In an access graft, the venous lumen diameter threshold used is 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 2 mm

Answer: (B)

In assessing an arteriovenous graft, the important idea is whether the venous limb is wide enough to carry the required dialysis flow. A venous lumen diameter of at least 4 mm is typically used as the threshold to indicate adequate caliber for dialysis cannulation and sufficient flow. If the vein measures smaller than 4 mm, it can signal potential stenosis or insufficient maturation, which may compromise dialysis.

Choosing 4 mm fits standard duplex criteria for graft surveillance, while smaller values (2 mm or 2.5 mm) would be too small to reliably support necessary flow, and a threshold of 6 mm is not the usual criterion for grafts (it's more aligned with expectations for some fistula maturation assessments).