Teaching Case

Post traumatic pancreatitis. Serial post contrast CT scans of the abdomen were obtained to assess the severity and progress of the disease.

Post traumatic pancreatitis. Post contrast CT scan of the abdomen to assess severity of pancreatitis.

Pseudoaneurysms are a recognised complication of pancreatitis. Necrotising vasculitis with resultant aneurysmal changes in peri-pancreatic vessels is more recognised in chronic pancreatitis. Similar pseudoaneurysms have been described in association with acute pancreatitis, but only occur in approximately 10% of cases. The damage in pancreatitis is caused by released and activated pancreatic enzymes. Necrotizing vasculitis and erosion of vessel walls results in aneurysmal changes in peripancreatic vessels. The vessels of the coeliac trunk are the most commonly affected. Haemorrhage from arterial pseudoaneurysm rupture is potentially fatal. In most cases, massive gastrointestinal bleeding is typical at onset and prognosis of these cases is usually poor. Early diagnosis and treatment of this complication is therefore important. It is well recognised and documented that radiology has a major role in diagnosis and management. Ultrasound may be useful in diagnosing pseudoaneurysm complicating acute pancreatitis. Colour Doppler ultrasound will exhibit the “to and fro” sign. Spectral Doppler will demonstrate evidence of bidirectional flow at the neck of the pseudoaneurysm. These two signs are diagnostic. However, thrombus within a pseudoaneurysm may result in poor flow and these signs may not be present. Therefore, negative ultrasound findings should not preclude post-contrast CT and selective angiography. CT of the abdomen is used to investigate the pancreatitic abdomen, either to diagnose pancreatitis in the first instance or to assess its progress. Pseudoaneurysms may appear on non-contrast CT scans as spheric, soft-tissue structures, which may mimic a haemorrhagic pancreatic pseudocyst. Contrast CT scans can demonstrate pseudoaneurysms. They usually demonstrate homogenous enhancement, with maximal intensity during the arterial phase of a post-contrast CT scan. The anatomical location of the mass may also increase the index of suspicion. Homogenous enhancement of a structure within or adjacent to a pancreatic pseudocyst, or contiguous with a vascular structure should be considered highly suspicious for an associated pseudoaneurysm. Selective arteriography is superior to CT in demonstrating pseudoaneurysms. Apart from being the gold standard in demonstrating pseudoaneurysms, angiography is also an important step in the management algorithm. Embolism of the pseudoaneurysm proximally and distally prevents arterial anterograde and retrograde flow. This should be the initial treatment of choice in these patients. Embolization may provide effective and definitive treatment. If surgical intervention is required, transcatheter embolization has a role in controlling haemorrhage and improving the haemodynamic status of the patient before surgery.