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E71GASTROINTESTINAL IMAGING

Robert A. Jesinger, MD, MSE • Andrew A. Thoreson, MD • Ramit Lamba, MBBS, MD

Abnormally enlarged visceral arteries in the abdomen and pelvis must be recognized radiologically because early treatment can improve the quality of life and prevent life-threatening complications. These lesions, typically classified as aneurysms and pseudoaneurysms, are being detected more fre-quently with increased utilization of imaging and have various causes (eg, atherosclerosis, trauma, infection) and complications that may be identified radiologically. Ultrasonography, computed tomography, and magnetic reso-nance imaging often enable detection of visceral vascular lesions, but an-giography is important for further diagnosis and treatment. Endovascular treatment is often the first-line therapy. Endovascular intervention or open surgical repair is necessary for all visceral pseudoaneurysms and is likely indicated for visceral aneurysms 2 cm or more in diameter. Endovascular exclusion of flow can be achieved with coils, stents, and injectable liquids. Techniques include embolization (“sandwich” or “sac-packing” technique), exclusion of flow with luminal stents, and stent-assisted coil emboliza-tion. Management often depends on the location and technical feasibility of endovascular repair. Embolization is usually preferred for aneurysms or pseudoaneurysms within solid organs, and the sandwich technique is often used when collateral flow is present. Covered stent placement may be preferred to preserve the parent artery when main visceral vessels are being treated. It is usually tailored to lesion location, and a cure can often be effected while preserving end-organ arterial flow. Posttreatment follow-up is usually based on treatment location, modality accuracy, and potential consequences of treatment failure. Follow-up imaging may help identify vessel recanalization, unintended thrombosis of an artery or end organ, or sequelae of nontarget embolization. Retreatment is usually warranted if the clinical risks for which embolization was performed are still present.radiographics.rsna.org

Abdominal and Pelvic Aneu-rysms and Pseudoaneurysms: Imaging Review with Clinical, Radiologic, and Treatment Correlation1

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LEARNING OBJECTIVES

After completing this journal-based SA-

CME activity, partic-ipants will be able to:

■ Describe the com-mon locations of and complications associated with ab-dominal and pelvic visceral artery aneu-rysms and pseudo-aneurysms.

■ Identify the key imaging features of abdominal and pel-vic aneurysms and pseudoaneurysms.

■ Discuss the endo-vascular treatment approaches to ab-dominal and pelvic aneurysms and pseudoaneurysms.

Abbreviations: CHA = common hepatic artery, GDA = gastroduodenal artery, LGA = left gastric artery, MIP = maximum intensity projection, PDA = pancreaticoduodenal artery, PHA = proper hepatic artery, SMA = superior mesenteric artery

RadioGraphics 2013; 33:E71–E96 • Published online 10.1148/rg.333115036 • Content Codes: 1From the Department of Radiology, David Grant USAF Medical Center, 101 Bodin Cir, Travis AFB, CA 94535 (R.A.J., A.A.T.); Department of Radiology and Radiological Sciences, Uniformed Services University of the Health Sciences, Bethesda, Md (R.A.J.); and Department of Radiology, University of California–Davis, Sacramento, Calif (R.L.). Presented as an education exhibit at the 2010 RSNA Annual Meeting. Received February 28, 2011; revision requested April 13; final revision received August 28, 2012; accepted September 25. For this journal-based SA-CME activity, the authors, editor, and reviewers have no relevant relationships to disclose. Address correspondence to R.A.J. (e-mail: [email protected]).

The views expressed in this material are those of the authors and do not reflect the official policy or position of the U.S. Government, the Depart-ment of Defense, or the Department of the Air Force.

E72 May-June 2013 radiographics.rsna.org

IntroductionVascular abnormalities in the abdomen and pelvis are of interest to all radiologists who perform and interpret abdominal imaging examinations. The incidence of vascular disease in adult patients, as identified during contrast material–enhanced ab-dominal computed tomography (CT) examina-tions, is high when atherosclerosis is considered, and most practicing radiologists are familiar with the diagnosis and management of abdominal aortic aneurysms and aortoiliac occlusive disease. Less commonly encountered anomalies of vascu-lar enlargement—specifically visceral aneurysms and pseudoaneurysms—are the focus of this article.

Abdominal and pelvic visceral vascular an-eurysms include true aneurysms, which have all three arterial wall layers intact, and false aneu-rysms (pseudoaneurysms), which lack a complete arterial wall. Most true visceral aneurysms result from degeneration of the arterial media in the setting of atherosclerosis, fibromuscular dyspla-sia, or collagen vascular disorders. Complications of true aneurysms can include compression of adjacent structures, in situ thrombosis with or without distal embolization, and life-threatening hemorrhage from rupture. Most abdominal and pelvic pseudoaneurysms result from trauma, in-flammation, or infection. Complications of pseu-doaneurysms include early rupture, compression of adjacent structures, and a higher frequency of aneurysm infection.

A second focus of this article will be a descrip-tion of the techniques for minimally invasive (in-terventional) endovascular treatment of visceral aneurysms and pseudoaneurysms. Many true aneurysms and essentially all pseudoaneurysms require treatment (1). For true aneurysms, size usually guides treatment, with visceral aneurysms larger than 2 cm in diameter thought to have a high risk of rupture and thus requiring treatment. For visceral pseudoaneurysms, the lack of an in-tact vessel wall leads to continued enlargement and subsequent rupture in nearly all cases, thus necessitating treatment.

Visceral Artery AnatomyKey abdominal and pelvic visceral arteries in-clude the celiac axis and its branches, the superior mesenteric artery (SMA), the inferior mesenteric artery, the renal arteries, the gonadal arteries, and the internal iliac arteries (IIAs) (Fig 1a). Numerous potential collateral arterial pathways between the celiac axis and the SMA and between the SMA and the inferior mesenteric artery can become enlarged or aneurysmal if flow through these pathways is chronically increased. Two clas-sic collateral flow pathways between the celiac axis and the SMA are the gastroepiploic artery and the pancreaticoduodenal arteries (PDAs) (Fig 1b).

Imaging ToolsNoninvasive imaging techniques for identifying visceral vascular abnormalities include ultraso-nography (US), CT, and magnetic resonance (MR) imaging.

UltrasonographyDiagnostic US is commonly used in screening for abdominal aortic aneurysms, confirming stenosis of native aortic branch vessels (eg, celiac, superior mesenteric, and renal arteries), and depicting sur-gically created anastomotic sites (eg, arterial grafts to organ transplants) (2). Typically, low-frequency (eg, 4-MHz) transducers with gray-scale and Dop-pler US capabilities are used, allowing estimation of vascular size and internal flow rates. Abdominal US is also ideally suited for assessing vascular abnormalities in the solid abdominal organs. However, US is limited by bowel gas, which can obscure visualization of retroperitoneal and mes-enteric vessels. As a result, tools such as CT and MR imaging play a greater role in confirming the diagnosis of and further characterizing abdominal and pelvic aneurysms and pseudoaneurysms, as well as in delineating approaches for endovascular treatment or depicting the vascular pathways that require surgical ligation for exclusion of flow.

Computed TomographyMulti–detector row CT is probably the most frequently used modality to formally assess arte-rial flow in the abdomen and pelvis. Multiphase acquisitions (precontrast, arterial phase, venous

RG • Volume 33 Number 3 Jesinger et al E73

Figure 1. Drawings illustrate the normal arterial and venous anatomy in the abdomen. cb = colic branches of the SMA, ch = common hepatic artery, ci = common iliac artery, ei = external iliac artery, g = gonadal artery, gda = gastroduodenal artery, ge = gastroepiploic artery, ii = internal iliac artery, ima = inferior mesenteric artery, jb = jejunal branches of the SMA, lg = left gastric artery, lh = left hepatic artery, pda = pancreaticoduodenal artery, ph = proper hepatic artery, r = renal artery, rg = right gastric artery, rh = right hepatic artery, s = splenic artery. (a) Arterial anatomy includes major abdominal aortic branch arteries. (b) More detailed visceral artery anatomy is shown. (Fig 1 courtesy of Gilbert Gardner, MA, CMI, David Grant USAF Medical Center, Travis AFB, Calif.)

phase, and delayed phase images) allow detailed assessment of vascular anatomy and disease. Ar-terial phase CT angiographic images are typically obtained 20–30 seconds after the onset of periph-eral intravenous injection at a rate of 3–4 mL/sec. The volume and mixture of contrast materials can vary, but typically 120–150 mL of iodinated contrast material is used. The degree of enhance-ment is dependent on the rate and timing of the injection and the patient’s cardiac output and body habitus (3). Visceral venous phase imaging typically occurs 70–120 seconds after the onset of peripheral intravenous injection. Delayed phases of imaging vary in timing.

MR ImagingSimilar to CT, MR imaging allows multiphase vascular depiction of the abdomen and pel-vis, but it utilizes potentially less nephrotoxic contrast agent and no ionizing radiation. MR imaging can also depict vascular flow without

injection of contrast material (eg, flow-sensitive, time-of-flight angiographic techniques). In addi-tion, newer MR systems allow rapid breath-hold vascular imaging and flow quantification with phase-contrast techniques.

Imaging Diagnosis of Aneurysms and Pseudoaneurysms

In the abdomen and pelvis, most visceral aneu-rysms arise from the origin of the celiac axis or its branches—the superior mesenteric, inferior mes-enteric, renal, and internal iliac arteries (Fig 2a). True aneurysms have all three arterial wall layers intact, whereas pseudoaneurysms lack a complete arterial wall (Fig 2b). Visceral artery aneurysms usually appear as circumscribed, anechoic tubular (fusiform) or saccular vascular enlargements at gray-scale US. Typically, turbulent internal flow is


seen at Doppler US. At CT, the aneurysm lumen attenuation follows that of other arterial lumina on unenhanced images and at all phases of con-trast material administration, assuming the aneu-rysm is patent. At MR imaging, similar enhance-ment patterns can be seen, but other features may include motion artifact in the phase-en-coding direction related to aneurysm pulsations. Visceral artery pseudoaneurysms can have an imaging appearance similar to that of aneurysms, but typically the margin of the pseudoaneurysm is more irregular than that of an aneurysm and the pseudoaneurysm is typically surrounded by a hematoma. Abdominal visceral aneurysms are rare, and, although true aneurysms are often in-cidentally discovered, pseudoaneurysms are more frequently encountered in specialist centers deal-ing with acute trauma patients or high volumes of abdominal interventions.

Endovascular Treatment PrinciplesFor visceral aneurysms and pseudoaneurysms, endovascular therapy may be performed with a variety of techniques. The usual treatment ap-proach begins with remote percutaneous access through a valved sheath placed in an arterial or

venous access site (eg, a 6-F [6-mm inner cir-cumference and approximately 2-mm internal diameter] sheath placed in the femoral artery or vein). From a remote access site, the visceral vascular lesion is selected with a series of endo-vascular guidewires and catheters (Fig 3). It is common to have a series of telescoping luminal catheter components, typically consisting of the sheath at the vascular access site and a “base” catheter (usually 4–5 F) used to access the main visceral vessel (eg, splenic artery). The base cath-eter, in turn, provides support for a smaller (<3-F) telescoped microcatheter used to subselect a more distal vascular location for treatment. Alter-natively, when remote access is not possible, di-rect puncture of the visceral vascular lesion with imaging guidance may be considered.

Regardless of approach, the overriding prin-ciple in treatment is “exclusion” of the vascular lesion from the circulation, where it is at risk for being symptomatic or overtly dangerous. Exclu-sion initially conjures up thoughts of embolization (the intentional endovascular placement of space-occupying material for vessel thrombosis), and this is often the treatment of choice. Embolization therapy not only occupies and excludes a vascular volume of interest (eg, aneurysm sac) from the adjacent vascular circulation, but it also reinforces

Figure 2. Abdominal arterial aneurysms and pseudoaneurysms. (a) Drawing il-lustrates abdominal aortic (a) and visceral aortic branch aneurysms. ch = common hepatic artery, ci = common iliac artery, lg = left gastric artery, r = renal artery, s = splenic artery. The aortic and common iliac aneurysms in the illustration are not a focus of this article. (b) Drawings show arterial cross-sections of a normal vessel, a false an-eurysm (pseudoaneurysm) with disruption of the intimal and medial layers of the arte-rial wall, and a true aneurysm with all three arterial wall layers intact. (Fig 2 courtesy of Gilbert Gardner, MA, CMI, David Grant USAF Medical Center, Travis AFB, Calif.)


the inherent properties of in vivo thrombosis by decreasing flow, facilitating thrombogenicity, and inciting an inflammatory response. Common em-bolization materials include simple (eg, coils) and complex (Amplatzer Vascular Plug; St Jude Medi-cal, St Paul, Minn) metallic structures; particulate materials such as a gelatin sponge (Gelfoam; Phar-macia Upjohn/Pfizer, Kalamazoo, Mich); and liq-uids such as n-butyl cyanoacrylate (Trufill; Cordis Neurovascular, Miami Lakes, Fla) and ethylene vinyl alcohol copolymer (Onyx; eV3 Endovascular/Covidien, Plymouth, Minn).

Coils are the most frequently used material and are available in a wide range of sizes and shapes, from simple tapered and cylindric forms to complex structures designed for a specific ap-plication. “Pushable” coils are typically placed by advancing them (with a telescoped “pusher” wire or an injected liquid) through a catheter, the tip of which lies within the vascular lesion or location to be thrombosed. Often, multiple coils are needed for adequate vessel occlusion, de-pending on the scenario or lesion size. At times, controlled, accurate deployment of a coil can be achieved with a coil design that involves a detach-able connection wire, which remains attached to the coil until a direct current, hydrostatic pres-sure, or other force is applied. This “detachable” feature facilitates accurate deployment of coils and allows their recapture or replacement until the precise location is reached. A newer method for vascular occlusion involves a complex metal-lic structure. The Amplatzer Vascular Plug (St

Jude Medical) is one such device, consisting of a three-dimensional nitinol meshwork that is advanced through a delivery catheter. Once in the desired location, the plug is deployed by un-screwing a detachable safety wire. This product is designed for precise deployment using a single self-expandable occlusion device.

Injectable liquid agents can also be used to exclude a vascular lesion from the circulation. “Cast-forming” agents such as n-butyl cyanoac-rylate and ethylene vinyl alcohol copolymer allow controlled injection of an initially flowing mate-rial that eventually hardens as a cast in the lumen of the vascular lesion. Also, time-tested agents such as gelatin sponges and thrombin (Throm-bin-JMI; King Pharmaceuticals, Bristol, Tenn) can be injected to initiate the coagulation cascade for lesion thrombosis.

The choice of material or method to exclude a vascular lesion from the circulation greatly de-pends on the anatomy of the lesion, the afferent-parent and efferent vessels, and the presence or absence of collateral circulation. Methods for the delivery of endovascular materials are numer-ous but are based on several core techniques or themes. The first technique is the most basic and consists of simply placing coils in a vascular sac until it is excluded from the circulation or oblit-erated (Fig 4a). This “sac-packing” technique is well suited for a saccular aneurysm with a narrow “neck,” allowing retention of the coils in the sac

Figure 3. Drawing shows the typical cath-eter-guidewire components used to access the visceral vasculature. bc = base catheter, mc = microcatheter, mw = microwire, s = sheath. (Courtesy of Gilbert Gardner, MA, CMI, David Grant USAF Medical Center, Travis AFB, Calif.)


Figure 4. Drawings illustrate endovascular techniques for the treatment of arterial aneurysms and pseudoaneurysms. (a) A coil is placed within the aneurysm sac to exclude flow (sac-packing technique). (b) Coils are placed within the parent vessel distal and proximal to the aneurysm sac to exclude flow (sandwich technique). Collateral flow (arrow) is blocked by the distal coil. (c) Cast-forming agents are instilled by using either direct transcutaneous puncture of the aneurysm sac or transcatheter intravascular delivery. (d) Aneurysm exclusion is achieved with a covered stent. (e) A bare metal stent and aneurysm coil placement are used for aneurysm exclusion (stent-assisted coil embolization). (Fig 4 courtesy of Gilbert Gardner, MA, CMI, David Grant USAF Medical Center, Travis AFB, Calif.)

and preserving the parent vessel flow to the vis-ceral end organ. The second technique, known as the “sandwich” technique, involves embolization of the afferent and efferent vessels to completely exclude all portions of the lesion from the circula-tion (Fig 4b). This method is used in scenarios in which collateral flow could “flow back” into the le-sion if only one segment of the vessel is occluded. A common example is that of splenic artery aneu-rysm embolization. Embolization of only the feed-ing-afferent artery would be unsatisfactory, since the aneurysm sac could continue to be pressurized through short gastric or distal pancreatic arteries acting as retrograde-filling collateral vessels. The efferent (“back door”) artery is usually closed first, followed by the afferent (“front door”) artery. The sandwich technique may also be applied in more complex settings of multiple afferent or efferent vessels. The third technique is embolization with cast-forming agents using transcatheter delivery or

direct percutaneous injection (Fig 4c). Scenarios in which this technique is beneficial include le-sions with high blood flow and lesions in which the desired position of the embolic device is more distal to the delivery catheter tip, circumstances in which the concepts of injection “control” and distal nidus “penetration,” respectively, make cast-forming agents desirable.

Vascular exclusion techniques beyond emboli-zation include the use of covered and uncovered (ie, bare metal) stents (Fig 4d). Several covered stent designs consist of a metallic superstructure covered with biocompatible material so that the interstices (holes) of the stents are no longer po-rous. The benefit of using a covered stent is that it provides a new lumen through a parent vessel to exclude a vascular lesion. This technique is par-ticularly useful in the setting of an aneurysm with a wide neck. If the aneurysm neck in the parent artery is large, use of conventional coil emboliza-tion is unwise because of the increased risk of coil dislodgement or migration from the aneurysm


sac, potentially resulting in nontarget emboliza-tion of other important structures or thrombosis of the parent vessel. A known drawback of cov-ered stents that can limit their use is difficulty in advancing the stents through small or tortuous vessels; hence, they are often reserved for more accessible, proximal vascular locations. Finally, stent-assisted coil embolization is a combination technique used in certain anatomically chal-lenging lesions (Fig 4e). This technique blends the use of a bare metal stent and coils. The bare metal stent is deployed across the lesion to serve as a scaffold, and a catheter is then “nosed” into the interstices of the uncovered stent. The safety of coil embolization has improved markedly be-cause the coils are now “caged” behind the stent.

In summary, many interventional techniques (some beyond the scope of this article) are avail-able to treat aneurysms and pseudoaneurysms. The techniques outlined in this section have been used to treat lesions described in this article. For visceral aneurysms and pseudoaneurysms, en-dovascular therapy with a combination of coils, gelatin sponges, liquid polymer embolization, and stent placement is often the first-line therapy. Management depends on the location and tech-nical feasibility of endovascular repair.

Follow-up ImagingPosttreatment follow-up imaging protocols for an-eurysms, pseudoaneurysms, varices, and vascular malformations vary considerably from institution to institution. Postprocedural surveillance typically consists of at least one clinical follow-up assess-ment with at least one cross-sectional imaging mo-

dality. In general, US studies of vascular structures after treatment can be of limited value if the mate-rials used to either occlude or preserve blood flow make assessment difficult. Similarly, CT and MR image quality may be degraded by artifact cre-ated by treatment materials (eg, beam-hardening or susceptibility artifact from coils). MR imaging may be superior to CT during follow-up when the frequency of artifacts is taken into account (4).

Given the limitations of imaging studies, fol-low-up assessments need to be tailored to the pa-tient on a case-by-case basis, taking into account both the clinical and anatomic risks of treatment failure and the potential consequences of future vessel recanalization or collateral pressurization. Potential adverse findings that can be encoun-tered after treatment include vessel recanaliza-tion, unintended thrombosis of an artery or end organ, and sequelae of nontarget embolization. With respect to recanalization, retreatment is warranted when the lesion continues to receive flow and be pressurized and the clinical risks for which embolization was performed remain.

Abdominal Aneu- rysms and Pseudoaneurysms

The frequency of occurrence of abdominal vis-ceral artery aneurysms (Table) has changed in recent decades as a result of their continued incidental discovery during imaging examina-tions (5,6). Historically, abdominal and pelvic visceral aneurysms were insidious because they were difficult to identify at clinical examination and had ominous outcomes when they ruptured, especially in the settings of the splenic artery and pregnancy. With extensive use of imaging, espe-cially in the emergency department, many more abdominal and pelvic vascular lesions are being identified early, and follow-up imaging with elec-tive repair is occurring well before vascular rup-ture. Open repair or catheter-based intervention is probably indicated for visceral aneurysms that are 2 cm in diameter or larger in women beyond childbearing age and in men (7). Additional indi-cations for treatment include (a) aneurysms with pain attributed to their vascular or anatomic dis-tribution, and (b) aneurysms that exhibit interval growth over the course of surveillance imaging. In the following paragraphs, we discuss abdomi-nal visceral and renal artery aneurysms and pseu-doaneurysms in terms of clinical manifestations, imaging findings, and treatment correlation.

Distribution of Abdominal Visceral Artery Aneurysms

Location of AneurysmFrequency of

Occurrence (%)

Splenic artery 60–80Hepatic artery 20SMA 5–7Celiac artery 3–4Gastric and gastroepiploic

arteries4

Jejunal, ileal, and colic arteries 3PDA 1–2GDA 1–2Inferior mesenteric artery <1

Note.—GDA = gastroduodenal artery.


Splenic Artery AneurysmA splenic artery aneurysm is the most common nontraumatic abdominal visceral aneurysm, ac-counting for 60%–80% of cases (Table). The true prevalence of splenic artery aneurysms is unknown, but estimates suggest that less than 0.1% of the general population is affected (8). Females are affected four times as often as males, potentially related to increased incidental or symptomatic discovery coinciding with use of US in pregnancy (9–11). One of the largest se-ries of splenic artery aneurysms available, span-ning 2 decades of experience with 217 patients, revealed that 79% of affected patients were female, with a mean age of 61 years (12). Addi-tional findings from this study revealed that 95% of the aneurysms were solitary and the majority were asymptomatic; however, other authors have reported that as many as 20% of splenic artery aneurysms are multiple (13).

The reason for development of splenic artery aneurysms is not well known. Established as-sociations include multiparity, portal hyperten-sion, liver transplantation, systemic hypertension, medial fibroplasia, and a-1 antitrypsin deficiency (12,14–16). Hormonal influences and changes in portal flow during pregnancy are believed to play a role in the development of splenic artery aneurysms (12,13). Although most often asymp-tomatic, patients may present with left upper quadrant abdominal pain, a pulsatile left upper quadrant abdominal mass, or hypotensive shock secondary to aneurysm rupture (3%–10% of cases). The mortality rate for ruptured splenic artery aneurysm in patients who are not pregnant ranges from 10% to 25%, but the risk of mater-nal death from rupture during pregnancy is esti-mated to be as high as 70%, with a fetal mortality rate greater than 90% (17). The risk of rupture is increased when the aneurysm measures more than 2 cm in diameter and during physiologic and pathologic states such as pregnancy, spleno-megaly, portal hypertension, liver transplantation, and pancreatitis (15).

Although abdominal radiographs are usually insensitive for the diagnosis of aneurysms, dense ovoid or signet ring–shaped calcifications seen at radiography may suggest a splenic artery an-eurysm (Fig 5) (18). If such abnormal calcifica-tions are incidentally discovered at radiography, additional cross-sectional imaging is warranted

to further characterize the finding and facilitate planning for potential future intervention. Cal-cification serves as a marker of the underlying disease and should not be interpreted as a sign of a stable, long-standing process. For example, calcifications have been seen in 90% of splenic artery aneurysms that progress to rupture, and their presence should not be used to guide man-agement decisions (12). Similarly, incidentally encountered curvilinear calcifications elsewhere in the abdomen and pelvis may herald other visceral artery aneurysms that require more de-tailed imaging assessment. Contrast-enhanced CT is usually the study of choice for identifying a splenic artery aneurysm. Typical imaging findings include a low-attenuation mass continuous with the splenic artery that demonstrates internal arte-rial phase enhancement if the aneurysm is patent. US facilitates real-time evaluation of aneurysm flow dynamics but may lead to underestimation of the true lesion size when color Doppler flow imaging is used. Similarly, at angiography, only the patent lumen of the aneurysm sac opacifies, causing underestimation of the true aneurysm size, and angiography provides little information on surrounding soft-tissue relationships.

Treatment options for splenic artery aneu-rysms include surgical repair or excision and en-dovascular management (14). Surgical repair or resection of the aneurysm with possible splenec-tomy is a second-line treatment option in most cases. Splenectomy is often not favored because of the increased long-term risk of bacterial infec-tions. The endovascular treatment of choice is coil or liquid casting agent embolization (typically reserved for saccular aneurysms and those with adequate or alternate flow to the spleen) (14,19–21). For fusiform aneurysms, in which the parent artery lumen requires preservation to spare end-organ flow, stent-graft placement is used if the arterial anatomy is favorable (13,14,22,23).

Most endovascular procedures (80%–90%) are technically successful, with typically only a small degree of splenic infarction. Collateral flow, pre-dominantly through the short gastric arteries, clas-sically maintains end-organ perfusion. However, splenic infarction risks increase with more distal embolizations and more commonly in the setting of nontarget vessel embolization or thromboem-bolism. Ischemic pancreatitis is another potential complication of splenic artery treatments that af-fect pancreatic artery branches, but it rarely occurs with an intact collateral arterial supply to the pan-


creas. Another theoretic complication associated with the treatment of splenic artery aneurysms is pneumococcal sepsis syndrome. To our knowl-edge, no recommendations have been published regarding the use of prophylactic vaccination against encapsulated organisms in the setting of splenic artery embolization. The use of antibiot-ics and vaccines in the setting of targeted partial splenic embolization for hypersplenism has been proposed, and some operators have modified these

treatment protocols for use in the setting of other splenic artery interventions (24).

Imaging follow-up at 1-year intervals has been proposed because of a 20% risk of reperfu-sion after successful coil embolization (14). If reperfusion does occur, the sac is again exposed to systemic pressures and may once again be at risk for rupture.

Figure 5. Splenic artery aneurysm. (a) Abdominal radiograph shows a rim-calcified ovoid lesion (arrowhead) in the left upper quadrant. (b) Axial contrast-enhanced CT image shows an enhancing ovoid saccular aneurysm (arrowhead) arising from the splenic artery. (c) Digital subtraction angio-gram shows a saccular splenic artery aneurysm (arrowhead). The angled base catheter is positioned in the splenic artery origin. (d) Digital subtraction angiogram shows exclusion of the aneurysm with use of coil embolization (arrowhead). Embolization through the tortuous splenic artery was facilitated with the use of a microcatheter (not shown).


Figure 6. Splenic artery pseudoaneurysm. (a) Axial contrast-enhanced CT image shows an intrasplenic saccular pseudoaneurysm (arrowhead) associated with a traumatic splenic laceration. (b) Digital subtraction angiogram helps confirm the splenic pseudoaneurysm (arrowhead). (c) Completion angiogram helps confirm the exclusion of the aneu-rysm with catheter-directed glue and coil embolization (arrowhead).

Splenic Artery PseudoaneurysmSplenic artery pseudoaneurysms are typically seen in the setting of splenic trauma (Fig 6), pancreatitis, or mycotic infection of the arterial wall (4,25). Pain is a typical presenting symptom when a splenic artery pseudoaneurysm is identi-fied at imaging, which usually demonstrates an arterial phase‒enhancing outpouching from the splenic artery or one of its intrasplenic branches, surrounded by hematoma. Perhaps a better de-scriptor is the term pulsatile hematoma, which describes both the disease and the risk of rupture encountered with any pseudoaneurysm. As with most pseudoaneurysms, there is a high risk of rupture without treatment, and all splenic lesions should be treated regardless of size or clinical manifestation (26).

The treatment of choice is typically coil embolization or possibly stent-graft placement across the lesion when the anatomy allows (ie, more proximal lesions and nontortuous arterial segments to facilitate device passage). Distal and proximal embolization (sandwich technique) across the aneurysm neck is typically required to prevent collateral circulation resulting in con-tinued sac pressurization. Alternatively, a sac-packing technique with coils or parent artery glue embolization has also been used (4,21).

Intentional embolization of the entire splenic artery may be required in complex, high-risk splenic pseudoaneurysms.

Hepatic Artery AneurysmHepatic artery aneurysm involving the common hepatic artery (CHA), proper hepatic artery (PHA), or intrahepatic artery branches is the second most common type of nontraumatic ab-dominal visceral artery aneurysm, accounting for 20% of cases (27). Men are affected 50% more frequently than women, and these lesions are usually discovered during the sixth decade of life (28). Approximately 80% of cases involve the extrahepatic arteries, with 63% involving the CHA, 28% involving the right hepatic artery, and 5% involving the left hepatic artery; in 4% of cases, both the right and left hepatic arter-ies are aneurysmal (28). The causes of hepatic artery aneurysm have evolved over time. Before the advent of antibiotics, a mycotic origin was most common; however, atherosclerosis now ac-counts for most cases (29).

Most hepatic artery aneurysms are incidentally discovered at imaging. Affected patients are often asymptomatic but may present with pain in the right upper quadrant of the abdomen, hemobilia, gastrointestinal hemorrhage, chronic anemia, and jaundice from extrinsic compression of bile ducts by the aneurysm (30). A triad of epigastric pain,


Figure 7. Hepatic artery aneurysm. (a) Left anterior oblique digital subtraction angiogram obtained with the catheter in the distal CHA shows a right hepatic artery branch aneurysm (arrowhead). (b) Digital subtraction completion angiogram shows exclusion of the aneurysm with use of the sac-packing coil embolization technique (arrowhead).

hemobilia, and obstructive jaundice (Quincke triad) is seen in up to one-third of cases (31,32). As noted with splenic artery aneurysms, curvi-linear calcifications on radiographs of the right upper quadrant of the abdomen should raise the possibility of hepatic artery aneurysm (33). Con-trast-enhanced CT is usually the study of choice for identifying a hepatic artery aneurysm.

Treatment of a hepatic artery aneurysm is indicated if the diameter exceeds 2 cm or if the patient is symptomatic (Fig 7) (8). Special con-sideration is given to high-risk lesions (eg, in pa-tients with polyarteritis nodosa or fibromuscular dysplasia, in whom treatment is recommended regardless of lesion size) (8,28). A retrospective meta-analysis has shown that 65% of reported hepatic artery aneurysms rupture, with a con-comitant rupture-associated mortality rate of 21% (34). No distinction has been made between extrahepatic and intrahepatic aneurysms with re-spect to rupture and mortality rates; however, the lack of a “tamponade” effect by the surrounding hepatic parenchyma likely makes an extrahepatic aneurysm more dangerous.

The choice of treatment for a hepatic artery aneurysm often depends on the involved vessel and the location of the aneurysm. Intrahepatic an-eurysms are usually treated with coil embolization, which is usually well tolerated because of the dual blood supply to the liver (hepatic artery and portal

vein). Alternate treatment approaches for intra-hepatic aneurysms include imaging-guided direct transhepatic puncture with subsequent coil place-ment or injection of thrombin or a liquid casting agent. Different treatment approaches exist for extrahepatic aneurysms, including open surgical repair, coil embolization, and endograft placement. Direct surgical repair of extrahepatic aneurysms is recommended in most patients, with endovas-cular treatment often being reserved for high-risk surgical candidates. Endovascular treatment of an aneurysm of the CHA may include embolization of the artery distal and proximal to the aneurysm, since collateral vascular pathways through the gastroduodenal artery (GDA), PDA, and right gastric artery usually provide adequate liver perfu-sion (8). Endovascular stent-grafts can be used to treat aneurysms of the CHA and preserve the native arterial lumen, but many patients do not have sufficient arterial caliber or length for suitable stent-graft placement (19). Aneurysms of the PHA are usually treated with the goal of maintaining luminal patency, since the lesion is beyond the col-lateral supply from the GDA to the liver. Despite the dual blood supply from the portal vein, embo-lization at this location could result in compromise of the entire hepatic arterial circulation. In cases of distal CHA aneurysms, embolization of the GDA


as to an increase in percutaneous interventions (33,34). As with most pseudoaneurysms, hepatic artery lesions have a high risk of rupture without treatment.

Contrast-enhanced CT usually shows an ar-terial phase–enhancing intrahepatic mass or an extrahepatic outpouching from the CHA or PHA (Fig 9). Surrounding hematoma is also often ob-served. For intrahepatic pseudoaneurysms, the treatment of choice is coil embolization. For ex-trahepatic pseudoaneurysms, treatment depends on the involved vessel and the location of the aneurysm.

Figure 8. CHA aneurysm. (a) Digital subtraction angiogram shows an aneurysm of the CHA (arrowhead). The selective catheter tip is at the origin of the celiac artery (projecting from behind the aneurysm). (b) “Coiling” of the GDA (arrowhead) is the first step in exclusion of the aneurysm and prevention of collateral flow with resultant pressurization of the sac. (c) Coil embolization of the junction of the PHA and distal CHA (arrowhead) is the second step in exclusion of the aneurysm. (d) Completion angiogram shows interval continuation of coil embolization within (arrowhead) and proximal to the aneurysm (sandwich technique).

and CHA may be needed to achieve aneurysm exclusion, provided an adequate liver supply is maintained by collateral flow (Fig 8). As with any visceral artery aneurysm, a detailed search for as-sociated findings should be made at angiography. Specifically, one should search for the possibility of aneurysm multiplicity, which is known to occur in 20% of hepatic artery aneurysms (35).

Hepatic Artery PseudoaneurysmHepatic artery pseudoaneurysms are typically seen in the setting of blunt or penetrating trauma, or as a complication of liver transplantation or an indwelling biliary catheter. The incidence of hepatic artery pseudoaneurysms has risen with the increase in percutaneous and laparoscopic biliary procedures. Together with hepatic artery aneurysms, hepatic artery pseudoaneurysms were the most common visceral aneurysmal dilatations over a 10-year period ending in 1995 (34). This finding has been attributed to the increased use of diagnostic CT in the trauma setting, as well


SMA AneurysmSMA aneurysm is the third most common type of nontraumatic visceral artery aneurysm (5%–7% of cases), but it represents a dangerous type because of the high incidence of ischemic bowel complications (5,36). Autopsy studies have reported an incidence of one in 12,000–19,000 cases with equal gender distribution, with most aneurysms occurring in the first 5 cm of the SMA. Unlike other visceral artery aneurysms, 70%–90% of these aneurysms are symptomatic, with significant and progressive abdominal pain. The natural history appears to be one of expan-

Figure 9. Right hepatic artery pseudo-aneurysm. (a) Axial contrast-enhanced CT image shows an enhancing saccular pseudoaneurysm (arrowhead) arising in the segment V right hepatic arterial distri-bution secondary to random liver biopsy. (b) Selective angiogram shows a partially thrombosed right hepatic artery branch pseudoaneurysm (arrowhead). (c) Comple-tion angiogram shows a “coil stack” (arrow-head) across the neck of the pseudoaneu-rysm. No residual filling of the sac was seen on subsequent images.

sion and eventual rupture, and 38%–50% of patients experience a ruptured aneurysm (36). Noncalcified aneurysms appear to have the high-est risk of rupture (7). In some patients with an-eurysms smaller than 2 cm, no adverse outcome has been demonstrated at follow-up CT and US (7). Infection and arterial dissection are the most common causes (37). Outside of the abdominal aorta, the SMA is the most likely location for a mycotic aneurysm, and subacute bacterial endo-carditis from nonhemolytic Streptococcus species is a primary consideration. Intimal dissection affects the SMA more than any other visceral artery. After infection and dissection, atheroscle-rosis and inflammation from pancreatitis rank as the third and fourth most common causes of SMA aneurysms, respectively.


Contrast-enhanced CT is usually the study of choice for identifying an SMA aneurysm (Fig 10). Because of the high incidence of rupture and complication, repair of SMA aneurysms is essen-tial, regardless of their size. The surgical mortality rate in the setting of a ruptured aneurysm is 38%, but no deaths have been reported after elective intervention (20). Direct surgical excision, bypass graft placement, and endovascular repair are all reasonable options depending on the location and size of the aneurysm. A saphenous vein graft is the conduit of choice for infected aneurysms or in the presence of intestinal ischemia. SMA dissections can be treated with bypass graft or stent-graft placement. Reported endovascular treatment success rates for these aneurysms vary between 75% and 100%, with recanalization rates of only 16% (20). Aneurysm coiling with distal and proximal branch vessel occlusion is a treatment option, since extensive collateral flow is usually available to the small bowel.

SMA PseudoaneurysmInflammation (usually from pancreatitis) and trauma seem to be the most frequent causes of SMA pseudoaneurysm formation. Both autodi-gestion of the arterial wall by pancreatic enzymes and pressure erosion of the arterial wall have been reported as causal factors in pseudoaneu-rysm formation in pancreatitis (38). Almost all SMA pseudoaneurysms are symptomatic, with moderate to severe progressive abdominal pain and possible bleeding. A mortality rate of up to 37% from SMA pseudoaneurysm rupture and hemorrhage has been reported (26). As with

most pseudoaneurysms, there is a high risk of rupture without treatment.

Treatment guidelines are similar to those for nontraumatic SMA aneurysms. Surgery is the standard treatment and involves ligation of the vessel below and above the aneurysm and, most important, aneurysm resection (5). Alternative treatments include embolization and covered stent placement (39,40).

Celiac Artery AneurysmCeliac artery aneurysm is the fourth most com-mon type of nontraumatic visceral artery an-eurysm (3%–4% of cases) (41). The estimated incidence varies from one in 10,000 to one in 20,000 individuals; fewer than 200 cases have been reported in the literature, with many older publications describing syphilis-related aneu-rysms in men (42). However, these statistics have changed with the increased utilization of CT. More than 50 years ago, 92% of patients presented with epigastric pain and 72%–87% of patients died of aneurysm rupture. Today, many noninfectious aneurysms are being found incidentally at CT in equal numbers of men and women, and the overall mortality rate has decreased to less than 15% (41). As with other visceral aneurysms, the larger the diameter of a celiac artery aneurysm, the more likely the risk of rupture, with an estimated risk of 50%–70% for celiac artery aneurysms greater than 3.2 cm in diameter (43).

Contrast-enhanced CT is usually the study of choice for identifying a celiac artery aneurysm (Fig 11). Complications found at imaging include end-organ (liver, spleen, stomach) hypoperfu-sion secondary to ischemia and hematoma in the

Figure 10. SMA aneurysm. Coronal contrast-enhanced maximum inten-sity projection (MIP) reformatted CT image shows a calcified and partially thrombosed saccular aneurysm (arrow-head) contiguous with the SMA. The patient deferred treatment.


Figure 11. Celiac artery aneurysm. (a) Sagittal contrast-enhanced MIP reformatted CT im-age shows a saccular aneurysm (arrowhead) arising from the celiac arterial trunk, just distal to the origin of the left gastric artery (lg). sp = splenic artery. (b) Digital subtraction angiogram helps confirm the celiac artery aneurysm (arrowhead), which measures 1.1 cm. (c) Native an-giogram (steep left anterior oblique projection) of the proximal abdominal aorta shows the ce-liac artery measurement for preintervention planning. Measurements of both length and diam-eter (not shown) are commonly obtained to appropriately “size” the stent, thereby preventing inadvertent coverage of an arterial branch origin and allowing appropriate sizing or “oversizing” of the stent to prevent stent migration. The known aneurysm is faintly visible (arrowhead). (d) Sagittal contrast-enhanced MIP reformatted CT image shows exclusion of the aneurysm by a covered stent (arrowhead) in the celiac artery.


Figure 12. Celiac arterial trunk pseudoaneurysm in a patient with a history of Whipple procedure, GDA ligation, and new gastrointestinal hemorrhage. (a) Digital subtraction angiogram shows a small saccular pseudoaneurysm (arrowhead) arising from the celiac arterial trunk. (b) Digital subtraction angiogram shows exclusion of the pseudoaneurysm with use of a sac-packing coil embolization technique (arrowhead).

doaneurysm by means of celiac artery coiling is dangerous in patients who have undergone distal gastrectomy or pancreaticoduodenectomy. Surgi-cally disrupted arterial anatomy is of particular importance in the setting of embolization because of the lack of available collateral arteries to pre-vent organ ischemia. For example, occlusion of the proximal CHA during celiac artery emboliza-tion (in the setting of a ligated GDA) can result in hepatic ischemia from lack of collateral flow to the PHA. This complication can occasionally be avoided in the setting of a “replaced” hepatic artery originating from the SMA (49).

PDA and GDA AneurysmsTrue peripancreatic aneurysms involving the PDA or GDA are uncommon and together ac-count for only 2%–4% of visceral artery aneu-rysms (Table) (Fig 13). Moore et al (50) pre-sented a useful review of the literature that found equal gender and ethnic distributions and an average patient age of 58 years at presentation. The most common presenting symptom was ab-dominal pain (in both ruptured and nonruptured aneurysms), but presenting symptoms can vary. Interestingly, reports in the literature suggest that the number of PDA aneurysms ruptured at pre-sentation was twice that of GDA aneurysms, but no correlation between aneurysm size and rup-ture rate has been identified (50). Furthermore, 18% of patients with GDA aneurysms and 24% of patients with PDA aneurysms had associated aneurysms in other mesenteric vessels, and less commonly in the renal arteries, abdominal aorta, and intracranial cerebral vessels (50).

Celiac stenoses and occlusions have been iden-tified in at least one-third of patients with PDA or GDA aneurysms (Fig 14), suggesting that in

lesser sac in the setting of an aneurysm rupture. Subsequent rupture of the hematoma in the lesser sac into the peritoneal cavity produces, by way of the foramen of Winslow (epiploic foramen), a phenomenon that is aptly termed double rupture. Unusual manifestations of celiac artery aneurysms include extrinsic compression of the pancreatic or hepatic ducts and bleeding gastric varices from splenic vein compression (44–46). Note that celiac artery aneurysms can be associated with abdomi-nal aortic aneurysms in up to 18% of cases and with other visceral artery aneurysms in as many as 50% of cases (42). Hence, identification of one aneurysm necessitates a search for others.

Because of high morbidity and mortality rates associated with rupture, repair of celiac artery aneurysms is essential. Direct surgical excision, bypass graft placement, and endovascular repair are all reasonable options depending on the loca-tion and size of the aneurysm as well as the suit-ability of the celiac artery (Fig 11). Terrinoni et al (47) reported the first successful embolization of a true celiac artery aneurysm with immediate oc-clusion of all efferent vessels of the celiac axis and suggested that this is a safe alternative to surgical intervention in high-risk patients.

Celiac Artery PseudoaneurysmCeliac artery pseudoaneurysm is rare. Inflam-mation, usually from pancreatitis or postsurgical pancreatic-enteric anastomosis (Fig 12), and trauma are the most frequently reported causes in the literature (48,49). Treatment guidelines are similar to those for nontraumatic celiac ar-tery aneurysms, but with standard treatment being surgical. Exclusion of a celiac artery pseu-


Figure 14. PDA aneurysm secondary to median arcuate liga-ment compression of the celiac arterial trunk. (a) Axial contrast-enhanced CT image shows an enhancing fusiform aneurysm with mural calcification (arrowhead) arising from the PDA. (b) Anterior digital subtraction angiogram shows the fusiform aneurysm (arrowhead) arising from the PDA. Note the collat-eral filling of the celiac artery branches despite SMA injection. (c) Lateral angiogram of the upper abdominal aorta shows a proximal celiac axis (arrow), a finding that is consistent with median arcuate ligament compression, and the PDA aneurysm (arrowhead), which is likely receiving increased relative flow. The patient subsequently underwent mesenteric bypass shunt place-ment and aneurysm ligation.

Figure 13. PDA aneurysm. (a) Axial contrast-enhanced MIP reformatted CT image shows a sac-cular aneurysm (arrowhead) arising from the PDA. (b) Digital subtraction angiogram (slight left anterior oblique projection) helps confirm the aneurysm (arrowhead) arising from the inferior PDA. The guidewire sheath projects at the SMA origin with the selective base catheter in the PDA. (c) Native completion angiogram shows exclusion of the aneu-rysm with coil embolization (arrowhead), including embolization of both afferent and efferent arteries. Contrast material in the image background, behind the coiled aneurysm, lies within the right renal col-lecting system.


some cases increased collateral flow from the SMA through peripancreatic vessels is a factor in the development of these aneurysms. How-ever, two-thirds of cases do not have a clearly identified causative factor. Cases with associated nonvisceral (eg, renal, intracerebral) aneurysms suggest that a systemic cause (atherosclerosis, degeneration) may have a role in the formation of peripancreatic aneurysms.

Because of the significant 21% mortality rate associated with rupture, surgical ligation or embolization of PDA and GDA aneurysms is important. Often, the retroperitoneal location of these aneurysms and collateral flow make surgi-cal repair, which may require partial pancreatec-

tomy, technically challenging. Coil embolization has been used more frequently in recent years because of these technical challenges (51). In cases of celiac occlusive disease, a mesenteric bypass procedure is usually performed first, fol-lowed by aneurysm ligation or embolization, to preserve arterial supply to the liver, spleen, and pancreas.

PDA and GDA PseudoaneurysmsPDA and GDA pseudoaneurysms are actually more common than true PDA and GDA aneu-rysms (50). Inflammation (usually from pancreati-tis), surgery, and trauma are the most frequently reported causes of PDA and GDA pseudoaneu-rysms (Fig 15). Treatment usually involves coil embolization of the pseudoaneurysm (19).

Figure 15. PDA pseudoaneurysm. (a) Axial contrast-enhanced CT image shows an enhanc-ing focus within the pancreatic head (arrowhead) with an attenuation similar to that of the aorta. (b) Left anterior oblique digital subtraction an-giogram shows a pseudoaneurysm (arrowhead) arising from a PDA branch. (c) Left anterior oblique digital subtraction angiogram shows exclusion of the pseudoaneurysm with use of coil embolization as well as coiling of a collateral branch vessel (arrowheads).


Figure 16. LGA pseudoaneurysm in a patient with recent trauma. (a) Axial contrast-enhanced CT image shows an enhancing focus (arrowhead) adjacent to the lesser curve of the stomach within a lesser sac hematoma. This finding has clinical significance because bleeding in this location is first contained by the lesser sac but may secondarily rupture into the greater peritoneal cavity, with con-comitant marked clinical deterioration. (b) Sagittal contrast-enhanced MIP reformatted CT image shows an enhancing focus (arrowhead) arising from the LGA, a finding that is consistent with a pseu-doaneurysm. (c) Selective angiogram shows a pseudoaneurysm (arrowhead) arising from the LGA. (d) Right anterior oblique digital subtraction angiogram shows exclusion of the pseudoaneurysm by means of coil embolization (arrowhead) of the LGA.

Gastric Artery Aneu- rysms and PseudoaneurysmsGastric and gastroepiploic artery aneurysms ac-count for approximately 4% of nontraumatic visceral artery aneurysms (5). Unfortunately, no comprehensive review of these cases is available in the literature. The mortality rate in several current case reports is 80%, since many patients present after rupture (52,53). As with other

visceral aneurysms, earlier detection of gastric aneurysms with the prevalent use of CT may im-prove this statistic. Embolization of the involved gastric artery is often successful because of collat-eral flow around the stomach. Left gastric artery (LGA) pseudoaneurysms as a consequence of trauma have been reported (Fig 16) (54,55).


Renal Artery AneurysmAlthough not considered classic visceral artery aneurysms, renal artery aneurysms are discussed in this article because they involve vascular sup-ply to a key abdominal organ system. True renal artery aneurysms have an incidence ranging between 1% and 10%, making them one of the more common abdominal aneurysms (Fig 17). Renal artery aneurysms have an equal gender dis-tribution, and the average patient age at presenta-tion ranges from 50 to 61 years. For unknown reasons, right-sided aneurysms are more com-mon than left-sided lesions. Approximately 80%

of renal aneurysms are saccular, with a variety of causes; most of the remaining 20% are fusiform aneurysms associated with advanced renal artery medial fibrodysplasia.

At least one-half of all renal artery aneurysms are discovered incidentally at imaging (56), most commonly at a first-order branch of the main renal artery. The risk of rupture was originally thought to increase in pregnancy, as with splenic artery aneurysm; however, extensive autopsy studies have not found a significant number of cases to sup-port this finding or other clear data identifying risk factors for rupture (56,57). Although the lower threshold for treatment is typically a diameter of 2 cm, rupture of aneurysms less than 2 cm has been reported (58). As a result, prospective research

Figure 17. Renal artery aneurysm. (a) Coro-nal contrast-enhanced MIP reformatted CT image shows an enhancing rim-calcified aneu-rysm (arrowhead) arising from the right renal artery. (b) Digital subtraction angiogram shows the aneurysm (arrowhead) arising from the right renal artery. (c) Completion angiogram shows exclusion of the aneurysm by means of coil embolization (arrowhead). Flow to the right kidney has been preserved.


Figure 18. Pseudoaneurysm in a renal transplant. (a) Axial T1-weighted MR im-age of a renal transplant shows a crescentic area of high signal intensity (arrow-head) within a recent renal biopsy site, a finding that is consistent with acute throm-bus. (b) Axial contrast-enhanced T1-weighted MR image of the renal transplant shows arterial enhancement (arrowhead) consistent with a pseudoaneurysm. The patient was subsequently treated with coil embolization.

studies are needed to determine if renal artery aneurysms can be safely followed up with imaging. In general, a conservative approach with CT or MR imaging is thought to be appropriate for le-sions less than 2 cm in diameter (1).

Duplex US, contrast-enhanced CT, and MR imaging are all reasonably effective tools for identifying renal artery aneurysms. Complica-tions seen at imaging include end-organ infarcts and adjacent hematoma in the setting of rup-ture. Symptomatic patients with renal artery aneurysms, including those lesions thought to contribute to renovascular hypertension, may benefit from surgical resection or endovascular therapy (56). Lack of collateral flow to the kid-ney can make endovascular exclusion of aneu-rysms of the main renal artery technically chal-lenging (eg, the sandwich technique is usually contraindicated).

Renal Artery PseudoaneurysmMost renal artery pseudoaneurysms are encoun-tered in the setting of penetrating trauma, in-cluding iatrogenic causes (Fig 18) (59). As with most pseudoaneurysms, there is a high risk of rupture without treatment, but a second reason

for intervention may be renovascular hyperten-sion, as is sometimes seen with renal artery an-eurysms. Although CT is reliable for identifying many renal injuries, it is not highly accurate for predicting the development of branch arterial injuries, including pseudoaneurysms (60). Typi-cal imaging findings of renal artery pseudo-aneurysm include solid internal arterial phase enhancement in a mass continuous with the renal artery or renal parenchyma. Color Dop-pler flow imaging can demonstrate arterial flow characteristics.

Angiography is the standard of reference for confirming a diagnosis of renal vascular injury, but it is often performed after potential renal vascular injuries are identified with US or CT. At angiography, renal pseudoaneurysms are round or oval structures that enhance from the main renal artery or one of its branches. Endovascular therapy with coil or gelatin sponge embolization has a success rate of greater than 80% in control-ling or preventing hemorrhage while preserving the renal parenchyma (61).


Figure 19. Multiple abdominal an-eurysms. Coronal contrast-enhanced three-dimensional reformatted CT image shows an infrarenal abdominal aortic (aa) aneurysm and multiple visceral and aortic branch aneurysms. The infrarenal abdominal aortic and common iliac artery (cia) aneurysms were treated with endografts, and the visceral aneurysms were surgically by-passed. ca = celiac axis.

Multiple Abdominal AneurysmsAn interesting observation concerning abdominal aneurysms is that they can be multiple. Athero-sclerosis is the most common cause of multiple aneurysms in the abdominal aorta and iliac arteries. As mentioned earlier, aneurysms of the celiac artery are associated with abdominal aortic aneurysms in 18% of cases and with other visceral artery aneurysms in as many as 50% of cases (Fig 19) (42,62). In general, causes of multiple abdominal aneurysms may include con-nective tissue disorders (eg, Marfan syndrome), vasculitis (eg, polyarteritis nodosa), and infection (63). Multiple small (1–5-mm) visceral and renal aneurysms are seen in up to 50% of patients with polyarteritis nodosa (64).

Pelvic Aneurysms and Pseudoaneurysms

Most pelvic aneurysms involve the iliac arteries and are extensions of aortic atherosclerotic disease. Isolated IIA aneurysms are rare, usually identified in men over 60 years of age, often large (3–8 cm in diameter) at the time of presentation, and usually attributed to atherosclerotic disease (Fig 20) (65). Isolated IIA branch aneurysms are also rare, with only isolated case reports in the literature (66,67).

In men, there are isolated reports of aneurysms involving the testicular and obturator arteries, but we found no reports of aneurysms of the inferior vesical or penile artery (66,68). In women, there are isolated reports of aneurysms of the uterine artery and ovarian artery (69–72).

Contrast-enhanced CT can be useful for identi-fying large pelvic aneurysms, but angiography of-ten better demonstrates a pelvic aneurysm and has the added potential advantage of allowing immedi-ate endovascular treatment (70,73,74). Because of their deep location in the pelvis, many aneurysms are not found until they are large or unless there are other symptoms (eg, compression of adjacent structures), including rupture in up to 50% of cases (67). Diagnosis of iliac artery aneurysms prior to rupture is important, since the mortality rate can be as high as 50% during attempts at sur-gical repair made after rupture (75).

Numerous reports have been made of pelvic pseudoaneurysms in patients of all ages and both genders. Penetrating and blunt trauma, infec-tion, dissection, and excessive athletic effort (eg, bicycle racing) are all reported causes of pelvic pseudoaneurysms. In women, uterine artery pseu-doaneurysm is a rare but important complication of cesarean delivery and is an often reported cause of pelvic pseudoaneurysm (76). Angiography has an important role in emergent treatment of active


Figure 21. Pelvic pseudoaneurysm. (a) Axial nonenhanced CT image shows a mass with minimal rim calcification (arrowhead) arising in the left iliac fossa (external iliac artery territory). (b) Axial T1-weighted MR image of the pelvis shows multiple internal high- and low-signal-intensity layers within the left pelvic mass (arrowhead) consistent with thrombus within a pseudoaneurysm. The patient underwent stent-graft placement.

Figure 20. Ruptured IIA aneurysm. (a) Axial contrast-enhanced CT image shows an arterially enhancing mass with internal thrombus and mural calcification (arrowhead) arising in the region of the left common iliac artery bifurcation and extending into the left internal iliac artery (iia) and left external iliac artery (eia), both of which are surrounded by apparent arterial wall thickening from adjacent extraperitoneal hemorrhage. (b) Right anterior oblique digital sub-traction angiogram shows a fusiform aneurysm (arrowhead) arising from the proximal left internal iliac (hypogastric) artery. (c) Right anterior oblique native angiogram obtained after coil embolization (arrowhead) of the IIA aneurysm shows “anchoring” of coils in the proximal anterior division of the IIA. A balloon (*) was inflated across the origin of the IIA during coil placement (balloon remodeling technique).

hemorrhage and pseudoaneurysms in patients with acute pelvic fractures (77). In addition to the well-described US, CT, and MR angiographic ap-pearances of pseudoaneurysms, the MR imaging feature of layered low- and high-signal-intensity bands is important in recognizing an aneurysm or pseudoaneurysm (Fig 21) (78).

ConclusionIt is important that abnormalities of the arter-ies in the abdomen and pelvis be recognized at abdominal imaging for early treatment and to avoid complications. Although endovascular


treatment was once reserved for high-risk surgi-cal patients, it has become the first-line therapy for aneurysms and pseudoaneurysms in many cases. Endovascular exclusion of flow is usually planned on the basis of vascular location and can often be achieved while still preserving ab-dominal and pelvic organ arterial flow.

Acknowledgment.—Special thanks to Gilbert Gardner, MA, CMI, for the medical illustrations in this article.

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This journal-based SA-CME activity has been approved for AMA PRA Category 1 CreditTM. See www.rsna.org/education/search/RG.

Teaching Points May-June Issue 2013

Abdominal and Pelvic Aneurysms and Pseudoaneurysms: Imaging Review with Clinical, Radiologic, and Treatment CorrelationRobert A. Jesinger, MD, MSE • Andrew A. Thoreson, MD • Ramit Lamba, MBBS, MD

RadioGraphics 2013; 33:E71–E96 • Published online 10.1148/rg.333115036 • Content Codes:

Page E74Abdominal visceral aneurysms are rare, and, although true aneurysms are often incidentally discovered, pseudoaneurysms are more frequently encountered in specialist centers dealing with acute trauma pa-tients or high volumes of abdominal interventions.

Page E77For visceral aneurysms and pseudoaneurysms, endovascular therapy with a combination of coils, gelatin sponges, liquid polymer embolization, and stent placement is often the first-line therapy.

Page E78A splenic artery aneurysm is the most common nontraumatic abdominal visceral aneurysm, account-ing for 60%–80% of cases.

Page E83Unlike other visceral artery aneurysms, 70%–90% of these aneurysms are symptomatic, with significant and progressive abdominal pain.

Page E93In addition to the well-described US, CT, and MR angiographic appearances of pseudoaneurysms, the MR imaging feature of layered low- and high-signal-intensity bands is important in recognizing an aneurysm or pseudoaneurysm.

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