Pancreaticoduodenal Artery Pseudoaneurysm Associated with Pancreatic Fibroinflammatory Mass and Duodenal Obstruction

Introduction

Pancreaticoduodenal artery aneurysms are a rare subset of visceral artery aneurysm, accounting for less than 2% of cases [1]. Despite their rarity, they are clinically significant due to their elevated risk of rupture and subsequent mortality [2]. These aneurysms typically develop in association with pancreatitis or as a consequence of celiac artery stenosis/occlusion. Their formation involves increased blood flow from the superior mesenteric artery to the peri-pancreatic arteries, potentially leading to compression of the pancreaticoduodenal artery and subsequent development of aneurysms [3,4].

While most pancreaticoduodenal artery aneurysms remain asymptomatic, their clinical manifestations range from abdominal pain, vomiting, and weight loss to hemodynamic instability. Primary management strategies involve surgical intervention or endovascular embolization, which is the preferred treatment modality [5]. The Society for Vascular Surgery recommends treating all aneurysms, regardless of their size or associated risk factors [5].

Case Report

A 60-year-old man presented in our Emergency Department with a 2-week history of abdominal pain associated with nausea, vomiting, anorexia, and weight loss of 4 kg. He denied any tobacco or alcohol use and did not have a recent history of abdominal surgery, pancreatitis, or recent travel. The family history was negative, and he was diagnosed 4 years earlier with Sneddon-Wilkinson disease, common variable immunodeficiency disease (CVID) and 2 episodes of pulmonary embolism treated by apixaban. The initial episode occurred during hospitalization for pustulosis, later identified as Sneddon-Wilkinson disease, and the second episode occurred 15 days after SARS-CoV-2 vaccination. Upon physical examination, the patient exhibited a distended abdomen with diffuse tenderness upon palpation. Additionally, there were significantly diminished bowel sounds, and a palpable mass was identified in the right upper quadrant. His vital signs were within normal range and there was no jaundice or rash. Initial laboratory tests showed mild inflammation (CRP 25 mg/L) and normal liver and pancreatic enzyme levels. An angio-CT scan revealed a pancreaticoduodenal artery aneurysm, retroperitoneal hematoma, enlarged stomach, duodenal obstruction, and heterogenous irregular pancreatic mass (Figure 1A, 1B). The aneurysm was successfully embolized through endovascular intervention (Figure 2A, 2B). Further laboratory examinations ruled out vasculitis and IgG4-related pancreatitis as the cause of the aneurysm (Table 1). Endoscopic ultrasound found mucosal hypertrophy at the duodenal obstruction and a pancreatic head lesion (Figure 3A–3C), prompting a biopsy, which ruled out autoimmune pancreatitis or malignancy, but revealed a fibroinflammatory process (Figure 4A, 4B). A subsequent abdominal MRI showed regression of the hematoma and reduction in the pancreatic lesion. Due to persistent but restricted gastric symptoms, despite the use of parenteral nutrition, a nasogastric tube, octreotide administration, and antiemetics, we considered performing an endoscopic ultrasound-guided gastrojejunostomy. However, a subsequent follow-up endoscopy demonstrated a regression in the duodenal obstruction, prompting cancellation of the initially planned intervention. Four months later, the patient’s follow-up revealed an excellent state of health with no gastrointestinal concerns.

Discussion

Posterior pancreatoduodenal artery aneurysm are a rare yet increasingly diagnosed vascular pathology [1]. Although it accounts for less than 2% of cases, it is associated with a high risk of rupture [2,3]. Unlike other aneurysms, rupture appears to be associated with male sex and seems to be unrelated to size [4]. Commonly reported symptoms include nausea, vomiting, and anorexia, often attributed to upper gastric obstruction, as observed in our patient. However, cases of duodenal obstructions linked to pancreatoduodenal artery aneurysms are extremely rare. For instance, Itoh et al documented only 11 cases between 1966 and 2000 [6]. Recently, duodenal obstruction has also been reported as a postoperative complication following successful embolization [7]. In contrast, our patient experienced duodenal obstruction prior to embolization. Furthermore, considering our patient’s 2-week history and the typical progression of pseudoaneurysms leading to enlargement and eventual rupture, we hypothesize that the aneurysm itself may have contributed to the duodenal obstruction, exacerbated by the hematoma, resulting in worsening symptoms. Pancreatoduodenal artery aneurysms can be classified as true or false (pseudoaneurysm), with various causative factors including atherosclerosis, infection, vasculitis, inflammatory diseases such as acute or chronic pancreatitis, malignancy, iatrogenic injury, and connective tissue diseases (eg, Marfan syndrome, Ehlers-Danlos syndrome) [3,10]. Interestingly, the patient’s medical history included 2 immune diseases, CVID and Sneddon-Wilkinson disease, encompassing many of these conditions, putting him at high risk of developing aneurysms [10–14].

Celiac artery stenosis or occlusion is recognized as the primary cause of true aneurysms [9], whereas pseudoaneurysms involve a vascular wall lesion and confined hematoma [8], and the latter typically are caused by proteolytic destruction of the artery wall by pancreatic enzymes released secondary to pancreatitis. This condition can be confused with segmental arterial mediolysis (SAM), a rare non-inflammatory, non-atherosclerotic vascular disorder characterized by vacuolization of the outer arterial media and lysis of the arterial media layer, leading to aneurysm formation and severe bleeding [15]. SAM often manifests autonomously without pancreatitis and primarily affects major arteries such as the superior mesenteric, celiac trunk, and renal arteries. The small arterial structure of pancreaticoduodenal arcades remains unaffected. However, there was a recent case report of an atypical ruptured aneurysm of the inferior pancreaticoduodenal artery causing duodenal obstruction attributed to SAM, despite not meeting angiographic criteria [16]. Our patient experienced abdominal and epigastric pain that spontaneously resolved 2 weeks before hospitalization. Due to the timing of symptom resolution and inconclusive diagnostic evidence, acute transient pancreatitis could not be definitively ruled out as the cause of the patient’s pain. The abdominal scan revealed a complete rupture of the vascular wall with contained hematoma. Therefore, while SAM could be considered as a diagnosis, the subacute symptoms and angiographic findings made SAM less likely in our patient. Furthermore, the clinical symptoms and an unidentified stenosis or occlusion of the main trunk artery excluded the diagnosis of a true aneurysm, making pseudoaneurysm the likely diagnosis. Importantly, the pseudoaneurysm was associated with the development of an inflammatory mass in the pancreatic head, compressing the duodenum while sparing the pancreatic duct. In contrast, pseudoaneurysms of the gastrointestinal artery often compress the pancreatic duct, leading to pancreatitis [17].

Given the limited data on pancreatoduodenal artery aneurysm, there is a lack of consensus on management guidelines. Nevertheless, due to the high risk of rupture, all aneurysms should be treated [8]. Available therapeutic strategies include surgery, endovascular intervention, or a combination of both [10]. Endovascular embolization is considered the first-line therapy [5]. Recent studies have compared open and percutaneous interventional techniques for managing pancreatoduodenal aneurysm [1,5,18]. There appears to be no significant difference in mortality rates between endovascular and open procedures in elective situations. However, under hemodynamically unstable conditions or with a ruptured aneurysm, endovascular treatment show is associated with a lower mortality rate. Therefore, an endovascular strategy proved the most suitable approach for our patient. Despite this intervention, gastrointestinal symptoms, including nausea and vomiting, persisted. Subsequent evaluation by CT scan and endoscopic ultrasound confirmed successful embolization without filling, in addition to the remaining duodenal obstruction. As the patient remained stable, a conservative approach was pursued. This included nasogastric tube suctioning, octreotide treatment to reduce the secretion, and supportive therapy with intravenous fluids and intravenous parenteral nutrition. While these measures alleviated the patient’s symptoms, restoring enteral nutrition remained unsuccessful. Gastro-jejunal bypass surgery using an endoscopic approach was considered, but prior endoscopic assessment revealed resolution of the pancreatic lesion and duodenal occlusion with conservative management. Consequently, the intervention was postponed, and the patient was gradually transitioned to a normal diet 4 weeks after hospitalization.

Conclusions

We presented a case of a posterior pancreaticoduodenal aneurysm alongside the development of an inflammatory mass in the pancreatic head and subsequent duodenal occlusion. Subacute symptoms suggestive of pancreatitis, along with imaging findings, supported the diagnosis of pseudoaneurysm in our case. Prompt interventions with early endovascular embolization and conservative approaches achieved significant symptom relief within 1 month.