The prevalence rate of abdominal visceral aneurysms is approximately 0.1–2% [3], and splenic artery aneurysms are the most common abdominal visceral aneurysms, accounting for 60% of all cases [5]. Although other abdominal visceral aneurysms are more common in males, splenic artery aneurysms are more common in females (1:4 ratio). Estrogen and other female hormones may be contributing factors [6].

Ekingen et al. [6] classified splenic artery bifurcations into 22 types using CT angiography, and splenic artery bifurcation from the SMA is classified as type 8 and is present in 0.13% of 750 patients. Aneurysm formation in the splenic artery with abnormal bifurcation, as in the present case, is extremely rare, with fewer than 50 cases reported so far [7, 8]. Splenic artery aneurysms without branching abnormalities are more common on the distal side [9,10,11]. In contrast, splenic artery aneurysms with an abnormal bifurcation are characterized by the fact that all aneurysms reported to date are located at the origin [2]. Splenic artery aneurysms are often associated with atherosclerosis, pancreatitis, essential and portal hypertension, pregnancy, and other conditions in the literature. They are often found incidentally, and most are asymptomatic [12]. However, the patient in our case was male and had no history of aneurysms that could have caused them, as described above. The abnormal splenic artery bifurcated proximal to the SMA and rose at a right angle. It has been hypothesized that congenital alterations, such as arterial media dysplasia and sudden hemodynamic changes resulting from this anomaly, could be the primary causes of splenic artery abnormalities with this anatomic anomaly [2, 12].

Several studies have reported the treatment for splenic artery aneurysms branching from the SMA, including open aneurysm ligation and resection [13, 14], and aneurysm resection with revascularization and splenectomy [15], as well as coil embolization [7] and stent graft insertion [2], which have recently been reported with the development of endovascular treatment techniques. Hogendoorn et al. [16] reported that endovascular treatment has better short-term results and lower perioperative mortality rates than open surgery, but it also has a high reintervention rate due to late complications. Specific complications of endovascular treatment include coil migration, splenic infarction, post-embolization syndrome, and revascularization [16, 17]. In splenic artery aneurysms with abnormal bifurcation, the indication for endovascular treatment should be carefully considered, because if the coil moves into the SMA, there may be intestinal necrosis [8]. In recent years, the placement of a Viabahn stent graft in the main trunk of the SMA to close an aneurysm has been reported [18]. However, stent grafts alone do not completely stop blood flow into the aneurysm from the periphery, and this method may be inadequate. Kuwada et al. [19] reported stent grafting of the SMA and peripheral splenic artery coiling. We have also reported the usefulness of the Viabahn stent graft for bleeding from gastroduodenal artery (GDA) pseudoaneurysms after pancreaticoduodenectomy [20]; even if a stent graft placed in the common hepatic artery becomes occluded, the liver is highly resistant to ischemia and can tolerate it until collateral blood vessels develop. Thus, the Viabahn stent graft for pseudoaneurysms from the GDA is useful for achieving hemostasis and saving lives. However, stent occlusion in SMA main stem stent grafting is likely to cause intestinal necrosis and other problems and should be avoided if possible.