Post-Pancreatitis Splenic Artery Pseudoaneurysm as a Luring Danger: A Case Report Open Access

The splenic artery aneurysm (SAA) is the most common splanchnic artery aneurysm [1, 2]. Atherosclerosis, inflammatory/infectious processes, as well as pathologies affecting the connective tissue and vessel wall are said to be responsible [3]. The course of the disease is usually asymptomatic. However, if symptomatic, the aneurysm has an increased risk of rupture. If rupture happens outside of the hospital setting, mortality is high. Size of the aneurysm, location (proximal vs. distal), morphology, and co-morbidities influence timing and type of therapy [3]. Often, the SAA is accidentally detected in CT scans performed for other reasons. For elective cases, endovascular techniques are preferred due to lower invasiveness. In the emergency setting, a surgical approach can become necessary [4].

A 39-year-old man was referred to our emergency room with acute onset of abdominal pain and pre-syncope at home. Apart from an anemia (Hb 99 g/L) and leukocytosis (11.4 × 10⁹/l), all other standard emergency laboratory parameters (incl. CK, troponin, BNP) were normal. Emergency CT scan ruled out pulmonary embolism, aortic dissection, and active bleeding. However, it showed a large mass associated to the stomach and a partially thrombotic pseudoaneurysm (27 × 24 mm) of the splenic artery with no signs of active bleeding (Fig. 1). Tentative diagnoses were gastrointestinal stroma tumor, mucosa-associated lymphoid tissue (MALT) lymphoma, or hematoma. A prior CT scan performed for an uncomplicated mild pancreatitis 1 year before had shown otherwise no abnormalities, especially no aneurysm. No follow-up imaging was performed. A biopsy and gastroscopy with endo-sonography were scheduled for the next working day to clarify the dignity of the mass. Around 30 h after an uneventful surveillance, the patient went suddenly hypotonous and tachycardic (Fig. 2). He was immediately transferred to the resuscitation unit where a sudden drop of Hb to 45 g/L indicated active bleeding. Despite aggressive volume management, he remained hemodynamically instable and therefore underwent immediate emergency laparotomy without further imaging. A large hematoma was found in the upper left quadrant with an active bleeding from a ruptured pseudoaneurysm of the distal splenic artery. The splenic artery was identified, ligated proximal to the aneurysm and splenectomy performed. After an uncomplicated postoperative course, the patient went home and presented in an excellent condition in a 3-month follow-up control.

Only 0.1–2% of arterial aneurysms present as aneurysmatic changes of visceral arteries. Most often affected is coeliac trunk with its branches. Herein, about 60% occur in the splenic artery followed by the hepatic artery with its branches. Interestingly, the splenic artery aneurysm occurs more often in women (80%) than in men (20%). Basically, two types can be differentiated: the true aneurysm and the pseudo-aneurysm [3, 5].

The true splenic aneurysm is typically the result of atherosclerotic changes in the vessel wall. Herein, all three layers (intima, media, adventitia) are affected. Less often, the true aneurysms find their origin in fibromuscular dysplasia, inherited defects of the connective tissue, trauma, or other infectious and/or inflammatory processes in the vessel wall. Known risk factors that lead to weakening of the elastic fibers in the splenic artery wall are, for example, hormonal disbalances during pregnancy, flow turbulences in the portal vein, and stasis in case of portal venous hypertension. A splenic pseudoaneurysm is even more rare than true aneurysm [3‒5]. It is said to be the consequence of erosive processes in the vessel wall [5, 6]. These can be triggered by the release of proteolytic enzymes following acute or chronic pancreatitis. In theory, the enzymes degrade the outer layer, damage the vessel wall, and allow the weaker inner layer to expand [5]. In the pseudoaneurysm only the adventitia or the adjacent hematoma remain as the last covering layer. Another risk factor is accidental lesions during endovascular procedures or gastroenterological interventions such as catheter drainage for the hepato-biliary system. In a case series, post-traumatic pseudo-aneurysm formation was reported, too [4]. The aneurysm can be located within the spleen or outside. Morphologically, they can be fusiform (affecting the whole diameter of the wall) or saccular [3].

The course of the disease is often asymptomatic. An exception are pregnant women and patients with portal hypertension who have such an aneurysm. It is said that, if present in pregnancy, up to 95% of the patients develop symptoms in the third trimester [3]. While the risk of a spontaneous rupture in general is up to 10%, it is supposed that a diameter of more than 20 mm is associated with an increased risk of up to 40%. The higher the diameter, the more fatal the complications and mortality. If a rupture occurs, bleeding can enter the retroperitoneal abdominal space. There, it can access the pancreatobiliary duct system and imitate a gastrointestinal bleeding. Sometimes, the pseudoaneurysm is accompanied by formation of a pseudocyst. Bleeding into such a pseudocyst can even further enlarge the pseudoaneurysm. In these cases, a hemorrhage into the pancreatic duct is called hemosuccus pancreaticus. Formation of an arterio-venous or arterio-colonic fistula is possible, too [4]. Before rupture, patients are said to complain of unspecific abdominal pain located in the upper left quadrant [4]. Apart from lethal bleeding events, more local complications such as splenic infarction, compression of splenic vein, and impairment of gastrointestinal passage can occur due to thrombo-embolic occlusion. In case of rupture, patients often present with symptoms of an acute abdomen and, as in our case, with hypovolemic shock [3‒5].

Gold standard for aneurysm detection is a contrast-enhanced CT angiography. Sometimes, the aneurysm is an incidental finding [3, 4]. From their literature review, Tessier et al. conclude that every hemodynamic stable patient should undergo angiography as this offers the opportunity for a transcatheter treatment. They also point out that if a high-density mass is visible within a peripancreatic fluid collection a clot within a pseudoaneurysm should be suspected [4].

As with other aneurysms, the therapy is guided primarily by the size of the aneurysm, localization, symptoms, and patient preferences and characteristics (sex, age, co-morbidities) [4]. While smaller aneurysms can be controlled serially, a diameter of 20 mm is a relative indication for an intervention [3, 4]. Due to the increased risk of rupture, the pseudo-aneurysm and the mycotic aneurysm are considered absolute indications, independent of size. Most durable and sustainable treatment in their series was splenectomy with or without pancreatectomy [4‒6].

In our case, it was clinically and radiographically challenging as the new detected mass was initially interpreted as a tumorous lesion associated to the stomach. Together with the stomach pain in the patient’s history and the initially suspected gastrointestinal stroma tumor or (mucosa-associated lymphoid tissue) lymphoma, our thinking and clinical approach was biased toward tumor diagnostic. Retrospectively, it is hypothesized that the patient suffered from a post-pancreatitis pseudoaneurysm that had ruptured twice. The large mass must be considered retrospectively as a hematoma that might have compressed and stopped bleeding from the first aneurysm rupture (first hit). The second hit (re-rupture) then led to hemorrhagic shock. Since there were no follow-up consultations after the pancreatitis 1 year before the current event, we can only hypothesize that the aneurysm developed in this period.

Around 200 cases of splenic artery pseudoaneurysm have been reported. Some of them were in association with chronic pancreatitis [7]. What makes this case special is the very delayed presentation. Other delayed splenic artery pseudoaneurysm bleeding events have been reported in association with post-pancreatic surgery (e.g., pancreaticoduodenectomy, sleeve gastrectomy/bariatric surgery, biliopancreatic diversion), stent placement procedures (i.e., lumen-apposing metal stent), or post-blunt trauma [8‒11]. One anecdotal case reports a ruptured aneurysm 2 years after penetrating trauma presenting as hematemesis [12]. Other bleeding reports support the contributing role of chronic pancreatitis with/without involvement of pseudocysts. These patients were treated with transcatheter arterial embolization [13‒15]. In another case, the so-called double-rupture phenomenon was illustrated by a patient with (true) splenic artery aneurysm rupture who became hemodynamically instable within 72 h after admission. Surgical intervention due to delayed hemoperitoneum was required there [2].

Surgery is indicated in case of free open rupture with hemodynamic instability [5]. However, endovascular methods are now preferred for cases with an elective procedure and in the emergency setting if hemodynamics allow this. Depending on aneurysm morphology and location in the artery, multiple strategies are possible (4): embolization of the aneurysmal sack without occluding the main vessel (when the aneurysm has a small neck), embolization of the aneurysmal sack with stenting of the adjacent artery if the neck is broad, stenting of the artery with a covered stent graft, or embolization (with coils or plugs) of the artery in sandwich technique proximally and distally of the aneurysm to prevent persistent retrograde blood flow via the collateral circulation [6, 16]. Due to this collateral circulation, a proximal embolization will not result in a splenic infarction. When an aneurysm is very distal and not suited for stenting, risk of splenic infarction rises, and surgical alternatives should be considered. An efficacy of 88–100% with a mortality of 0% are mentioned in the literature for these endovascular approaches [17, 18]. Anecdotally, trans-abdominal percutaneous approaches with thrombin or glue injection are mentioned in the literature, too [17].

In open surgery, several treatment options exist. They range from vascular ligation of the splenic artery aneurysm over aneurysmectomy resection to exclusion with or without splenectomy, depending on the aneurysm location [19, 20]. An open approach with/without splenectomy is favored over endovascular interventions in case of distal splenic artery aneurysm adjacent to the hilus of the spleen (risk of end-organ ischemia, e.g., splenic infarction, pancreatitis). A preservation or revascularization of the artery is not needed, routinely [20].

Treatment decision depends not only on hemodynamic stability but also co-morbidities (e.g., obesity) and location/anatomy of the pseudoaneurysm. Typically, they are in the intermediate or the distal splenic artery segment [8].

For the gastroenterologist, it is important to be aware of this entity of a possible splenic artery pseudoaneurysm following pancreatitis. An understanding of risk factors, pathology, symptoms, and treatment options is essential. Correct diagnosis can be challenging if patients have a concomitant gastrointestinal disease (irritable bowel syndrome, food intolerances, small bowel bacterial overgrowth) that can present with recurrent abdominal pain, too. A potential aneurysm could be missed [4]. Early involvement of other disciplines (visceral surgeon, interventional radiologist) and an interdisciplinary treatment approach is crucial after detection of a splenic artery pseudoaneurysm. The CARE Checklist has been completed by the author for this case report, attached as online supplementary material (for all online suppl. material, see https://doi.org/10.1159/000546314).

Ethical approval is not required for this study in accordance with local or national guidelines as the patient was treated according to guidelines and not as a study participant. Written and informed consent was obtained for publication of the information presented in this manuscript.

The authors declare that they have no conflict of interest.

No funding was received for this manuscript.

D.S. drafted and wrote the manuscript. K.L. and V.V.d.B. co-wrote and reviewed the manuscript.

All data generated or analyzed during this study are included in this article and its online supplementary files. Further inquiries can be directed to the corresponding author.