In a hemodialysis access graft, the venous lumen diameter should be at least which measurement?

• A. Greater than or equal to 2.5 mm
• B. Greater than or equal to 4 mm
• C. Greater than or equal to 6 mm
• D. Greater than or equal to 3 mm

Answer: (B)

The key idea is ensuring enough lumen in the venous portion of a dialysis graft to allow reliable cannulation and adequate flow. For a hemodialysis graft, the venous limb must be wide enough to accommodate the needles used for dialysis and to sustain the required blood flow without collapsing. A venous diameter of about 4 mm or larger provides a safe minimum that supports cannulation and effective dialysis; smaller diameters—around 2.5–3 mm—are usually inadequate and increase the risk of poor flow, thrombosis, or cannulation complications. A larger diameter, like 6 mm, is preferable but not required as the minimal standard. In practice, 4 mm is the threshold clinicians use to judge suitability of the venous lumen for a functioning graft.