Lumen stenosis can occur due to the accumulation of thrombosis or plaque particles in a similar manner to peripheral arterial disease. The accumulation of these plaque particles has also been shown to cause calcification. Lumen stenosis is a considerable problem for both AV access surgical grafts and native fistulae because they have poor vessel patency. Due to their tendency to acquire blockages, AV access surgical grafts will require revascularization twice a year, and native fistulae will need to be cleared at least once a year.