A port systemic shunt (PSS) also known as an Abernethy malformation or a liver shunt is vascular connection effect the body's circulatory system. In most people, blood from the stomach, intestines, spleen and pancreas drains into the liver through a large vein called the "portal" vein. With a port systemic shunt, blood draining from the portal system bypasses ("shunts" past) the liver and directly enters the general circulation. As a result the liver does not get a chance to clean or filter the blood. A port systemic shunt can be present at birth (i.e. congenital) or acquired as the result of an underlying liver disease that was not present at birth. Abernethy malformation is a very rare congenital vascular malformation defined by diversion of portal blood away from liver. It is commonly associated with multiple congenital anomalies.