Splenic Artery Aneurysm: An Endovascular Approach to Therapy

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Introduction
Aneurysms of the splenic artery are the third most common intra-abdominal aneurysms, with aneurysms of the aorta and iliac arteries being most and second most common, respectively.¹ However, splenic artery aneurysms (SAAs), with an incidence as high as 10% in certain series, are the most common visceral artery aneurysms.² The detection of SAAs is likely rising in the setting of increasing frequency of advanced abdominal imaging.³ The most commonly cited risk factors for SAAs are portal hypertension and multiple pregnancies.^1,4 Presentation varies from benign, incidental findings on abdominal imaging studies to hypovolemic shock secondary to aneurysmal rupture. The incidence of aneurysm rupture has been reported to occur in about 5% of cases at presentation.⁵

Because they are relatively rare, the optimal treatment of SAAs is unknown; there are no guidelines as to which aneurysms should be treated with what modalities. Traditionally, surgery has been considered the best invasive management strategy. However, with the advent of advanced endovascular techniques and growing interest from interventionalists, the approach to management is changing. Here, we present a case of an incidentally found SAA, describe its treatment with endovascular coil embolization, and review the literature on SAAs and their management.

Case Presentation
A 71-year-old man with hypertension, glucose intolerance, hyperlipidemia, aortic stenosis, and peripheral arterial occlusive disease presented to an outside hospital with sudden onset nausea, vomiting, and abdominal pain, eventually presumed to be secondary to viral gastroenteritis. During his hospital stay, he underwent computed tomography (CT) of the abdomen. While there was no bowel pathology, note was made of a calcified 2.8 x 2.5 cm SAA, with no evidence of surrounding hematoma. He was referred for endovascular management of his SAA.

A 5-Fr sheath was inserted in the right femoral artery via the modified Seldinger technique. Angiography was performed, revealing a large splenic artery aneurysm > 2.5 cm in size. Through a 7-Fr Arrow sheath (Arrow International, Reading, Pennsylvania), the vessel was engaged with an angled soft glidewire (Boston Scientific, Natick, Massachusetts), which was then positioned near the aneurysmal sac. A glide catheter (Boston Scientific) was advanced into the sac, and four Nestor coils (Cook UK Ltd, Letchworth, United Kingdom), measuring 12 mm x 14 cm, were deployed into the aneurysm. Stent implantation into the neck of the aneurysm could not be performed due to vessel tortuosity and severe angulation of the neck. Final angiography revealed continued flow in the splenic artery and decreased flow in the aneurysmal sac. The procedure was well tolerated, and there were no immediate complications.

Follow-up CT of the patient’s abdomen two months later revealed no obvious opacification of the aneurysm sac, with IV contrast and normal perfusion of the splenic parenchyma.

Discussion
Splenic artery aneurysms are the third most common intra-abdominal arterial aneurysm and the most common visceral artery aneurysm.^1,2 Autopsy studies have revealed an incidence of 0.1% in the general population, as high as 10% in those over 60 years of age and up to 50% in those with portal hypertension.⁶ Risk factors for splenic aneurysm include portal hypertension, systemic hypertension, multiparity, arterial fibrodysplasia, chronic inflammatory processes, and arteriosclerosis.⁷

Most patients are asymptomatic and present after aneurysms are incidentally discovered on abdominal imaging. Symptoms that have been attributed to SAAs include left upper quadrant pain, nausea, and vomiting. The most ominous presentation is hypovolemic shock secondary to aneurysmal rupture. This occurs in approximately 3–10% of cases,⁸ more often, after liver transplantation, and carries with it a 10–25% risk of mortality among nonpregnant patients, and up to a 70% risk of mortality in pregnant women.^7,9

Because of the relative rarity of SAAs, indications for intervention are not standardized. It has been suggested that aneurysms in pregnant women, women of childbearing age, patients with symptoms possibly related to their aneurysm, and those undergoing liver transplantation should undergo repair.¹⁰ Other groups have recommended repairing asymptomatic aneurysms based on their size, with initial cutoffs starting at 1.5 cm.⁵

Therapeutic options for the treatment of SAAs include open or laparoscopic surgical repair or endovascular repair with coil embolization, stent graft implantation, or glue embolization. Rupture is most often treated with emergent open surgical repair, although there are case reports of percutaneous coil embolization in the acute setting.¹¹ The strategies most often implemented in patients presenting for elective repair are laparoscopic surgery, which is limited by technical constraints or endovascular coil embolization.

Traditional surgical techniques have been associated with a high degree of morbidity, including splenectomy (about 25%) and distal pancreatectomy (about 10%), and mortality (5% in elective cases and up to 40% in emergent cases).^5,7

Endovascular techniques for the treatment of vascular disease have rapidly gained interest, due to a less invasive approach, shorter hospital stays, and less patient morbidity. The first reported transcatheter embolization of a SAA occurred in 1978.¹² Reported success rates of percutaneous coil embolization approach 90%, and associated morbidity and mortality are significantly lower than traditional surgical techniques.¹³ In addition to coil embolization, stent-graft implantation across the neck of the aneurysm14 and, more recently, use of N-butyl cyanoacrylate glue embolization have been described.¹¹

The most common complication following percutaneous embolization techniques is an ill-defined post-embolization syndrome, which occurs in approximately 30% of cases and is defined as any combination of fever, abdominal pain, slow transit, and pancreatitis.¹³ Other possible complications include need for reintervention, splenic infarct, infection, and bleeding at the access site.

Conclusion
We report a case of an asymptomatic SAA discovered incidentally during abdominal imaging. It was successfully treated percutaneously with coil embolization. Treatment options for SAAs include open and laparoscopic surgical techniques, as well as a number of percutaneous techniques. Given the increase in abdominal imaging, the number of incidental SAAs is likely to rise, although which patients require therapy to reduce the morbidity and mortality associated with SAAs remains to be defined. As operators become more facile with endovascular techniques, the number of SAAs treated percutaneously is also likely to rise. Given the improved delivery of devices and lower morbidity of this technique, an endovascular approach may become the preferred method of therapy.