# Performance of Doppler ultrasound parameters for the detection of stenosis in distal arteriovenous fistulas

Jean Bréro, Adelaïde Guézais, Marjolaine Talbot, Quentin Tollenaere, Estelle

Le Pabic, Jean-Eudes Trihan, Damien Lanéelle, Guillaume Mahé

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Jean Bréro, Adelaïde Guézais, Marjolaine Talbot, Quentin Tollenaere, Estelle Le Pabic, et al. Performance of Doppler ultrasound parameters for the detection of stenosis in distal arteriovenous fistulas. Scientific Reports, 2025, 15 (1), pp.18622. 10.1038/s41598-025-03425-6. hal-05095229

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# Performance of Doppler ultrasound parameters for the detection of stenosis in distal arteriovenous fistulas

Jean Bréro<fnref n="1" />,³, Adelaïde Guézais<fnref n="1" />,³, Marjolaine Talbot<fnref n="1" />,³, Quentin Tollenaere<fnref n="1" />,³, Estelle Le Pabic<fnref n="1" />,³, Jean-Eudes Trihan⁴,⁵, Damien Lanéelle⁶,⁷ & Guillaume Mahé<fnref n="1" />,²,³✉

End-stage renal disease patients undergoing hemodialysis with arteriovenous fistula (AVF) access are at risk of stenosis in the draining vein of the AVF, which may lead to AVF thrombosis. However, Doppler ultrasound (DUS) parameters used to assess venous stenosis are numerous, and the thresholds to be used vary widely in the literature. Aims were to define DUS parameters to detect venous stenosis either severe or significant. This is a single-centre retrospective study including patients who underwent a routine DUS surveillance for distal radiocephalic AVF. At the axillary (Ax) and brachial (Brach) levels, blood flow (Q), resistance index (RI), Q/RI at Ax (Q/RI<sub>Ax</sub>) and Brach levels (Q/RI<sub>Brach</sub>) were studied. Severe (> 70%) and significant (> 55%) venous stenosis were defined in DUS B-mode as a minimal lumen diameter < 1.8 mm and < 2.7 mm, respectively. The receiver operating characteristic curve was used to define a specific cutoff point to detect venous stenosis. From January 2022 to November 2022, a total of 105 consecutive patients were included. For severe stenosis, the best Area Under the Curve (AUC) was 0.97 [95% Confidence Interval (CI): 0.94;1.00] for Q/RI<sub>brach</sub> with a cutoff value < 1284 ml/min/RI. Sensitivity and specificity were 100% [100;100] and 90.7% [84.9;96.5]. For significant stenosis, the best AUC was 0.89 [0.83;0.95] for Q/RI<sub>brach</sub> with a cutoff value < 2157 ml/min/RI. Sensitivity and specificity were 95.8% [87.8;100] and 70.4% [60.4;80.3]. In this pilot study, Q/RI was found to obtain the best AUC to exclude venous stenosis greater than 55 and 70% for radiocephalic AVF. A larger study remains to be performed to confirm these results.

**Keywords** Arterio-venous fistula, Stenosis, Blood flow, Resistive index

End-stage renal disease affects approximately 2 500,000 patients worldwide<fnref n="1" />. In France, approximately 93 000 patients will receive a renal replacement therapy in 2022 (of which 51,662 will receive hemodialysis)². Hemodialysis is therefore one of the ways (in addition to renal transplant) to replace kidney function, for which different vascular accesses can be used. A central venous catheter can used as the primary access for initiating hemodialysis, but is not a long-term solution due to the risk of infection³.

An arteriovenous fistula (AVF) is then the preferred vascular access⁴, providing sufficient blood flow for an effective hemodialysis by by-passing resistant arterioles. Unfortunately, stenosis is the most common complication of AVFs⁵, often due to neointimal hyperplasia⁶, which can lead to decreased blood flow and thus an increased risk of AVF thrombosis.

Depending on the degree of stenosis, the difficulty to perform the hemodialysis and the patient's symptoms, these stenoses may be candidates for an angioplasty⁷⁻⁹. Given their prevalence, a surveillance strategy seems to be justified, especially by Doppler ultrasound (DUS) evaluation, which is a non-invasive, effective, and accessible method¹⁰⁻¹².

Several DUS parameters such as blood flow (Q), resistance index (RI) and peak systolic velocity for the most used have been proposed and validated for the screening and evaluation of these AVFs stenoses¹¹,¹³⁻¹⁵. For instance, some authors have proposed to diagnose AVF stenosis using a Q<500 mL/min, or ≥25% decrease

<footnote n="1">¹Vascular Medicine Unit, CHU Rennes, 2 Rue Henri Le Guilloux, 35033 Rennes Cedex, France. ²Univ Rennes, M2S (Laboratoire Mouvement, Sport, Santé), Rennes, France. ³Inserm, CIC 1414 (Clinical Investigation Center), CHU Rennes, 35000 Rennes, France. ⁴Vascular Medicine Unit, Cholet Hospital, Cholet, France. ⁵Vascular Medicine Unit, CHU Angers, Angers, France. ⁶Vascular Medicine Unit, CHU Caen, Caen, France. ⁷UNICAEN, INSERM 1075, COMETE, Caen, France. ✉email: maheguillaume@yahoo.fr</footnote>
in Q compared to the previous measurement, or stenosis with anatomical significance (> 50% reduction in the vessel lumen) associated with hemodynamic significance (peak systolic velocity greater than 400 cm/s or PSV pre-stenosis/PSV stenosis ratio > 3); or using a peak systolic ratio > 2<sup>11,14,16</sup>. However, the ways of analyzing all these criteria and their thresholds vary widely from one study to another, taking into account the variability of the AVF anatomy, the number and location of the stenoses, the global cardio-vascular environment of the patient<sup>11,14,16-18</sup>.

The aim of this study is to determine the ability of different DUS parameters to detect stenosis of the draining vein defined as severe (> 70%) or significant (> 55%).

## Materials and methods

### Study population

From January to November 2022, we have retrospectively collected data over a period of 11 months from consecutive patients who underwent routine surveillance (one DUS/year) of their arteriovenous fistula (AVF) at the university hospital using duplex ultrasound (DUS). The study was approved by an institutional review board. The study protocol conforms to the ethical guidelines of the 1975 Declaration of Helsinki. We included patients with distal radiocephalic AVFs.

We excluded the following patients with: (i) examinations with patient redundancy (only the first examination was kept for a same patient), (ii) AVFs with multiple stenosis on their draining vein, (iii) draining vein occlusion, (iv) radial artery stenosis, (v) AVFs with a lack of maturation (i.e. less than 3 months after the AVF creation), (vi) and proximal AVFs (draining vein connected to the brachial artery).

### Demographic characteristics

The following data were collected: age, gender, presence or absence of diabetes, hypertension, dyslipidaemia, smoking status, personal vascular history (myocardial infarction, ischemic stroke, diagnose of lower extremity artrey disease), previous kidney transplant, previous AVF thrombosis, previous AVF angioplasty.

### Ultrasound methodology

Doppler ultrasound was performed at our vascular unit using a 7–10 MHz transducer as recommended (10) connected to echograph (Siemens Acuson Sequoia and Mindray Resona 7) by three different operators experienced in the AVF surveillance by DUS. Patients were assessed in a semi-recumbent position.

The DUS examination was then realized following a standardized protocol, for every patient:

* Recording of the blood flow (Q) and resistive index (RI) in the axillary (Q<sub>ax</sub> and RI<sub>ax</sub>) and brachial artery (Q<sub>brach</sub> and RI<sub>brach</sub>). The blood flow (Q) was automatically calculated by measuring the vessel diameter (D) and the time average velocity (TAV) through the formula: Q (mL/min) = TAV (cm/s) × D/2 (cm) × D/2 (cm) × π × 60. The RI was automatically calculated using the following formula: (PSV – EDV)/PSV, (PSV: Peak Systolic Velocity, EDV: End Diastolic Velocity).

* Assessment of the inflow artery, anastomosis and outflow veins through B-mode and color Doppler to determine the presence of a stenosis.

* If a stenosis was detected on the draining vein, its minimal vessel diameter (D) was measured (in mm, using B-mode in an axial view, and delimited by the inner limits of the vessel lumen).

For the DUS procedure, the operator performed the following sequence: (i) measurement of the axillary artery diameter; (ii) three measurements of the Q<sub>ax</sub> and measurement of the RI<sub>ax</sub>; measurement of the brachial artery diameter; (iv) three measurements of the Q<sub>brach</sub> and measurement of RI<sub>brach</sub>; (v) measurement of the anastomosis; (vi) measurement of the venous stenosis; (vii) measurements of the cephalic vein diameter and basilic vein diameter. This sequence allows Q and RI to be measured without knowing whether or not there is a venous stenosis. The transducer was oriented to obtain an insonation angle ≤ 60° with the window size encompassed the entire arterial lumen to sample the total blood flow velocity. The arterial diameter was measured from intima to intima and three consecutive measurements of Q were performed. Finally, the mean Q/RI ratio was calculated for the axillary (Q/RI<sub>ax</sub>) and brachial artery (Q/RI<sub>brach</sub>)<sup>17</sup>. In theory, stenosis leads to a decrease in Q and an increase in RI, but these variations may not be significant enough to be detected, which has led to the development of this index which, by dividing the former by the latter, seems to improve the prediction of AVF thrombosis<sup>17</sup>.

### Statistical analysis

For data description, quantitative results are expressed as mean ± standard deviation and (min; Q1; median; Q3; max). Qualitative results are expressed as number (%). For group comparisons between stenosis (either severe or significant) group and no stenosis group, the Mann-Whitney Wilcoxon test (W) if necessary was used to compare quantitative variables, and the Chi2 test or Fisher's exact test if necessary was used to compare qualitative variables.

Diagnostic accuracy (sensitivity, specificity, positive predictive value, negative predictive value) were first performed for the different DUS parameters in all the groups (Q<sub>ax</sub>, Q<sub>brach</sub>, RI<sub>ax</sub>, RI<sub>brach</sub>, Q/RI<sub>ax</sub>, Q/RI<sub>brach</sub>).

The receiver-operating-characteristic (ROC) curve was used to define a cut-off point corresponding to the best area under the curve (AUC; [Confidence Interval 95%]) to detect venous stenosis of the AVFs as determined by the DUS B-mode<sup>19</sup>. We calculated the positive (PPV) and negative predictive values (NPV) of the thresholds determined from the ROC curves. The aim of this exploratory analysis was to compare the AUCs of the different parameters, without prejudging the interest of maximizing the PPV (as in the case of AVF dysfunction) or the NPV (as in the case of systematic follow-up).
We performed two levels of analysis according to the previous definition of venous stenosis published in the literature. We defined severe venous stenosis in mode B as a diameter of the venous lumen less than or equal to 1.7 mm. This threshold was chosen as corresponding to 30% of circulating diameter from an expected diameter of 6 mm at 6 weeks⁴. We chose this criterion considering the rules of 6 from the KDOQI guidelines, stating that AVFs are functional with a minimum vessel diameter of the draining vein of 6 mm; thus, a stenosis equal or superior to 70% lumen reduction in diameter (30% of circulating diameter) corresponded to a diameter inferior or equal to 1.7 mm (6 mm × 30% = 1.8 mm). Furthermore, a significant stenosis corresponds to a venous lumen diameter inferior or equal to 2.7 mm²⁰. This diameter was previously defined as a threshold to discriminate functional from dysfunctional AVFs among patients with radiocephalic AVF who were dialyzing inadequately.

Then comparisons of the AUC of the ROC curves for all the DUS parameters were performed using the Delong test, in the *Severe stenosis* group and the *Significant stenosis* group¹⁹,²¹.

All statistical tests had a significance level of 0.05. Statistical analyses were performed using Sas software, v.9.4 (Sas Institute, Cary, NC, USA).

# Results

## Main population

From January to November 2022, 190 examinations were performed for routine surveillance of an AVF (Fig. 1). A total of 105 patients were included from January to November 2022. Thirty were excluded because of patient redundancy (only the first examination for the same patient was considered), 23 were excluded because of the presence of multiple stenosis, 3 were excluded because of a draining vein occlusion, 3 were excluded because of the presence of a radial artery stenosis, 2 were excluded because of an AVF lacking maturation, and 25 were excluded because the AVF was located on the brachial artery. For the *Severe stenosis* branch of analysis, 8 of

<figure><img src="image_3.png" /><figcaption>**Fig. 1.** Flow chart of the included patients</figcaption></figure>
them were categorized in the stenosis group (and 97 in the control group). For the *Significant stenosis* branch of analysis, 24 of them were categorized in the stenosis group (and 81 in the control group).

The mean age of the population was 62.64±16.95 years. The majority were men (66.7%), and a large proportion had hypertension (82.9%) and a history of vascular events (66.7%). About half of them were active or former smoker (46.7%). Few had a previous kidney transplant (2.9%) and most had never undergone angioplasty of the draining vein (67.6%). Of the 105 patients included in this study, 16 had an AVF created for less than one year, 61 had an AVF created between 2 and 5 years, and 28 had an AVF created for more than 5 years. The characteristics of the patients according to the severity of the venous stenosis are presented in Tables 1 and 2. There were no significant differences between the characteristics of the *Stenosis* either severe or significant groups and *No stenosis* groups.

## DUS parameters analysis

In the overall population, the mean Q<sub>ax</sub> was 1358.9±454.8 ml/min and the mean Q<sub>brach</sub> was 1194.7±441.0 ml/min. The mean RI<sub>ax</sub> and RI<sub>brach</sub> were 0.64±0.10 and 0.54±0.09, respectively. Compared to the *No stenosis* group, the both *stenosis* groups had significantly lower mean levels of Q and Q/RI at the axillary artery and brachial artery levels (Tables 1 and 2).

For the diagnosis of severe stenosis, the best AUC (0.97[0.94;1.00]) was found for the Q/RI<sub>brach</sub> whereas the lowest AUC (0.73[0.52;0.93]) was found for the RI<sub>brach</sub>. All results are presented in Table 3; Fig. 2.

For the diagnosis of significant stenosis, the best AUC (0.89[0.83;0.95]) was found for the Q/RI<sub>brach</sub> whereas the lowest AUC (0.68 [0.54;0.81]) was found for the RI<sub>ax</sub>. All results are presented in Table 3; Fig. 3.

In the *Severe stenosis* group, the performance of Q/RI<sub>ax</sub> and Q/RI<sub>brach</sub> was significantly superior only to RI<sub>brach</sub> (p = 0.0247 and p = 0.0129; respectively), as well as for the performance of Q<sub>brach</sub> which was only significantly superior to RI<sub>brach</sub> (p = 0.0217). For Q<sub>ax</sub> and RI<sub>ax</sub>, there was no significant difference with the other parameters AUC (and thus, no difference statistically significant in terms of performance). This is represented in Table 4.

<table><caption>**Table 1.** Characteristics of the population in the *Severe stenosis* branch Qualitative results are presented as: effectives (%) for each modality. Fisher (F). Quantitative results are presented as: mean ± standard deviation or (min; Q1; median; Q3; max). Mann-Whitney Wilcoxon (W) DUS Doppler ultrasound, CV cardio vascular, LEAD lower extremity artery disease, AVF arterio-veinous fistula</caption><thead><tr><th>Variable</th><th>Global<br>n=105</th><th>Severe stenosis<br>n=8</th><th>No severe stenosis<br>n=97</th><th>p</th></tr></thead><tbody><tr><td><strong>Clinical characteristics</strong></td><td></td><td></td><td></td><td></td></tr><tr><td>Age (years)</td><td>62.64 ± 16.95 (20; 50; 64; 75; 91)</td><td>67.00 ± 21.14 (20; 63; 72; 77.5; 91)</td><td>62.28 ± 16.65 (20; 50; 63; 75; 89)</td><td>p = 0.2742<br>(W)</td></tr><tr><td>Gender</td><td></td><td></td><td></td><td></td></tr><tr><td>Male</td><td>70 (66.7%)</td><td>5 (62.5%)</td><td>65 (67.0%)</td><td>p = 1.0000 (K)</td></tr><tr><td><strong>Medical history</strong></td><td></td><td></td><td></td><td></td></tr><tr><td>Diabetes</td><td>36 (34.3%)</td><td>2 (25.0%)</td><td>34 (35.1%)</td><td>p = 0.7122 (F)</td></tr><tr><td>High blood pressure</td><td>87 (82.9%)</td><td>8 (100%)</td><td>79 (81.4%)</td><td>p = 0.3457 (F)</td></tr><tr><td>Dyslipidemia</td><td>55 (52.4%)</td><td>6 (75.0%)</td><td>49 (50.5%)</td><td>p = 0.2744 (F)</td></tr><tr><td>History of smoking</td><td>49 (46.7%)</td><td>3 (37.5%)</td><td>46 (47.4%)</td><td>p = 0.7209 (F)</td></tr><tr><td>History of CV events (LEAD, stroke, myocardial infarction)</td><td>35 (33.3%)</td><td>3 (37.5%)</td><td>32 (33.0%)</td><td>p = 1.0000 (F)</td></tr><tr><td>Number of renal transplant</td><td></td><td></td><td></td><td></td></tr><tr><td>0</td><td>83 (79.0%)</td><td>7 (87.5%)</td><td>76 (78.4%)</td><td>p = 1.0000 (F)</td></tr><tr><td>1</td><td>18 (17.1%)</td><td>1 (12.5%)</td><td>17 (17.5%)</td><td>p = 1.0000 (F)</td></tr><tr><td>2</td><td>4 (3.8%)</td><td>0 (0.0%)</td><td>4 (4.1%)</td><td>p = 1.0000 (F)</td></tr><tr><td>History of AVF thrombosis</td><td>3 (2.9%)</td><td>0 (0.0%)</td><td>3 (3.1%)</td><td>p = 1.0000 (F)</td></tr><tr><td>History of AVF angioplasty</td><td></td><td></td><td></td><td></td></tr><tr><td>No</td><td>71 (67.6%)</td><td>3 (37.5%)</td><td>68 (70.1%)</td><td>p = 0.0957 (F)</td></tr><tr><td>Less than 5</td><td>31 (29.5%)</td><td>5 (62.5%)</td><td>26 (26.8%)</td><td>p = 0.0957 (F)</td></tr><tr><td>More than 5</td><td>3 (2.9%)</td><td>0 (0.0%)</td><td>3 (3.1%)</td><td>p = 0.0957 (F)</td></tr><tr><td><strong>Dus criteria</strong></td><td></td><td></td><td></td><td></td></tr><tr><td>Axillary blood flow (Q<sub>ax</sub>) (mL/min)</td><td>1358.9 ± 454.78 (457.0; 1025.0; 1367.0; 1661.0; 1734.0)</td><td>683.50 ± 225.25 (457.0; 521.0; 629.0; 789.5; 1132.0)</td><td>1414.6 ± 423.34 (660.0; 1080.0; 1422.0; 1696.0; 1734.0)</td><td>p < 0.0001<br>(W)</td></tr><tr><td>Brachial blood flow (Q<sub>brach</sub>) (mL/min)</td><td>1194.7 ± 440.96 (339.0; 921.0; 1137.0; 1479.0; 2533.0)</td><td>517.13 ± 140.74 (339.0; 395.0; 509.5; 639.5; 710.0)</td><td>1250.5 ± 409.63 (437.0; 1001.0; 1171.0; 1511.0; 2533.0)</td><td>p < 0.0001<br>(W)</td></tr><tr><td>Axillary resistive index (RI<sub>ax</sub>)</td><td>0.64 ± 0.10 (0.42; 0.58; 0.63; 0.70; 0.88)</td><td>0.75 ± 0.09 (0.58; 0.71; 0.76; 0.81; 0.84)</td><td>0.63 ± 0.09 (0.42; 0.57; 0.62; 0.69; 0.88)</td><td>p = 0.0020<br>(W)</td></tr><tr><td>Brachial resistive index (RI<sub>brach</sub>)</td><td>0.54 ± 0.09 (0.37; 0.47; 0.53; 0.59; 0.79)</td><td>0.61 ± 0.11 (0.46; 0.54; 0.61; 0.69; 0.77)</td><td>0.53 ± 0.09 (0.37; 0.47; 0.52; 0.58; 0.79)</td><td>p = 0.0348<br>(W)</td></tr><tr><td>Axillary Q/RI (Q/RI<sub>ax</sub>) (mL/min/RI)</td><td>2231.2 ± 915.96 (544.05; 1562.3; 2223.5; 2790.9; 6085.7)</td><td>920.05 ± 268.54 (544.05; 717.25; 897.26; 1111.7; 1363.9)</td><td>2339.3 ± 865.2 (750.0; 1725.4; 2294.0; 1854.8; 6085.7)</td><td>p < 0.0001<br>(W)</td></tr><tr><td>Brachial Q/RI (Q/RI<sub>brach</sub>) (mL/min/RI)</td><td>2322.8 ± 1060.5 (490.41; 1551.7; 2258.9; 2888.9; 6846.0)</td><td>862.76 ± 258.82 (490.41; 643.53; 919.91; 1000.4; 1284.0)</td><td>2443.2 ± 1010.6 (620.0; 1738.6; 2298.0; 2983.0; 6846.0)</td><td>p < 0.0001<br>(W)</td></tr></tbody></table>
<table><caption>**Table 2.** Characteristics of the population in the *Significant stenosis* branch Qualitative results are presented as: effectives (%) for each modality. Chi2 (K) or Fisher (F). Quantitative results are presented as: mean ± standard deviation or (min; Q1; median; Q3; max). Mann-Whitney Wilcoxon (W) DUS Doppler ultrasound, CV cardio vascular, LEAD lower extremity artery disease, AVF arterio-veinous fistula</caption><thead><tr><th>Variable</th><th>Global<br>n=105</th><th>Significant stenosis<br>n=24</th><th>No significant stenosis<br>n=81</th><th>p</th></tr></thead><tbody><tr><td colspan="5"><strong>Clinical characteristics</strong></td></tr><tr><td>Age (years)</td><td>62.64 ± 16.95<br>(20; 50; 64; 75; 91)</td><td>67.50 ± 17.87<br>(20; 58; 70; 79; 91)</td><td>61.20 ± 16.61<br>(20; 50; 63; 74; 88)</td><td>p = 0.0604<br>(W)</td></tr><tr><td>Gender</td><td></td><td></td><td></td><td></td></tr><tr><td>Male</td><td>70 (66.7%)</td><td>16 (66.7%)</td><td>54 (66.7%)</td><td>p = 1.0000 (K)</td></tr><tr><td colspan="5"><strong>Medical history</strong></td></tr><tr><td>Diabetes</td><td>36 (34.3%)</td><td>5 (20.8)</td><td>31 (38.3%)</td><td>p = 0.1139 (K)</td></tr><tr><td>High blood pressure</td><td>87 (82.9%)</td><td>20 (83.3%)</td><td>67 (82.7%)</td><td>p = 1.0000 (F)</td></tr><tr><td>Dyslipidemia</td><td>55 (52.4%)</td><td>16 (66.7%)</td><td>39 (48.1%)</td><td>p = 0.1106 (K)</td></tr><tr><td>History of smoking</td><td>49 (46.7%)</td><td>12 (50.0%)</td><td>37 (45.7%)</td><td>p = 0.7094 (K)</td></tr><tr><td>History of CV events (LEAD, stroke, myocardial infarction)</td><td>35 (33.3%)</td><td>11 (45.8%)</td><td>24 (29.6%)</td><td>p = 0.1391 (K)</td></tr><tr><td>Number of renal transplant</td><td></td><td></td><td></td><td></td></tr><tr><td>0</td><td>83 (79.0%)</td><td>20 (83.3%)</td><td>63 (77.8%)</td><td rowspan="3">p = 0.8959 (F)</td></tr><tr><td>1</td><td>18 (17.1%)</td><td>3 (12.5%)</td><td>15 (18.5%)</td></tr><tr><td>2</td><td>4 (3.8%)</td><td>1 (4.2%)</td><td>3 (3.7%)</td></tr><tr><td>History of AVF thrombosis</td><td>3 (2.9%)</td><td>0 (0.0%)</td><td>3 (3.7%)</td><td>p = 1.0000 (F)</td></tr><tr><td>History of AVF angioplasty</td><td></td><td></td><td></td><td></td></tr><tr><td>No</td><td>71 (67.6%)</td><td>13 (54.2%)</td><td>58 (71.6%)</td><td rowspan="3">p = 0.2430 (F)</td></tr><tr><td>Less than 5</td><td>31 (29.5%)</td><td>10 (41.7%)</td><td>21 (25.9%)</td></tr><tr><td>More than 5</td><td>3 (2.9%)</td><td>1 (4.2%)</td><td>2 (2.5%)</td></tr><tr><td colspan="5"><strong>DUS criteria</strong></td></tr><tr><td>Axillary blood flow (Q<sub>ax</sub>) (mL/min)</td><td>1358.9 ± 454.78<br>(457.0; 1025.0; 1367.0; 1661.0; 1734.0)</td><td>1017.7 ± 415.25<br>(457.0; 673.0; 916.0; 1375.0; 1852.0)</td><td>1460.0 ± 417.15<br>(660.0; 1147.0; 1451.0; 1718.0; 2734.0)</td><td>p < 0.0001<br>(W)</td></tr><tr><td>Brachial blood flow (Q<sub>brach</sub>) (mL/min)</td><td>1194.7 ± 440.96 (339.0; 921.0; 1137.0; 1479.0; 2533.0)</td><td>795.29 ± 293.70 (339.0; 517.0; 770.50; 1075.0; 1207.0)</td><td>1313.0 ± 407.38 (599.0; 1081.0; 1231.0; 1597.0; 2533.0)</td><td>p < 0.0001<br>(W)</td></tr><tr><td>Axillary resistive index (RI<sub>ax</sub>)</td><td>0.64 ± 0.10 (0.42; 0.58; 0.63; 0.70; 0.88)</td><td>0.69 ± 0.10 (0.50; 0.59; 0.69; 0.76; 0.88)</td><td>0.62 ± 0.09 (0.42; 0.56; 0.62; 0.67; 0.84)</td><td>p = 0.0083<br>(W)</td></tr><tr><td>Brachial resistive index (RI<sub>brach</sub>)</td><td>0.54 ± 0.09 (0.37; 0.47; 0.53; 0.59; 0.79)</td><td>0.60 ± 0.09 (0.46; 0.53; 0.59; 0.66; 0.77)</td><td>0.52 ± 0.08 (0.37; 0.46; 0.50; 0.57; 0.79)</td><td>p = 0.0002<br>(W)</td></tr><tr><td>Axillary Q/RI (Q/RI<sub>ax</sub>) (mL/min/RI)</td><td>2231.2 ± 915.96 (544.05; 1562.3; 2223.5; 2790.9; 6085.7)</td><td>1559.2 ± 781.72 (544.05; 956.85; 1330.1; 2375.3; 3193.1)</td><td>2430.3 ± 859.87 (838.10; 1892.2; 2294.9; 2936.4; 6085.7)</td><td>p < 0.0001<br>(W)</td></tr><tr><td>Brachial Q/RI (Q/RI<sub>brach</sub>) (mL/min/RI)</td><td>2322.8 ± 1060.5 (490.41; 1551.7; 2258.9; 2888.9; 6846.0)</td><td>1355.9 ± 549.41 (490.41; 919.91; 1345.2; 1909.2; 2269.8)</td><td>2609.3 ± 1005.9 (857.53; 2053.7; 2361.4; 3302.4; 6846.0)</td><td>p < 0.0001<br>(W)</td></tr></tbody></table>

Concerning the comparisons of the AUC for all the parameters in the *Significant stenosis* group, the performance of Q/RI<sub>brach</sub> was significantly superior to all the other parameters. The other parameters had no other statistically significant difference between one another.

### Patients follow-up

Of the patients in the *Severe stenosis* group, all of them had an AVF angioplasty in the month following the DUS appointment. Of the patients in the *Significant stenosis* group, 10 had an AVF angioplasty in the month following the DUS appointment, nine had an angioplasty with a delay between the DUS and the angioplasty equal to 8.4+/-4.0 months and 5 had no AVF angioplasty by the end of follow-up (i.e. 3 years of follow-up).

### Discussion

Our study confirms that DUS parameters are accurate for excluding severe and significant venous stenosis of distal radiocephalic AVFs. For both degrees of venous stenosis studied, the best AUC was found for the Q/RI<sub>brach</sub> index while the lowest AUC was found for the RI.

The RI and Q parameters, which are recommended in several consensus, are commonly used in clinical practice to assess the AVF function<sup>22</sup>. However, our results suggest that they may not to be the most accurate DUS parameters to detect venous stenosis in case of AVFs. RI mainly depends on vascular resistances below the point of DUS recording whereas Q depends on vessel diameter but also on central hemodynamics and can be modified by arrhythmia, tachycardia and left ventricular ejection function<sup>23,24</sup>. This may explain some inaccuracies in some cases to detect venous stenosis. Therefore, it was important to compare the accuracies of these parameters to other DUS parameters.

A previous study by Colombo and colleagues has suggested the use of a new surrogate DUS marker called Q/RI index with a high AUC greater than 0.95<sup>17</sup>. Our results are consistent with these previous findings. Of
<table><caption>**Table 3.** Thresholds and AUC from the ROC curves for the different DUS criteria in the *Severe stenosis* branch and *Significant stenosis* branch. Results are presented in percentage with a 95% confidence index $Q_{ax}$. Blood flow in the axillary artery, $Q_{brach}$. Blood flow in the brachial artery, $RI_{ax}$. Resistive index in the axillary artery, $RI_{brach}$. Resistive index in the brachial artery, $Q/RI_{ax}$. Q/RI index in the axillary artery, $Q/RI_{brach}$. Q/RI index in the brachial artery, *PPV*. Positive predictive value, *NPV*. Negative predictive value, *AUC*. Area under curve, *DUS*. Doppler ultrasound</caption><thead><tr><th colspan="7">Severe stenosis branch</th></tr><tr><th>DUS criteria</th><th>Threshold</th><th>Sensitivity</th><th>Specificity</th><th>PPV</th><th>NPV</th><th>AUC</th></tr></thead><tbody><tr><td>Q<sub>ax</sub> (mL/min)</td><td>&lt;893</td><td>87.5% [64.6%; 100%]</td><td>88.66% [82.3%; 95%]</td><td>38.89% [16.4%; 61.4%]</td><td>98.85% [96.6%; 100%]</td><td>0.95 [0.88; 1.00]</td></tr><tr><td>Q<sub>brach</sub> (mL/min)</td><td>&lt;710</td><td>100% [100%; 100%]</td><td>89.69 [83.6%; 95.7]</td><td>44.44% [21.5%; 67.4%]</td><td>100% [100%; 100%]</td><td>0.97 [0.94; 1.00]</td></tr><tr><td>RI<sub>ax</sub></td><td>&gt;0.73</td><td>75% [45%; 100%]</td><td>86.8% [79.8%; 93.4%]</td><td>31.58% [10.7%; 52.5%]</td><td>97.67% [94.5%; 100%]</td><td>0.83 [0.66; 1.00]</td></tr><tr><td>RI<sub>brach</sub></td><td>&gt;0.60</td><td>62.5% [29%; 96%]</td><td>79.38 [71.3%; 87.4%]</td><td>20% [4.3%; 35.7%]</td><td>96.25% [92.1%; 100%]</td><td>0.73 [0.52; 0.93]</td></tr><tr><td>Q/RI<sub>ax</sub> (mL/min/RI)</td><td>&lt;1363</td><td>100% [100%; 100%]</td><td>86.6% [79.8%; 93.4%]</td><td>38.1% [17.3%; 58.9%]</td><td>100% [100%; 100%]</td><td>0.96 [0.91; 1.00]</td></tr><tr><td>Q/RI<sub>brach</sub> (mL/min/RI)</td><td>&lt;1284</td><td>100% [100%; 100%]</td><td>90.72 [84.9%; 96.5%]</td><td>47.06% [23.3%; 70.8%]</td><td>100% [100%; 100%]</td><td>0.97 [0.94; 1.00]</td></tr></tbody><thead><tr><th colspan="7">Significant stenosis branch</th></tr><tr><th>DUS criteria</th><th>Threshold</th><th>Sensitivity</th><th>Specificity</th><th>PPV</th><th>NPV</th><th>AUC</th></tr></thead><tbody><tr><td>Q<sub>ax</sub> (mL/min)</td><td>&lt;966</td><td>58.33 [38.6%; 78.1%]</td><td>88.89 [82%; 95.7%]</td><td>60.87% [40.9%; 80.8%]</td><td>87.8% [80.7%; 94.9%]</td><td>0.78 [0.66; 0.89]</td></tr><tr><td>Q<sub>brach</sub> (mL/min)</td><td>&lt;983</td><td>70.83 [52.6%; 89%]</td><td>81.48 [73%; 89.9]</td><td>53.13% [35.8%; 70.4%]</td><td>90.41% [83.7%; 97.2%]</td><td>0.84 [0.76; 0.92]</td></tr><tr><td>RI<sub>ax</sub></td><td>&gt;0.68</td><td>62.5% [43.1%; 81.9%]</td><td>76.54 [67.3%; 85.8%]</td><td>44.12% [27.4%; 60.8%]</td><td>87.32% [79.6%; 95.1%]</td><td>0.68 [0.54; 0.81]</td></tr><tr><td>RI<sub>brach</sub></td><td>&gt;0.52</td><td>87.5% [74.3%; 100%]</td><td>53.09 [42.2%; 64%]</td><td>35.59% [23.4%; 47.8%]</td><td>93.48% [86.3%; 100%]</td><td>0.76 [0.65; 0.86]</td></tr><tr><td>Q/RI<sub>ax</sub> (mL/min/RI)</td><td>&lt;1637</td><td>66.67 [47.8%; 85.5%]</td><td>8.95 [76%; 91.9%]</td><td>55.17% [37.1%; 73.3%]</td><td>89.47% [82.6%; 96.4%]</td><td>0.77 [0.66; 0.89]</td></tr><tr><td>Q/RI<sub>brach</sub> (mL/min/RI)</td><td>&lt;2156</td><td>95.83 [87.8%; 100%]</td><td>70.37 [60.4%; 80.3%]</td><td>48.94% [34.6%; 63.2%]</td><td>98.28% [94.9%; 100%]</td><td>0.89 [0.83; 0.95]</td></tr></tbody></table>

interest, the patients included in the study by Colombo et al. had to have at least one clinical sign of possible AVF stenosis and could have either proximal or distal AVFs. Thus, the interest of our study is that we focused only on distal AVFs, which is the most common localization of AVFs, avoiding possible heterogeneous results by assessing proximal fistulas with DUS measurement at the brachial artery level. All of these elements especially the outcome can also explain the difference between our cut-offs for the Q/RI index (1 284 mL/min/RI to detect a severe stenosis and 2156 mL/min/RI to detect a significant stenosis) and the cut-off of Q/RI index (3 333 mL/min/RI) found by Colombo¹⁷.

Furthermore, our results show that the Q/RI index is significantly better than the other parameters studied in this work when the degree of venous stenosis is lower. This means that the Q/RI index should be preferred in clinical practice when looking for the exclusion of an early venous stenosis in radiocephalic AVFs.

Another question that remains is where to measure the DUS parameters when assessing an AVF. Our study suggests a trend towards more accurate results when DUS parameters are measured at the brachial level for radiocephalic AVFs. This issue remains for proximal AVFs.

At the brachial level, the blood flow cut-off found in our study ranges from <710 to <983 ml/min depending on the degree of venous stenosis. This is slightly higher than the usual blood flow values found in the literature⁴,¹¹,²⁵,²⁶. Several reasons may explain these discrepancies, including: (i) the definition of the vascular access dysfunction itself (e.g., are the criteria a degree of stenosis or difficulties during hemodialysis or a combination of several criteria?)²⁷,²⁸; (ii) the gold standard used to measure the degree of stenosis when this criterion is chosen; (iii) the localization of the AVFs, since it is said that blood flow is usually higher in proximal than in distal AVFs¹¹,²⁹; (iv) the methodological issues (localization, diameter) for the blood flow measurement (e.g., some authors performed the measurement in the venous branch of the AVF, while others performed the measurement in the artery); (v) the type (native, graft) of AVF has to be considered; and (vi) the number of venous stenosis. Thus, all of these factors need to be considered when comparing results across studies.

Our cut-offs for RI at the brachial level were 0.52–0.60 which are close to the published RI³⁰. As expected, the RI cut-off increases with the degree of venous stenosis measured. The strength of our study is that we included consecutive patients with a distal AVF and a unique venous stenosis on the AVF.

## Limitations

Our study has several limitations. First the gold standard used to quantify the degree of venous stenosis was DUS and not fistulography. However, due to ethical considerations, it was not possible to propose a systematic fistulography, which is an invasive procedure, to patients with no clinical or DUS evidence of venous stenosis. Of interest, all patients who had a severe stenosis described with DUS had and angioplasty confirming the severity of the stenosis. Furthermore, good accuracy between DUS findings and fistulography has been reported¹⁰,²⁷.
<figure><img src="image_4.png" /><figcaption>**Fig. 2.** ROC curves of the DUS parameters, considering the presence of AVF severe stenosis as status variable. Q<sub>ax</sub> Blood flow in the axillary artery, Q<sub>brach</sub> Blood flow in the brachial artery, R<sub>I ax</sub> Resistive index in the axillary artery, R<sub>I brach</sub> Resistive index in the brachial artery, Q/R<sub>I ax</sub> Q/RI index in the axillary artery, Q/R<sub>I brach</sub> Q/RI index in the brachial artery</figcaption></figure>

Second, we studied only two degrees of venous stenosis: one corresponding to a criterion proposed by Fahrtash et al. and another corresponding to 70% stenosis when considering a normal development of the AVF with a 6 mm venous diameter proposed by the KDOQI guidelines⁴,²⁰. Third, we did not assess the reproducibility of the DUS measurements in this specific situation. However, coefficients of variation (i.e. CV = standard deviation of the measurements divided by the mean Q*100) in this study for Q<sub>ax</sub> and Q<sub>brach</sub> were 6.9% and 6.2%, respectively. Fourth, other parameters as peak velocity inside the stenosis or peak velocity ratio were also proposed as stenosis criterion in the literature but were not studied in this study. These parameters remain to be studied. Fourth, no sample size calculation was done for this pilot study. However, there was no previous study with a well-characterized population, so we conducted this pilot study with the idea that the present study could be used for further studies to calculate sample size. Fifth, this is a retrospective monocentre study that should be considered as a pilot study and larger multicentre study are needed to confirm these results with another gold standard (fistulography or computed tomography angiography) and to study of the intra and inter-operator reproducibility.

Conclusion

This study confirms that an impaired Q/RI index is a criterion of interest to investigate the existence of a venous AVF stenosis. External validation of this criterion should be performed in a larger study to confirm this promising result.
<figure><img src="image_5.png" /><figcaption>**Fig. 3.** ROC curves of the DUS parameters, considering the presence of AVF significant stenosis as status variable. Q<sub>ax</sub> Blood flow in the axillary artery, Q<sub>brach</sub> Blood flow in the brachial artery, RI<sub>ax</sub> Resistive index in the axillary artery, RI<sub>brach</sub> Resistive index in the brachial artery, Q/RI<sub>ax</sub> Q/RI index in the axillary artery, Q/RI<sub>brach</sub> Q/RI index in the brachial artery</figcaption></figure>
<table><thead><tr><th colspan="6">Severe stenosis branch</th></tr><tr><th></th><th>Q<sub>ax</sub></th><th>Q<sub>brach</sub></th><th>RI<sub>ax</sub></th><th>RI<sub>brach</sub></th><th>Q/RI<sub>ax</sub></th><th>Q/RI<sub>brach</sub></th></tr></thead><tbody><tr><th>Q<sub>ax</sub></th><td></td><td>0.5505</td><td>0.2506</td><td>0.0567</td><td>0.7450</td><td>0.5889</td></tr><tr><th>Q<sub>brach</sub></th><td>0.5505</td><td></td><td>0.0915</td><td><strong>0.0217</strong></td><td>0.4982</td><td>0.8511</td></tr><tr><th>RI<sub>ax</sub></th><td>0.2506</td><td>0.0915</td><td></td><td>0.2513</td><td>0.1439</td><td>0.0677</td></tr><tr><th>RI<sub>brach</sub></th><td>0.0567</td><td><strong>0.0217</strong></td><td>0.2513</td><td></td><td><strong>0.0247</strong></td><td><strong>0.0129</strong></td></tr><tr><th>Q/RI<sub>ax</sub></th><td>0.7450</td><td>0.4982</td><td>0.1439</td><td><strong>0.0247</strong></td><td></td><td>0.4901</td></tr><tr><th>Q/RI<sub>brach</sub></th><td>0.5889</td><td>0.8511</td><td>0.0677</td><td><strong>0.0129</strong></td><td>0.4901</td><td></td></tr></tbody></table>

<table><caption>**Table 4.** AUC comparison between all the DUS criteria in the *Severe stenosis* branch and *Significant stenosis* branch. DUS criteria were all compared with each other using Delong test $Q_{ax}$ Blood flow in the axillary artery, $Q_{brach}$ Blood flow in the brachial artery, $RI_{ax}$ Resistive index in the axillary artery, $RI_{brach}$ Resistive index in the brachial artery, $Q/RI_{ax}$ Q/RI index in the axillary artery, $Q/RI_{brach}$ Q/RI index in the brachial artery Bold represents the results are statistically significant with the Delong test.</caption><thead><tr><th colspan="6">Significant stenosis branch</th></tr><tr><th></th><th>Q<sub>ax</sub></th><th>Q<sub>brach</sub></th><th>RI<sub>ax</sub></th><th>RI<sub>brach</sub></th><th>Q/RI<sub>ax</sub></th><th>Q/RI<sub>brach</sub></th></tr></thead><tbody><tr><th>Q<sub>ax</sub></th><td></td><td>0.1308</td><td>0.1453</td><td>0.7679</td><td>0.9212</td><td><strong>0.0124</strong></td></tr><tr><th>Q<sub>brach</sub></th><td>0.1308</td><td></td><td><strong>0.0084</strong></td><td>0.1690</td><td>0.1185</td><td><strong>0.0206</strong></td></tr><tr><th>RI<sub>ax</sub></th><td>0.1453</td><td><strong>0.0084</strong></td><td></td><td>0.2558</td><td>0.0682</td><td><strong>0.0002</strong></td></tr><tr><th>RI<sub>brach</sub></th><td>0.7679</td><td>0.1690</td><td>0.2558</td><td></td><td>0.7808</td><td><strong>0.0070</strong></td></tr><tr><th>Q/RI<sub>ax</sub></th><td>0.9212</td><td>0.1185</td><td>0.0682</td><td>0.7808</td><td></td><td><strong>0.0080</strong></td></tr><tr><th>Q/RI<sub>brach</sub></th><td><strong>0.0124</strong></td><td><strong>0.0206</strong></td><td><strong>0.0002</strong></td><td><strong>0.0070</strong></td><td><strong>0.0080</strong></td><td></td></tr></tbody></table>

## Data availability

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation. Please contact Prof G. Mahé: maheguillaume@yahoo.fr.

Received: 25 January 2025; Accepted: 20 May 2025

Published online: 28 May 2025

## References

1. Thurlow, J. S. et al. Global epidemiology of end-stage kidney disease and disparities in kidney replacement therapy. *Am. J. Nephrol.* **52**, 98–107 (2021).

2. Rapport, R. E. I. N. & Rapport, R. E. (Réseau Epidémiologique et Information En Néphrologie) 2022 [Internet]. Agence de La Biomédecine; https://www.Agencebiomedecine.fr/IMG/Pdf/Rapport_2022_-_202400905_-_sans_lien1.Pdf. I.N. (Réseau Epidémiologique et Information en Néphrologie) 2022 [Internet] (2022).

3. Patel, P. R., Kallen, A. J. & Arduino, M. J. Epidemiology, surveillance, and prevention of bloodstream infections in Hemodialysis patients. *Am. J. Kidney Dis.* **56**, 566–577 (2010).

4. Lok, C. E. et al. KDOQI clinical practice guideline for vascular access: 2019 update. *Am. J. Kidney Dis.* **75**, S1–S164 (2020).

5. Riella, M. C. & Roy-Chaudhury, P. Vascular access in haemodialysis: strengthening the Achilles’ heel. *Nat. Rev. Nephrol.* **9**, 348–357 (2013).

6. Roy-Chaudhury, P. et al. Cellular phenotypes in human stenotic lesions from haemodialysis vascular access. *Nephrol. Dial Transpl.* **24**, 2786–2791 (2009).

7. Glanz, S. et al. Dialysis access fistulas: treatment of stenoses by transluminal angioplasty. *Radiology* **152**, 637–642 (1984).

8. Beathard, G. A. Percutaneous transvenous angioplasty in the treatment of vascular access stenosis. *Kidney Int.* **42**, 1390–1397 (1992).

9. Rokoszak, V. et al. A systematic review and meta-analysis of plain versus drug-eluting balloon angioplasty in the treatment of juxta-anastomotic hemodialysis arteriovenous fistula stenosis. *J. Vasc. Surg.* **71**, 1046–1054e1 (2020).

10. Huguet, B., Giauffret, F., Hocq, F., Gulino, R. & Simonnet, M. Quantification des sténoses de fistules artério-veineuses: comparaisons des différentes méthodes ultrasonographiques avec La fistulographie. *JMV-Journal De Médecine Vasculaire.* **43**, 117 (2018).

11. Pichot, O. et al. Standardized methodology for duplex ultrasound examination of arteriovenous access for hemodialysis: A proposal of the French society of vascular medicine and the French-Speaking society of vascular access. *Ultrasound Med. Biol.* **49**, 2213–2220 (2023).

12. Schmidli, J. et al. Editor (eds) 's Choice Vascular access: 2018 clinical practice guidelines of the European society for vascular surgery (ESVS). *Eur. J. Vasc. Endovasc. Surg.* **55** 757–818 (2018).

13. Ibeas, J. et al. Spanish clinical guidelines on vascular access for haemodialysis. *Nefrologia* **37** (Suppl 1), 1–191 (2017).

14. Aragoncillo, I. et al. Adding access blood flow surveillance reduces thrombosis and improves arteriovenous fistula patency: a randomized controlled trial. *J. Vasc Access.* **18**, 352–358 (2017).

15. Aragoncillo, I. et al. The impact of access blood flow surveillance on reduction of thrombosis in native arteriovenous fistula: a randomized clinical trial. *J. Vasc Access.* **17**, 13–19 (2016).

16. Sidawy, A. N. et al. The society for vascular surgery: clinical practice guidelines for the surgical placement and maintenance of arteriovenous Hemodialysis access. *J. Vasc. Surg.* **48**, S2–S25 (2008).

17. Colombo, A. et al. Utility of blood flow/resistance index ratio (Qx) as a marker of stenosis and future thrombotic events in native arteriovenous fistulas. *Front. Surg.* **7**, 604347 (2020).

18. Malik, J. et al. Surveillance of arteriovenous accesses with the use of duplex doppler ultrasonography. *J. Vasc Access.* **15**, 28–32 (2014).

19. Hanley, J. A. & McNeil, B. J. The meaning and use of the area under a receiver operating characteristic (ROC) curve. *Radiology* **143**, 29–36 (1982).
20. Fahrtash, F. et al. Defining a significant stenosis in an autologous radio-cephalic arteriovenous fistula for Hemodialysis. *Semin Dial.* **24**, 231–238 (2011).

21. DeLong, E. R., DeLong, D. M. & Clarke-Pearson, D. L. Comparing the areas under two or more correlated receiver operating characteristic curves: a nonparametric approach. *Biometrics* **44**, 837–845 (1988).

22. Gallieni, M. et al. Clinical practice guideline on peri- and postoperative care of arteriovenous fistulas and grafts for haemodialysis in adults. *Nephrol. Dial Transpl.* **34**, i1–ii42 (2019).

23. White, J. J., Ram, S. J., Jones, S. A., Schwab, S. J. & Paulson, W. D. Influence of luminal diameters on flow surveillance of Hemodialysis grafts: insights from a mathematical model. *Clin. J. Am. Soc. Nephrol.* **1**, 972–978 (2006).

24. Paulson, W. D., Moist, L. & Lok, C. E. Vascular access surveillance: an ongoing controversy. *Kidney Int.* **81**, 132–142 (2012).

25. Lomonte, C., Meola, M., Petrucci, I., Casucci, F. & Basile, C. The key role of color doppler ultrasound in the work-up of Hemodialysis vascular access. *Semin Dial.* **28**, 211–215 (2015).

26. Castro, A. et al. The role of doppler ultrassonography in significant and borderline stenosis definition. *Blood Purif.* **46**, 94–102 (2018).

27. Gadallah, M. F., Paulson, W. D., Vickers, B. & Work, J. Accuracy of doppler ultrasound in diagnosing anatomic stenosis of Hemodialysis arteriovenous access as compared with fistulography. *Am. J. Kidney Dis.* **32**, 273–277 (1998).

28. Schwarz, C. et al. Flow monitoring: performance characteristics of ultrasound dilution versus color doppler ultrasound compared with fistulography. *Am. J. Kidney Dis.* **42**, 539–545 (2003).

29. Sadaghanloo, N. & Declemy, S. Création des abords vasculaires pour hémodialyse: stratégie et techniques opératoires. *EMC Tech. Chirurgic. Chirurgie Vasc.* **36**, 1–15 (2020).

30. Itoga, N. K. et al. Use of a proactive duplex ultrasound protocol for hemodialysis access. *J. Vasc Surg.* **64**, 1042–1049e1 (2016).

## Author contributions

Conception and design: JB, QT, GM. Analysis and interpretation: JB, MT, ELP, JET, DL, GMData collection: JB, AG, GM. Writing the article: JB, GM. Critical revision of the article: AG, MT, QT, ELP, JET, DL. Final approval of the article: JB, AG, MT, ELP, QT, JET, DL, GM. Statistical analysis: ELP. Obtained funding: Not applicable. All the authors reviewed and approved the manuscript. Overall responsibility: GM.

## Funding

No funding was provided.

## Declarations

### Ethics approval and consent to participate

The ethics review board of our institution (named "Comité d'éthique du CHU de Rennes") approved this study (n°24.140). All included subjects signed an informed consent. This study has been conducted according to the principles expressed in the declaration of Helsinki.

### Consent for publication

Not applicable.

### Competing interests

The authors declare no competing interests.

### Additional information

Correspondence and requests for materials should be addressed to G.M.

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