Discrepancy between clinical maturation rate and Rule of 6s criteria in Japanese arteriovenous fistulas: A focus on vessel depth and cannulation site

BACKGROUND: Arteriovenous fistula (AVF) non-maturation is a major challenge in Western countries (rates up to 60%), yet clinical maturation rates in Japan are exceptionally high. This discrepancy is not fully understood. We hypothesized that this success is not due to adherence to anatomical "Rule of 6s" criteria, but rather to a unique clinical practice prioritizing shallow vessel depth. METHODS: We conducted a single-center, retrospective study of 22 consecutive incident hemodialysis patients with a temporary catheter who underwent AVF construction. All patients were cannulated exclusively with plastic cannulas by residents (3rd-5th year) after a collaborative assessment with the surgeon and pre-cannulation ultrasound confirmation. The primary outcome was the clinical maturation rate. Secondary outcomes included the anatomical maturation rate based on the "Rule of 6s" (FV >600 mL/min, Diameter >6 mm, Depth