A pancreatic pseudoaneurysm is an uncommon clinical entity. However, it is important to recognize this condition early as it can result in life-threatening complications. A pancreatic pseudoaneurysm usually occurs when there is an erosion of a peripancreatic or pancreatic artery into a pseudocyst. The most common cause of a pancreatic pseudoaneurysm is pancreatitis, but this pathology can also occur in patients who do not develop a pseudocyst. The key difference between a true aneurysm and a pseudocyst is that in the latter, the wall does not consist of normal components of a vessel but instead consists of fibrous and connective tissue.
Pancreatic pseudoaneurysm develops in the background of pancreatitis or pancreaticobiliary surgery. Rarely it has been reported after pancreatic transplantation. Today another relatively common cause of pancreatic pseudoaneurysm is trauma and motor vehicle accidents. Some patients may develop the pseudoaneurysm after undergoing biliopancreatic surgery for malignancy. The pseudoaneurysm tends to occur following an anastomotic leak, followed by an intraabdominal abscess. Pancreatic pseudoaneurysms tend to occur in the presence of enzyme-rich pancreatic fluid, which causes autodigestion and weakening of the walls of the nearby vessels.
In patients with chronic pancreatitis who undergo angiography, the incidence may be as high as 10%. There is a reported incidence of 5% to 10% occurrence of bleeding due to arterial causes in pancreatitis. When there is an associated pseudocyst formation in pancreatitis the frequency of bleeding due to arterial lesions rises to 15% to 20%.
A pseudoaneurysm differs from a true aneurysm because the wall does not contain arterial tissue but consists of fibrous tissue which contains a hematoma which can enlarge or rupture. This damage to the occurs as a consequence of autodigestion and weakening of arterial wall by pancreatic juices or leak from a pancreatic anastomosis. Eventually, if the autodigestion continues, this leads to the formation of a total or partial vascular cystic structure. Because the splenic artery runs its course along the pancreas towards the spleen, it is affected in pancreatitis. This anatomical position explains why splenic artery is the commonest site of developing pseudoaneurysm in any visceral artery. The pseudoaneurysms can enlarge and rupture into an associated pseudocyst filling the biliopancreatic ducts. In such case, bleeding occurs through the ampulla of Vater into the gastrointestinal tract. The pseudoaneurysms can also rupture into the peritoneal cavity or retroperitoneum. When there is bleeding through the ampulla of Vater from the pancreatic duct, it is known as Hemosuccus pancreaticus or pancreatitis.
Most patients are asymptomatic until the pseudoaneurysm ruptures. Often, patients have nonspecific symptoms before a bleed. A high index of suspicion is necessary especially in patients with backgrounds of pancreatitis or pancreaticobiliary surgery. When a patient experiences recurrent hematemesis or hematochezia, a pancreatic pseudoaneurysm should be ruled out.When a patient complains of a sudden increase in abdominal pain associated with falling hematocrit or becoming hemodynamically unstable postoperatively following pancreaticobiliary surgery, bleeding pseudoaneurysm should be ruled out. At times the earliest warning postoperatively is minimal intermittent bleeding from an abdominal drain placed intraoperatively, before a catastrophic bleed. This initial bleed is known as sentinel bleed. In a patient who is documented to have a pseudocyst, when there is rapid enlargement of the cyst with the appearance of a pulsatile mass, strongly suggests a bleeding pseudoaneurysm. Apart from all the signs mentioned above the patient will present with obvious physical evidence of significant blood loss such as pallor, tachycardia, and hypotension.
Angiography has been demonstrated to be the most informative investigation for diagnosis as well as treatment. CT angiography has a high rate of sensitivity and specificity but does not facilitate intervention concurrently. Angiography defines the character and location of the lesion as well as provides an opportunity to gain temporary control over the bleeding by transcatheter embolization or possible stenting.
There is a classification of pancreatic pseudoaneurysms based on the following features:
The current standard of therapy is to control the bleeding by endovascular transarterial catheter embolization or by placement of a covered stent. Patients in whom arterial embolization is unsuccessful, or there is rebleeding after embolization surgery is the only option. The surgical procedure can be either direct ligation of the bleeding vessel or resection of the pancreas along with the pseudoaneurysm.
The percutaneous intervention does have a success rate of 70% to 90%. Embolization is often the choice of treatment in very ill unstable patients and in patients in whom the bleeding is diffuse. Embolization may also be an option when bleeding occurs following unsuccessful surgery or a complication of the surgery. Despite the wide use of percutaneous techniques to stop bleeding, the long-term history of the pseudoaneurysm is not well understood. There are limited data on whether these patients develop recurrent complications.
A bleeding pseudoaneurysm communicating to a pseudocyst situated at the tail of the pancreas can be an indication for surgical intervention. Surgery carries a higher risk when compared to angiographic vascular intervention.
Sometimes surgery is undertaken to debride an abscess combined with hemostatic control. In patients who have had bleeding from pseudocysts, endoscopic drainage is not recommended.
Patients who only have basic supportive measures have a mortality rate in excess of 90%. Even after surgery for pancreatic pseudoaneurysms, the mortality rates vary from 20-30%. The mortality for pancreatic pseudoaneurysm depends on the location of the pathology and not the type of treatment.
The highest mortality rates occur when the pseudoaneurysm is located int he head of the pancreas whereas surgery for the same pathology on the tail of the pancreas carries a low mortality
Embolization therapy has increased the success rates but there still is a high recurrence rate and an overall mortality of about 16%.
Post-surgery, the patient must be monitored for hemorrhage which has a reported incidence of 20-70%. The bleeding may be due to trauma to the vessels, inadequate vessel control or loose sutures.
Pancreatic pseudoaneurysm though uncommon can present with life-threatening complications. Accurate diagnosis and timely intervention can improve outcome. However, these patients are often hemodynamically unstable and need aggressive resuscitation and invasive hemodynamic monitoring. Blood should always be made available for transfusion even when a percutaneous intervention is being planned.
If the patient is unstable, angiography may not be an option, and an immediate exploratory laparotomy is required. Following entry into the abdomen, all four quadrants should be packed with lap pads to tamponade the bleeding. The lap pads should then be removed in succession starting from the area which is least suspicious for bleeding. In rare cases, there may be torrential bleeding which makes viewing the surgical field difficult. In such cases, cross-clamping of the aorta just above the take of the celiac artery can be life-saving. These patients are best monitored in the intensive care unit, and presence of post-surgical hemorrhage carries a mortality of 7% to 70%
There are no evidence-based guidelines on the diagnosis and management of pancreatic pseudoaneurysm. However, expert evidence suggests that prompt diagnosis of the pathology at presentation is vital if survival is to be improved. Without treatment, the condition is fatal. Because bleeding is a major source of morbidity and mortality, consultation with an interventional radiologist is recommended. Embolization therapy carries far less mortality than surgery and should be the procedure of choice, when available.  (level III)
The best way to treat pseudoaneurysms is to prevent them in the first place. The pharmacist should be vigilant about drugs that can cause acute pancreatitis and suggest alternatives to the primary care provider. In some patients with pancreatitis requiring anticoagulants, a multidisciplinary approach should be considered when selecting the medications. (Level III)
The nurse should educate the patient and family members to abstain from alcohol, as it is one of the major causes of pancreatitis.
Small case series reveal that when a multidisciplinary team is involved, patients with pancreatic pseudoaneurysms can be successfully managed.