Which statement correctly describes the relationship between the venous thresholds for fistulas and grafts?

Which statement correctly describes the relationship between the venous thresholds for fistulas and grafts?

• A. The fistula venous threshold is greater than the graft venous threshold.
• B. The graft venous threshold is greater than the fistula venous threshold.
• C. They are equal.
• D. Thresholds apply only to arterial lumen.

Answer: (B)

The main idea is that maturation and cannulation readiness rely on venous thresholds—the minimum vein size and flow needed for safe, effective dialysis access. Native fistulas generally achieve adequate outflow with smaller veins and lower flows, while arteriovenous grafts produce a higher-volume, high-flow circuit that stresses the venous outflow more. To accommodate this and maintain patency, the venous segment in a graft must reach a larger caliber (and higher flow) before it’s considered ready. That’s why the graft venous threshold is greater than the fistula venous threshold. Thresholds pertain to the venous lumen, not the arterial side, and the difference in demands between grafts and native fistulas explains why they’re not equal and why graft thresholds are higher.

The main idea is that maturation and cannulation readiness rely on venous thresholds—the minimum vein size and flow needed for safe, effective dialysis access. Native fistulas generally achieve adequate outflow with smaller veins and lower flows, while arteriovenous grafts produce a higher-volume, high-flow circuit that stresses the venous outflow more. To accommodate this and maintain patency, the venous segment in a graft must reach a larger caliber (and higher flow) before it’s considered ready. That’s why the graft venous threshold is greater than the fistula venous threshold.

Thresholds pertain to the venous lumen, not the arterial side, and the difference in demands between grafts and native fistulas explains why they’re not equal and why graft thresholds are higher.