What is the minimal acceptable size for an arteriovenous fistula?

• A. 30 mm
• B. 10 mm
• C. 25 mm
• D. 40 mm

Answer: (C)

The key idea is that the vessel used for an arteriovenous fistula must be large enough to carry the high-volume flow required for dialysis and to mature into a reliable, cannulable access. In this context, a diameter of about 25 mm is considered the minimal acceptable size because it provides a comfortable margin for achieving adequate flow after arterialization and for developing a usable cannulation segment. If the vein were much smaller, the fistula is more prone to failing to mature due to insufficient flow or early stenosis; if it were much larger, you’d simply be meeting a bigger-than-needed threshold, not a stricter requirement. In real-world practice, maturation criteria also involve flow measurements and a reasonable vein diameter (often cited around several millimeters to ensure patency and cannulation), but for this item the intended threshold is 25 mm as the minimal acceptable size.