Arc of Buhler pseudoaneurysm complicated by an arterioportal fistula: a combined endovascular and open surgical approach

Abstract

The Arc of Buhler (AoB) is a rare anatomic variant characterized by direct anastomosis between the celiac artery and the superior mesenteric artery. There is a relative paucity of data regarding this anatomy, likely due to its rather low incidence. The most common pathology associated with AoB is aneurysm formation, and while AoB aneurysm is exceedingly rare, a pseudoaneurysm appears even more so. We present a case of an AoB pseudoaneurysm in a 62-year-old male which was complicated by an arterioportal fistula (APF) between the pseudoaneurysm and the main portal vein. A multidisciplinary team of surgeons, interventional radiologists, and body radiologists worked together to treat this complex pathology. To our knowledge, this is the first reported case of an AoB pseudoaneurysm with an APF. This case emphasizes the importance of multispecialty collaboration in treating such unusual and complex vascular pathology.

Introduction

First described in 1904, the Arc of Buhler (AoB) is a rare direct anatomic connection between the celiac artery and the superior mesenteric artery [1]. Some theories propose this is a failure of regression of the ventral anastomosis of the 10th and 13th segmental arteries of the aorta formed in utero [2]. The most common pathology associated with AoB is aneurysm formation, which is almost always symptomatic [3].

There is a relative paucity of data regarding the AoB, likely due to its low incidence. A recent meta-analysis by Kowalczyk et al. determined that the pooled prevalence of AoB in the general population is ~1.7% [3]. The overall incidence of visceral artery aneurysms is estimated to be 0.1%–2%, with 5% of these being pseudoaneurysms [4]. Therefore, an AoB aneurysm appears to be exceedingly rare, with a pseudoaneurysm becoming even more uncommon [3, 4].

Here we present a case of an AoB pseudoaneurysm (PSA) complicated by an arterioportal fistula (APF) to the main portal vein.

Case report

The patient is a 62-year-old male with hypertension, diabetes, and alcohol-induced chronic pancreatitis who presented with severe abdominal pain. A contrast-enhanced computed tomography (CT) revealed changes of acute-on-chronic pancreatitis associated with a large walled-off necrotic collection at the region of the pancreatic body and tail. There was an incidental note of an irregularly shaped, avidly enhancing lesion at the region of the pancreatic head measuring ~2.5 × 1.9 cm. This lesion appeared intimately associated with an anomalous and torturous artery in region of the pancreatic head that appeared to communicate with the superior mesenteric artery (SMA). Additionally, early opacification of the portal vein was also appreciated, raising concern for fistulous communication with this vascular lesion (Fig. 1). A differential diagnosis was provided that included an arteriovenous malformation versus an APF. Management included opinions from both interventional radiologists (IR) and surgeons.

An angiogram revealed an irregularly shaped PSA communicating with a hypertrophied AoB, demonstrating high-flow fistulous outflow into the portal vein at the confluence of the splenic and superior mesenteric veins (Figs 2 and 3). Several attempts to access the AoB from the common hepatic artery (CHA) side were unsuccessful due to the acute angle of origin of the AoB from the CHA.

The decision was made to access the AoB from the SMA side, and after several attempts it was successfully embolized with coils. However, the final angiogram showed persistent supply of the PSA from the CHA side of the arc, but with slowed shunting through the APF (Figs 4 and 5).

A repeat CT was performed 5 days after coil embolization, which showed a slight decrease in size of the PSA, now measuring 2.2 × 1.7 cm (previously 2.5 × 1.9 cm) with no significant flow through the embolized SMA contribution to the AoB. However, there was persistent opacification of the PSA from the CHA side with persistent APF. At this point, the decision was made to proceed with surgery to control the vascular contribution from the CHA side. Surgery identified two branch arteries arising from the CHA proximal to the origin of the gastroduodenal artery. The larger of these two branches was felt to be supplying the PSA and was clipped.

Another CT was performed which showed no change in size of PSA. To assess post-surgical vascular changes, angiography was performed and showed a persistent feeding artery to the PSA form the CHA side, but this was again unable to accessed endovascularly. The next day, the patient returned to the OR for repeat ligation. The relevant feeding artery from the CHA side was identified with intraoperative ultrasound and ligated. Repeat CT was done and showed significant reduction of the PSA with peripheral mural thrombus formation with the aneurysm, now measuring 1.9 × 1.5 cm. The patient continued to receive treatment for necrotizing pancreatitis and was eventually discharged home in stable condition. Follow-up imaging performed 43 days after the last CT showed complete thrombosis of the PSA and resolution of the APF (Fig. 6). There was no subsequent portal vein thrombosis; patient never received antiplatelets/anticoagulation and d-dimer levels were not assessed.

Discussion

The initial approach to treating AoB aneurysms is based on the standard of care for visceral and mesenteric aneurysms and PSAs elsewhere: an endovascular approach given the high rate of PSA rupture and subsequent mortality [5]. The endovascular approach may confer a higher success rate and a lower complication rate in treatment of PSAs especially, as these often arise in the setting of inflammation and injury which would complicate open repair [5]. However, complex PSAs may pose challanges such as acute angles preventing guidewire access, imminent risk of portal venous thrombosis or PSA rupture – factors that all necessitate consideration for open surgery.

In this patient’s case, endovascularly coiling the main AoB supply from the SMA was important to decrease the extent of high flow AP shunting, allowing for partial thrombosis of the PSA. However, failure to completely embolize the PSA during the initial session and persistent AP shunting highlights the importance of isolating all potential collateral branches supplying the PSA. An open surgical approach using intraoperative Doppler ultrasound to identify the source of residual arterial inflow allowed for successful ligation of the contributing artery. This resulted in a significant reduction of AP fistulous flow that allowed for progressive thrombosis of the PSA and eventual resolution of the fistula.

Alternative treatment approaches such as direct thrombin injection into the PSA were not deemed appropriate as it carried a higher risk of thrombin migration and subsequent portal venous thrombosis.

AoB aneurysms are relatively rare with a total of 12 cases in the literature (Table 1). However, to our knowledge this is the first case associated with APF. This high flow, fistulous communication significantly increased the complexity of treating the PSA and brought a unique opportunity for collaboration between surgery and IR.

Conflicts of interest

None declared.

Funding

None declared.

References