Visceral Artery Aneurysm

A visceral artery aneurysm is an aneurysm of the coeliac, superior mesenteric or inferior mesenteric arteries or their branches. It is uncommon, found in up to 0.1 to 2% of angiograms.

Most are found incidentally. Rupture is a surgical emergency with a high mortality.

Causes are atherosclerosis, fibromuscular dysplasia and medial degeneration, pancreatitis (pseudoaneurysm), trauma and procedure injury, infection (endocarditis), vasculitis (polyarteritis nodosa, Behçet disease, Takayasu arteritis), connective tissue disease (vascular Ehlers-Danlos, Marfan and Loeys-Dietz syndromes), portal hypertension and segmental arterial mediolysis.

Pathophysiology. Medial weakening or wall injury allows dilatation. Pseudoaneurysms (wall breach with a contained haematoma) rupture more readily than true aneurysms. Rupture goes into the peritoneum, bowel, bile ducts or pancreatic duct.

• Usually asymptomatic.
• Epigastric or upper abdominal pain, sometimes with eating (mesenteric ischaemia), and a pulsatile mass or bruit.
• Gastrointestinal bleeding, haemobilia (biliary colic, jaundice and bleeding), and intraperitoneal haemorrhage with shock.
• Features of the cause: previous pancreatitis, trauma or procedure, fever with a new murmur, systemic vasculitis, or a connective tissue syndrome.

Red flags.

• Shock, sudden abdominal pain or gastrointestinal bleeding
• Pseudoaneurysm, or aneurysm with pancreatitis
• Pregnancy or a woman of childbearing age
• Rapid growth (5 mm or more in a year), or diameter of 20 mm or more
• Fever or raised inflammatory markers (infection)

• CT angiography with arterial phase imaging. Site, size, morphology (saccular or fusiform), neck, wall thrombus, relation to adjacent organs, and extravasation.
• Duplex ultrasound for surveillance and the proximal vessels. MR angiography for follow up and pregnancy (without gadolinium).
• Catheter angiography for diagnosis with treatment in the same session.
• Cause workup. CRP, ESR, ANCA, antinuclear antibody, blood cultures, amylase and lipase. Imaging of the head, neck, renal arteries and pelvis for fibromuscular dysplasia. Genetic testing for connective tissue disease.
• Endoscopy for gastrointestinal bleeding when the source is unclear.

Differential diagnosis.

• Pancreatic pseudocyst and cystic pancreatic tumour
• Duplicated or tortuous arteries
• Arteriovenous fistula and malformation
• Pancreatic or hepatic cystic tumour, and renal or adrenal mass
• Lymphadenopathy
• Other causes of gastrointestinal haemorrhage and haemobilia

Indications for treatment. All pseudoaneurysms, all symptomatic aneurysms, true aneurysms of 20 mm or more (earlier for hepatic aneurysms in transplant candidates), growth of 5 mm or more in a year, any aneurysm in a pregnant woman or in a woman who plans pregnancy, mycotic aneurysms, and aneurysms with segmental arterial mediolysis or vasculitis that is not controlled. Superior mesenteric and coeliac aneurysms are treated at smaller sizes because of their risk.

Surveillance for asymptomatic aneurysms under 20 mm with no risk features: CT or MR angiography at 6 months, then yearly.

Interventions.

• Endovascular repair first: coil embolisation (including sandwich technique), covered stents, stent assisted coiling, vascular plugs, and thrombin injection for pseudoaneurysms. Preserve flow to the organ where possible.
• Surgery: ligation, resection, bypass or aneurysmectomy for failed endovascular repair, mycotic aneurysms and anatomy not suitable for embolisation.
• Embolisation risks are organ infarction, abscess, rupture, coil migration and post-embolisation syndrome.
• Pancreatitis related pseudoaneurysm: embolisation first, with drainage of the collection.

Rupture. Emergency. Resuscitation with blood and permissive hypotension (systolic pressure 70 to 90 mm Hg), then emergency embolisation or surgery. Avoid anticoagulants and antiplatelet drugs.

Medical therapy. Blood pressure under 130/80 mm Hg. Atorvastatin 40 mg orally once daily for atherosclerotic disease, with liver enzymes at baseline and 3 months. Aspirin 75 to 100 mg once daily only for another vascular indication. After a covered stent: aspirin 75 to 100 mg plus clopidogrel 75 mg once daily for 1 to 3 months.

Infected aneurysm. Vancomycin 25 to 30 mg/kg intravenously as a loading dose (maximum 3 g), then 15 to 20 mg/kg every 8 to 12 hours (usual maximum 2 g for each dose), adjusted to a trough of 15 to 20 mg/L or an AUC of 400 to 600 mg·h/L (lengthen the interval and use levels in renal impairment), with piperacillin-tazobactam 4.5 g every 6 hours (4.5 g every 8 hours at creatinine clearance 20 to 40 mL/min, every 12 hours under 20 mL/min), narrowed by culture, for at least 6 weeks, with surgical control.

Vasculitis. Prednisolone 1 mg/kg orally once daily (maximum 60 mg) with a taper and a steroid sparing drug chosen with rheumatology, after screening for tuberculosis and hepatitis B.

Special groups.

• Pregnancy: rupture carries a very high maternal and foetal mortality. Repair before conception, or in the second trimester by endovascular means.
• Portal hypertension and liver transplantation: treat at smaller sizes, because rupture is more likely and the aneurysm complicates the operation.
• Vascular Ehlers-Danlos syndrome: intervene only for symptoms or rapid growth, because tissue is fragile.

Monitoring. Imaging 1 month and 6 months after intervention and then yearly. CRP and white cell count weekly on antibiotics. Blood pressure at every visit.

Referral and escalation. Refer to vascular surgery and interventional radiology. Emergency for shock, bleeding or suspected rupture.