For a fistula in a hemodialysis access, which venous lumen diameter meets the adequacy threshold?

• A. Greater than or equal to 2.5 mm
• B. Greater than or equal to 3.0 mm
• C. Greater than or equal to 2.0 mm
• D. Greater than or equal to 4.0 mm

Answer: (A)

In evaluating a fistula for hemodialysis access, a key goal is to have a vein that is large enough to be cannulated repeatedly with dialysis needles. The minimum venous lumen diameter that meets adequacy is 2.5 mm. This size is considered enough to accommodate standard dialysis needles and allow repeated punctures without collapsing the vessel, while still reflecting a vein that has expanded due to the fistula’s increased flow. Diameters smaller than this (for example, 2.0 mm) are generally insufficient for reliable cannulation and can lead to inadequate dialysis or fistula failure. Larger diameters (3.0 mm or 4.0 mm) indicate better cannulation ease and maturation, but the question targets the threshold of adequacy, which is 2.5 mm. In practice, diameter is assessed along with flow and depth to determine true maturity.