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 <6 mm) and the cannulation site. Results: The clinical maturation rate was exceptionally high at 95.5% ( N = 21/22). The median time to fistula use was 8 days. In stark contrast, the anatomical maturation rate (“Rule of 6s”) was only 4.8% ( N = 1/21). While 100% of sites met the depth criterion (<6 mm; mean 1.9 mm), most failed the size criterion (mean 4.0–4.3 mm). The elbow area was heavily utilized, accounting for 90.5% of blood removal or return sites. The median QB at discharge was low at 180 mL/min. Conclusion: High AVF clinical maturation rates were achieved rapidly in this Japanese cohort despite near-total failure to meet “Rule of 6s” criteria for size and flow. This success was strongly associated with a clinical practice prioritizing shallow vessel depth—often found in the elbow joint—a strategy enabled by plastic cannulas and low QB settings. Vessel depth, rather than diameter or flow, appears to be the most critical anatomical factor for clinical success in this setting.
Suemitsu et al. (2026) studied this question.