The most common cause of APFs is trauma including blunt trauma, stab wounds, and gunshot wounds, followed by iatrogenic causes such as surgical and nonsurgical interventions, congenital abnormalities, tumors, and aneurysms (Vauthey et al. 1997). Our patient was diagnosed with an acquired extrahepatic APF caused by rupture of an anterior inferior pancreaticoduodenal arterial pseudoaneurysm. The pseudoaneurysm developed suddenly and ruptured within 4 days. The cause of pseudoaneurysm formation was presumed to be cholangitis, which had triggered the admission. The tentative diagnosis of cholangitis was based on the presence of gallstones, elevation of hepatobiliary enzymes, and a mild inflammatory response. However, CT showed neither bile duct dilatation nor edematous thickening of the bile duct wall. Thus, whether the cholangitis caused enough inflammation to form the pseudoaneurysm in this case remains questionable. The rupture of the pseudoaneurysm resulted in a hematoma in the mesentery and perforation of the portal tributary. We have herein reported our experience from onset to treatment of this rare condition.
Patients with APFs may be asymptomatic or symptomatic with complications of portal hypertension (ascites, diarrhea, and gastrointestinal bleeding), congestive heart failure, and intestinal ischemia due to the blood steal phenomenon (Vauthey et al. 1997; Al-Khayat et al. 2008). This case of an acquired large extrahepatic APF corresponds to type 2 in the classification of APFs established by Guzman et al. (2006). Type 2 APFs have large shunt flow and are therefore likely to cause symptoms of portal hypertension. The symptoms associated with APFs depend on the location and size of the fistula (i.e., shunt flow). However, these symptoms do not develop immediately after APFs formation. In this case, the rupture of the pseudoaneurysm was urgently treated, so no symptoms of portal hypertension after APF formation were seen.
The main treatment for APFs was surgery (Vauthey et al. 1997); in recent years, however, IR has become mainstream. This technique allows treatment while confirming the fistula site by arteriography. Simple TAE (Siablis et al. 2006; Marrone et al. 2006; Yamazaki et al. 2017) is indicated at sites where collateral blood flow to the basin is maintained and organ ischemia cannot occur. Because covered stent treatment can block the fistula while preserving the main arterial blood flow, it is adopted in relatively large arterial regions such as the common hepatic artery, gastroduodenal artery (Krishan et al. 2010), splenic artery, and superior mesenteric artery trunk (Narayanan et al. 2008; Yeo et al. 2008). If a pseudoaneurysm or fistula exists in the main arcade of the pancreaticoduodenal artery, stent treatment may be considered. In this case, however, stent placement was not appropriate because both a pseudoaneurysm and APF were present in a branch that diverged from the mainstream of the arcade, and even a microcatheter could not reach this site. Some reports have described successful treatment of an APF using transportal embolization after TAE was unsuccessful or inadequate (Denys et al. 1998; Cekirge et al. 1998; Wada et al. 2016). In this case, we embolized the inflow of the pseudoaneurysm with TAE and the outflow from the APF with transportal embolization. The outflow was blocked with a balloon catheter to prevent the microcoils from flowing out to the portal vein. Because one report described a case in which the coil for TAE flowed to the portal vein through the APF (Weinstein et al. 2009), it seems important to back up the portal vein side with a balloon. A pseudoaneurysm should not be densely packed because it does not have a wall structure and is easily ruptured by coil filling. In this case, the microcatheter via the portal vein could be advanced beyond the APF to the pseudoaneurysm; thus, coil embolization was started from within the pseudoaneurysm as a foothold to avoid dense packing. We added embolization to the outflow vessels of the portal side. As a result, the blood flow of the pseudoaneurysm was completely controlled.
In an emergency, necessary and sufficient treatment can save lives even if the treatment is slightly overzealous. Even in cases of difficult treatment, an accurate understanding of the present situation and a flexible response will lead to success.