Intrahepatic arterioportal shunt
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Intrahepatic arterioportal shunts, also known as arterioportal fistulas, represent abnormal flow between the portal venous system and a hepatic arterial system within the liver. They can be a reversible cause of portal hypertension.
Clinical features will depend on the size and other underlying pathology. Small shunts can be asymptomatic.
Intrahepatic vascular shunts can be divided according to the cause into:
transtumoural shunt is due to abnormal communication between the feeding artery and draining vein of the tumor which results in increased vascularity around the tumor manifested as peritumoral transient hepatic attenuation differences (THAD)
portal vein may show early enhancement in the dynamic arterial scan without enhancement of its main tributaries, the splenic and superior mesenteric veins
mainly due to liver biopsy and other hepatic intervention
may be due to liver cirrhosis itself owing to deformation of hepatic sinusoids which increases arterial pressure or portal vein extrinsic compression that also leads to increased arterial pressure
Sometimes arterioportal shunts appear in dynamic CT as enhancing nodules, which can mimic hepatocellular carcinoma. The best way to differentiate is by using MRI with SPIO (superparamagnetic iron oxide) which is deposited in hepatocellular carcinoma and washed out in vascular shunt.