Which venous lumen size is considered adequate specifically for a fistula?

• 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: (A)

The key point is the minimum vein size used when assessing suitability for a native AV fistula. A venous lumen diameter of about 2.5 mm or larger is generally considered adequate for fistula creation because veins at or above this size have the potential to mature with increased blood flow and become usable for dialysis over time. Veins smaller than 2.5 mm tend to have poorer maturation rates and may not develop enough flow to sustain a fistula.

Larger diameters, such as 4 mm or 6 mm, are even more favorable and are often associated with easier cannulation once the fistula has matured, but the simplest criterion used in mapping to deem a vein workable starts at 2.5 mm. This threshold balances practicality with the likelihood of successful maturation.