A vascular bypass (or vascular graft) is a surgical procedure performed to redirect blood flow in a region of the body. It is commonly performed due to inadequate blood flow (ischemia) and as a part of organ transplantation. In general, someone's own vein is the preferred graft material (or conduit) for a vascular bypass, but other materials such as ePTFE, dacron or a different person's vein (allograft) are also commonly used. Arteries can also be redirected and serve as vascular grafts. A surgeon sews the graft to the target vessel by hand using surgical suture, creating a surgical anastomosis.