Portal Vein Aneurysm

Portal vein aneurysm is a focal saccular or fusiform dilatation of the main portal vein or its branches to more than 20 mm in cirrhotic patients, or 15 mm in non-cirrhotic patients. It is a rare vascular anomaly, accounting for about 3% of venous aneurysms.

It is found incidentally in most cases. Congenital forms arise from weakness of the venous wall, and acquired forms from portal hypertension, pancreatitis, trauma or abdominal surgery. Cases of the congenital type occur in children and young adults, and acquired cases in older adults with cirrhosis.

Pathophysiology.

Raised portal pressure, venous wall inflammation or developmental weakness leads to dilatation. Slow flow in the sac predisposes to thrombosis and, rarely, rupture.

Mostly asymptomatic. Abdominal pain, nausea, upper gastrointestinal bleeding from varices, jaundice from compression of the bile duct, portal vein thrombosis and, rarely, rupture with haemoperitoneum.

Red flags.

• Sudden severe abdominal pain with hypotension (rupture).
• Variceal bleeding.
• Jaundice from compression.
• Thrombosis extending into mesenteric veins.

Doppler ultrasound shows an anechoic vascular structure continuous with the portal vein with swirling flow. CT or magnetic resonance angiography defines size, location, thrombus and relation to the bile duct and pancreas. Measure the portal vein diameter and screen for portal hypertension (elastography, endoscopy).

Differential diagnosis.

• Pancreatic or hepatic cyst.
• Hepatic artery aneurysm.
• Choledochal cyst.
• Portal vein varix after thrombosis.
• Cavernous transformation.

Observe asymptomatic aneurysms with imaging. Surgery (aneurysmorrhaphy, resection with grafting, or shunt) is for symptoms, thrombus extension, rapid growth, or compression, and endovascular techniques are used in selected cases. Treat cirrhosis and portal hypertension.

• Enoxaparin (portal vein thrombosis in the aneurysm): 1 mg/kg subcutaneously every 12 hours for 5 to 7 days; maximum 100 mg for each dose; monitor platelets and anti-Xa level in renal impairment and obesity; reduce to 1 mg/kg once daily when creatinine clearance is under 30 mL/min.
• Warfarin (continuation): target INR 2.0 to 3.0 for 3 to 6 months, started with enoxaparin cover for at least 5 days and until INR is in range for 24 hours; monitor INR; reduce the dose in hepatic impairment and older adults.

Variceal prophylaxis follows the severity of portal hypertension.

Monitoring. Ultrasound or MR angiography at 6 months, then yearly; sooner with new pain.

Referral and escalation. Hepatobiliary surgery and vascular radiology.