Giant aortic pseudoaneurysm

Clinical History

A 60-year-old male who was being treated for acute-on-chronic pancreatitis with a large pancreatic-pseudocyst presented with acute abdomen to the emergency department. On presentation he was hypotensive. Laboratory parameters confirmed low haemoglobin (8.6 gm/dl) and mildly elevated serum amylase levels (180IU). Serum electrolytes revealed a low sodium and pottasium.

Imaging Findings

Contrast CT abdomen revealed atrophic and papery-thin body-tail of pancreas with relatively spared pancreatic-head. Adjacent peripancreatic fat planes were dirty. No overt fluid collection was seen in its vicinity. Additionally, a giant aneurysmal sac from the right postero-lateral aspect of the abdominal aorta at L1-L2 vertebral level was seen. It had a wide patent mouth/neck of calibre approx. 4 cm. The sac itself measured more than 10 x 9 x 8 cm in size. The sac was seen extending into the right paravertebral gutter with extension also seen into the right psoas sheath. Contained peri-aneurysmal haematoma was also seen within the right psoas sheath. The caeliac, SMA and renal arteries were arising from the aneurysmal sac and displayed contrast opacification. However, the right renal artery was draped, stretched and compressed along the anterior aspect of the sac resulting in hypoperfused right kidney.

Discussion

Pseudoaneurysm formation is a recognised but relatively uncommon complication associated with pancreatitis. The most common artery affected is the splenic artery, followed by gastroduodenal, pancreaticodudenal, left gastric, hepatic and small intrapancreatic arteries in decreasing order of frequency. The probable aetiopathogenesis suggests that the release of proteolytic pancreatic enzymes (especially trypsin and elastase) into the perivascular space results in enzymatic digestion and weakening of the arterial wall. The damaged vessel wall under the influence of sustained arterial pressure leads to dissection of blood into the perivascular tissues forming a perfused sac that communicates with the arterial lumen [2, 4, 8]. This sac is either contained by the tunica-media or adventitia, or simply by perivascular soft-tissues. The transformation of a pseudocyst into a pancreatic pseudoaneurysm has also been described following erosion of a pseudocyst into a visceral artery [3, 7].

The majority of pseudoaneurysm involve the peripancreatic visceral arteries. The involvement of abdominal aorta is definitely a rare occurrence with only scanty reports available in the literature [1, 5]. The exact cause as to why the aorta seems resistant to autodigestion by pancreatic enzymes than other peripancreatic vessels is not clear [1]. This case report describes a giant aortic pseudoaneurysm of the abdominal aorta that developed in patient with acute-on-chronic pancreatitis. The patient was reported to have a large pseudocyst in relation to the pancreatic uncinate process in his previous scan done elsewhere approx. 4 weeks before (unfortunately images were not available). There was no vascular complication reported at that time. However, at the time of presentation at our institute the patient was recognised to have a giant aortic aneurysm which extended into the right psoas sheath and was also eroding the L-1 vertebral body. The absence of pseudocyst at the present scan suggested the probability that the pseuodocyst might have eroded into the aortic lumen and got converted into a perfused giant aneurysmal sac. The patient within few hours of presentation succumbed to massive intra-abdominal bleed and shock.

The management of pancreatic pseudocyst-associated pseudoaneurysms continues to be a challenging problem with high morbidity and death rates. For peripancreatic pseudoaneurysms, percutaneous arterial embolisation has been recommended as the initial therapy in haemodynamically stable patients, while surgery is generally reserved for actively bleeding, haemodynamically unstable patients; cases of failed embolisation; and for other secondary complications such as infection or extrinsic-compression [3]. Unlike visceral pseudoaneurysm there are no established guidelines for management of pancreatitis associated aortic pseudoaneurysm [1].

Differential Diagnosis List

Final Diagnosis

Giant aortic pseudoaneurysm

URL:	https://www.eurorad.org/case/9467
DOI:	10.1594/EURORAD/CASE.9467
ISSN:	1563-4086