Snuffbox Radiocephalic Arteriovenous Fistula Creation for End-Stage Kidney Disease

Abstract

The snuffbox arteriovenous fistula (SBAVF) is a distal-first dialysis access strategy connecting the posterior branch of the radial artery and cephalic vein within the anatomical snuffbox to preserve proximal vascular sites for patients requiring long-term hemodialysis (HD). This low-flow forearm fistula, which represents only 4% of forearm access creations in a contemporary large registry, provides significant clinical advantages over high-flow alternatives. These benefits include a significantly lower risk of high-output heart failure (HOHF) and negligible rates of access-related hand ischemia (ARHI). Contemporary literature confirms that SBAVF offers primary and secondary patency rates comparable to wrist AVFs at 18 months, supporting a "snuffbox first" approach for eligible candidates. 

The procedure demands precise technique due to the small vessel diameters, typically around 2 mm, necessitating magnification with loupes. Key technical steps involve a longitudinal incision, dissection of the posterior radial artery branch and cephalic vein, and creation of an end-to-side anastomosis. Care must be taken to avoid injury to the superficial branch of the radial nerve, which is in close proximity, and to combat vasospasm, often managed with regional anesthesia and liberal use of vasorelaxing solutions. Tourniquet control rather than vascular clamps can also help reduce vasospasm and minimize crowding in a tight space when constructing the anastomosis. Low-dose systemic heparin is often administered as an adjunct to combat early thrombosis. 

This case details successful SBAVF creation in a 38-year-old male with ESKD, which was selected to maximize vessel preservation given his prolonged expected duration of HD. Postoperatively, the patient was discharged without complication and subsequently cleared to trial HD after successful maturation. Although it is common for SBAVFs to require adjunctive procedures and more time to achieve maturation, long-term durability (5–9 years) remains outstanding, reinforcing the value of this technically precise procedure as a safe and durable primary access option.

Keywords

Dialysis access; snuffbox arteriovenous fistula; forearm arteriovenous fistula.

Case Overview

Background

Reliable and durable hemodialysis (HD) vascular access is one of the most important and costly aspects of care for this form of renal replacement therapy (RRT). The first autogenous arteriovenous fistula (AVF) creation occurred in 1966, coined as the Brescia-Cimino radiocephalic AVF.¹ Shortly following the inception of the autogenous AVF, the anatomical snuffbox arteriovenous fistula (SBAVF) was pioneered in the late 1960s and 1970s (Figure 1).² The SBAVF creates a connection between the posterior branch of the radial artery and cephalic vein within the dorsoradial depression of the hand, in accordance with the distal-first paradigm.³ For patients with an expected prolonged duration of HD, the distal-to-proximal approach should be utilized to preserve sequential access sites and cannulation zones.⁴

Figure 1. Snuffbox AVF Anatomy.

Distal dialysis access has other advantages beyond preserving future access options. Distal AVF creation utilizes smaller vessels, which function to limit flow and increase resistance.⁵ Low-flow forearm cannulation zone fistulas have lower risk of high-output heart failure (HOHF), a disease which greatly increases the three-year mortality to 38%.^6–9 More distal access, along with the redundancy of the hand vasculature, contributes to significantly lower rates of access-related hand ischemia (ARHI), less than 1% compared to more proximal, high-flow vascular access.^8–11 

Despite the notable advantages, SBAVF is underutilized in current practice, with the Vascular Quality Initiative (VQI) database demonstrating SBAVF as 4% of the forearm access creations.¹⁰ Recent literature supports SBAVF, which demonstrates comparable outcomes to wrist fistulas at 18 months.¹² This prompted the concept of a “snuffbox first” approach when feasible in anatomically appropriate candidates, given the number of advantages and comparable outcomes.¹³

Our case involves a 38-year-old male with end-stage kidney disease (ESKD) secondary to focal segmental glomerulosclerosis (FSGS) undergoing his first permanent vascular access creation. The patient was young and had adequately sized vasculature; therefore, he underwent SBAVF creation.

Focused History of the Patient

The history for a first-time dialysis access begins with characterizing the kidney disease, expected timing of initiation and duration of HD, comorbidities, and social support to develop an individualized ESKD life-plan.⁴ The evaluation should include handedness, surgical history, and any dysfunction in the upper extremities that would help determine which extremity should be utilized. History of peripherally inserted central catheters (PICCs), tunneled dialysis lines, implanted cardiac devices, or upper extremity deep vein thrombosis (DVT) is important to uncover. These factors can predispose patients to central venous stenosis or outflow obstruction.⁴ Specific to snuffbox fistulas, a scoring system called DISTAL has been developed to assess risk factors for failure. It includes diabetes, ischemic heart disease, stroke, two prior snuffbox procedures, age greater than 70, and vein less than 2 mm. Scoring less than or equal to 3 has a 23% reduction in early failure.¹⁴

Our patient is a left-handed, 38-year-old male who has ESKD secondary to FSGS. He was previously on peritoneal dialysis for a year prior to transitioning to HD through a right internal jugular dialysis catheter. He did not have any prior dialysis access procedures performed in his upper extremity. The patient did not have other notable comorbidities. The patient’s body mass index (BMI) is 31.99 kg/m² and he has an American Society of Anesthesiologist (ASA) score of 3.

Physical Exam

The physical exam aims to assess the arterial inflow, venous outflow, and signs of central venous obstruction, which has been shown to have a 70–80% success rate for predicting an adequate AVF site.¹⁵ Arterial exam includes palpation of the radial artery in the snuffbox as well as performance of an Allen test to confirm a complete palmar arch. Venous exam includes inspection and palpation to assess size and depth of the cephalic vein. Edema should be assessed as it may indicate venous outflow issues.⁴ Patients with arm edema or large collateral veins of the chest or neck may have underlying central venous obstruction that requires intervention.⁴ Our patient did not have any arm edema or dilated collateral veins. His radial artery was palpable to the snuffbox.

Imaging

The current Kidney Disease Outcomes Quality Initiative (KDOQI) guidelines recommend selective preoperative imaging (duplex ultrasound or venogram) prior to access creation for patients at high risk for access failure.⁴ Factors that can elevate the risk of failure are older age, female sex, PAD, or ischemic heart disease—these patients particularly benefit from preoperative imaging.⁴ Duplex ultrasound measures the artery diameter, which should generally be at least 2 mm, and assesses the quality, including calcifications or atherosclerotic disease. Ultrasound should also assess the vein for size. KDOQI guidelines recommend at least 2 mm, compressibility, and lack of thrombus.⁴ For suspected central vein occlusion on physical exam or history, venography can be performed to assess the central vasculature.⁴ Our practice is to perform point-of-care ultrasound assessment selectively in clinic and immediately before the procedure as well as preoperative venogram to evaluate distal vein size and overall venous anatomy. Our patient had venography performed (Figure 2), which demonstrated left forearm vein sizes of 2.5–4 mm, adequate for a distal forearm AVF. Our technique for preoperative vein mapping with venogram has been previously described, and it facilitates high rates (70%) of forearm AVF creations in our practice, with 30% at the snuffbox.¹⁶

Figure 2. Preoperative venogram.

Natural History

ESKD is the final, irreversible stage of chronic kidney disease that requires renal replacement therapy (RRT).¹⁷ Looking at the SBAVF specifically, the venous outflow is exposed to increased flow and wall shear stress, which over time leads to venous dilation and vascular remodeling with smooth muscle cell hypertrophy and wall thickening, termed maturation.¹⁸ Contemporary fistula studies demonstrate 4-week maturation of 69.7%, 1-year clinical maturation of 83.7%, and 6-month primary patency of 87%.^13,19,20 The SBAVF demonstrates long-term patency following an early thrombosis risk as well, with a 5–9-year primary patency of 58–61%.¹¹

The SBAVF is at risk for early failure within six weeks, which demonstrates an 11% failure rate with many occurring within 24 hours due to technical factors, disturbed flow, or endothelial cell injury, each of which leads to early thrombosis.^3,11 Vascular access is also prone to inward remodeling and intimal hyperplasia, which causes failure when it outpaces outward remodeling, occurring most commonly at the juxta-anastomotic site.^18,21 In our reported series, adjunctive procedures (especially side branch ligations to enhance augmentation) were frequently necessary.¹³ Once mature, the access serves as the conduit for HD until late failure and access abandonment occurs, which is predominantly due to cannulation mishaps as well as stenosis and thrombosis from progressive neointimal hyperplasia at the juxta-anastomotic segment.⁸

Options for Treatment

SBAVF is one of the many options for HD access that depends on the patient’s anatomy and ESKD life-plan. Other autologous configurations include radiocephalic, brachiocephalic, and brachiobasilic depending on the sizes and quality of the artery and vein.⁸ For patients who have exhausted autologous options or unsuitable anatomy, a conduit is used to create an arteriovenous graft (AVG) for HD access. An AVG can be performed in the forearm, upper arm, chest, or lower extremity.⁸ Patients with a limited life expectancy or who are not surgical candidates may be best served with dialysis catheter for HD access.^4,22 Lastly, peritoneal dialysis and kidney transplant are RRT options for patients with adequate social support and decision-making capacity, which require specific equipment use and medication regimens.²³

Rationale for Treatment

Our patient is a 38-year-old male who previously utilized peritoneal dialysis prior to transitioning to HD. This procedure represented his first permanent vascular access. He is left-handed and presented with a right internal jugular dialysis catheter. Bilateral venogram was used to adequately define venous options. The venogram and outpatient assessment revealed better vein size and quality in the left forearm vasculature. A physical exam revealed a palpable artery in the anatomic snuffbox with an adequate size on ultrasound. Given the expected long duration of HD in a young and healthy patient, and his physical examination and imaging, he was scheduled for an AVF creation in the distal left upper extremity, which prepares and preserves more proximal options. The dominant arm was chosen for this procedure due to the better quality vasculature in the distal arm in order to provide the best chance for maturation at the snuffbox. The long-term benefits and durable patency of SBAVF provided justification for this procedure, while a dominant arm AVF is less convenient during HD sessions and risks dysfunction from complications.

Special Considerations

Patients who benefit considerably from this procedure are young patients with adequately sized vessels to perform the procedure. SBAVF preserves proximal options, demonstrates long-term patency, and limits flow to combat long-term issues with high-flow.¹⁹ Smaller or diseased distal vasculature is a relative contraindication where patients may be better served with a more proximal AVF.⁴ An incomplete palmar arch demonstrated by an abnormal Allen test may contraindicate SBAVF, which could predispose hand ischemia.⁴ Lastly, older frail patients with limited life expectancy may not benefit given the maturation process or primary failure, so they could be better served with an AVG or dialysis catheter.^4,22

Discussion

Our case involves a 38-year-old undergoing his first vascular access procedure who underwent the creation of an SBAVF. The SBAVF creation represents 4% of the contemporary forearm AVF creations in the VQI database, which demonstrates the relative rarity of the procedure compared to forearm and upper arm AVF creations.¹⁰ In contrast to the United States focus on wrist or upper arm AVF creations, international dialysis access practice patterns in Japan and European nations have a higher usage of wrist or snuffbox AV, which is in concordance with the Society for Vascular Surgery initiatives.^{12,13,20,24–27} For our procedure, a longitudinal incision was made over the anatomical snuffbox on the dorsoradial left hand. The posterior branch of the radial artery and the cephalic vein were dissected free. Systemic heparin was administered, and a tourniquet was used for control of the vasculature. The distal vein was ligated, then the proximal vein was anastomosed to the artery in an end-to-side fashion using a bifurcation of the vein to create a large anastomotic hood. The patient tolerated the procedure well, and the AVF had a continuous bruit on postoperative Doppler assessment. The procedure lasted 46 minutes with minimal estimated blood loss, and he was discharged following the procedure. The patient did not suffer any postoperative complications (Figure 3). Approximately 8 weeks following the operation, the venous outflow measured 7 mm and was less than 6 mm from the skin with a palpable, continuous thrill without pulsatility. The AVF was deemed ready to begin a cannulation program to prepare the AVF for dialysis.

Figure 3. Postoperative incision.

Experience with SBAVF has continued to evolve since the 1970s.² The procedure demands precise technique to avoid injury to the superficial branch of the radial nerve, which lies within 5 mm of the artery in 49% of patients, and to create an anastomosis between small vessels that measure 2 mm requiring 2.5–3.5x magnification with loupes.^28,29 Vasospasm is a major issue when working with small, distal vasculature (especially in chronically young patients); therefore, vein solution consisting of pH-balanced crystalloid, heparin, and papaverine is liberally used to combat spasm, as well as keeping the operating room temperature elevated and minimizing vein and artery dissection and handling.³⁰ Holding a heat source in the hand for 20 minutes can increase the cross-sectional area by 43.9% in the radial artery, demonstrating the variable size the vasculature can achieve.³¹ Another important aspect affecting vein size is regional anesthesia. Regional anesthesia protects against spasm by sympathetic blockade, leading to an increase in diameter with lower spasm rates compared to local anesthesia.^32,33 Such anesthetics can be safely utilized in patients even if on antithrombotic therapies.³⁴ Lastly, tourniquet control was chosen for this operation. Tourniquet control limits the amount of required arterial dissection and keeps the field clear of instruments. Operative times using tourniquets have been shown to be shorter compared to circumferential dissection and clamps (72.5 vs 84 minutes, p = 0.029).³⁵ Controlling vessels with clamps can produce endothelial and medial injury, which is limited by vessel loops or tourniquets.³⁶

Despite the rarity and technical demands of the SBAVF, the outcomes appear comparable to wrist AVFs. Primary patency, the time from AVF creation to reintervention or abandonment, and secondary patency, the time from AVF creation to access abandonment, at 1 year are 75–79% and 86–92.3% respectively.^11,13,20 When SBAVF was compared to wrist AVF, 18-month primary patency (72% vs 65%) and secondary patency (93% vs 94%) were not significantly different.¹² This finding was also demonstrated in the VQI database along with comparable complication rates and freedom from reintervention.¹⁰ SBAVF does have significant early failure secondary to thrombosis; however, if persevering past this period, the procedure has acceptable long-term outcomes with significant patency out to 9 years.^3,11 Given the acceptable and comparable outcomes, SBAVF is preferred over wrist AVF for patients with amenable anatomy.

SBAVF complications can be split into early and late complications. Early complications consist of failure to mature, thrombosis, hematoma, or nerve injury. Failure to mature ranges from 14–50%, which is comparable to wrist AVFs and within the range of the overall AVF maturation failure of 20–60%.^4,13,37 Risk factors for failure to mature include diabetes, smaller artery diameter, and PAD.^13,37 Regarding early complications and reinterventions, Heindel et al. demonstrated that SBAVF required a median of 2 interventions within the first year, but the majority (78%) were side branch ligations to improve augmentation or angioplasty for juxta-anastomotic stenosis.¹³ Hematoma can develop postoperatively, which can compress the AVF and contribute to thrombosis of the low pressure SBAVF in this small confined surgical site. Low doses of heparin can be safely used to combat this issue with many providers opting to administer 2000–3000 units.^30,38 Late complications include stenosis, ARHI, ischemic monomelic neuropathy (IMN), HOHF, infection, carpal tunnel syndrome, and aneurysmal dilation. Stenosis is the most common complication, usually occurring within the first few centimeters of the outflow vein secondary to negative wall remodeling and intimal hyperplasia.¹³ Infection, ARHI, and IMN are extremely rare (< 1%) following SBAVF, which is a major advantage over upper arm AVF.^9,11 The risk of HOHF is decreased due to lower flow from the distal artery compared to upper arm AVF.⁹ The long-term complication profile is favorable for SBAVF if able to traverse the early failure risk, demonstrated by the negligible infection, ARHI, or HOHF.

An important aspect of SBAVF and vascular access is postoperative follow-up. The surgical site should be monitored for healing and evidence of high flow in the AVF. The AVF should be evaluated by the vascular access team in 4–6 weeks to observe for maturation.⁴ Examination involves palpation for continuous thrill in the outflow vein, auscultation of continuous bruit, and inspection for an accessible, ideally straight, outflow vein that partially collapses with elevation.²¹ Augmentation can be tested by occluding the AVF at the distal end of the cannulation zone and observing for increased pulsatility. Duplex ultrasound can be used to assist maturation evaluation by measuring the depth, vein size, and flow volume to understand whether the “Rule of 6s” criteria are present. The Rule of 6s criteria include at least a 6-mm diameter vein less than 6 mm from skin with a flow volume of at least 600 mL/min, and a straight 6-cm cannulation segment, although a longer segment of 10 cm is more advantageous.³⁹ This criteria comes with some scrutiny as only 67% of clinically mature AVFs met the criteria using extreme measurements during the duplex evaluation.⁴⁰ New prediction models such as PREDICT-AVF are currently under development that may predict AVF readiness for use more accurately using machine learning.^41,42 However, the criteria are a good framework for what aspects contribute to a functional access. Long-term surveillance hinges on physical examination and evaluation of dysfunction during or after HD. Any perceived access dysfunction should prompt evaluation by a vascular access specialist where duplex, fistulogram, or other intervention will be determined by the clinical scenario. After a physical exam and ultrasound demonstrated characteristics of successful maturation in our patient, the AVF was mapped by interventional nephrology (Figure 4). The map serves as a guide for the dialysis center for the specific cannulation program. The cannulation program starts with 17-gauge needle cannulation before progressing to low flow dialysis after two weeks followed by progressive increases in flow and number of needles before dialysis catheter removal around two months after beginning the cannulation program.

Figure 4. Venous outflow map.

Our case of a 38-year-old male with ESKD successfully demonstrates the application of an SBAVF as a primary vascular access, prioritizing the distal-first paradigm and preserving all proximal options. Compared to more proximal high-flow alternatives, the SBAVF provides clear advantages, including a significantly lower risk of HOHF and negligible rates of ARHI. The procedure's 18-month primary and secondary patency rates are comparable to standard wrist AVFs, despite an observed risk of early failure due to thrombosis. Given these favorable long-term outcomes and advantages in vascular preservation, the SBAVF remains an underutilized access option in many practices. To fully realize the benefits of this procedure, a concerted effort is needed to promote the "snuffbox first" approach in eligible candidates, which inherently requires increased procedural performance and specialized technical precision to overcome the challenges associated with small vessel anastomosis and early access failure.¹³

Equipment

• Standard vascular access tray
• Heparin for IV administration
• Suture:
  • 6-0 polypropylene (for smaller sized vessels 7-0 is sometimes utilized)
• Duplex ultrasound for preoperative assessment
• Doppler for qualitative postoperative assessment
• Vein solution:
  • 500 mL pH balanced crystalloid
  • 2000 units heparin
  • 60 mg papaverine
• Sterile tourniquet
• Esmarch
  

Disclosures

BJS: No disclosures.

CHW: No disclosures.

MAH: MAH reports research grants from Vascular Therapies (ACCESS-2 Trial), Humacyte (V-012 Trial), VenoStent (SAVE-FistulaS Trial), Voyager Biomedical (ACT II Trial), Laminate Technologies (Post Market Study for VasQ), AMPLIFI Medical (AMPLIFI-1 Trial), and Venova Medical; and consulting fees from Humacyte, Venova Medical, and LeMaitre Vascular.

CKO: CKO reports current consultant work with Getinge, Laminate Medical Technologies, and Linton Lifesciences. Former consultant work includes: Humacyte, Mitobridge, Semma Therapeutics, Medtronic Corporation, Merck Sharp & Dohme Corporation, Gecko Biomedical, and Proteon Therapeutics. Former advisory board work includes: Humacyte, Proteon Therapeutics, and Vascular Silk Technologies. Former data monitoring committee work includes: Neograft Technology and The Angioshield Study.

Statement of Consent

The patient referred to in this video article has given their informed consent to be filmed and is aware that information and images will be published online.