CAS is a relatively common finding, identified in 12.5–24% of patients undergoing abdominal angiography [1, 16]. The typical symptoms of CAS are weight loss, postprandial abdominal pain, or nausea and vomiting [17, 18], although most patients with CAS are asymptomatic unless the perfusion decreases by 60 to 75% [1, 4]. The most common causes of CAS are MALS in Eastern countries and atherosclerosis in Western countries [7, 19]. In addition, congenital causes, acute and chronic aortic dissection, pancreatitis, invasion of malignancies, or iatrogenicity are known as causes of CAS . In the present case of the complete CA occlusion, the preoperative MDCT did not detect a lower location of the median arcuate ligament  or direct invasion of the CA by the tumor, and the patient did not have a past medical history of aortic dissection and pancreatitis. Instead, there was severe arteriosclerosis throughout the systemic arteries, including the CA; therefore, the cause of complete occlusion of the CA in the patient was considered to be atherosclerosis.
Severe stenosis or obstruction of the CA often induces the formation of collateral arterial pathways from the SMA system to the CA system to compensate the decrease of splanchnic arterial flow of the upper abdomen. The main collateral pathway is reported to be the GDA or DPA in most cases, whereas various arteries, such as the DPA, jejunal artery, omental artery, left gastric artery, arc of Buhlar, and Riolan or Drummond artery can be a collateral pathway [1, 5]. Song et al. described a total of 181 anastomoses in 94 CAS patients, including 89 pancreaticoduodenal arcades and 71 dorsal pancreatic arcades . Heo et al. described 22 collateral circulations in 37 MALS cases, including 14 pancreaticoduodenal arcades and 2 dorsal pancreatic arcades. The other 6 arcades were found in the arc of Buhler, splenic artery, jejunal artery, omental artery, hepatic artery, and left gastric artery . Therefore, the evaluation of the collateral pathways in patients with CAS is critical, especially before upper abdominal surgeries, to avoid organ ischemia. In the present case, the complete occlusion of the CA and the formation of complicated collateral arterial pathways were found in the two-dimensional MDCT images. In order to identify the accurate collateral pathways, a 3D image was reconstructed from MDCT and we clearly detected enlarged arteries around the pancreatic head, including the anterior superior pancreaticoduodenal artery (ASPDA), the posterior superior pancreaticoduodenal artery, the anterior inferior pancreaticoduodenal artery, and the posterior inferior pancreaticoduodenal artery, which perfuse from the SMA to the CHA through the GDA. In addition, we identified the well-developed DPA as a substantial anastomosis from the SMA to the SPA, suggesting that the DPA could function as one of the collateral arterial pathways from the SMA system to the CA system.
In the context of CAS, the formation of collateral arterial pathways is surgically relevant for arterial division in PD. Although the GDA is the main collateral pathway from the SMA system to the CA system in most of the cases of CAS, the GDA must be divided in PD. Therefore, various procedures were attempted to avoid organ ischemia after PD in patients with CAS . There are numerous reports regarding interventional radiological procedures that describe stenting of the CA for CAS with atherosclerosis . Various methods of vascular reconstruction during surgery were also proposed , including bypass between aorta or SMA and CA system using saphenous vein or prosthetic vascular graft [7, 21,22,23], bypass between SPA and iliac artery using autogenous vein , GDA reconstruction using middle colic artery , reimplantation of celiac trunk into the aorta , and arterial reimplantation of the proximal end of the divided SPA into the side of SMA . Median arcuate ligament division surgery is also considered as an effective method for CAS caused by MALS . In the present case, we identified the DPA as a collateral pathway from the SMA to the SPA, and the DPA is assumed to perfuse the CA system after division of the GDA. To confirm this hypothesis, we performed a GDA clamping test during the surgery, and favorable arterial waveform in the PHA was detected, suggesting that the arterial blood supply in the CA system was secured by the DPA. Indeed, a typical PD with GDA division was performed for this patient, and we did not find any signs or symptoms of upper abdominal organ ischemia, including the liver and stomach after the surgery. Although we used only Doppler ultrasonography to confirm arterial flow in the liver after GDA clamping, ICG fluorescence would also be useful to evaluate the arterial flow via collateral pathways in this case . The PD procedure performed for this patient with CAS was simple and easy to implement.