PDAA accounts for only 2% of visceral artery aneurysms but has a high mortality rate [1]. Previous studies have reported that the mortality rate of ruptured PDAA is 21–26% [10, 11]. Therefore, PDAA should be treated adequately in the early stages; however, diagnosis is often difficult because it is asymptomatic before rupture and is diagnosed incidentally [2, 7]. Therapeutic strategies are selected based on the shape and location of the PDAA [6, 12]. In this study, we present a case of triple PDAAs with celiac axis occlusion, and aneurysmectomy of SPDAA and aorto-splenic bypass regressed the IPDAAs spontaneously by reducing the high blood flow of the PDA arcade. Therefore, we identified two important clinical issues. Decreasing the hyperinflow to the PDA arcade can lead to regression of the PDAA, and additional endovascular therapy may not be required in all cases when the dilation of the PDA is improved in selected cases.

PDAA can regress spontaneously by reducing the high blood flow in the PDA arcade. Our patient underwent bypass surgery and the PDAAs regressed completely without planned endovascular embolization. A few case reports have reported regression of PDAA, similar to ours [13, 14]. In 2017, Mont et al. reported complete regression of PDAA only by undergoing revascularization without operation for ruptured PDAA with median arcuate ligament (MAL) [13]. In 2020, Yamana et al. reported regression of PDAA after bypass surgery [14]. They performed endovascular embolization for multiple ruptured PDAAs, but the PDAAs increased in size in the early stages [14]. Subsequently, aorta-common hepatic artery bypass and MAL resection were performed, and the size of the PDAA regressed [14]. These reports support that regression of PDAA with celiac axis occlusion can be achieved by the improvement of unusual dynamic hyperinflow into the PDA arcade, as in our case.

Reducing the dynamic hyperblood flow into the PDA arcade is crucial for treating PDAA with celiac axis stenosis or occlusion, and improving the unusual dilation of the PDA arcade after treatment may be a successful sign. In a previous study, volumetric CT analysis revealed that the PDA arcade in PDAA cases was larger than that in gastroduodenal artery aneurysm cases [15]. PDA arcade dilation is an important characteristic of its pathogenesis [15]. In our case, PDAAs were caused by celiac arterial axis occlusion. There was no evidence of risk factors such as Marfan syndrome or Behçet’s disease, although other vasculitis and genetic investigations were not investigated in this case. The pathological findings revealed partial intimal thickening and atherosclerotic changes in the media without evidence of segmental arterial mediolysis. There were some options for the bypass for our case, such as aorto-splenic artery, iliac artery–hepatic artery, aorto-hepatic artery, and SMA–hepatic artery. For our case, we chose the aorto-splenic artery bypass using a retroperitoneal approach. This approach helps to maintain stable blood flow and prevent graft kinking. We also considered the possibility of pancreaticoduodenectomy if coil embolization for multiple PDAAs fails. Thus, we performed an aorto-splenic bypass to reduce abnormal inflow into the PDA arcade and support celiac artery blood flow into the hepatic artery. Previous reports suggested that reducing the PDA arcade blood flow may be sufficient to treat PDAA with celiac arterial axis stenosis [16]. Other reports have revealed that PDA arcades undergo an initial expansion phase, followed by the formation of focal aneurysms that have the potential to rupture. To the best of our knowledge, we have reviewed CT and angiography images in case reports published within a few decades. In most cases that can be assessed both before and after treatment, the dilated PDA arcade seemed to be normalized after successful treatment for celiac root stenosis or occlusion by revascularization or bypass [6, 8, 13, 14, 17, 18].

We must carefully follow-up and understand the risk of rupture because PDDA has the potential to rupture even if the size is small. The association between aneurysm size and the risk of rupture has not been clarified. Bageacu et al. reviewed the true PDAAs cases, and the sizes of the ruptured and unruptured aneurysms were 4–30 mm and 5–18 mm, respectively [17]. Takao et al. reported that true PDAAs might have a lower rupture risk than expected [19]. They followed six unruptured and untreated PDAA aneurysms with celiac axis stenosis or occlusion, and there was no rupture or size increase, but only one anterior pancreaticoduodenal artery aneurysm increased in size without rupture during 45 months of follow-up [19]. Therefore, novel criteria or assessments are required to predict whether additional endovascular interventions should be performed for PDAA and to assess rupture risk.

Evaluating the risk of PDAA rupture can be difficult using current methods; however, recent research has provided helpful information to accurately assess the risk of aneurysms. High aneurysm wall enhancement (AWE) values are associated with late sac shrinkage after endovascular repair of abdominal aortic aneurysms [20]. This study revealed a significant association between the AWE value on postoperative days 4–7 and the rate of sac shrinkage (R2 = 0.0139) [20]. In addition, other studies have quantified hemodynamic alterations in the PDA arcade in cases of celiac artery stenosis using computational simulations [21]. Numerical predictions indicate that the arterial network structure can be altered by the blood flow [21]. Furthermore, they also suggested with an electronic circuit model that severe celiac artery stenosis could cause drastic changes in blood flow increase in the PDAA [22]. It can predict the redistribution of blood inflow into the PDA arcade and hepatic artery and may be applied to evaluate the risk of PDAA rupture after treatment. These data support the establishment of criteria to predict the prognosis of PDAA before and after treatment.