Currently, the most prevalent and effective treatment for kidney failure is renal replacement therapy, which encompasses peritoneal dialysis, hemodialysis, and kidney transplantation. Among these modalities, hemodialysis is the most commonly employed.1 The radiocephalic arteriovenous fistula (AVF) is the preferred first-line vascular access for hemodialysis in patients with kidney failure, due to its superior patency compared to grafts and catheters with cost effectiveness and lower complication rates translating into significantly reduced morbidity and mortality.2 However, inadequate maturation and early failure remain significant challenges due to insufficient vein diameter, often resulting in increased reliance on central venous catheters and tunnelled catheters with a lack of long-term access for hemodialysis. Studies have documented that patients with larger vein diameters on preoperative vein mapping are at a reduced risk for fistula maturation failure and exhibit increased AVF patency.3

The maturation failure rate of AVF is relatively high, ranging between 6% and 40%, depending on factors such as female gender, the presence of diabetes mellitus, surgical technique and insufficient diameter or poor compliance of the candidate vessels.4 Some studies suggest a minimum vein diameter of 2.0mm as sufficient for AVF creation.5 For radiocephalic AVFs at wrist, a post-dilatation diameter of at least 2.5mm is considered optimal.6 Various modifications in operative technique have been proposed to optimize vessel calibre and improve AVF outcomes.

Intraoperative cephalic vein dilatation using balloon catheters or other means has been proposed as a novel technique to improve venous diameter and facilitate fistula maturation.7 Few studies have evaluated its efficacy in improving AVF outcome; however, the technique has not been standardized. Despite its potential benefits, there is still limited high-quality evidence on efficacy of intraoperative cephalic vein dilatation in improving short-term AVF outcomes. This study evaluates the impact of intraoperative cephalic vein dilatation on short-term clinical and radiological outcomes of radiocephalic AVF in kidney failure patients.

This was a prospective non-randomised comparative study conducted at the department of urology in a tertiary care centre of eastern India from January 2022 to December 2022, in compliance with relevant laws and institutional guidelines and after approval by the institutional ethical committee, in accordance with declaration of Helsinki. After taking informed written consent, adult patients with kidney failure on maintenance hemodialysis and planned for radiocephalic AVF creation were included in the study. Suitable radial artery and cephalic vein were ensured based on preoperative clinical evaluation and colour doppler mapping. Exclusion criteria comprised of pre-emptive AVF creation, anatomical abnormalities of the upper limb vasculature, previous surgery or trauma or active infection at the planned fistula site, severe vascular calcification, central venous stenosis, previous unsuccessful fistula or graft and incomplete data or loss to follow up.

All patients underwent a standardized preoperative evaluation, including clinical examination of the upper limb vasculature and colour doppler ultrasonography to assess vessel suitability. All the eligible patients (n=91) fulfilling the inclusion criteria during the study period were allocated alternately into two groups by the operating surgeon as per chronological order of presentation: group A (n=46) included patients who underwent intraoperative cephalic vein dilatation and group B (n=45) included patients who underwent conventional AVF creation without dilatation. 57 patients were undergoing hemodialysis through central venous catheter and 34 patients were undergoing hemodialysis through tunnelled cuffed catheter in the internal jugular vein at the time of AVF creation. All the surgeries were performed by a single experienced surgeon.

Procedure details: Under local anaesthesia, after keeping the arm outstretched in 90-degree abduction, oblique incision was given in the radial aspect of the forearm proximal to the wrist. The cephalic vein was dissected from the surrounding tissue for about 5cm proximally with preservation of adventitia and all the tributaries were ligated. The vein was clamped distally, cut and the distal end was transfixed. In group A patients, a 24G or 22G cannula was inserted into the proximal end of the vein and 50–70ml heparinised saline (2500U unfractionated heparin in 250ml normal saline) was instilled into the vein using 10ml syringe by a low pressure manual technique, while the forearm was being compressed proximally by the assistant in an ascending manner up to the elbow and back to the cut end till there was resistance to the flow of saline being instilled and vein got dilated by hydrostatic pressure with visual luminal expansion to ≥3mm external diameter and free retrograde flow without blanching or extravasation (Fig. 1). In patients included in group B, this step of intraoperative venous dilatation was omitted. The vein was then spatulated for about 10mm proximally. The radial artery was then dissected out and its branches were ligated. An arteriotomy of approximately 10mm was performed after controlling both ends and an end to side anastomosis was performed between the artery and the vein using continuous 6-0 polypropylene suture. After securing hemostasis, the skin incision was closed with 3-0 nylon sutures in interrupted fashion.

Fig. 1.

Technique of intraoperative cephalic vein dilatation, A and B – heparinised saline instillation by inserting cannula into distal cut end of cephalic vein, C – proximal pressure being applied by assistant's fingers during instillation of saline, D – pressure being applied by assistant at the distal end of cephalic vein after returning from elbow.

All the patients in both groups were advised to actively squeeze a soft ball for 15min thrice daily in the postoperative period.

Radiological parameters including vein diameter and AVF flow rate were assessed at 6 weeks postoperatively by colour doppler. Fistula maturation by Hemodialysis Fistula Maturation (HFM) criteria was assessed at 10–12 weeks postoperatively by a clinician blinded to group allocation. According to HFM study, AVF was considered to have matured when the fistula could be used clinically with two needles for at least 75% of dialysis sessions over a continuous 4-week period. Additionally, the fistula had to meet at least one of these criteria: an average blood pump speed on the dialysis machine of more than 300ml/min in four sessions in a row or a Kt/V higher than 1.4, or a urea reduction ratio (URR) exceeding 70%.8

The primary outcome of the study was clinical fistula maturation at 10–12 weeks, based on HFM criteria, while the secondary outcomes were postoperative doppler measurements of vein diameter and AVF flow rate at 6 weeks. All the doppler studies were performed by a single experienced radiologist blinded to the group allocation.

Data was analyzed using SPSS v26.0 statistical package (SPSS Inc., Chicago, IL, USA). Continuous variables were expressed as mean±standard deviation (SD) and were considered normally distributed if Z score of skewness was within ±3.29 and compared between both groups using the independent t-test. Categorical variables were compared between both the groups using the Chi-square test or Fisher's exact test. Statistical significance was set at p<0.05.

A total of 91 patients underwent radiocephalic AVF creation, with 46 patients in the cephalic vein dilatation group (Group A) and 45 patients in the non-dilatation group (Group B). Baseline demographic and clinical characteristics were statistically comparable between both the groups, but duration of dialysis was significantly lesser in group B (Table 1). Postoperative colour doppler parameters at 6 weeks have been compared between both groups in Table 2. At 10–12 weeks postoperatively, overall functional AVF maturation was achieved in 84.6% of patients (77/91), with a significantly higher maturation rate observed in Group A compared to Group B (93.5% vs. 75.6%, p=0.017) (Table 3). Multivariate logistic regression analysis for fistula maturation was performed based on the preoperative variables (Table 4). Minor complications, including localized haematoma and superficial wound infection, were infrequent and comparable between groups, and no cases of thrombosis or early fistula failure were reported.

AVF remains the gold standard for vascular access in maintenance hemodialysis due to its superior long-term patency, lower complication rates, improved patient survival and reduced healthcare costs compared to synthetic grafts or central venous catheters.9 The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) and the Fistula First Initiative advocate for autogenous AVF as the primary choice for hemodialysis access, followed by prosthetic grafts and lastly, hemodialysis catheters.10 They also recommend creating the AVF in kidney failure patients 4–6 months before beginning hemodialysis. However, a meta-analysis from India found the benefit in eGFR improvement with this approach to a very small extent with low certainty.11 Following creation, the venous segment undergoes adaptive remodelling, characterized by dilation and wall thickening in response to increased flow, shear stress and pressure, ultimately achieving “maturation” suitable for dialysis.12 However, 20–60% of AVFs do not mature.13 According to the KDOQI 2006 clinical practice guidelines, a mature fistula should achieve a blood flow of 600ml/min and have a diameter exceeding 6mm.14 However, the 2019 update suggested that AVF maturation should be considered based on clinical judgement.15 The HFM study highlighted utilization of AVF for 75% of dialysis sessions over 4 weeks with adequate blood flow and clearance as strong indicators of clinical success.8 Vein diameter has been found to be the only independent predictor of fistula maturation in a study.16 A vein diameter of ≥4mm has been associated with successful cannulation and AVF maturation.17,18

Our study shows that intraoperative cephalic vein dilatation significantly enhances fistula maturation and doppler-measured haemodynamic parameters without increasing postoperative complications. Successful maturation of radiocephalic AVF involves endothelial activation, nitric oxide-mediated vasodilation, and structural reorganization of the venous wall leading to adaptive remodelling of the venous segment.19 The pathophysiological rationale behind our technique of intraoperative cephalic vein dilatation lies in mechanical preconditioning. Hydrostatic expansion of the cephalic vein increases luminal diameter, thus reducing venous tone, and facilitates vascular anastomosis mechanically. Transient dilatation enhances venous elasticity, mitigates spasm, and supports earlier recruitment of adaptive endothelial and smooth muscle cell responses that may facilitate endothelial remodelling to tolerate elevated flow post-operatively.19 Vein distensibility is a known predictor of AVF success. By physically assessing and improving vein compliance intraoperatively, the surgeon can tailor the approach based on real-time feedback.

Previous studies such as Fila et al. showed 70% clinical maturation after intraoperative venous dilatation; however, they performed serial dilatation by probes which may lead to possible intimal injury.20 Zhang et al. in 2020 reported a fistula maturation rate of 44.44% and identified a significant link between fistula maturation and preoperative cephalic vein dilation using a tourniquet.6 Our maturation rate was higher than these two studies (93.5% in venous dilatation cohort), however Zhang et al. performed venous dilatation only for cephalic veins<2mm in diameter which may have reduced their maturation rate, while the mean venous diameter in our study was 2.4mm or above. We only used hydrostatic pressure to dilate the vein which has low chances of intimal injury due to no direct intervention on the intimal layer of vein. In another study, cephalic vein was dilated by using hydrostatic pressure in all patients, but their proximal limit of dilatation was 3cm from the cut end of vein by applying a titanium aneurysm clip to clamp the vein.21 They also measured intraoperative pre- and post-dilatation venous dimeter and showed that post dilatation venous diameter>4mm and vein distensibility of >2.2mm predicted successful maturation of radiocephalic AVF. We have shown the impact of venous dilatation by hydrostatic pressure on fistula maturation by comparing to a non-dilatation cohort, while the above study showed the effect of degree of intraoperative dilatation using various parameters on fistula maturation. In that study, the clinical significance of post-dilatation venous diameter≤4mm or a vein distensibility≤2.2mm remains unclear regarding the appropriateness of radiocephalic AVF creation. We feel that intraoperative venous dilatation helps in fistula maturation, however degree of intraoperative dilatation by hydrostatic pressure may not directly correlate with fistula maturation, as the process of remodelling may be variable in all patients.

The preoperative mean diameter of the cephalic vein was 2.4±0.35mm in group A, which increased to 4.8±0.9mm at six weeks postoperatively and was significantly higher than the venous diameter in group B at 6 weeks, which also translated to higher fistula maturation in group A. None of the preoperative factors was significantly different between both the groups on univariate as well as multivariate analysis, except for dialysis duration with longer dialysis predicting higher maturation, while it has been found in literature to affect the vessel characteristics negatively, leading to lower fistula maturation rate.4 Thus, intraoperative venous dilatation leads to improvement in radiocephalic AVF maturation rate with no significant confounding factors, preserving proximal access for later requirements.

Postoperative flow rates progressively increased to 1092±476ml/min in the cephalic vein dilatation group by week 6, compared to 836±289 in the non-dilatation group. According to the KDOQI guidelines, a flow rate>600ml/min is considered adequate for dialysis.15 Our findings demonstrate that by week 6, the mean flow exceeded this threshold, suggesting successful maturation in most cases.

Importantly, no significant difference in infection or haematoma rates was observed, suggesting the safety of this manoeuvre. However, all procedures were performed by an experienced surgeon, which may influence outcomes. Larger trials with multicentric design, stratified analyses and longer follow-up are warranted to confirm these findings and assess long-term patency outcomes.

The study focuses on a practical and replicable solution for improving AVF outcomes independent of patient anatomy or comorbidity. The method is simple, cost-effective, and can be easily integrated into standard surgical procedure with minimal increase in operative time. Our findings are corroborated by previous literature indicating that preoperative ultrasound mapping alone may not adequately predict outcomes unless functional dynamics are considered. Moreover, unlike complex interventions requiring additional resources or imaging modalities, saline dilatation is universally accessible. However, excessive force must be avoided to prevent endothelial injury or rupture, as manual pressure may be uncontrolled and carries a theoretical risk of endothelial barotrauma. If there is resistance to the flow of saline being instilled, the manual pressure should be removed and shifted to a proximal point going up to elbow and then should come back to the distal end of cephalic vein at the incision site. The entire venous segment intended for anastomosis and early outflow should be dilated (up to elbow for radiocephalic AVF) to ensure uniform distension.

Although this study provides valuable insights, it is important to acknowledge its various limitations. Firstly, the non-randomized aspect of the study introduces inherent biases and restricts control over data gathering procedures. Multivariate analysis to identify potential confounding factors showed only duration of dialysis to be significantly different between the two groups. The limited sample size of 91 individuals, along with the exclusion criteria that excluded certain comorbidities, may limit the applicability of the findings to larger patient populations. Being a single centre study, operator technique, experience, and intraoperative decision-making may be affected, potentially limiting external validity. Furthermore, surgical methodology including manual pressure generated by the assistant's fingers and duration of dilation was not uniformly standardized, which may lead to technical variability and interoperator differences. The histological changes in endothelium due to dilatation were not studied but long term follow up may reveal complications like venous stenosis or aneurysmal dilatation. Longer-term data may also be necessary to determine whether the early results persist and translate into durable functioning of AVF. This information could be important for improving clinical practices.

Intraoperative cephalic vein dilatation during radiocephalic AVF surgery significantly improves early fistula maturation and doppler ultrasonography parameters without added complications. Incorporating this technique may help in technical feasibility of radiocephalic AVF surgery with improvement in short term AVF success for initiation of hemodialysis.

Naveen Kumar: 0000-0001-6176-6913

Jeetendra Jaidiya: 0009-0004-0829-9681

Vipin Chandra: 0000-0001-9401-9404

Saket Singh: 0000-0003-0536-0155

Naveen Kumar and Md Kashif Rizwi contributed to the study conception and design. Data collection was performed by Jeetendra Jaidiya, Indranuj Roy, and Saket Singh; statistical analysis was conducted by Naveen Kumar; and data analysis and interpretation were carried out by Abhishek Raman, Vipin Chandra, and Preety Prasad. The first draft of the manuscript was written by Naveen Kumar and Md Kashif Rizwi, and all the authors provided critical revisions on previous versions of the manuscript. All the authors critically revised the manuscript. All the authors read and approved the final manuscript and agree to be accountable for all aspects of the work.

Ethical clearance was obtained before conducting this study vide approval number Med/Pat/2022/IEC/003.

Informed written consent was obtained from all the patients included in the study.

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

None.