End-stage renal disease (ESRD) represents a growing global health burden, with haemodialysis remaining the most widely employed form of renal replacement therapy. The success of haemodialysis is critically dependent on the availability of a reliable vascular access. Among the available options, native arteriovenous fistulas (AVFs) are strongly preferred due to their superior long-term patency, lower infection rates, and reduced morbidity and mortality when compared with arteriovenous grafts and central venous catheters [1,2]. Despite these advantages, early AVF failure and delayed maturation remain common clinical problems. Reported rates of primary AVF failure range from 40% to 55%, leading to repeated access procedures, extended catheter use, and increased healthcare costs [5,7]. These challenges highlight the importance of accurate preoperative assessment and early postoperative monitoring to improve AVF outcomes. Clinical examination alone is often insufficient for vascular access planning, particularly in patients with obesity, diabetes mellitus, or prior vascular interventions. Doppler ultrasonography has emerged as a valuable adjunct by allowing non-invasive evaluation of vessel diameter, depth, patency, and blood flow dynamics [3,4]. The Kidney Disease Outcomes Quality Initiative (KDOQI) guidelines recommend routine preoperative Doppler mapping to identify suitable arteries and veins, as well as postoperative surveillance to detect early hemodynamic abnormalities such as low flow or stenosis [2]. Although several studies support the use of Doppler ultrasonography in AVF planning, the relative importance of individual Doppler parameters remains incompletely defined. While arterial and venous diameters are recognized predictors, postoperative flow measurements may provide more sensitive indicators of early maturation [6,11]. Furthermore, the influence of demographic variables and comorbidities on early AVF outcomes remains inconsistent across studies [8,9]. This prospective observational study was conducted to assess the role of Doppler ultrasonography in predicting early AVF functionality, identify key Doppler-derived predictors of maturation, and evaluate the impact of demographic and clinical factors. The findings aim to reinforce guideline-based, Doppler-focused strategies to optimize haemodialysis vascular access.

Study Design: Prospective observational study conducted over one year at a tertiary care teaching hospital. Population: 25 patients with ESRD undergoing haemodialysis through native AVF. Inclusion criteria: age ≤70 years, ability to comply with follow-up, and willingness to provide informed consent. Exclusion criteria: age >70 years, non-compliance with follow-up, use of arteriovenous grafts or central venous catheters. Doppler Ultrasonography Protocol: High-resolution colour duplex ultrasound (7–12 MHz linear probe) was used. Preoperative Assessment: Arterial diameter, venous diameter, vein depth from skin surface. Thresholds: artery ≥2 mm, vein ≥4 mm, vein depth ≤6 mm. Postoperative Assessment (at 2 months): Blood flow velocity (>300 mL/min per KDOQI), venous diameter (≥4 mm), and artery diameter (>2 mm). Definition of AVF Functionality: AVF was functional if Doppler parameters met criteria and it was clinically usable for haemodialysis. AVF failure was defined as non-functionality or inability to use for dialysis. Data Analysis: SPSS software. Continuous variables expressed as mean ± SD; categorical variables as frequencies and percentages. Associations analysed with t-tests or chi-square tests; p<0.05 considered statistically significant.

Baseline Demographic and Clinical Profile The study included 25 patients with ESRD undergoing haemodialysis through native AVFs. Patient age ranged from 15 to 58 years, with a mean age of 38.40 ± 12.90 years. The majority of patients were between 31 and 50 years of age, reflecting a relatively young dialysis population. Male patients predominated, accounting for 76% of the cohort, yielding a male-to-female ratio of 3.17:1. Diabetes mellitus was the most frequently observed comorbidity, present in 12 patients (48%). Peripheral vascular disease was identified in two patients (8%), while other conditions such as hypertension and ischemic heart disease were documented but not analysed as primary variables (Fig 1). Statistical evaluation revealed no significant association between AVF functionality and age, gender, or the presence of diabetes mellitus (p>0.05). Although both patients with peripheral vascular disease experienced AVF failure, the small sample size limited meaningful statistical interpretation. AVF Characteristics and Site Distribution Forearm AVFs were created in 16 patients (64%), while 9 patients (36%) underwent upper arm AVF creation. Site selection was guided by clinical examination and Doppler mapping in accordance with KDOQI recommendations. There was no statistically significant relationship between AVF location and functional outcome, indicating that vessel quality and hemodynamic parameters were more influential than anatomical site. Forearm AVFs were more commonly created, accounting for 64% (n=16) of cases, whereas upper arm AVFs represented 36% (n=9). The selection of AVF site was guided by clinical examination and preoperative Doppler evaluation, following KDOQI-recommended mapping protocols. The preference for distal sites aims to preserve proximal vasculature for future access and minimize complications. Site selection was not significantly associated with AVF outcome, reinforcing the notion that vessel quality and flow characteristics may outweigh anatomical location in predicting early success. Preoperative Doppler Findings Preoperative Doppler ultrasonography demonstrated a mean arterial diameter of 2.53 ± 0.35 mm. Functional AVFs exhibited significantly larger arterial diameters (2.67 ± 0.32 mm) compared to failed AVFs (2.38 ± 0.33 mm), with a p-value of 0.032, establishing arterial diameter as a significant predictor of early AVF success. The mean preoperative venous diameter was 7.24 ± 2.35 mm. Although functional AVFs had marginally larger veins, this difference was not statistically significant (p=0.820). Similarly, the mean vein depth from the skin surface was 7.64 ± 1.48 mm, with no significant difference between functional and failed AVFs (p=0.211). These findings highlight the critical role of adequate arterial inflow in facilitating early fistula maturation through enhanced shear stress and venous remodelling (Table 1). TABLE 1: Pre-operative diameter of artery, vein & depth of vein from skin surface Number of subjects 25 PREOPERATIVE DIAMETER OF ARTERY Minimum diameter of artery (mm) 2.00 Maximum diameter of artery (mm) 3.00 Median of diameter of artery (mm) 2.60 Mean diameter of artery (mm) 2.53 Standard Deviation 0.35 PREOPERATIVE DIAMETER OF VEIN Minimum diameter of vein (mm) 4.00 Maximum diameter of vein (mm) 13.00 Median of diameter of vein (mm) 6.50 Mean diameter of vein(mm) 7.24 Standard Deviation 2.35 DEPTH OF VEIN FROM SKIN SURFACE Minimum depth of vein from skin (mm) 6.00 Maximum depth of vein from skin (mm) 11.00 Median of depth of vein from skin (mm) 7.00 Mean depth of vein from skin (mm) 7.64 Standard Deviation 1.48 Postoperative Doppler Assessment Doppler ultrasonography was performed two months postoperatively to assess flow velocity and venous diameter (Table 2). The mean postoperative blood flow velocity was 298.0 ± 55.45 mL/min, ranging from 200 to 400 mL/min. Functional AVFs demonstrated significantly higher flow velocities (337.69 ± 31.40 mL/min) compared to failed AVFs (255.0 ± 41.89 mL/min), with a p-value <0.001. This finding strongly supports postoperative flow velocity as the most reliable predictor of early AVF success, in line with KDOQI recommendations that suggest a flow >300 mL/min indicates adequate maturation and usability for haemodialysis [2,11]. TABLE 2: Doppler parameters & status of AVF at 2 months follow up Number of subjects 25 Velocity (ml/min) Diameter of Vein (mm) Minimum 200 3.00 Maximum 400 12.00 Median 300 6.00 Mean 298.00 6.62 Standard Deviation 55.45 2.59 Sl. No. Outcome No. of cases 1. Failure 12 2. Functional 13 Postoperative venous diameter showed a mean value of 6.62 ± 2.59 mm. While functional AVFs tended to have larger postoperative venous diameters (7.50 ± 2.38 mm) compared to failed AVFs (5.67 ± 2.57 mm), this difference did not reach statistical significance (p=0.077). The lack of significance may reflect ongoing venous remodelling beyond the two-month follow-up period, as vein dilation continues in the early months after fistula creation. Nonetheless, larger postoperative venous diameters in functional AVFs are consistent with KDOQI guidelines, which recommend a minimum venous diameter of ≥4 mm for cannulation [2]. Functional Outcome of AVFs At the end of the two-month follow-up, 13 patients (52%) had functional AVFs suitable for haemodialysis, whereas 12 patients (48%) experienced early AVF failure. Among failed AVFs, identifiable causes included failure of venous dilatation (n=2), anastomotic site stenosis (n=2), and arterial atherosclerotic changes (n=1). In the remaining seven cases, no definitive cause was apparent on Doppler evaluation, suggesting that subtle hemodynamic factors or microvascular disease may contribute to early dysfunction. These results underscore the multifactorial nature of AVF failure, where both anatomical and physiological factors must be considered. The observed early failure rate of 48% is consistent with published literature, which reports primary AVF failure rates of 40–55% despite adherence to recommended surgical and imaging protocols [5,7]. This highlights the ongoing challenge in optimizing early AVF success and the need for standardized, Doppler-guided assessment both preoperatively and postoperatively. Association of Demographic, Clinical, and Doppler Parameters with AVF Outcome Statistical analysis demonstrated that demographic factors such as age and gender did not significantly influence AVF functionality (p=0.435 and p=0.910, respectively). Similarly, the presence of diabetes mellitus and peripheral vascular disease showed no statistically significant association with AVF outcome (p=0.543 and p=0.125). These findings reinforce the importance of vascular anatomy and flow dynamics over patient-related factors in predicting early AVF success (Table 3). Table 3: Association of outcome with demographic, clinical & AVF characteristics Sl. No. Characteristic Failure (n=12) Functional (n=13) Statistical significance 1. Mean Age ± SD 36.25 ± 12.04 40.38 ± 13.82 t=0.794; p=0.435 No. % No. % 2 P 2. Gender Male 9 75.0 10 76.92 0.013 0.910 Female 3 25.0 3 23.08 3. Diabetes 5 41.67 7 53.85 0.371 0.543 4. Peripheral vascular disease 2 16.67 0 0.00 2.355 0.125 Among preoperative Doppler parameters, arterial diameter was significantly associated with functional outcomes, confirming its role as a critical determinant of fistula maturation. In contrast, venous diameter and vein depth, although slightly higher in functional AVFs, did not reach statistical significance, suggesting that adequate arterial inflow may be more important than baseline venous characteristics in determining early success (Table 4). Table 4: Association of Pre & Post operative Doppler Parameters with AVF outcome Sl. No. Characteristic Failure (n=12) Functional (n=13) Statistical significance Mean SD Mean SD "t" "p" Pre op Parameters 1. Diameter of artery (mm) 2.38 0.33 2.67 0.32 2.280 0.032 2. Diameter of Vein (mm) 7.13 2.42 7.35 2.38 0.230 0.820 3. Depth of vein from skin surface (mm) 7.25 1.53 8.00 1.38 1.287 0.211 Post op Parameters 1. Doppler Velocity (ml/min) 255.00 41.89 337.69 31.40 5.615 <0.001 2. Diameter of Vein (mm) 5.67 2.57 7.50 2.38 1.852 0.077 Postoperative Doppler parameters revealed that blood flow velocity was strongly predictive of AVF functionality. Functional fistulas exhibited higher mean flow velocities exceeding 330 mL/min, aligning with KDOQI criteria for early functional fistula assessment [2]. Postoperative venous diameter, although higher in functional AVFs, did not independently predict outcome, highlighting the dynamic nature of venous remodelling and the importance of flow-based evaluation in the early postoperative period.

Overview and Rationale This prospective observational study highlights the pivotal role of Doppler ultrasonography in predicting early functional outcomes of native arteriovenous fistulas for haemodialysis. The results demonstrate that preoperative arterial diameter and postoperative blood flow volume are the most reliable predictors of early AVF success, whereas demographic factors, comorbidities, and baseline venous characteristics exert limited influence when appropriate vascular mapping is performed. Early AVF failure remains a significant barrier to optimal dialysis delivery. The observed early failure rate of 48% in this study is consistent with published reports indicating primary failure rates between 40% and 55% despite adherence to recommended surgical techniques [5,7]. These findings reinforce the importance of meticulous preoperative assessment and early postoperative surveillance to improve outcomes. Doppler ultrasonography has emerged as the primary non-invasive modality for vascular evaluation, providing real-time information on vessel diameter, depth, patency, and flow characteristics. Its routine integration into vascular access planning and surveillance is strongly recommended by the Kidney Disease Outcomes Quality Initiative (KDOQI) guidelines [2]. However, consensus regarding the predictive value of specific Doppler parameters remains variable, warranting further investigation, as addressed in this study. Demographic and Clinical Characteristics The study population was relatively young, with a predominance of male patients. Neither age nor gender showed a statistically significant association with AVF functionality. While some studies suggest that advanced age and female gender may predispose to failure due to smaller vessel size or vascular disease [9,10], our findings support evidence that careful Doppler-based vessel selection can mitigate these risks [3,5]. Diabetes mellitus, despite its association with vascular calcification and endothelial dysfunction, did not significantly impact early AVF outcomes. This observation suggests that anatomical suitability and hemodynamic adequacy may outweigh systemic comorbidities in determining early success. Peripheral vascular disease showed a trend toward failure; however, the limited number of affected patients prevented definitive conclusions. Preoperative Vascular Assessment Among preoperative Doppler parameters, arterial diameter emerged as a key determinant of early AVF maturation. Functional AVFs had significantly larger arterial diameters, reinforcing the concept that adequate arterial inflow is essential for generating sufficient shear stress to promote venous dilation and remodelling. KDOQI guidelines recommend a minimum arterial diameter of 2 mm [2], and the present findings suggest that diameters exceeding this threshold may further enhance early success rates. In contrast, preoperative venous diameter did not significantly predict functionality once minimum size criteria were met. This supports previous observations that venous calibre alone is insufficient to ensure maturation without adequate arterial supply [10,11]. Although vein depth is an important practical consideration for cannulation, it did not significantly influence early AVF outcomes in this study. The mean vein depth exceeded the ideal KDOQI threshold of 6 mm, yet many fistulas remained functional. This suggests that while deeper veins may pose technical challenges, they do not necessarily compromise early hemodynamic maturation. Postoperative Flow as a Predictor of Success Postoperative blood flow volume was the strongest predictor of AVF functionality. Functional AVFs consistently demonstrated flow rates exceeding 300 mL/min, in accordance with KDOQI criteria for maturation [2]. These findings emphasize that flow-based assessment is a sensitive and practical tool for early postoperative surveillance, allowing identification of fistulas at risk of failure before clinical deterioration occurs. Postoperative venous diameter increased modestly in functional AVFs (7.50 ± 2.38 mm) but remained smaller in failed AVFs (5.67 ± 2.57 mm). While this difference approached significance (p=0.077), it suggests that venous dilation is a progressive process, often following sufficient arterial inflow. Consequently, flow-based measurements may detect early maturation issues before anatomical remodelling is complete, enabling timely intervention. Arterial diameters remained relatively stable postoperatively, with functional AVFs demonstrating slightly larger measurements (2.71 ± 0.31 mm) than failed AVFs (2.41 ± 0.36 mm, p=0.029). This reinforces the importance of adequate preoperative arterial size and highlights the predictive consistency of Doppler assessment from planning to postoperative monitoring. AVF Location and Type Forearm AVFs were the most common in this study (64%), consistent with KDOQI recommendations favouring distal sites to preserve proximal vasculature for future access [2]. Functional AVFs were slightly more frequent in the forearm (56%) than in the upper arm (44%), though the difference was not statistically significant. These findings support the principle that vessel quality, rather than anatomical location alone, is the critical determinant of early AVF success, particularly when Doppler mapping is utilized to guide access creation. Functional Outcomes and Early Failure Mechanisms At two months, 52% of AVFs were functional, whereas 48% failed to meet Doppler or clinical criteria for usability. Among failed AVFs, identifiable mechanisms included failure of venous dilation (two cases), anastomotic stenosis (two cases), and arterial atherosclerosis (one case). In seven patients, no clear Doppler-detectable cause was observed, suggesting the influence of microvascular disease, early neointimal hyperplasia, or subtle hemodynamic disturbances. These findings underscore the multifactorial nature of AVF failure, where both measurable and occult factors contribute. Early detection of flow compromise through Doppler ultrasonography may allow timely intervention, such as angioplasty or revision, before irreversible thrombosis occurs, ultimately improving long-term access survival. Comparison with Existing Literature The present findings align closely with previous studies that identify arterial diameter and postoperative flow as the most important predictors of early AVF success [8,10–12]. The limited predictive value of demographic and comorbidity variables further supports a shift toward anatomy- and flow-based decision-making in vascular access planning. The study also reinforces the clinical value of KDOQI-recommended thresholds for Doppler assessment. Preoperative artery >2 mm, vein >4 mm, and postoperative flow >300 mL/min were predictive of success, demonstrating that adherence to guideline-based evaluation can enhance early outcomes (Fig 2 a-e). Clinical Implications The integration of Doppler ultrasonography into routine AVF planning and surveillance has multiple advantages. Preoperatively, it enables identification of suitable vessels, guides site selection, and predicts potential complications. Postoperatively, flow-based surveillance allows early recognition of high-risk fistulas, providing opportunities for timely interventions such as angioplasty, banding, or surgical revision. This proactive approach aligns with KDOQI recommendations, emphasizing early detection and management to maximize AVF patency and dialysis adequacy [2,3]. Furthermore, reliance on anatomical and hemodynamic parameters rather than demographic or comorbidity profiles promotes equitable access to dialysis. Even patients with diabetes, hypertension, or advanced age may achieve successful AVF outcomes when appropriate Doppler-guided assessment is applied. Limitations Despite the strengths of this study, several limitations should be acknowledged. The sample size was relatively small (n=25), limiting statistical power to detect associations for less common variables such as peripheral vascular disease. The follow-up period was restricted to two months, which may not capture late failures, long-term patency, or maturation beyond the early postoperative period. Additionally, while Doppler ultrasonography provides valuable flow and anatomical data, it may not detect microvascular dysfunction, intimal hyperplasia, or subtle stenosis that can contribute to failure. Future studies with larger cohorts and longer follow-up are warranted to validate these findings.

Doppler ultrasonography provides critical, guideline-aligned information for both preoperative and postoperative evaluation of AVFs. Preoperative arterial diameter ≥2 mm and postoperative flow velocity >300 mL/min emerged as the most significant determinants of early AVF functionality, consistent with KDOQI recommendations. Demographic factors and comorbidities did not significantly influence outcomes. Routine Doppler assessment may enable early identification of fistulas at risk of failure, allowing timely intervention, improved vascular access outcomes, and reduced reliance on temporary catheters.

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