial thrombolysis should be promptly undertaken (47). Other potential complications include venous thrombosis and allergic reactions such as generalized urticaria and anaphylaxis (9,10,21, 37,45,48,49). In fact, contraindications for this method include a history of allergic reaction to thrombin. Skin testing prior to therapy has been proposed for avoiding potentially fatal reactions (37,46). Other contraindications include local infection and distal limb ischemia (40,45).
Although thrombin is the preferred agent for percutaneous embolization of pseudoaneurysms, other materials such as coils may be used, either independently or in conjunction with thrombin (4,10).
Endoluminal Management
Endoluminal management serves to exclude a pseudoaneurysm from the circulation. Selecting the optimal method depends on the size of the pseudoaneurysmal neck and the expendability of the donor artery (4). Exclusion methods fall into two broad categories: embolization and stent placement (Figs 7, 8) (4,10). Figure 8 illustrates an algorithm for the management of non-catheter-related extremity pseudoaneurysms.
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Figure 8. Schematic illustrates an algorithm for the management of all but superficial postcatheterization pseudoaneurysms, which should be treated with US-guided thrombin injection.
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A pseudoaneurysm that arises from an expendable donor artery and does not have a collateral supply such as a visceral branch (eg, a segmental or intralobar renal arterial branch) is treated with embolization of the afferent artery (Fig 9) (4). There are several visceral arteries that have a well-established collateral supply, including the gastroduodenal, hepatic, and splenic arteries and other upper gastrointestinal arteries (4,26). In addition, some pelvic and distal extremity arteries have a collateral supply—for example, the internal iliac artery and the profunda femoris artery, respectively. When embolizing arteries with numerous collateral vessels, one must embolize both proximal and distal to the pseudoaneurysm to completely exclude it from the circulation by preventing backflow from the collateral circulation (Fig 10) (4).
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Figure 9a. Occlusion of a pseudoaneurysm with coil embolization in a 67-year-old man who presented to the emergency department after sustaining a gunshot wound to the right arm. (a) Digital subtraction angiogram shows a pseudoaneurysm of the circumflex humeral artery (arrowhead). (b) Digital subtraction angiogram shows exclusion of the pseudoaneurysm from the donor artery by means of coil embolization (arrowhead).
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Figure 9b. Occlusion of a pseudoaneurysm with coil embolization in a 67-year-old man who presented to the emergency department after sustaining a gunshot wound to the right arm. (a) Digital subtraction angiogram shows a pseudoaneurysm of the circumflex humeral artery (arrowhead). (b) Digital subtraction angiogram shows exclusion of the pseudoaneurysm from the donor artery by means of coil embolization (arrowhead).
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Figure 10a. Occlusion of a pseudoaneurysm with proximal and distal embolization in a 61-year-old woman with cholangiocarcinoma. The patient had undergone a Whipple procedure, percutaneous transhepatic cholangiography on several occasions, and biliary drainage catheter placement. (a) Digital subtraction angiogram demonstrates a pseudoaneurysm off a branch of the right hepatic artery (arrowhead). (b) Digital subtraction angiogram shows the pseudoaneurysm with its afferent (arrowhead) and efferent (arrow) hepatic arterial segments. (c) Digital subtraction angiogram demonstrates exclusion of the pseudoaneurysm by means of distal (arrow) and proximal (arrowhead) embolization.
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Figure 10b. Occlusion of a pseudoaneurysm with proximal and distal embolization in a 61-year-old woman with cholangiocarcinoma. The patient had undergone a Whipple procedure, percutaneous transhepatic cholangiography on several occasions, and biliary drainage catheter placement. (a) Digital subtraction angiogram demonstrates a pseudoaneurysm off a branch of the right hepatic artery (arrowhead). (b) Digital subtraction angiogram shows the pseudoaneurysm with its afferent (arrowhead) and efferent (arrow) hepatic arterial segments. (c) Digital subtraction angiogram demonstrates exclusion of the pseudoaneurysm by means of distal (arrow) and proximal (arrowhead) embolization.
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Figure 10c. Occlusion of a pseudoaneurysm with proximal and distal embolization in a 61-year-old woman with cholangiocarcinoma. The patient had undergone a Whipple procedure, percutaneous transhepatic cholangiography on several occasions, and biliary drainage catheter placement. (a) Digital subtraction angiogram demonstrates a pseudoaneurysm off a branch of the right hepatic artery (arrowhead). (b) Digital subtraction angiogram shows the pseudoaneurysm with its afferent (arrowhead) and efferent (arrow) hepatic arterial segments. (c) Digital subtraction angiogram demonstrates exclusion of the pseudoaneurysm by means of distal (arrow) and proximal (arrowhead) embolization.
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A pseudoaneurysm arising from an inexpendable donor artery must be excluded from the circulation while preserving the donor artery. The width of the pseudoaneurysmal neck relative to the diameter of the donor artery is the determining factor in the method used. A vital donor artery may be embolized in certain emergent situations (eg, rupture with active bleeding); however, distal blood flow must then be restored by means of a surgical bypass procedure (Fig 11).
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Figure 11a. (a) Digital subtraction angiogram shows a pseudoaneurysm of the suprageniculate popliteal artery. (b) Digital subtraction angiogram demonstrates successful embolization distal (arrowhead) and proximal (arrow) to the pseudoaneurysm. The patient subsequently underwent a surgical bypass procedure for occlusion of the popliteal artery.
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Figure 11b. (a) Digital subtraction angiogram shows a pseudoaneurysm of the suprageniculate popliteal artery. (b) Digital subtraction angiogram demonstrates successful embolization distal (arrowhead) and proximal (arrow) to the pseudoaneurysm. The patient subsequently underwent a surgical bypass procedure for occlusion of the popliteal artery.
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If the neck is narrow, the pseudoaneurysm may be embolized with catheter-directed delivery of coils (the preferred embolization material) into the sac itself (Fig 12) (4,24,25). Coils fall into two main categories: nondetachable and detachable. The first category includes coils that reassume their shape immediately after deployment from the catheter. These coils are available in a wide array of diameters and lengths. They are made of either stainless steel or platinum. Polyester fibers are incorporated into the body of the coil to increase its thrombogenicity. Newer coils are made of platinum, are softer, and have a more complex (helical) shape; consequently, such coils conform to the shape of and fill the pseudoaneurysmal sac, thereby allowing the use of fewer coils for embolization. However, because platinum coils are softer, initial placement of stainless steel coils may be required to act as scaffolding. Detachable coils are held to the pusher guide wire by either a mechanical or electrochemically dissolvable connection, which is released to deploy the coil. This facilitates more accurate deployment and the possibility of readjusting the position of the coil before its final deployment. A disadvantage of using coils as an embolization material is the potential for recanalization of the embolized sac if the coils are not tightly packed. However, this drawback has been largely overcome with the use of soft helical coils, which may be tightly packed in the pseudoaneurysmal sac (50). Other agents such as thrombin or N-butyl 2-cyanoacrylate (glue) may be used, either alone (25,41) or in addition to coils (4).
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Figure 12a. (a) Digital subtraction angiogram shows a pseudoaneurysm of the proper hepatic artery (arrow). (b) Digital subtraction angiogram demonstrates embolization of the pseudoaneurysm (arrow) with preservation of flow in the distal hepatic artery (arrowhead).
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Figure 12b. (a) Digital subtraction angiogram shows a pseudoaneurysm of the proper hepatic artery (arrow). (b) Digital subtraction angiogram demonstrates embolization of the pseudoaneurysm (arrow) with preservation of flow in the distal hepatic artery (arrowhead).
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If the neck is wide, the pseudoaneurysm can still be embolized with catheter-directed delivery of embolization materials. However, remodeling is required to prevent outflow of these materials into and distal embolization of the donor artery and to ensure adequate embolization of the pseudoaneurysmal sac. This remodeling may be performed with the use of a stent cage, with the catheter tip directed through the lattice of the stent prior to release of the coils (Fig 13), or by trapping the coils by means of temporary balloon occlusion of the donor artery between coil deployments (10). If distal arterial embolization is a concern, detachable balloons may be used as the embolic agent (9,22). Another option, if the pseudoaneurysmal neck is wide, is stent-graft (covered stent) placement across the neck to exclude the pseudoaneurysm (Figs 14, 15) (10). This method is relatively contraindicated in mycotic pseudoaneurysms due to potential stent-graft infection. Stent-graft placement requires a higher profile and a stiffer delivery system than does catheter-directed coil embolization. As a result, the arterial anatomy and the caliber of the arteries leading to and at the pseudoaneurysm site should be favorable (ie, reduced arterial tortuosity and large-diameter arteries). An additional reason for placing stent-grafts only in larger arteries is that in small arteries they pose a higher risk of thrombosis. Visceral pseudoaneurysms, which are usually smaller and located off small and tortuous donor arteries, pose a particular challenge for stent-graft placement.
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Figure 13a. (a) Digital subtraction angiogram shows a posttraumatic pseudoaneurysm of the common carotid artery (arrow). (b) Digital subtraction angiogram demonstrates exclusion of the pseudoaneurysm with use of a bare (uncovered) stent and coil embolization through the interstices of the stent (arrow). The stent acts as a barrier, confining the coils to the pseudoaneurysm and keeping them out of the patent vital carotid artery.
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Figure 13b. (a) Digital subtraction angiogram shows a posttraumatic pseudoaneurysm of the common carotid artery (arrow). (b) Digital subtraction angiogram demonstrates exclusion of the pseudoaneurysm with use of a bare (uncovered) stent and coil embolization through the interstices of the stent (arrow). The stent acts as a barrier, confining the coils to the pseudoaneurysm and keeping them out of the patent vital carotid artery.
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Figure 14a. Exclusion of a pseudoaneurysm by means of stent-graft placement in a 61-year-old man who had undergone prostatectomy and cystectomy with Indiana pouch creation for bladder carcinoma. A Jackson-Pratt drain placed in the surgical bed at the time of surgery had subsequently eroded into the left external iliac artery. (a) Contrast-enhanced CT scan reveals a pseudoaneurysm of the left external iliac artery (arrowhead). (b) Digital subtraction angiogram shows the pseudoaneurysm (arrowhead) prior to stent-graft (covered stent) placement. (c) Digital subtraction angiogram shows successful exclusion of the pseudoaneurysm with the stent-graft.
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Figure 14b. Exclusion of a pseudoaneurysm by means of stent-graft placement in a 61-year-old man who had undergone prostatectomy and cystectomy with Indiana pouch creation for bladder carcinoma. A Jackson-Pratt drain placed in the surgical bed at the time of surgery had subsequently eroded into the left external iliac artery. (a) Contrast-enhanced CT scan reveals a pseudoaneurysm of the left external iliac artery (arrowhead). (b) Digital subtraction angiogram shows the pseudoaneurysm (arrowhead) prior to stent-graft (covered stent) placement. (c) Digital subtraction angiogram shows successful exclusion of the pseudoaneurysm with the stent-graft.
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Figure 14c. Exclusion of a pseudoaneurysm by means of stent-graft placement in a 61-year-old man who had undergone prostatectomy and cystectomy with Indiana pouch creation for bladder carcinoma. A Jackson-Pratt drain placed in the surgical bed at the time of surgery had subsequently eroded into the left external iliac artery. (a) Contrast-enhanced CT scan reveals a pseudoaneurysm of the left external iliac artery (arrowhead). (b) Digital subtraction angiogram shows the pseudoaneurysm (arrowhead) prior to stent-graft (covered stent) placement. (c) Digital subtraction angiogram shows successful exclusion of the pseudoaneurysm with the stent-graft.
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Figure 15a. Exclusion of a pseudoaneurysm by means of stent-graft placement in a patient who had sustained traumatic injury in a motor vehicle accident. (a) Digital subtraction angiogram demonstrates a pseudoaneurysm of the aorta (arrowhead). (b) Digital subtraction angiogram shows a deployed stent-graft. (c) Digital subtraction angiogram obtained after stent-graft deployment demonstrates minimal residual filling of the pseudoaneurysm.
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Figure 15b. Exclusion of a pseudoaneurysm by means of stent-graft placement in a patient who had sustained traumatic injury in a motor vehicle accident. (a) Digital subtraction angiogram demonstrates a pseudoaneurysm of the aorta (arrowhead). (b) Digital subtraction angiogram shows a deployed stent-graft. (c) Digital subtraction angiogram obtained after stent-graft deployment demonstrates minimal residual filling of the pseudoaneurysm.
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Figure 15c. Exclusion of a pseudoaneurysm by means of stent-graft placement in a patient who had sustained traumatic injury in a motor vehicle accident. (a) Digital subtraction angiogram demonstrates a pseudoaneurysm of the aorta (arrowhead). (b) Digital subtraction angiogram shows a deployed stent-graft. (c) Digital subtraction angiogram obtained after stent-graft deployment demonstrates minimal residual filling of the pseudoaneurysm.
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Endovascular techniques have a lower complication rate in the treatment of visceral pseudoaneurysms than does surgical management (22,25). Complications associated with endovascular techniques include intraprocedural rupture of the pseudoaneurysm (24). In addition, recanalization of the embolized vessel and reconstitution of arterial flow to the pseudoaneurysm (delayed failure of embolization) has been reported; however, this phenomenon is very rare (24).
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Summary
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Pseudoaneurysms are common vascular abnormalities. The advent of new noninvasive diagnostic imaging techniques with increased sensitivity for asymptomatic disease has led to more frequent diagnosis of pseudoaneurysms. Conventional angiography remains the standard of reference for diagnosis but is invasive, and noninvasive diagnostic modalities should be included in the initial work-up. The potential complications of many pseudoaneurysms carry high morbidity and mortality rates, and the development of these complications is unpredictable. Surgery has classically been the treatment of choice. However, radiology has introduced alternative minimally invasive treatment techniques that are associated with lower morbidity and mortality rates. A complete work-up to determine the location of the pseudoaneurysm and to evaluate surrounding structures and relevant vascular anatomy is essential in the selection of the treatment technique. Treatment options include observation and should be tailored to the location, rupture risk, and clinical setting of the pseudoaneurysm and to any patient comorbidities.
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Abstract
LEARNING OBJECTIVES
