Creation of Arteriovenous Fistulas for Hemodialysis Using the End-to-side Anastomotic Technique vs. Piggyback.

Creation of Arteriovenous Fistulas for Hemodialysis: End-to-Side vs. Piggyback Anastomosis - A Randomized Clinical Trial 1. Background and Rationale Chronic Kidney Disease (CKD) affects an estimated 15.1% of the Spanish population and is a growing public health concern, especially due to its progression to advanced stages requiring renal replacement therapy (RRT). Hemodialysis is the most common RRT, and the quality of vascular access significantly influences outcomes in these patients. Among vascular access options, arteriovenous fistulas (AVFs) are preferred over central venous catheters (CVCs) and arteriovenous grafts (AVGs), due to superior durability, fewer complications, and lower hospitalization rates. However, AVFs suffer from high early failure rates, with maturation failures occurring in up to 60% of cases. Traditionally, the end-to-side (ETS) anastomosis is the gold standard for AVF creation. In recent years, an alternative technique called the Piggyback Straight Line Onlay Technique (pSLOT) has shown potential benefits, including improved hemodynamics, reduced stenosis, and lower rates of thrombosis and dysfunction. Despite promising retrospective data and small prospective studies, no robust randomized controlled trial has conclusively determined whether pSLOT offers superior outcomes compared to the classical ETS technique. 2. Study Hypothesis The null hypothesis is that there will be no significant difference between ETS and pSLOT techniques in terms of: * Clinical and ultrasound-based maturation at 1 month * Clinical and ultrasound-based maturation, patency, and functionality at 12 months 3. Study Objectives Primary Objective To compare the rate of clinical and ultrasonographic maturation at 1 month, and the combined rate of maturation, patency, and functionality at 12 months between ETS and pSLOT groups. Secondary Objectives To compare: * Juxta-anastomotic stenosis rate * Thrombosis rate * Reintervention rate * Fistula blood flow * Maturation and surgery times * Wound-related complications 4. Methods and Study Design This is a single-center, prospective, randomized, controlled trial with two parallel groups: * Group A: ETS technique * Group B: pSLOT technique Randomization occurs intraoperatively (1:1 allocation) using a centralized system. The patient is blinded to the allocation. The surgical team is not blinded due to the nature of the procedure, and follow-up staff are aware of the technique due to its visibility on ultrasound. The trial will enroll 130 patients to account for a 15% dropout rate, aiming for 56 evaluable patients per group. This sample size is based on previous data indicating differences in juxta-anastomotic stenosis rates (16.7% vs. 40.3%). 5. Inclusion and Exclusion Criteria Inclusion * Adults ≥18 years * CKD stage 4 or 5 (pre-dialysis or on hemodialysis) * Anatomically suitable for native AVF creation * No prior AVFs in the same or proximal site * Informed consent provided Exclusion * Pregnant women * Life expectancy \<1 year * Central vein stenosis or occlusion * Known coagulopathy, active infection, or severe systemic disease * Scheduled kidney transplant within 60 days * Previous upper extremity vascular surgery in the planned site 6. Procedure and Follow-Up Preoperative Assessment * Clinical history and physical examination * Duplex ultrasound mapping of arteries and veins in both upper limbs * Eligibility based on standard anatomical criteria * Consent obtained post-screening Surgical Procedure * Performed under local/regional anesthesia * Intraoperative data: type of fistula (distal/proximal), duration, success, Doppler flow, diameter, and complications Follow-up Visits * 1 Month: Clinical and Doppler ultrasound to assess maturation and flow * 12 Months: Same assessments plus record of any interventions or complications Remote follow-up may be permitted if patients cannot attend physically. 7. Definitions of Key Outcomes * Clinical Maturation: Fistula suitable for two-needle cannulation and achieving dialysis flow * Ultrasound Maturation: Diameter \>5mm, depth \<5mm, and flow \>500 ml/min * Functionality: Used for regular dialysis with adequate flow * Patency: Defined as primary, assisted primary, or secondary per European Vascular Society guidelines 8. Statistical Analysis * Software: SPSS v23 * Descriptive statistics for demographics and clinical variables * Chi-square for proportions * Kaplan-Meier survival curves and log-rank test for time-to-event analysis * Multivariate regression for confounders: age, sex, diabetes, vessel diameter, fistula location Significance threshold: p \< 0.05 9. Ethics and Regulatory Aspects * Protocol complies with Declaration of Helsinki (2013) and Spanish Biomedical Research Law (14/2007) * Approved by institutional ethics committee * Data anonymized and managed per EU Regulation 2016/679 * Participation is voluntary, with informed consent required