Stent graft with a valve arrangement

A stent graft (10) has a cylindrical wall (12), an internal lumen (14) within the cylindrical wall and a fenestration (16) in the wall. The fenestration is closed off by a valve arrangement (18) to prevent the flow of liquids from within the internal lumen to outside of the wall. The valve arrangement is a tube of graft material (20) which can be closed off by pressure on its outside surface. The end (24) of the tube remote from the fenestration can be held shut by having its periphery fastened to a flattened resilient ring (26). Fluid pressure on the tube of graft material causes the tube to close off to prevent fluid flow therethrough and by resilient deflection of the resilient ring the end of the tube of graft material can be opened to enable the passing of a medical device therethrough.