evaluated the difference in clinical outcomes between TBBAVF and AVG in a meta-analysis of 11 studies (1 randomized controlled trial [RCT] and 10 retrospective studies) involving a total of 1,135 patients. The pooled estimated ORs for the primary and secondary failure rates at 1 year were 0.67 (CI 0.41–1.09) and 0.88 (CI 0.69–1.12), respectively, showing no difference in the outcome between the 2 groups. In 8 studies, however, the re-intervention rate was higher for prosthetic grafts (0.54 per TBBAVF vs. 1.32 per graft) [13]. The most recent RCT by Davoudi et al. [14] in 2013 also demonstrated no statistically significant difference in the mean primary patency time or access-related complication rate at 1 year between the 2 techniques. Several recent cohort studies published since 2008 have assessed the differences in various clinical outcomes between these 2 VA options. On the whole, TBBAVF offers a compatible or better patency rate, fewer infection-related complications, a lower rate of long-term adverse events, and a lower requirement for interventions, all of which should contribute to the higher cost-effectiveness of TBBAVF than AVG. However, AVG requires a shorter length of hospital admission, total intervention time, and mean interval to the first cannulation than TBBAVF, which could be beneficial for older patients with a short life expectancy and urgent need for VA or patients with compromised clinical conditions and unreliability for temporary VA [4, 5] (Table 1).
Table 1. Recent comparative studies of TBBAVF versus AVG
One- and Two-Step TBBAVF
Amid the growing methodological heterogeneity in TBBAVF, studies have been performed in an attempt to clarify the optimal procedure for TBBAVF construction. In a recent meta-analysis, Jun Yan Wee et al. [15] assessed 12 comparative studies between one- and two-stage TBBAVF (2 RCTs and 10 cohort studies involving 1,135 patients) and found that the two-stage procedure had significantly better 2-year primary patency rates; however, there were no statistically significant differences in the failure rates, 1-year primary and secondary patency rates, and 2-year secondary patency rates between the 2 groups. Their meta-analysis also showed no differences in the time to first fistula use or complication rates of steal syndrome, hematoma, infection, pseudoaneurysm, or stenosis between the 2 procedures. These results indicate the potential benefits of the two-stage versus one-stage procedure for construction of a TBBAVF [15] (Table 2). The superficialized basilic vein in the two-stage procedure could conceivably be associated with a reduced risk of kinking, twisting, or compression in the relocated subcutaneous space because of the sufficient interval for venous arterialization and wall thickening. An additional advantage of the two-stage technique is that the development of complications such as steal syndrome or venous hypertension after the arteriovenous anastomoses in the first stage could be managed before superficialization [16].
Table 2. Recent comparative studies of methodological differences in TBBAVF
TBBAVF Construction Using Tunnel Transposition or Elevation
The differences in the clinical outcomes between tunnel transposition and elevation for TBBAVF construction have been evaluated in a few retrospective observational studies. Hossny [9] reported no differences in cumulative primary patency and secondary patency between tunnel transposition and one- or two-stage elevation. The author found that the total complication rate was significantly higher in the elevated group. However, most complications involved postoperative arm edema or hematoma formation and could be treated conservatively without fistula failure [9]. In another recent study, Wang et al. [8] also found that for TBBAVF construction, both tunnel transposition and elevation achieved high cumulative patency rates of the whole fistula conduit, including the vasculature from the arteriovenous anastomosis to the right atrium, with an acceptable early postoperative complication profile despite the need for repeated endovascular interventions in a subset of patients. Interestingly, the authors found that compared with tunnel transposition, elevation was associated with better primary patency of the superficialized basilic vein segment and a lower requirement for interventions [8] (Table 2).
Tunnel Transposition of the Cephalic Vein
The clinical feasibility of AVF superficialization using tunnel transposition of the forearm and upper arm cephalic veins has been suggested by several groups. In a study evaluating the outcomes of 3 different types of one-stage AVF tunnel transposition (forearm cephalic vein transposition, upper arm cephalic vein transposition, and upper arm basilic vein transposition) by Korepta et al. [17], no statistically significant difference was found in the access maturation rate, primary 1-year patency, or primary assisted 1-year patency among the 3 groups. These results indicate that cephalic vein transposition in the forearm and upper arm could be a reliable alternative AVF procedure with patency equivalent to that of TBBAVF. In addition, a revisional tunnel transposition procedure using a minimal incision technique to ensure accessibility was introduced by Inkollu et al. [18].
Methodological Diversity of the Superficialization Procedure
Elevation
The elevation procedure of the arterialized vein was originally introduced as a surgical revision for the purpose of facilitating AVF cannulation. Adequate maturation of the fistula is required for the successful implementation of repeatable, safe cannulation in clinical practice. The updated NKF-K/DOQI guideline proposes the following parameters associated with maturity of a newly created AVF, famously known as “the rule of 6s:” flow of > 600 mL/min, diameter of ≥0.6 cm, depth of ≤0.6 cm, and discernible margins [2].
In general, the rate of initial or early non-maturation AVF failure ranges from 20 to 60% [19]. Moreover, according to a study by van Loon et al. [20], during the first 6 months of a newly placed VA, a substantial proportion of patients encounter cannulation-related complications resulting in the need for temporary VA methods such as single-needle dialysis (33%) and catheter dialysis (22%). Cannulation-related complications of VA, such as hematoma formation, infection, and aneurysms, might lead to morbidity, hospitalization, access revision, loss of the VA, and the consecutive occurrence of other serious adverse events potentially attributable to the temporary VA [20, 21]. Ultrasound-guided
