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A 64-year-old woman underwent surgical resection of a posterior inferior pancreaticoduodenal arterial aneurysm in the subacute phase of acute aortic dissection (AAD). Concomitantly, a distal pancreatectomy was also required. The aneurysm was approximately 20 mm in diameter. Surgical resection of the aneurysm was performed because endovascular treatment was considered to be technically difficult due to dissecting lesions that had remained at the abdominal aorta. Histopathological findings suggested this aneurysm to be a pseudoaneurysm, which had arisen as a result of segmental arterial mediolysis. Approximately 1 year after surgery, no recurrence of the aneurysms was detected.
Visceral artery aneurysm (VAA) is a rare disease, although the number of incidentally detected VAAs has increased due to the development of imaging technologies, with incidence of approximately 1% in all populations.1) Various etiologies of VAAs are known, such as inflammation, infection and atherosclerosis. The treatment for VAAs is still controversial, and there is no definite guideline. We report a case of surgical resection of the posterior inferior pancreaticoduodenal artery (PIPDA) pseudoaneurysm.
We emergently performed ascending aortic and total arch replacement in a 64-year-old woman with Stanford A type acute aortic dissection (AAD) that reached the abdominal aortic bifurcation. Concomitantly, coronary artery bypass grafting to the right coronary artery was also required. After AAD surgery, the patient recovered normally and did not experience any specific symptoms.
Follow-up computed tomography (CT) images obtained 23 days after AAD surgery revealed a VAA with enhancement, which appeared to lie in front of superior mesenteric artery (SMA) and behind the pancreas body (Fig. 1A). The aneurysm was approximately 20 mm in diameter, and the artery that seemed to be responsible was the PIPDA (Fig. 1A and 1B1B). This aneurysm could not be enhanced on CT images obtained before AAD surgery (Fig. 1C). Additionally, follow-up CT images showed that dissecting lesions remained at the abdominal aorta, especially around the orifices of the celiac artery, SMA and renal arteries. Percutaneous interventional approach with coil embolization could be one of available treatments to be performed, but endovascular treatment for this patient was considered to be so difficult technically and carry the risk of aortic rupture. Therefore, the surgical resection of the aneurysm was determined to be performed to prevent the aneurysm rupture.
The patient had undergone a total gastrectomy, including splenectomy and cholecystectomy, due to gastric carcinoma 17 years prior to AAD surgery. No recurrence of the gastric carcinoma was found. The patient had no history of abdominal trauma or pancreatitis. Similarly, she did not have any characteristics associated with vasculitis, such as Behçet’s disease, and hereditary collagen diseases, such as Ehlers-Danlos syndrome.2) In the clinical course after AAD surgery, complete blood cell counts and C-reactive protein levels were within accepted limits for patients recovering from AAD surgery, and pancreatic amylase was within the normal range. There were no bacteria isolated from the patient’s blood culture. Etiologies resulting in VAA for this patient were unclarified.
Forty-four days after AAD surgery, this patient underwent a second operation. The aneurysm was accessed via an upper median and left subcostal incision. Intraperitoneal adhesion between each organ was severe due to the previous open surgery. Macroscopically, the aneurysm appeared to lie behind the pancreas body, and two vessels, which were probably PIPDA, appeared to be connected to this aneurysm, as seen on the CT images. The whole aneurysm and its feeding arteries could not be exposed due to severe adhesion to the surrounding tissues nearby pancreas, and it was impossible to resect only the aneurysm or to ligate the feeding arteries. A distal pancreatectomy was required concomitantly to complete the resection of the aneurysm. Observation of the resected aneurysm showed that its surface was smooth, and neither inflammation, infection, nor atherosclerosis was found. The operation time was 6 hours and 13 minutes.
Microscopic examination using hematoxylin and eosin staining and elastica van Gieson staining revealed the resected tissue to be a pseudoaneurysm (Fig. 2A). Closer observation showed intermittent disruption of the internal elastic lamina of the aneurysmal wall, known as “medial islands” (Fig. 2B). Vacuolar degeneration of the vascular media was also observed in the surrounding small arteries. These findings suggested that a pseudoaneurysm had arisen as a result of segmental arterial mediolysis (SAM).
The operation was completed uneventfully, and the patient recovered satisfactorily. There was no recurrence of the aneurysm visible on CT images obtained after the pseudoaneurysm resection, and good surgical results were confirmed. The patient walked without assistance when she was discharged from the hospital. Approximately 1 year after surgery, she was continuing to do well without recurrence of the aneurysms.
The treatment for VAAs is still controversial, and the size of the aneurysm that can be at risk of rupture is unverified.3) Some reports described that VAAs larger than 2 cm in diameter might rupture; another reported the rupture of even small VAAs that were less than 2 cm in diameter.4–6) On the contrary, a report described that the risk of rupture of pancreaticoduodenal artery aneurysms might be lower than expected from data on ruptured aneurysms.3) Treatment decisions cannot be made on the basis of aneurysm size alone. Two strategies are available for management of VAA; endovascular treatment and surgical resection. Endovascular treatment, which includes coil embolization and stent grafting, is a less invasive technique than surgical resection. This technique can be particularly beneficial for treatment of VAA in patients with comorbidities,7,8) whereas, surgical resection of the aneurysm can achieve the prevention of rupture with certainty, and is also an effective treatment.9)
In this case, surgical resection of the aneurysm was performed but endovascular treatment was not for the following reason: subacute phase dissecting lesions remained at the abdominal aorta, especially around the orifices of the celiac artery, SMA and renal arteries. Therefore, endovascular treatment was considered to be technically difficult and carry risk of aortic rupture. Additionally, a distal pancreatectomy needed to be performed concomitantly because the whole aneurysm could not be exposed due to severe adhesion to the surrounding tissues nearby pancreas, and it was impossible to resect only the aneurysm or ligate the feeding arteries. This pseudoaneurysm was believed to have existed at the time when AAD was diagnosed although not enhanced. This may be because the phase of the contrast enhancement of CT images obtained before and after AAD surgery were not identical. Moreover, histopathological findings indicated chronic changes in the wall tissue of the pseudoaneurysm, which can support that this aneurysm had likely existed before.
Microscopic findings suggested that this pseudoaneurysm had arisen as a result of SAM. SAM is a noninflammatory and nonatherosclerotic degenerative disease that was first reported by Slavin, et al. in 1976.10) SAM is a rare vasculopathy that most often occurs in visceral muscular arteries. In most cases, aneurysmal formation progresses without symptoms and may sometimes lead to rupture. The present patient had no symptom, and no history of infection, pancreatitis, or vasculitis.2) Some reports described that VAAs caused by SAM may occur heterotypically or heterochronically.11–13) In this case, approximately 1 year after surgery, there is no recurrence of the aneurysm visible. Close follow-up is required to verify the recurrence of the aneurysms.
We report a case of surgical resection for the posterior inferior pancreaticoduodenal artery pseudoaneurysm. Etiologies resulting in asymptomatic visceral artery aneurysm were unclarified clinically, but histopathological examinations revealed to be the pseudoaneurysm which had arisen as a result of SAM.
We thank Dr. Yutaka Nakashima, MD, Department of Pathology, Japanese Red Cross Fukuoka Hospital, for consultation of pathological examination and diagnosis, and Dr. Kiyoshi Kajiyama, MD, Department of Surgery, Aso Iizuka Hospital, for surgical treatment.
We have no conflict of interest to disclose with respect to this paper.