Where is the most common site for neointimal hyperplasia in a hemodialysis access graft?

• A. Inflow artery
• B. Arterial anastomosis
• C. Graft mid segment
• D. Venous outflow

Answer: (D)

Neointimal hyperplasia arises from injury to the vessel wall and abnormal flow, triggering smooth muscle cell proliferation and extracellular matrix buildup that narrows the lumen. In a hemodialysis graft, the venous outflow zone—where the graft connects to and feeds into the native vein—experiences the most disturbed flow patterns. This area has jetting from the graft into the vein, low and oscillatory shear stress, and is subjected to cannulation-related trauma. These factors promote the greatest neointimal response, making stenosis most likely to develop there. The arterial inflow and the mid-graft regions are less prone to this combination of flow disturbance and injury, so they’re less commonly the sites of hyperplasia. Thus, the venous outflow area is the location where neointimal hyperplasia most often causes graft stenosis.