A method for treating an aneurysm can include inserting a medical device partially in a first artery and partially in a third artery. The device can be expanded radially outwardly from a first, position to a second position to engage an inner surface of the first artery and an inner surface of the third artery, so as to maintain a fluid pathway through said arteries. Further, the device can be positioned such that, when the device is in the second position, a porous membrane of the device is located at a neck of the aneurysm.