Overview of visceral artery aneurysm and pseudoaneurysm

INTRODUCTION — Visceral artery aneurysms (VAAs) and visceral artery pseudoaneurysms (VAPAs) are defined as aneurysms affecting the celiac, superior, or inferior mesenteric arteries and their branches. VAA and VAPA are relatively rare. The splenic artery (VAA) and hepatic artery (VAPA) are most commonly involved. VAA and VAPA can be life-threatening conditions with high incidences of rupture and hemorrhage. The clinical features of symptomatic disease differ for each anatomic location; however, clinical symptoms and signs are nevertheless nonspecific. VAA and VAPA are often not suspected initially in patients presenting with abdominal complaints, due to their rarity, which can lead to a delay in diagnosis. Consequently, these often present with life-threatening hemorrhage due to a high incidence of rupture [1-3]. Thus, the general approach to VAA/VAPA is early elective intervention rather than watchful waiting, to minimize the risk of rupture.

The clinical features of visceral artery aneurysms and pseudoaneurysms will be reviewed here. The surgical and endovascular management of VAAs and VAPAs are discussed separately. (See "Treatment of visceral artery aneurysm and pseudoaneurysm".)

The clinical features and management of renal artery aneurysms are presented separately. (See "Renal artery aneurysm".)

DEFINITIONS AND ANATOMIC DISTRIBUTION — Visceral artery aneurysms (VAAs) and visceral artery pseudoaneurysms (VAPAs) are defined as those affecting the celiac, superior, or inferior mesenteric arteries and their branches. Aneurysms of the renal artery are usually regarded separately.

True VAA involves all layers of the wall, each of which is thinned but intact. False aneurysms, visceral artery pseudoaneurysms (VAPAs), result from a tear in the vessel wall due to trauma with subsequent periarterial hematoma formation [4]. As with any blood vessel, a given artery is defined as aneurysmal if there is a focal dilation of the artery that has a diameter more than 1.5 times the normal diameter of the artery. As an example, the most common true VAA, splenic artery aneurysm, is usually noted when the diameter of the artery is around 1 cm. VAAs/VAPAs are often not clinically detected until their diameters are well beyond the diameter that is considered aneurysmal.

Average normal diameters of the various visceral vessels are as follows (±standard deviation) [5,6]:

●Celiac trunk: 0.79±0.06 cm

●Common hepatic artery: 0.50±0.04 cm

●Proper hepatic artery: 0.45±0.03 cm

●Splenic artery: 0.46±0.03 cm

The splenic artery (VAA) and hepatic artery (VAPA) are commonly involved. Among VAA, the splenic artery is affected in 60 to 70 percent of patients, the hepatic artery in 20 percent, and the celiac or mesenteric arteries in 10 percent [7]. Gastric, intestinal, pancreatic, gastroduodenal, pancreaticoduodenal, and inferior mesenteric artery aneurysms are less frequently reported.

●Splenic artery aneurysms are typically solitary, saccular in shape, and frequently localized to the distal third of the splenic artery, the bifurcation region distal to the takeoff of the short gastrics, and the splenic hilum [8]. One third of patients with splenic artery aneurysm may have other associated visceral artery or renal artery aneurysms [8].

●Hepatic artery aneurysms most commonly involve the extrahepatic arteries (approximately 80 percent). Of extrahepatic hepatic artery aneurysms, 60 percent are located in the common hepatic artery, 30 percent involve the right hepatic artery, and 5 percent involve the left hepatic artery.

●Superior mesenteric artery aneurysms most commonly involve the proximal 5 cm of the superior mesenteric artery [9].

EPIDEMIOLOGY AND ASSOCIATIONS — Visceral artery aneurysms (VAAs) and pseudoaneurysms (VAPAs) are relatively rare with a reported incidence of 0.1 to 0.2 percent, although the true incidence is not known since many are asymptomatic [4,10-12]. The diagnosis is increasingly more frequent due to the detection of incidental disease using advanced imaging modalities often performed to evaluate unrelated complaints [1,3]. In addition, instrumentation used to diagnose and treat trauma and other conditions (eg, biliary disease) has increased the incidence of iatrogenic pseudoaneurysm [2,13]. Demographic features of specific VAAs are discussed below. (See 'Clinical features' below and 'Specific aneurysms' below.)

The pathogenesis of visceral artery aneurysm is poorly characterized. VAA may be associated with a variety of conditions, including atherosclerosis, medial degeneration, and conditions of increased flow (eg, pregnancy, portal hypertension, liver transplantation).

Risk factors associated with VAA include:

●Atherosclerosis

●Pregnancy

●Portal hypertension (splenic artery aneurysm)

●Liver transplantation (splenic artery aneurysm)

●Marfan disease

●Ehlers-Danlos syndrome

●Osler-Weber-Rendu disease

●Fibromuscular dysplasia

●Kawasaki disease

●Hereditary, hemorrhagic telangiectasia

●Cardiac valve infection

In retrospective reviews, atherosclerosis accounted for most VAAs (32 percent), followed by medial degeneration/dysplasia (24 percent), abdominal trauma (22 percent), and infection and inflammatory disease (10 percent) [1,14,15]. Other etiologies include connective tissue disorders (Marfan syndrome, Ehlers-Danlos syndrome, Osler-Weber-Rendu disease, fibromuscular dysplasia, Kawasaki, hereditary hemorrhagic telangiectasia), and hyper flow conditions (portal hypertension, pregnancy). An association with antiphospholipid syndrome has been suggested [16].

Risk factors for VAPA include:

●Iatrogenic injury from instrumentation

●Blunt and penetrating abdominal trauma

CLINICAL FEATURES — Visceral artery aneurysms (VAAs) and visceral artery pseudoaneurysms (VAPAs) are usually asymptomatic and identified as incidental, unexpected findings on imaging of the abdomen, particularly on computed tomography (CT) of the abdomen or CT angiography [17]. (See 'Diagnosis' below.)

General observations — Some generalizations can be made, but the clinical presentation of individual aneurysms differs depending on their anatomic location and organ associations. (See 'Specific aneurysms' below.).

In general:

●For patients who are symptomatic, but not ruptured, the most common symptoms are malaise, vague abdominal pain, and nausea or vomiting. These nonspecific symptoms are often attributed to another etiology and may lead to a delay in diagnosis.

●Symptoms associated with rupture are variable but may include abdominal pain associated with an expanding hematoma (contained rupture), or signs of free intra-abdominal hemorrhage (eg, hemodynamic collapse).

●Physical examination is not usually helpful in the diagnosis of most symptomatic VAAs/VAPAs given their deep location in the abdomen. In cases where a VAA/VAPA has expanded to a large size (eg, >4 cm), it may present as a palpable mass in thin individuals [18]; however, this is uncommon.

●Laboratory studies are usually nonspecific.

Specific aneurysms

Hepatic artery aneurysm — The increasing number of percutaneous biliary procedures, nonoperative management of trauma, and liver transplantations has led to an increase in hepatic artery pseudoaneurysms, making the hepatic artery the most commonly reported site of VAA/VAPA overall [19-23]. Hepatic artery aneurysm is more common in men (male:female = 2:1). Most hepatic artery aneurysms are extrahepatic (80 percent) with 60 percent of these located in the common hepatic artery, 30 percent located in the right hepatic artery, and 5 percent located in the left hepatic artery.

It is not unusual for patients with hepatic aneurysms to present with multiple aneurysms involving the visceral (31 percent) and nonvisceral circulation (42 percent) [14]. Atherosclerosis is considered the most common etiology (approximately 30 to 50 percent) followed by cystic medial necrosis (24 percent) and trauma (22 percent) [24]. Posttraumatic false aneurysms are most often the result of penetrating and crush injuries or wounds, surgical procedures, liver transplantation, or occurring after percutaneous needle biopsy of the liver (transhepatic cholangiography) [25].

Most hepatic artery aneurysms are incidentally identified on routine imaging to investigate unrelated symptoms and pathology. This is in contrast to the era prior to widespread abdominal imaging, in which most hepatic artery aneurysms presented with rupture or were discovered during autopsy [26,27]. Symptomatic hepatic artery aneurysm presents with nausea and right upper quadrant or midepigastric pain radiating to the back. In many instances, hepatic artery aneurysm becomes clinically apparent when there is erosion into the biliary tree and/or portal vein with the subsequent development of portal hypertension, or rupture in the retroperitoneal space and/or peritoneal cavity. Hemobilia, which is suggested by Quincke's classic triad (jaundice, biliary colic, and gastrointestinal bleeding) occurs in one third of patients with hepatic artery aneurysm [25]. Rarely, large hepatic artery aneurysms may present as a pulsatile right upper quadrant mass. Less than 10 percent of hepatic artery aneurysms present as infected (mycotic) aneurysms, which was the dominant clinical presentation before the antibiotic era.

Splenic artery aneurysm — Splenic artery aneurysms are the third most common true aneurysm occurring in the abdomen after aortic and iliac artery aneurysms [28,29]. Splenic artery aneurysms are more common in women (female:male = 4:1) and in the sixth decade of life, with as many as 80 percent occurring in patients >50 years of age [30]. Splenic artery aneurysms are associated with intra-abdominal aneurysms involving other visceral arteries (3 percent) and renal arteries (14 percent) [8,17]. One third of patients have multiple aneurysms [8]. Splenic artery aneurysms are usually solitary, saccular in shape, and frequently localized to the distal third of the artery, the bifurcation region, and the splenic hilum [8,18]. False aneurysms of the splenic artery are uncommon but can occur, particularly in association with pancreatitis, but also as a result of instrumentation.

True splenic artery aneurysms are commonly associated with conditions of increased flow, such as pregnancy (particularly multiparity), arterial venous fistulas and malformations, and portal hypertension [10,17,31,32]. Increased blood flow through the splenic artery has been suggested to lead to irreversible damage of the tunica media predisposing to aneurysm formation; muscle atrophy and calcification are secondary [33]. In pregnancy, hormonal changes combined with portal congestion are thought to degrade the structural integrity of the artery [17,33]. The prevalence of splenic artery aneurysm in females of childbearing age is less than 0.1 percent [34]. By contrast, the prevalence of splenic artery aneurysm in patients with liver cirrhosis and portal hypertension is 7 to 20 percent [17]. Eight to 13 percent of patients awaiting and following liver transplant develop splenic artery aneurysm because of the large portosystemic shunt [17,34,35]. Splenic artery aneurysm rupture after liver transplantation is not uncommon.

Patients with symptomatic splenic artery aneurysm present with nausea and vague abdominal discomfort in the midepigastric or left upper quadrant. This may be associated with left shoulder discomfort associated with irritation of the diaphragm. Nearly half of patients with splenic artery aneurysm have moderate splenomegaly [36]. Giant splenic artery aneurysms can occur, but these are rare [18]. In a large series, rupture was the presenting symptom for splenic artery aneurysm in approximately 5 percent of patients, with a mean diameter of 3.5 cm (3.2 cm for males, 2.3 cm for females) [30]. The mean diameter of the nonruptured splenic artery aneurysms was 2.2 cm.

The classic presentation of ruptured splenic artery aneurysm is the "double rupture phenomenon." Initial rupture of splenic artery aneurysm is associated with severe abdominal pain and initial hemodynamic instability, which is compensated for and followed by a period of relative normalization. This latent period is due to containment rupture within the lesser sac and tamponade of the splenic artery aneurysm. If untreated, the lesser sac can give way leading to free rupture into the peritoneal cavity with recurrent hemodynamic instability.

Celiac artery aneurysm — Aneurysms of the celiac trunk are one of the rarest types (4 percent) of visceral artery aneurysm, with an incidence of 0.01 percent [7,26,27].

The etiology of celiac artery aneurysms is usually atherosclerosis or medial degeneration, with infectious causes (eg, treponema pallidum causing syphilis), which were common in the 19^th century, now very rare. The average age of newly diagnosed patients is 55 years, and women now comprise almost half of all cases [37]. True arterial aneurysms can occur distal to sites of chronic vascular compression due to poststenotic dilatation and have been reported for compression of the celiac artery by the median ligament [38]. (See "Celiac artery compression syndrome".)

Most celiac artery aneurysms are asymptomatic, with approximately 85 percent discovered incidentally on imaging, while only 7 percent are discovered by autopsy. Of note, association with other aneurysms, such as aortic, renal, popliteal, and femoral, is common, occurring in two thirds of patients in one series [39].

Symptoms, such as midepigastric and back pain, can mimic pancreatitis due to the location of the arteries [40].

Superior mesenteric artery aneurysm — Superior mesenteric artery aneurysms are also rare. Atherosclerosis is the main cause of superior mesenteric artery aneurysms. In the past, 60 percent were infected (mycotic) due to septic emboli (eg, endocarditis) [7,21,26,27]. Other etiological factors include polyarteritis nodosa, Behcet syndrome, systemic lupus erythematosus, systemic connective tissue disorders, vasculitis, trauma, cystic medial necrosis, neurofibromatosis, and history of intravenous drug abuse.

Symptoms related to superior mesenteric artery aneurysms are generally nonspecific but, if the aneurysm is large enough, can rarely present as a palpable mass. Superior mesenteric artery aneurysms most commonly involve the proximal 5 cm of the superior mesenteric artery [9]. Extension of aneurysm-related thrombus or dissection that affects the collateral circulation of the celiac and inferior mesenteric arteries may result in ischemic symptoms, leading to pain after meals [9,40]. (See "Overview of intestinal ischemia in adults".)

Pancreaticoduodenal artery aneurysm — Pancreaticoduodenal artery (PDA) aneurysms are also rare VAAs but are increasingly prevalent [41]. PDA aneurysms are diagnosed at a mean age of 60 years.

True PDA aneurysms may arise from altered blood flow and pressure within the pancreaticoduodenal arcades, which serve as collaterals (figure 1), when there is celiac artery stenosis or occlusion. The presence of celiac stenosis has been observed in 50 to 80 percent of patients with true PDA aneurysms. Celiac artery compression by the median arcuate ligament (ie, celiac artery compression syndrome or median arcuate ligament syndrome [MALS]) can also alter flow in the pancreaticoduodenal arcades. (See "Celiac artery compression syndrome".)

In the face of celiac artery stenosis/occlusion, flow in the peripancreatic arterial arcades is retrograde via the superior mesenteric artery and a so-called "jet disorder phenomenon [42]" may cause aneurysm formation from the increase in turbulence in arterial flow. 

Rupture of PDA aneurysms necessitates urgent or emergency endovascular or open surgical intervention but leads to fatal hemorrhage in up to 50 percent of cases. The rupture risk of PDA aneurysms is independent of diameter, and rupture risk appears decreased in patients with concomitant atherosclerotic celiac disease or calcification in the aneurysm wall.

DIAGNOSIS — Visceral artery aneurysm (VAA) and visceral artery pseudoaneurysm (VAPA) are often not suspected initially in patients presenting with abdominal complaints, due to their rarity. For patients in whom the diagnosis is suspected (eg, pregnant women with sudden left upper quadrant pain), imaging is required to confirm the diagnosis. For patients who complain of abdominal pain, correlation of the location of the pain and location of the aneurysm is necessary, and other likely causes for the pain should be excluded before concluding that the symptoms are due to an incidentally identified aneurysm. (See 'Differential diagnosis' below.)

Plain abdominal films may raise suspicion of the presence of VAA, particularly when there is visible calcification in the wall of the aneurysm sac. Calcification, which is often viewed as evidence of chronicity and stability, was reported in one study to occur in 90 percent of the ruptured aneurysms, and thus, its prognostic value is not clear [30]. Upper gastrointestinal tract contrast imaging may detect the existence of a filling defect in the stomach or duodenum [43].

Ultrasonography and cross-sectional abdominal vascular imaging (computed tomography, magnetic resonance) provide an accurate diagnosis of VAA. Duplex ultrasound is an important and helpful diagnostic tool, particularly for demonstrating intrahepatic lesions. Ultrasound can measure blood flow inside the aneurysm sac, and portal venous waveforms will be arterialized if a fistula is present. Ultrasound is also the preferred initial imaging modality for identifying VAA in pregnant women because it is noninvasive and has no adverse fetal effects. The main disadvantage of ultrasound is that it is technician dependent and obesity and overlying bowel gas reduce its sensitivity, especially for smaller lesions. Magnetic resonance imaging is avoided in the first trimester. (See "Diagnostic imaging in pregnant and lactating patients".)

For patients who are known to have VAA and who are being managed conservatively, evidence for aneurysm expansion should be sought by comparing current with prior abdominal vascular imaging studies.

Differential diagnosis — The differential diagnosis of abdominal pain is broad. Given their rarity, VAAs are often not suspected during the patient's initial presentation. (See "Causes of abdominal pain in adults".)

The more common abdominal conditions for which symptoms associated with VAA/VAPA might be confused include the following:

●Biliary colic – (See "Functional gallbladder disorder in adults".)

●Pancreatitis [44] – (See "Clinical manifestations and diagnosis of acute pancreatitis".)

●Gastroesophageal reflux – (See "Clinical manifestations and diagnosis of gastroesophageal reflux in adults".)

●Other vascular conditions – On vascular imaging, VAA has a characteristic appearance; however, tortuous arteries can be mistaken as aneurysmal.

MANAGEMENT — Due to the rarity of visceral artery aneurysm (VAA) and visceral artery pseudoaneurysm (VAPA) and absence of controlled studies, management is based on the available observational studies, but there is no consensus guideline for management. The general approach to VAA and VAPA is early elective treatment when recognized, rather than watchful waiting, to minimize the risk of rupture. Rupture is associated with high rates of morbidity and mortality ranging from 10 to 25 percent for splenic artery aneurysm, and considerably higher for other sites [45]. Medical optimization may not be feasible for patients who present acutely with bleeding or rupture. Although VAA and VAPA in poor risk surgical candidates might previously have been observed with serial imaging studies, many can be approached percutaneously, provided the lesion is anatomically suitable for endovascular techniques [11,12]. (See "Treatment of visceral artery aneurysm and pseudoaneurysm", section on 'Open versus endovascular'.)

Natural history and role of observation — Retrospective reviews suggest that rupture rarely occurs in VAA with a diameter <2.5 cm [30,39,46]. Observation, at least in high-risk medical patients, may be a reasonable option for some sites. However, hepatic artery aneurysms have a higher rupture risk (80 percent) compared with other sites [47]. Based on this risk and correspondingly high rates of rupture-related mortality, most hepatic artery aneurysms warrant treatment, rather than observation.

●In one review of 168 patients, the mean splenic aneurysm diameter was 2.1 cm at the initial presentation. Of the 79 patients in whom follow-up measurements were obtained, 11 had evidence of aneurysm expansion; of these, 3 underwent elective repair. None of the observed aneurysms ruptured during a mean follow-up period of 75 months [30].

●In another study, patients with calcified superior mesenteric artery aneurysms did not rupture either at presentation or follow-up [46]. There was not an accurate description of aneurysm diameter in patients who ruptured, but the mean diameter in patients who did not rupture was 2.2 cm. Male patients were more prone to rupture. In a small series, 10 out of 13 patients with intact superior mesenteric artery aneurysms were asymptomatic. Good risk surgical patients underwent repair. Although elective repair did not require bowel resection, repair for rupture was associated with small bowel resection for bowel ischemia in three of the eight patients.

●In a small series of patients with celiac artery aneurysms, eight patients were considered too high risk for repair and were followed with serial imaging [39]. The mean aneurysmal diameter was 2.1 cm (range: 1.5 to 3.5 cm) at baseline. One patient with a 2.5 cm aneurysm who declined repair ruptured five years after presentation, whereas the others did not demonstrate any signs of expansion over a 91-month mean follow-up period (range: 1 to 371 months) [39].

Indications for treatment — The indications for treatment at the different anatomic sites are derived from the natural history of disease at that site, in particular the propensity for rupture, and the consequences of thrombotic occlusion, which depend upon the collateral circulation for that site. Our recommendations are consistent with the Society for Vascular Surgery (SVS) clinical practice guidelines for the management of visceral aneurysms [11]. Generally accepted indications for treatment of VAA and VAPA include:

●VAPA, when identified, regardless of symptoms – VAPA represents essentially a contained rupture that is only constrained by a fibrous capsule since all three layers of the arterial wall are disrupted. Pseudoaneurysm has a higher risk for overt rupture compared with true aneurysm, and thus, VAPA is typically treated when identified. Depending upon the diameter and the location, pseudoaneurysm rupture is associated with a mortality rate ranging from 25 to 70 percent [1].

●Symptomatic VAA – As with other vascular aneurysms, symptomatic VAA should be treated whenever symptoms can be directly attributable to the aneurysm [4]. (See 'Clinical features' above.)

●Asymptomatic VAA larger than 2 cm in diameter – For patients with asymptomatic VAA, the optimal diameter threshold for repair is not certain. In general, elective treatment asymptomatic VAA >2 cm diameter (good risk patient) is suggested, regardless of anatomic location, based upon natural history studies that suggest rupture rarely occurs when VAA diameter is less than 2.5 cm [30]. Patients with significant medical comorbidities who have asymptomatic superior mesenteric or celiac artery aneurysm can be safely observed. (See 'Natural history and role of observation' above.)

●Asymptomatic VAA with rapid expansion – Asymptomatic VAA that expands more than 0.5 cm/year during a period of observation should be treated.

●Asymptomatic VAA during pregnancy or in women of childbearing age – Asymptomatic VAA that presents during pregnancy, or in a woman of childbearing age, should be treated to minimize the risk of rupture, which, in pregnant women, is associated with high maternal and fetal mortality [11,47]. Decision making, particularly timing of intervention, needs to be individualized and should take into account the patient's age, and the site and diameter of the VAA [28].

●Asymptomatic VAA in a patient undergoing liver transplantation – Asymptomatic VAA identified in a patient undergoing an orthotopic liver transplantation is also at high risk for rupture and should be treated [1,23].

Evaluation for other aneurysms — Visceral artery aneurysms are frequently associated with aneurysmal disease at other locations [8,14,39]. As such, abdominal imaging (computed tomography or magnetic resonance) should be obtained, if not already done. Additional imaging should be based on clinical suspicion and clinical examination.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Aortic and other peripheral aneurysms" and "Society guideline links: Intestinal ischemia".)

SUMMARY AND RECOMMENDATIONS

●Although aneurysmal degeneration of visceral vessels is rare, visceral artery aneurysms (VAAs) are detected more often than in the past due to the increased use of cross-sectional body imaging and ultrasonography. True visceral artery aneurysms involve all layers of the wall, each of which is thinned but intact. Visceral artery pseudoaneurysms (VAPAs) result from a tear in the vessel wall due to trauma (iatrogenic, blunt, or penetrating injury) with subsequent periarterial hematoma formation.

●The splenic artery (VAA) and hepatic artery (VAPA) are most commonly involved. Less commonly involved are the celiac and mesenteric arteries, and gastric, intestinal, pancreatic, gastroduodenal, pancreaticoduodenal, and inferior mesenteric artery aneurysms are much less frequently reported.

●Visceral artery aneurysms are usually asymptomatic and identified as incidental, unexpected findings on imaging of the abdomen, particularly on computed tomography (CT) of the abdomen or CT angiography.

●The pathogenesis of VAA is poorly characterized as VAAs may be associated with a variety of conditions, including atherosclerosis, medial degeneration, and conditions of increased flow (eg, pregnancy, portal hypertension, liver transplantation). The natural history for VAA located in different anatomic locations is not uniform and also not well defined.

●The clinical presentation of symptomatic VAAs differs for each anatomic location; however, clinical symptoms and signs are nonspecific, and VAA and VAPA are often not suspected initially in patients presenting with abdominal complaints, due to their rarity, which can lead to a delay in diagnosis. For patients in whom the diagnosis is suspected (eg, pregnant women with sudden left upper quadrant pain), imaging demonstrating the aneurysm is required to confirm the diagnosis. For patients presenting with rupture, the diagnosis may necessarily be made in the operating room.

●The general approach to VAA/VAPA is early elective intervention, rather than watchful waiting, to minimize the risk of rupture. Observation with surveillance is an option for some small aneurysms in those who are poor risk for intervention, or who have a limited life expectancy.

●Treatment is indicated for:

•Any VAPA, when identified (symptomatic or asymptomatic)

•Symptomatic VAA

•Asymptomatic VAA that:

-Has a diameter more than 2 cm

-Expands more than 0.5 cm/year during observation

-Occurs in a woman who is pregnant

-Occurs in a woman of childbearing years

-Occurs in a patient undergoing orthotopic liver transplantation