What is the preferred minimum venous lumen diameter for an access graft?

• A. Greater than or equal to 2.5 mm
• B. Greater than or equal to 4 mm
• C. Greater than or equal to 2 mm
• D. Greater than or equal to 6 mm

Answer: (D)

The key idea is that an access graft needs a venous outflow channel large enough to carry the high-flow required for dialysis. A venous lumen of 6 mm or larger provides sufficient cross-sectional area to keep resistance low and maintain adequate flow through the graft for effective dialysis. Using a vein smaller than this dramatically increases resistance (roughly following Poiseuille’s principle, where flow drops sharply as radius decreases), raising the risk of inadequate dialysis flow, early graft failure from thrombosis or stenosis at the anastomosis, and makes cannulation more challenging. Therefore, the preferred minimum venous diameter for an access graft is 6 mm or greater. Smaller diameters like 2.0–4.0 mm would not reliably support the required high-flow state.