BackgroundPancreaticoduodenal artery aneurysm (PDAA) is a rare, but fatal disease. However, the association between aneurysm size and the risk of rupture remains unclear. There are many options for therapeutic strategies that should be discussed well because the treatment options are often complicated and highly invasive. However, it remains unclear whether additional endovascular therapy is essential for all patients undergoing bypass surgery. Here, we present a case of triple PDAAs with celiac axis occlusion and spontaneous complete regression of inferior PDAAs (IPDAA) after aneurysmectomy of superior PDAA (SPDAA) and aorto-splenic bypass.Case presentationA 68-year-old woman presented with one SPDAA and two IPDAAs caused by celiac axis occlusion. Aneurysmectomy for IPDAAs was difficult because of their anatomical location and shape. Therefore, we planned a two-stage hybrid therapy. The patient underwent aorto-splenic bypass and resection of the SPDAA. Follow-up CT was performed to evaluate the IPDAAs before planned endovascular embolization. Spontaneous regression of the IPDAAs and normalized PDA arcade decreased the blood flow in the PDA arcade. The patient is doing well without graft occlusion, and the IPDAAs have completely regressed 7 years after surgery.ConclusionNormalization of hyperinflow to the PDA arcade can lead to the regression of PDAA. Potentially, additional endovascular therapy may not be required in all cases when dilation of the PDA improves. However, more cases must be accumulated to establish criteria for predicting the risks of short- and long-term PDAA ruptures.