Aneurysms of the portal venous system

Aneurysms of the portal vein are extremely rare and represent only 3% of all aneurysms of the venous system ¹.

Clinical presentation

Most patients are asymptomatic but may present with nonspecific abdominal pain as a major symptom ^2-4.

Pathology

Both congenital and acquired causes have been proposed. Acquired causes may include ^2-3:

• portal hypertension: could be contributory but is not essential to the development of portal venous system aneurysms; indeed, the majority of patients do not have portal hypertension or chronic liver disease
• necrotising pancreatitis
• abdominal trauma or surgery
• liver cirrhosis

Location

The most common locations for aneurysms of the portal venous system are ^2-3:

• splenomesenteric venous confluence
• main portal vein
• intrahepatic portal vein branches at bifurcation sites

The rarest locations are the splenic, mesenteric, and umbilical veins.

Radiographic features

Diagnosis can be made when the portal vein exceeds 20 mm in diameter.

Ultrasound

Colour Doppler ultrasound is the most helpful diagnostic tool. Further workup may not be necessary ⁴. An aneurysm appears on ultrasound as an anechoic mass showing direct luminal continuity with the portal venous system and displays spectral findings characteristic of the portal venous system on colour Doppler interrogation ^5-6.

CT

Dynamic helical CT demonstrates simultaneous enhancement with the portal system ^5-6.

MRI

In T1-weighted images, aneurysms are hypointense owing to the flow void phenomenon ⁵.

Complications

Complications include ^2-4:

• thrombosis and distal embolism
• portal hypertension
• rupture
• compression of the duodenum
• compression of the common bile duct causing jaundice, cholestasis, and cholelithiasis