What is an Arteriovenous (AV) Fistula and Why is it Created?
An arteriovenous (AV) fistula is a surgically created connection between an artery and a vein, primarily created in patients with end-stage renal disease (ESRD) to provide reliable vascular access for hemodialysis. 1
Definition and Structure
An AV fistula is an autologous (using the patient's own vessels) surgical connection that directly anastomoses an artery to a vein. 1 The most common type is the Brescia-Cimino (radiocephalic) fistula, which connects the radial artery to the cephalic vein at the wrist. 1 Other configurations include:
- Gracz fistula: Connects the proximal radial artery to a perforating branch of the cephalic or median cubital vein below the elbow 1
- Snuff-box fistula: Connects a branch of the radial artery to an adjacent vein in the anatomic snuff box of the hand 1
- Endovascular fistula (endoAVF): Created using endovascular techniques, typically anastomosing the proximal ulnar artery and proximal ulnar vein 1
Primary Purpose: Hemodialysis Access
The fundamental reason for creating an AV fistula is to provide adequate vascular access for patients requiring chronic hemodialysis. 1, 2 Native AV fistulas are the gold standard and preferred vascular access method because they demonstrate superior long-term outcomes compared to synthetic grafts or central venous catheters. 1, 3
Why AV Fistulas are Superior
- Longest patency rates: Native AV fistulas have the best 4-5 year patency rates compared to all other access types 1
- Fewest interventions required: They require significantly fewer procedures to maintain patency compared to synthetic grafts 1
- Lower infection rates: Native tissue has inherently lower infection risk than synthetic materials or indwelling catheters 1
- Adequate blood flow: Arterialized superficial veins provide optimal blood flow (typically 600-1200 mL/min) necessary for effective hemodialysis 3
- Cost-effectiveness: Reduced need for interventions and hospitalizations decreases overall healthcare costs 1
The Maturation Process
After surgical creation, the fistula undergoes a critical maturation process where the vein adapts to arterial pressure and flow. 1 This involves:
- Outward remodeling of the outflow tract 2
- Vessel dilation to accommodate increased blood flow 2
- Vein wall thickening to withstand repeated needle cannulation 1
The fistula must mature for at least 1 month, and ideally 3-4 months, before it can be used for dialysis. 4 A mature fistula has sufficient vein diameter for successful cannulation and can reliably provide prescribed dialysis with two needles for more than two-thirds of dialysis sessions within 4 consecutive weeks. 1
Clinical Rationale for Early Creation
Patients with progressive chronic kidney disease should be referred for AV fistula creation well before dialysis is needed to allow adequate time for maturation and potential revision procedures if the initial fistula fails to mature. 4 This proactive approach addresses several critical issues:
- Prevents emergency catheter placement: Early referral reduces the need for temporary dialysis catheters, which are associated with higher infection rates and central venous stenosis 1, 4
- Allows time for revision: Approximately 15-40% of fistulas experience failure to mature, requiring additional interventions within the 6-month window 1
- Preserves vascular real estate: Protects potential access sites by avoiding unnecessary venipuncture and IV placement in arm veins 4
Common Pitfalls to Avoid
Never allow subclavian vein catheterization in patients with kidney disease, as this causes high rates of central venous stenosis that can compromise all future ipsilateral access options. 4 Similarly, avoid peripherally inserted central catheters (PICCs) in patients with advanced kidney disease. 4
Premature cannulation before adequate maturation results in infiltration, hematoma formation, and permanent access loss. 4 The access must be fully mature with adequate vessel diameter and subsided swelling before any cannulation attempts. 4
Alternatives When Fistulas Are Not Feasible
When native fistula creation is not possible due to inadequate vessels, alternatives include synthetic AV grafts (typically polytetrafluoroethylene) or central venous catheters, though both have inferior outcomes. 1, 5 Grafts require at least 14 days before cannulation and ideally 3-6 weeks for proper tissue integration. 5