In an apparatus and method for treating an aneurysm, a flow control member is positioned within a blood vessel at least in part upstream of an aneurysm and extending radially inward of the blood vessel wall into the flow path of blood flowing within the blood vessel. The flow control member alters the blood flow path within the blood vessel upstream of the aneurysm to inhibit blood flow to the aneurysm. A retention member may be positioned within the blood vessel at least in part upstream from the aneurysm and having an outer surface engageable with the blood vessel wall. In such an instance, the flow control member is retained by the retention member and extends radially inward of the blood vessel wall upstream from the aneurysm.
