Hepatic Artery Pseudoaneurysm

Hepatic artery pseudoaneurysm is a contained rupture of the arterial wall, with blood held by surrounding tissue or clot and communicating with the arterial lumen. Unlike a true aneurysm it has no complete arterial wall and has a high rupture risk.

It is mostly iatrogenic or traumatic: percutaneous liver biopsy, transhepatic biliary drainage, endoscopic and laparoscopic cholecystectomy, liver resection and transplantation (anastomotic), blunt or penetrating trauma, and radiofrequency ablation. Other causes are pancreatitis, infection (mycotic) and tumour erosion.

Presentation may be delayed by days to weeks after the procedure. Rupture is the main hazard, and mortality is high without treatment.

Pathophysiology.

Arterial injury lets blood escape into a cavity, which is then walled by fibrous tissue or haematoma. Inflammation or infection weakens the wall, and the cavity can enlarge and rupture into the peritoneum, bile duct (haemobilia) or gut.

Haemobilia (the triad of biliary colic, jaundice and gastrointestinal bleeding), abdominal pain, fall in haemoglobin, haemoperitoneum and shock after rupture, fever and a pulsatile mass or bruit.

Red flags.

• Haemodynamic instability.
• Gastrointestinal bleeding after a hepatobiliary procedure.
• Fever suggesting infection (mycotic).
• Falling haemoglobin with abdominal pain.

CT angiography in the arterial phase shows a contrast filled sac that fills early and washes out with the arterial pool. Doppler ultrasound shows a "yin yang" swirling flow. Catheter angiography confirms and permits treatment. Send blood count, clotting and liver tests, blood cultures when mycotic infection is possible, and endoscopy to exclude other sources of gastrointestinal bleeding.

Differential diagnosis.

• True aneurysm.
• Arteriovenous fistula.
• Peptic ulcer bleeding.
• Haemorrhagic cyst or tumour.
• Bile leak or abscess.

Treat every pseudoaneurysm because of rupture risk. Resuscitate, give blood when haemoglobin is under 70 g/L (80 g/L with cardiovascular disease), and correct coagulopathy.

• Transcatheter embolisation (coil, glue or plug) or a covered stent is the first choice and succeeds in over 80% of cases. Preserve hepatic arterial flow where possible, especially after liver transplant.
• Surgery (ligation, resection or reconstruction) is used for failed embolisation, rupture with instability or infection needing debridement.
• Vancomycin plus piperacillin-tazobactam for mycotic pseudoaneurysm: 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; maximum piperacillin-tazobactam 18 g daily; monitor renal function, vancomycin levels and cultures; extend the vancomycin interval and reduce piperacillin-tazobactam for creatinine clearance under 40 mL/min.

Clear obstructing clots from the bile duct by endoscopic retrograde cholangiopancreatography and treat cholangitis.

Monitoring. Haemoglobin and haemodynamics every 4 to 6 hours initially; liver function after embolisation (risk of ischaemic injury); repeat CT at 1 month.

Referral and escalation. Interventional radiology and hepatobiliary surgery urgently; critical care for instability.