Elsevier

The Surgeon

Volume 8, Issue 4, August 2010, Pages 223-231
The Surgeon

Review
Aneurysms of the splenic artery – A review

https://doi.org/10.1016/j.surge.2009.11.011Get rights and content

Abstract

Splenic artery aneurysm is the third most common intra-abdominal aneurysm with a prevalence as high as 10% in some studies. Widespread use of abdominal imaging has resulted in the increasing detection of asymptomatic incidental aneurysms. In this manuscript we review the changing incidence, risk factors and evolving therapeutic options in the era of minimally invasive therapy and have developed a treatment algorithm for practical use.

Aneurysms with a low risk of rupture may be treated conservatively but require regular imaging to ascertain progress. Available evidence suggests that splenic artery aneurysms that are symptomatic, enlarging, more than 2 cm in diameter or those detected in pregnancy, childbearing age or following liver transplantation are at high risk of rupture and should undergo active treatment. Prophylactic screening should be reserved for those with multiple risk factors, such as pregnancy in liver transplant recipients. All false aneurysms should also be treated. The primary therapeutic approach should be endovascular therapy by either embolization or stent grafting.

Introduction

Splanchnic artery aneurysms present an uncommon, but potentially life-threatening condition. The prevalence has been reported to be as high as 10% in some studies based on autopsies.1 Aneurysm of the splenic artery accounts for up to 60% of all splanchnic artery aneurysms and is the third most common intra-abdominal aneurysm following those of the aorta and the iliac arteries.2 It is defined as an abnormal dilatation of the splenic artery more than 1 cm in diameter. Splenic artery aneurysm (SAA) was first described on cadavers in 1770 by Beaussier.3 The first pre-operative diagnosis was made nearly 150 years later by Hoegler in 1920.4 The incidence of splenic artery aneurysm varies from 0.1 to 10.4% in the general population.1, 5, 6 It is four times more common in females compared to males.7, 8, 9 Although the pathogenesis is not fully understood, risk factors include trauma, hormonal and local hemodynamic events in pregnancy, portal hypertension (including Caroli's syndrome), arterial degeneration (medial fibrodysplasia) and atherosclerosis.10, 11 Patients suffering from portal hypertension are particularly at risk with an incidence of 7.1–13.0%.12, 13 Development of new SAA after liver transplantation is a rare event. However, they have been reported to occur as late as 16 years after transplantation.14, 15

False or pseudoaneurysms of the splenic artery are less prevalent than true SAA. They differ from true SAA in that the dilatation occurs following the disruption of one or more layers of the vessel wall. The splenic artery accounts for the majority of splanchnic pseudoaneurysms. Unlike true SAA, these have a slight male predominance. The underlying causes in most of the cases are trauma, infection, or weakening of the splenic artery wall from exposure to pancreatic enzymes. The latter is usually associated with pancreatic anastomotic leaks, severe pancreatitis and pancreatic pseudocysts.16 The significance of diagnosing and treating SAA lies behind its risk of rupture, which increases significantly beyond a diameter of 2 cm. Mortality after rupture varies from 25 to 70% depending on the underlying pathology.

Although surgical intervention has long been the mainstay of therapy, recent advances in imaging and minimally invasive techniques have revolutionized the diagnosis and management of SAA. In this manuscript we review the recent advances and current concepts in the management of SAA.

The splanchnic circulation includes the coeliac, superior mesenteric, and inferior mesenteric arteries, which arise from the abdominal aorta. The most proximal is the coeliac artery, which has three branches. These are the left gastric, splenic, and common hepatic arteries. The splenic artery arises from the coeliac artery distal to the origin of the left gastric artery and undergoes a primary bifurcation at the hilum of the spleen. It lies closely applied to the upper border of the pancreas. It is the primary vascular inflow to spleen and pancreas. In addition it supplies the greater curvature of the stomach through the short gastric and left gastro-epiploic arteries.17 Most aneurysms develop in the main trunk of the splenic artery. Aneurysms distal to the primary bifurcation are uncommon and occasionally involve small branches at the hilum. True SAA mostly occurs in the distal third of the artery (75%) followed by the middle third (20%). They are usually solitary and saccular in nature.10, 18 The mean size of the SAA at the time of detection is approximately 2.1 cm, and rarely exceeds 3 cm.19 Mycotic aneurysms are more commonly located at the bifurcation of the artery.20 Concomitant splanchnic aneurysms are found in 3% of patients and non-splanchnic aneurysms have been documented in up to 14% of cases, most of which are occur in the renal artery.21

True aneurysms are contained by all three layers of the arterial wall. Arterial degeneration in the form of medial fibrodysplasia is commonly seen along with varying degrees of focal inflammation, atherosclerosis,10, 22 cystic medial degeneration and myxoid degeneration.10, 23, 24 Infective elements with micro-abscesses may be seen in mycotic aneurysms.25 On the other hand, false SAA lacks one or more of the layers of the vessel wall (intima, media and adventitia), making it weaker and more susceptible to rupture.

The natural history of splenic artery aneurysms is similar to other intra-abdominal aneurysms 26 with progressive increase in size leading ultimately to rupture. However, the majority (80%) are asymptomatic and discovered incidentally.27 Symptomatic SAA (20%) may present with abdominal pain in the epigastrium or left upper quadrant. Other general symptoms may include anorexia, nausea or vomiting which are often attributed to co-existing hiatal hernia or other pathology such as gallstones and peptic ulcer disease. Even amongst those presenting with such non-specific symptoms the final diagnosis is nearly always a fortuitous discovery by abdominal imaging.23, 28 Rarely a mass, pulsatile or otherwise, may be detected on clinical examination.

A more dramatic mode of presentation is spontaneous rupture of the aneurysm which is reported to occur in 2–10% of patients as the initial presentation.10 Although historically nearly 10% of patients presented with an acute rupture 19, 29 the widespread availability of modern imaging systems has reduced this to approximately 3% based on recent studies. Risk factors for rupture of the aneurysms include pregnancy, development of symptoms, expanding aneurysms, a diameter greater than 2 cm, portal hypertension, portocaval shunt and liver transplantation.10, 30, 31 False aneurysms have a significantly higher risk of rupture compared to true aneurysms. A rupture presents with sudden onset sharp abdominal pain in the epigastrium or more often left upper quadrant, left shoulder tip pain (Kehr's sign) and hemodynamic instability.32, 33, 34, 35 Occasionally they may present with the double rupture phenomena within 48 h. In this scenario the first haemorrhage occurs in to the lesser sac leading to temporary tamponade. This is followed by flooding through the foramen of Winslow into the peritoneal cavity with resultant severe shock. The double rupture phenomenon was first described by Bockerman in 1930.5, 6, 10, 23, 30, 36, 37 Apart from intra-peritoneal bleeding, secondary erosion of the aneurysm into an adjacent viscous may lead to gastrointestinal haemorrhage. This has been described in up to 13% of patients with rupture of the aneurysm into the stomach, colon or the duct of Wirsung in the pancreas. Erosion in to the splenic vein may result in an arterio-venous fistula and portal hypertension.4, 5, 6, 37, 38 Rarely, the high flow through a splenic arterio-venous fistula leads to mesenteric steal syndrome and small bowel ischemia.39 Pseudoaneurysm may also rupture into the duodenum or the pancreatic duct with resultant anaemia, melaena or haematemesis. Pseudoaneurysms that develop in the presence of pancreatic fistula resulting from surgery or severe pancreatitis often present with a small sentinel bleed that precedes the major haemorrhage. In the post-operative situation a third of such patients would suffer from intra-luminal haemorrhage while the majority will bleed intra-abdominally which will be detected in the abdominal drains if present.

Spontaneous rupture is the most serious complication of SAA with an overall mortality rate of 25%. This is particularly high when it occurs in pregnancy where it has been found to be as high as 75%.40 The majority of splenic artery aneurysm ruptures (95%) occur in pregnancy.27 Mortality rate in case of spontaneous rupture of pseudoaneurysms is close to 100%.41 Treatment should be initiated as soon as possible, independent of their size and even in the absence of bleeding.42, 43, 44

Section snippets

Investigations

The increasing diagnosis of incidental splenic artery aneurysms is primarily related to the aging population and the liberal use of US and cross-sectional imaging.6, 10, 29, 45 Occasionally a calcified splenic artery aneurysm may be seen on plain abdominal X-ray. However, US, CT, MRI, MRA and endoscopic US are all modalities which are more likely to make the initial diagnosis of an asymptomatic aneurysm.32, 46 US has the advantage of being non-invasive, cost effective and radiation-free with

Conclusion

Splenic artery aneurysms with features suggestive of low risk for rupture may be successfully managed without intervention. Radiological follow up with six monthly US or CT scan should be mandatory to assess progression of the aneurysm. Active intervention should be considered if the aneurysm is symptomatic, enlarging, more than 2 cm in diameter or if found in pregnancy or childbearing age. All false aneurysms of the splenic artery should be treated as soon as possible. Prophylactic screening

Acknowledgements

Thanks to Mr H.AL-KHAFFAF, FRCS (Ed)

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      Citation Excerpt :

      Symptomatic cases often involve enlargement of the aneurysm by more than 2 cm and they account for 20 % of all SAA cases with spontaneous rupture being the most common complication in those patients [10]. Some (2–10 %) patients will present spontaneous rupture [5], with mortality of 10–40 %. Rupture can be instant or can happen in two stages, which occur in 20 to 25 % of cases [6].

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