Snuffbox Versus Wrist Radiocephalic Arteriovenous Fistulas: 10 Years Experience

Background The wrist radiocephalic arteriovenous fistula (RCAVF) is the initial suggested procedure for establishing hemodialysis vascular access (HVA) in the most distal site of the upper limb. The anatomical snuffbox arteriovenous fistula (SBAVF) is barely utilised, despite its remote location. In this study, we aimed to analyse and compare the results of SBAVF and RCAVF in terms of their maturity, patency, and failure rates. Methodology This descriptive, retrospective study compared outcomes between SBAVF and RCAVF in terms of maturation, patency, and failure. All patients with chronic kidney disease who attended and underwent either procedure at Betsi Cadwaladr University Health Board between 2013 and 2023 were studied. Results In a period of 10 years, 179 patients were included. Overall, 102 (57%) were male and 77 (43%) were female, with a male-to-female ratio of 1.3:1. Wrist radiocephalic fistula was the dominant type of surgery done in 76% (n = 136), while the snuffbox radiocephalic fistula was done in fewer than 24% (n = 43) of patients. Most patients underwent a successful arteriovenous (AV) fistula (n = 105, 58.7%), in contrast to 67 patients whose fistulas failed. There was a significant relationship between fistula failure and complications (p = 0.000). There was no significant effect of the fistula site, hypertension, diabetes, cardiac diseases, smoking, peripheral vascular disease, or central vein stenosis on the failure of the AV fistula (p = 0.127, 0.534, 0.510, 0.397, 0.017, 0.68, and 0.371, respectively). Conclusions The snuffbox AV fistula is a suitable and feasible first choice for patients on hemodynamic therapy.


Introduction
Chronic kidney disease (CKD) is a global public health challenge, and the number of patients with end-stage renal disease (ESRD) has been increasing globally through the years.In Europe, patients with CKD account for 10% of the population.The dialysis population is growing at a rate of about 2% each year [1].Despite the advances in kidney transplantation, hemodialysis remains the most widely used modality of treatment for patients with ESRD [2,3].
Native arteriovenous fistula (AVF) is the definitive haemodialysis vascular access (HVA) used for chronic haemodialysis.According to guidelines, AVF should be end-to-side radiocephalic (RCAVF), as the most distal site, in the non-dominant upper limb [4].
The anatomical snuffbox AVF (SBAVF) was first described by Rassat et al. in 1969.Despite being more distal compared to RCAVF, it is not frequently used in the United Kingdom [5].
The Fistula First Initiative advocates for the insertion of autogenous haemodialysis access before utilising a prosthetic graft [4,6].
At our centre, SBAVF is considered a first choice for AVF.It is hypothesized that this would spare RCAVF as a second option if it is used as HVA for a period and occluded eventually.In addition, it may reduce the maturity time for future RCAVFs.On the other hand, when occluded, the relatively close wrist cephalic vein may become unusable, which might affect haemodialysis patients negatively until a definitive native HVA is achieved.
This study aims to assess the access outcomes, complications, primary, primary assisted, and secondary patency rates of SBAVF and RCAVF and determine if SBAVF should be the first recommended HVA (in suitable patients) or if it has its drawbacks.

Study design and population
This descriptive, observational, and retrospective study compared the outcomes between the snuffbox and wrist arteriovenous (AV) fistula in terms of maturation, patency, and failure.All patients with CKD who attended and underwent snuffbox or wrist AV fistula at Betsi Cadwaladr University Health Board were studied.

Data collection
We retrieved the data of AV fistula patients who underwent snuffbox and wrist AV fistula at Betsi Cadwaladr University Health Board between January 2013 and January 2023.The clinical evaluation included factors such as the patient's age, gender, site of fistula creation, smoking history, comorbidities, fistula failure, primary, assisted primary, and secondary patency.

Surgical technique
The fistula was established using local anaesthesia (0.5% bupivacaine and 0.5% lidocaine).An initial antibiotic was administered.A 2-3 cm-long skin incision was made across the first interosseous gap or the wrist.This provides adequate exposure to both the artery and vein.Continuous polypropylene sutures (6/0 or 7/0 proline) were used to create an end-to-side anastomosis between the cephalic vein and radial artery.
The wound was closed in layers, and a palpable thrill was palpated to indicate success.

Follow-up
The AV fistula was assessed by Doppler ultrasound after six weeks of creation and considered mature if the flow was more than 400 mL/minute.The patient underwent a surveillance Doppler ultrasound scan every six months.

Definition
Fistula failure was considered when the fistula maturation failed or the ability to use the fistula for dialysis failed.

Data analysis
The data collected for this study was analysed using SPSS version 21 software (IBM Corp., Armonk, NY, USA), including data entry, cleaning, and analysis.Descriptive statistics were utilised to present the frequency tables with corresponding percentages.The means and standard deviations were also reported.A bivariate analysis was conducted to assess the associations between the outcome variables and other relevant influencing factors.The statistical tests employed were the chi-square test for categorical variables and the t-test for quantitative variables.Kaplan-Meier curves were used for survival analysis to compare the two groups using the log-rank test.A significance level of 0.05 or less was considered statistically significant, indicating a substantial relationship between the variables.

Results
In a period of 10 years, 179 patients were included.Overall, 102 (57%) were male and 77 (43%) were female, with a male-to-female ratio of 1.3:1.The mean age was 68.7 ± 13.1 years.Regarding the comorbidities, hypertension and diabetes were recorded for most patients, while the other comorbidities were less frequent (Table 1).
This table shows the factors that were significantly related to fistula failure.
When performing the regression analysis to identify the independent diameter for fistula failure, it was 1.8 mm for the vein and 1.5 mm for the artery (p = 0.003 and 0.004, respectively).
A total of 78 patients underwent a procedure to salvage AVF.Eight underwent surgery and 70 underwent an endovascular intervention.The vein diameter by duplex ultrasound ranged from 1.5 to 5 mm, with a mean of 2.99 ± 0.6 mm.The artery diameter ranged from 1 to 4.4 mm, with a mean of 2.5 ± 0.5 mm.The mean weeks for fistula maturation were 6 ± 7 weeks.On comparing the means of maturation among the two groups, there was a significant difference in maturation time (Table 4).The primary patency ranged from 1 to 118 months, with a mean of 8.4 ± 16.4 months.The mean primary assisted patency ranged from 1 to 76 months, with a mean of 3.3 ± 11.5 months.The secondary patency ranged from 1 month to 72 months, with a mean of 2.9 ± 9 months, as shown in the Kaplan-Meier survival curves (Figures 1-3, respectively).On comparing the mean between the two groups, it did not show any significant difference between primary, primary assisted, or secondary patency (p = 0.052, 0.233, and 0.065, respectively).

Discussion
Our study concluded that there were similar outcomes between snuffbox AVFs and wrist AVFs concerning maturation, postoperative complications, patency, and failure.According to this result, the more proximal radial artery can be retained without compromising outcomes, resulting in snuffbox AVF as a viable option for wrist AVF for distal access.
Our study showed that only 43 SBAVFs were created during the study duration in our centre in comparison to wrist AVFs.This may be due to the unfamiliarity of most surgeons with this particular type of access or the anatomic site, as well as the comfort of the surgeon with the procedure.Moreover, these factors might also affect the outcome, as reported in previous studies [6][7][8][9][10].
There was no significant impact of the comorbidities, smoking, and peripheral arterial disease on fistula maturation or failure.Horimi et al. examined the impact of diabetes on outcomes [11].Diabetics generally have significantly reduced fistula patency and flow rates.However, no risk-adjusted analysis was done.Our analysis did not turn out to be a significant predictor.
Previous studies attempted to determine the typical characteristics of vessels necessary for a successful AVF; however, they obtained various results.Kim et al. determined that the lack of development in RCAVF is associated with preexisting intimal hyperplasia in the radial artery, a condition frequently found in patients with renal disease.Lauvao et al. showed that vein diameter is a significant predictor of fistula success [12][13][14][15][16][17].
In their study, Hull et al. established the criteria that the vessels (artery and vein) used in the AVF creation should have a diameter greater than 2 mm, which is consistent with the findings of our investigation [18].Early failure of the distal AVF has been observed in many studies [6,11,13].In our study, we did not examine the time when the failure occurred because of a lack of this information in the records and because the data were collected retrospectively.
In our study, there was no significant difference in terms of primary, assisted primary, and secondary patency rates.Therefore, the SBAVF is a good option for starting [10,13,19].Some studies have mentioned the early high patency rate of SBAVF, which aligns with our earlier results.However, most studies have not addressed the long-term patency rate [7,19].Simoni et al. compared the patency rates of SBAVF to those of wrist AVF and found that the results were comparable, with SBAVF patency rates of 77.3% at one year, 36.3% at five years, and 18.9% at 10 years compared to wrist AVF patency rates of 75.5% at one year, 54.5% at five years, and 30.7% at 10 years [10].There was no significant difference among the two groups in terms of outcome, which is aligned with some previous studies [10,17].
Our study has a few limitations.We retrospectively collected data.The reason why a particular access type was chosen remains unknown.It is a monocentric, descriptive, comparative analysis between two heterogeneous small groups.Indeed, there was a large difference between the total number of patients in the two groups.

Conclusions
There was no significant difference between the SBAVF and the wrist AVF.Regarding outcome, patency, and rate of complications, the SBAVF fistula is a viable and realistic option for patients undergoing hemodialysis.If the wrist AVF is performed first, the opportunity to create the SBAVF is lost.To provide vascular access, we recommend using SBAVF, especially for younger patients who do not have any comorbidities.