Splenic artery aneurysm associated with anatomic variations in origin

Abstracts

O aneurisma de artéria esplênica foi descrito pela primeira vez por Beaussier em 1770, e o primeiro tratamento bem-sucedido foi apresentado por McLeod em 1940. O aneurisma da artéria esplênica é considerado o mais comum do território esplâncnico, afetando 46 a 60% dos doentes com aneurismas viscerais. A maioria dos doentes é assintomática, e o achado do aneurisma de artéria esplênica costuma ser casual, durante a investigação de outra doença abdominal por imagem. Descrevemos o caso incomum de uma doente do sexo feminino, com 31 anos de idade, com um grande aneurisma de artéria esplênica que se originava da artéria mesentérica superior.

Aneurisma; artéria esplênica

CASE REPORT

Splenic artery aneurysm associated with anatomic variations in origin

Ana Terezinha Guillaumon^I; Elinton Adami Chaim^II

^IDoutora. Professora associada livre-docente e chefe, Disciplina de Moléstias Vasculares, Departamento de Cirurgia, Faculdade de Ciências Médicas, Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brazil. Chefe, Serviço de Referência de Alta Complexidade em Cirurgia Endovascular, Hospital de Clínicas, UNICAMP, Campinas, SP, Brazil

^IIDoutor. Professor assistente, Disciplina de Moléstias do Aparelho Digestivo, Área Vias Biliares, Departamento de Cirurgia, Faculdade de Ciências Médicas, UNICAMP, Campinas, SP, Brazil

Correspondence

ABSTRACT

Splenic artery aneurysm was first described by Beaussier in 1770, and the first successful treatment was reported by McLeod in 1940. The splenic artery aneurysm is considered the most common splanchnic site for aneurysm formation, affecting 46 to 60% of patients with visceral aneurysms. Most patients are asymptomatic, and splenic artery aneurysm is often found during imaging investigation of other abdominal diseases. We describe an unusual case of a 31-year-old female patient with a large splenic artery aneurysm originating from the superior mesenteric artery.

Keywords: Aneurysm, splenic artery.

Introduction

The first case of splenic artery aneurysm was described in 1770 by Beaussier. In 1869, Corson reported the association of ruptured splenic aneurysm with pregnancy. Only in 1920 splenic artery aneurysm was diagnosed preoperatively by fluoroscopy. McLeod, in 1940, described the first case of successful surgical repair in a patient with splenic artery aneurysm.^1,2

Splenic artery aneurysms are the most common visceral artery aneurysms (46 to 60%),^1-4 followed by aneurysms involving the hepatic artery (approximately 20%) and the superior mesenteric artery (5 to 6%), and the highest incidence is in women (75 to 87%) aged between 50 and 79 years.^5,6 The splenic artery is the third most common site of intra-abdominal aneurysms, after the aorta and iliac arteries.^3,7 The incidence and natural history of splenic artery aneurysms are unknown, since they are asymptomatic and often found during imaging investigation of other abdominal diseases² or due to aneurysmal rupture, with a high perioperative mortality rate. For this reason, treatment should start immediately after diagnosis for aneurysms greater than 2 cm in diameter. Prompt treatment is also recommended for women of childbearing age, for pregnant women prior to the third trimester of gestation, and for patients with systemic hypertension or growing aneurysms.^6,8,9 Aneurysmal rupture occurs in 3 to 9.6% of patients, with an operative mortality rate of approximately 0.5% for non-ruptured aneurysms and 25% for ruptured aneurysms. The etiology of the aneurysm might include processes directly related to the splenic artery, atherosclerosis, congenital anomalies, and polyarteritis nodosa. There is also an association with pregnancy, portal hypertension, fibromuscular dysplasia, hypertension, and processes not associated with the splenic artery, such as trauma, pancreatitis, septic emboli, and inherited and connective tissue diseases (Ehlers-Danlos syndrome, vascular type). Treatment varies according to aneurysm site and size and patient-related factors, such as age, hostile abdomen, and comorbidities, as well as vascular anatomy, the latter being an item to be considered in the selection of a suitable approach to the aneurysm (endovascular or open surgical procedures). In the present study we report an unusual case of an anomalous splenic artery aneurysm originating from the proximal portion of the superior mesenteric artery.

Case report

A 31-year-old female patient presented with low back pain and pain in the left hypochondrium radiating to the left lower limb. Her physician suggested the diagnosis of renal calculus. Past medical history revealed as significant data the use of oral contraceptive and a normal pregnancy. The patient had not undergone previous abdominal surgery. Clinical examination revealed, on abdominal palpation, a periumbilical pulsatile mass with a systolic bruit. Other clinical signs were normal. Abdominal ultrasound revealed a 3-cm anechoic mass located behind the pancreas (Figure 1).

Contrast-enhanced computed tomography revealed patent abdominal aorta without aneurysms or stenoses, celiac trunk giving rise to hepatic and left gastric arteries with normal diameter, splenic artery with saccular aneurysm formation with an 8-cm neck and greater diameters of 4.3 x 3.9 x 3.8 cm (Figure 2).

Magnetic resonance angiography of the abdominal aorta and branches revealed patent abdominal aorta with normal diameter. Presence of saccular aneurysmal dilatation in the splenic aorta, originating from the emergence of the superior mesenteric artery, measuring 3.6 x 3.0 cm. Considering that common hepatic, splenic and gastric arteries branch off the celiac trunk, we verified a splenic artery with anomalous anatomy branching off the superior mesenteric artery (Figure 3).

In view of the imaging findings, a preoperative evaluation was performed with biochemical tests showing normal results.

The patient underwent endoaneurysmorrhaphy through a median supraumbilical incision for aneurysm exclusion. The aneurysm was then dissected from the superior mesenteric and splenic arteries, with arterial repair using vessel loops at pre- and post-aneurysm regions.. After systemic heparinization, hemostatic vascular clamps were applied and the aneurysm was opened. Splenic artery ostium was closed with intra-arterial, intra-aneurysmal suture, with ligation of splenic artery distal to aneurysm using appropriate suture (polypropylene 5-0) (Figure 4). The fragment extracted from the aneurysm wall was submitted to histopathological examination that revealed absence of inflammatory or dysphasic process, presence of a thinned wall with focal interstitial hemorrhage, changes compatible with a degenerative aneurysm. The patient was discharged from hospital on the third postoperative day and progressed without clinical events in the immediate postoperative period as well as in the last 6-month postoperative period.

Discussion

Visceral aneurysms are uncommon, but their treatment is of paramount importance due to their significant potential for rupture and elevated mortality rates. Splenic artery aneurysms are the most common visceral aneurysms, accounting for approximately 46 to 60% of cases. The highest incidence is in women, three- to seven-fold higher than in men,^5,4,10,11 occurring primarily in the third and seventh decades of life.^5,4 The distal portion of the artery (20% of cases) is the most common site for aneurysm formation, which is usually saccular in form. Since most cases are asymptomatic (80%), with uncharacteristic and vague pain, these aneurysms are likely to be detected only after rupture, which occurs in 3 to 9.6% of cases, translating into a high mortality rate when compared to that of elective surgery (0.5%).^4,7,12,13 Among visceral aneurysms, the splenic artery aneurysm is the most common (95%) in young pregnant women, and a greater number of diagnoses are made during pregnancy, often due to aneurysmal rupture. The highest incidence of rupture is during the third trimester of gestation (69% of cases), resulting in peritoneal or visceral hemorrhage.^9,10,14,15 Although the occurrence of splenic artery aneurysms during pregnancy is explained by an increase in arteriovenous shunts resulting from the increased flow at this site, in such situation maternal mortality reaches 70% and fetal mortality reaches 75% of cases during surgical repair.^3,4,16,17

Splenic artery aneurysms are usually caused by defects of the medial coat and loss of elastic and muscle fibers, and the etiology might include processes directly related to the artery wall, to facilitating processes, traumatic injuries by both external and internal causes, and inherited diseases. Processes directly related to the occurrence of aneurysms include: atherosclerosis (the most common), congenital anomalies and polyarteritis nodosa; facilitating processes include: pregnancy, portal hypertension, fibromuscular dysplasia, and traumatic injuries by both external and internal causes, such as pancreatitis, septic emboli resulting from mycotic aneurysms, intravenous drug users, road-traffic accidents, and inherited diseases, such as Marfan syndrome.^18-20

Differential diagnosis of pancreatic cysts or pseudocysts should be made, by location, this condition being more frequent in patients with past history of pancreatitis. Serous cystadenoma should also be considered as a hypothesis, but it occurs mainly in the seventh decade of life.^21,22

Treatment for splenic artery aneurysm should be performed when there is risk of rupture, diameter greater than 2 cm, in symptomatic, transplant patients, associated with inflammatory processes, and in women of childbearing age or pregnant women.²³ Recent advances in diagnostic imaging have provided essential information on anatomic criteria to guide decision-making in the surgical technique to be used, which depends on the anatomic location and vascular anatomy of the aneurysm. When the aneurysm is located in the distal portion of the artery, repair may be performed by open surgery with ligation, splenectomy may be necessary^24,25 or not, bearing in mind that this organ is supplied mainly by the splenic artery, but there are alternative pathways, such as the gastroepiploic artery, which branches from the gastroduodenal artery. Coil embolization is not recommended for the management of giant aneurysms due to ineffective occlusion of the aneurysm, intense inflammatory process, and risk of embolization. When the aneurysm is located in the proximal or middle portion of the artery, the patient may be treated with placement of a covered stent,^11,26,27 excision of the aneurysm with arterial reconstruction, or simple ligation of the artery proximal and distal to the aneurysm, via open surgery or laparoscopy. Although some authors recommend aneurysm repair only for patients with a low operative risk,⁸ we believe that treatment is determined based on aneurysm dimensions, anatomy, risk of rupture, and the patient's clinical history. In the case herein reported, the open surgical technique was considered the best approach, based on the anatomic variation present, with the splenic artery emerging from the mesenteric artery, showing great tortuosity that hinders endovascular access for placement of a covered stent, in addition to a small-diameter vessel. It is important to point out that this was a young patient and, since long-term outcome of stent placement is unknown, this technical hypothesis was ruled out. Pre- and post-aneurysm ligation of the splenic artery was performed, without splenectomy, since the alternative supply pathways managed to sustain organ vitality. The patient progressed without splenic infarction, organ removal was not necessary, and without clinical events that might complicate a good clinical evolution.

The authors concluded that splenic artery aneurysms should be investigated and treated even in asymptomatic patients, considering that aneurysm rupture has a high mortality risk. The use of imaging investigation such as magnetic resonance angiography was of paramount importance, since tridimensional evaluation of the aneurysm determined the anomalous anatomic finding and the precise location of the lesion, which facilitated the choice of repair technique.

References

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Publication Dates

• Publication in this collection
  02 Oct 2009
• Date of issue
  June 2009

History

• Accepted
  13 Feb 2009
• Received
  18 Feb 2008