What is an Arteriovenous Fistula and Why is it Created?
An arteriovenous (AV) fistula is a surgically created connection between an artery and a vein, typically in the upper extremity, that serves as the preferred vascular access for patients requiring long-term hemodialysis. 1
Definition and Anatomy
An AV fistula is an autologous (using the patient's own vessels) connection that directly anastomoses an artery to an adjacent vein. 1 The most common types include:
- Brescia-Cimino (radiocephalic) fistula: Created between the radial artery and cephalic vein at the wrist 1
- Gracz fistula: Constructed between the proximal radial artery and a perforating branch of the cephalic or median cubital vein below the elbow 1
- Snuff-box fistula: Made between a branch of the radial artery and an adjacent vein in the anatomic snuff box of the hand 1
- Endovascular fistula (endoAVF): Created using endovascular techniques, originally described by anastomosis of the proximal ulnar artery and proximal ulnar vein 1
Why AV Fistulas are Created
Primary Indication: Hemodialysis Access for End-Stage Kidney Disease
AV fistulas are created specifically to provide reliable, high-volume vascular access for patients with end-stage kidney disease (ESKD) who require maintenance hemodialysis. 2, 3 The fistula allows blood to be withdrawn from the patient, circulated through the dialysis machine for filtration, and returned to the patient at flow rates sufficient to provide adequate dialysis (typically >600 mL/min). 4
Advantages Over Alternative Access Types
AV fistulas are the gold standard for hemodialysis access because they offer superior outcomes compared to arteriovenous grafts (synthetic conduits) and central venous catheters. 2, 5 The key advantages include:
- Lower infection rates: Unlike catheters, fistulas do not provide a direct portal for bacteria into the bloodstream 6
- Better long-term patency: Fistulas have superior functional cumulative patency compared to grafts or catheters 1
- Lower thrombosis risk: Native vessel connections are less prone to clotting than synthetic materials 6
- Reduced mortality: Patients using fistulas have better survival outcomes than those using catheters 2
The Maturation Process
After surgical creation, the fistula must undergo a maturation process before it can be used for dialysis. 1, 4 This involves:
- Vein enlargement: The connected vein must dilate and develop thicker walls to withstand repeated needle cannulation 4, 3
- Increased blood flow: Arterial blood flowing into the vein causes progressive vessel remodeling 7, 3
- Timeline: Fistulas should not be used until at least 1 month after creation, with ideal maturation occurring at 6-8 weeks 4
- "Rule of 6s" criteria: A mature fistula should have blood flow >600 mL/min, diameter >0.6 cm, and depth of approximately 0.6 cm 4
Common Pitfall: Premature Cannulation
Never attempt to use a fistula within the first month after creation, as premature cannulation results in higher rates of infiltration, hematoma formation, and access failure. 4 The fistula vein requires adequate time to develop the structural integrity needed to withstand repeated needle punctures during dialysis sessions.
Role in the ESKD Life-Plan
The creation of an AV fistula is part of the individualized ESKD Life-Plan, which encompasses the set of kidney replacement modalities (hemodialysis, peritoneal dialysis, transplantation) required to sustain a patient's life. 1 Early identification of patients with progressive kidney disease and timely fistula creation (ideally months before dialysis is needed) allows adequate maturation time and avoids the need for temporary catheter use. 6
Maturation Failure Risk Factors
Despite being the preferred access, AV fistulas have significant failure-to-mature rates. 3 Key risk factors include:
- Distal location: Wrist fistulas have an adjusted odds ratio of 8.21 for primary failure 4
- Diabetes mellitus: Diabetic patients have an adjusted odds ratio of 3.19 for failure 4
- Chronic kidney disease environment: Uremic toxins, oxidative stress, and chronic inflammation in CKD adversely affect vascular wall cells and impair maturation 3
Failure to mature is defined as an AV access that, despite radiologic or surgical intervention, cannot be used successfully for dialysis by 6 months after creation. 1
Monitoring and Interventions
Regular monitoring during the postoperative 4-6 weeks is essential to detect maturation failure early. 4 Interventions that may enhance maturation include: