Hepatic Artery Aneurysm

Hepatic artery aneurysm is a localised dilatation of the hepatic artery to over 1.5 times its normal diameter. It is the second commonest visceral artery aneurysm after splenic artery aneurysm, accounting for about 20%.

About 80% arise in the extrahepatic arteries (common hepatic 63%, right 28%, left 5%) and the rest in intrahepatic branches. It is found mainly in men over 60 years.

Causes are atherosclerosis and medial degeneration, trauma, infection (mycotic), polyarteritis nodosa and other vasculitides, fibromuscular dysplasia and pancreatitis. Rupture risk is about 20% with a mortality of about 35%, and the risk is higher in non-atherosclerotic aneurysms and pseudoaneurysms.

Pathophysiology.

Weakening of the arterial wall from elastic fibre loss, inflammation or injury allows progressive dilatation. Rupture occurs into the peritoneum, bile duct (haemobilia) or portal vein, or the gut.

Most are asymptomatic and found incidentally. Symptoms include epigastric or right upper quadrant pain, haemobilia (biliary colic, jaundice and gastrointestinal bleeding), a pulsatile mass and bruit, and obstructive jaundice from compression. Rupture presents with abdominal pain, shock and haemoperitoneum.

Red flags.

• Hypotension with abdominal pain.
• Gastrointestinal bleeding with jaundice and biliary colic.
• Rapid growth or new pain.
• Aneurysm in pregnancy.

CT angiography is the best test and shows size, shape, neck and collateral supply. Doppler ultrasound screens; magnetic resonance angiography is an alternative; catheter angiography is used for treatment planning. Look for coexisting visceral aneurysms and for vasculitis (inflammatory markers, antibodies) and infection (blood cultures).

Differential diagnosis.

• Pseudoaneurysm.
• Splenic or gastroduodenal artery aneurysm.
• Pancreatic pseudocyst.
• Arteriovenous malformation.
• Hepatic cyst or tumour.

Treat aneurysms that are over 2 cm, symptomatic, growing (over 0.5 cm in a year), non-atherosclerotic, mycotic or pseudoaneurysmal, and all aneurysms in pregnancy or in women of childbearing age. Smaller asymptomatic atherosclerotic aneurysms are watched.

• Endovascular: coil embolisation or covered stent placement (first choice for most).
• Surgery: ligation or excision, with arterial reconstruction when the proper hepatic artery is involved or collateral flow is inadequate; ligation of the common hepatic artery is tolerated with an intact gastroduodenal collateral.
• Intrahepatic aneurysms: transcatheter embolisation.
• Metoprolol succinate (blood pressure and heart rate control in untreated aneurysms): 50 mg orally once daily, increased every 1 to 2 weeks to a target systolic pressure under 130 mmHg; long term; maximum 200 mg daily; monitor heart rate, blood pressure and glucose; avoid in asthma and heart block, and reduce in severe hepatic impairment.
• Vancomycin plus piperacillin-tazobactam for mycotic aneurysm: vancomycin 25 to 30 mg/kg IV loading dose, then 15 to 20 mg/kg every 8 to 12 hours (area under the curve 400 to 600), with piperacillin-tazobactam 4.5 g IV every 6 hours; 4 to 6 weeks or longer with surgery; maximum piperacillin-tazobactam 18 g daily; monitor renal function and levels; extend the vancomycin interval and reduce piperacillin-tazobactam for creatinine clearance under 40 mL/min.

Monitoring. CT or ultrasound at 6 months, then yearly for untreated aneurysms; after treatment, imaging at 1, 6 and 12 months.

Referral and escalation. Vascular surgery and interventional radiology; urgent for symptoms, rapid growth or rupture.

Special groups. In pregnancy, treat before conception when known, since rupture risk and maternal mortality are high.