Splenic Artery Pseudoaneurysm in Pancreatitis

Splenic artery pseudoaneurysm in pancreatitis is a contained arterial wall defect that develops when pancreatic enzymes erode the splenic artery. It carries a high risk of rupture into the peritoneum, a pseudocyst, the stomach or the pancreatic duct.

It occurs in 3% to 10% of chronic pancreatitis and a smaller share of acute necrotising pancreatitis. The splenic artery is the vessel most often involved (about 40% of cases), then the gastroduodenal and pancreaticoduodenal arteries. Rupture carries a mortality of 20% to 40%.

Pathophysiology.

Enzyme rich fluid or necrosis digests the arterial wall, and arterial pressure expands the defect into a pulsatile sac with only a fibrous wall.

Often silent and found at imaging. Pain, a pulsatile epigastric mass or bruit, a sentinel gastrointestinal bleed, haemoperitoneum or sudden collapse suggest rupture.

Red flags.

• Haemodynamic collapse.
• Bleeding into a pseudocyst or the gastrointestinal tract.
• Rapid enlargement of a pseudocyst.
• Pseudoaneurysm over 2 cm.

Contrast CT angiography shows an enhancing sac with arterial phase filling, and is the test of choice. Doppler ultrasound shows a swirling flow pattern (yin yang sign) in the cyst. Angiography confirms and treats. Do not drain a pseudocyst before excluding a pseudoaneurysm.

Differential diagnosis.

• Simple pseudocyst.
• Cystic neoplasm of the pancreas.
• True splenic artery aneurysm.
• Haemorrhagic pseudocyst.

Treat all pseudoaneurysms in pancreatitis, even if asymptomatic, because of rupture risk. Transcatheter arterial embolisation with coils, plugs or glue (or a covered stent if flow must be kept) succeeds in 80% to 90% of cases. Surgery (ligation, aneurysmectomy, distal pancreatectomy with splenectomy) is for failed embolisation, infection or instability.

Resuscitate and transfuse at haemoglobin 70 g/L (80 g/L with cardiovascular disease). Correct coagulopathy.

• Piperacillin-tazobactam (infected collection or mycotic sac): 4.5 g IV every 6 hours for 7 to 14 days after source control; maximum 18 g daily; monitor renal function and counts; reduce for creatinine clearance under 40 mL/min.
• Aspirin after covered stent placement: 75 mg orally once daily for at least 3 months; maximum 100 mg daily; monitor bleeding; avoid in active bleeding and peptic ulcer.

Monitoring. CT angiography at 1 and 6 months after embolisation, with monitoring for splenic infarct and abscess.

Referral and escalation. Interventional radiology urgently; pancreatic surgery; critical care.