1046827 research-article2021 JVA0010.1177/11297298211046827The Journal of Vascular AccessVallespin et al. Original research article JVA The Journal of Vascular Access The Journal of Vascular Access Upper limb anatomy and preoperative 2021, Vol. 22(1S) 9­–17 © The Author(s) 2021 mapping Article reuse guidelines: https://doi.org/10.1177/11297298211046827 sagepub.com/journals-permissions DOI: 10.1177/11297298211046827 journals.sagepub.com/home/jva Joaquim Vallespin1, Mario Meola2 and Jose Ibeas3 Abstract Vascular access is absolutely essential for haemodialysis due to its relationship with quality of dialysis and associated morbidity. Therefore, it must be monitored and continuously surveilled from the moment it is created to prevent failure in maturation and thrombosis. Multidisciplinary collaboration is necessary when the main aim is to achieve the adequate vascular access flow with the fewest possible complications. The starting point, and probably the main one, is vascular access planning. This planning requires both a deep understanding of the anatomy of the upper limb and enough skill to examine it by Doppler ultrasound. The aim of this article is to review the anatomical and haemodynamical concepts of the arterial and venous vascular tree and explain how to perform ultrasound mapping, optimising the technical resources provided by this tool. Likewise, adequate access creation criteria that minimise the risk of failure and associated complications will be discussed. Keywords Ultrasonography – Doppler evaluation, dialysis access, preoperative mapping, anatomy, atlas, vascular access, artery, vein, haemodynamics, maturation, haemodialysis Date received: 23 May 2021; accepted: 29 August 2021 Introduction dependence which often leads to delays in diagnosing and treating the pathology associated with VA morbidity. Renal replacement therapy is currently the treatment used Therefore, the availability of a point-of-care of ultrasound for patients with end-stage renal disease; hence, as most or portable ultrasound scanner in Nephrology and Dialysis patients will require haemodialysis, clinical workup of Units is mandatory to drastically increase diagnosis effi- vascular access (VA) is pivotal for the patient with chronic ciency and treatment choice. Moreover, at the moment, kidney disease. VA relevance is pivotal for two reasons: there is a tendency to progressively use ultrasound more firstly, it is a key factor in receiving high-quality dialysis; and more in clinical practice as the main tool both to plan secondly, an important part of the patient’s morbidity and the new VA and to detect and treat complications. mortality depends on VA efficiency. Thus, it has become progressively more important to optimise all the steps 1 related to VA survival and morbidity: VA creation, moni-  epartment of Vascular Surgery, Parc Taulí University Hospital, D Parc Taulí Research and Innovation Institute (I3PT), Autonomous toring and surveillance to prevent thrombosis due to steno- University of Barcelona, Barcelona, Spain sis and early diagnosis of complications leading to 2 Department of Internal Medicine, Sant’Anna of Advanced Studies – significant morbidity.1 Life Sciences Institute, University of Pisa, Pisa, Italy Multidisciplinary collaboration between all health pro- 3 Department of Nephrology, Parc Taulí University Hospital, Parc Taulí fessionals involved in presurgical mapping, implantation, Research and Innovation Institute (I3PT), Autonomous University of Barcelona, Barcelona, Spain follow-up and treatment of complications (nephrologists, vascular surgeons, interventional radiologists and nephro- Corresponding author: logical nursing) is necessary. This collaboration must be Jose Ibeas, Department of Nephrology, Parc Taulí University Hospital, Parc Taulí Research and Innovation Institute (I3PT), Autonomous close and fluid, and, of course, it must be adapted to each University of Barcelona, Parc del Taulí 1, Sabadell, Barcelona 08208, centre’s policy, resources and organisation. However, the Spain. nephrologist depends highly on other specialist’s skills – a Email: jibeas@telefonica.net 10 The Journal of Vascular Access 22(1S) When planning to create a new VA, the clinical workup proximal cuff placement to identify the main drainage must be based on correct history, arterial and venous phys- veins of the superficial venous system (cephalic and basilic ical examination. This offers a global vision of the venous vein) and their collateral tributaries up to the antecubital and arterial network and allows for the diagnosis of any fossa. It is essential to determine diameter, continuity and possible anomaly/pathology. Insonation, that is, the five vein compliance.3 pillars of the modern semiotic, must complete this clinical workup.2 Indications of presurgical ultrasound This article reviews the upper limb’s ultrasound vascu- lar anatomy and the advantage of preoperative mapping in mapping planning a new VA. The widespread use of Doppler ultrasound in clinical prac- tice has developed new protocols to evaluate vessel char- Clinical history acteristics and optimise decision-making when creating new VA. In this respect, papers have been published docu- The patient should be asked about their medical history, menting Doppler ultrasound’s usefulness in vascular such as Diabetes Mellitus, which may compromise the access planning in cases where the physical examination prognosis of the future VA. The medial calcinosis present was inconclusive, such as in obese patients, with the in these patients usually prevents proper maturation due to absence of peripheral pulses or with previous surgeries.4,5 lack of arterial dilation.3 Antecedents that may have com- That is precisely why ultrasound has been included promised the central veins must also be known, such as regularly in the preoperative check-up as an essential com- current or previous central venous catheters, pacemakers plement to physical examination. Despite this, there is no or any other devices that may have caused stenosis.3 consensus when considering the use of ultrasound map- Finally, the physician must suspect the presence of arterial ping as a routine examination in all patients who are can- stenosis/occlusion in patients that present a history of clin- didates for VA implantation. Although different studies ically relevant vasculopathy in lower limbs and rule out and a meta-analysis show the usefulness of ultrasound,5,6 atherosclerotic stenosis or occlusions of the VA feeding some studies suggest that overall benefit in patients with artery (risk of maturation failure) and the limb’s distal favourable anatomy is not evident.7,8 There is still some arteries (risk of distal ischaemia/steal syndrome).3 controversy about it today. However, the main clinical practice guidelines published,3,9,10 based on good clinical practice and existing evidence, recommend ultrasound Physical examination mapping before surgery to obtain a global and accurate Correct physical examination of the patient can be more view of the patient’s venous and arterial capital and mainly helpful than medical history to detect the possible presence in cases in which the physical examination is not of significant vascular pathology. This examination should conclusive. be performed in a warm environment with the patient’s arm in decline, relaxed, before and after the placement of a Ultrasound examination: General proximal cuff to correctly fill the limb’s veins.3 Adequate inspection can detect a collateral circulation considerations in the shoulder and pectoral region, representing a sign of Ultrasound mapping of the upper limb vessels before VA haemodynamically significant central venous pathology. implantation is based on three different applications11: The existence of morbid obesity will also condition VA prognosis, especially as it hinders needling. In these cases, 1. B-mode ultrasound, which provides a two-dimen- vessel depth should be carefully evaluated with some sional greyscale image to study vessel morphology image test to determine the draining vein’s appropriateness and anomalies. for superficialisation/transposition procedures. 2. Pulse wave Doppler (PWD), which records the Arterial examination includes palpation of pulses at all velocity over time curve in veins and arteries, ana- levels (radial, ulnar and brachial), evaluating their width lysing red blood cells (RBCs) velocities. and detecting the presence of asymmetries. The physician 3. Colour Doppler (CD) sampling reproduces real- should detect asymmetries in systolic blood pressure time mean velocities of RBCs over time in a colour between upper extremities; an Allen test must be per- box. formed to determine the hand’s arterial dominance and the palmar arch’s functionality. The examination should be carried out with abundant gel Vein examination aims to find a palpable and compress- to avoid losing information on the sides of the probe in the ible conduit without tortuosity, adequate calibre and forearm’s curved fields, and excessive pressure avoided on length, which continues towards the deep venous system.2 the skin, given the marked tendency of the superficial Limb inspection must be attempted before and after the veins to collapse. Vallespin et al. 11 Figure 1. Atlas of the arterial and venous vascular bed. Patient position in anteroposterior or latero-lateral direction, parallel to the transducer long axis; (2) axial-transverse scan on the ves- The patient’s ideal position is supine decubitus, without sel short axis. Such scans are helpful even with ‘on-plane’ bending the elbow, when examining the arterial system, or ‘out of plane’ needle guidance. and evaluating the subclavian and axillary veins. However, The vessel spectral curve must be clean, regular and to assess the arm’s veins, it is advisable to raise the head of without great artefacts. Doppler parameters must be meas- the bed to 45°, with the arm in a relaxed position and study ured on the frozen image, after the angle adjustment at 60°. them before and after proximal tourniquet placement to This value enables proper vessel sampling and introduces achieve maximum vein dilation. Alternatively, the patient a constant error, which does not invalidate the quantitative can be placed in a sitting position by extending the upper analysis. In this way, quantitative and semiquantitative limbs alternately on the examination table, at 45° to the data from different operators and devices can be vertical axis. It is important to maintain a warm environ- compared. ment during the test to prevent venous vasospasm. The leg High intensity and low-frequency spectral frequencies, should be placed in a slight external rotation to assess the originating from the vibrations of the vessel wall and adja- lower limbs. Correct ultrasound mapping requires knowl- cent structures, should be eliminated by a 100–200 kHz edge of the limb anatomy, especially regarding arterial high-pass filter. In existing platforms, the wall noise filter vessels and the deep and superficial venous system.12 self-adjusts with the Doppler transmission frequency. Probe and scans Arterial ultrasound examination Vessel examination should be carried out with high-resolu- tion small-part transducers (7.5–20 MHz), with a 4 cm, or Arterial anatomy of the upper limb smaller, head. The deepest central veins can be also Arterial vascularisation of the arm depends on the subcla- insonated with microconvex transducers. The use of a lin- vian artery, which is a branch of the aorta on the left side, ear probe requires steering activation, that is, the activation while on the right, it is one of the terminal branches where of a 20° electronic angular deviation of the colour box and the brachiocephalic trunk bifurcates (Figure 1).13 Doppler line in a centrifugal direction. In this way, the ves- sels are non-orthogonally insonated because, from a tech- nical point of view, this is the most unfavourable condition Subclavian artery for the Doppler effect recording since a cosine of 90° is Anatomically, this is not a long artery and is shorter on the equal to 0. This technical rule applies both to colour-power right side, as mentioned above. It is also located deep in Doppler sampling and spectral analysis. There are two the tissue known as the thoracic outlet until it passes helpful scans for superficial vessels: (1) longitudinal scans immediately below the clavicle. Both its deep trajectory 12 The Journal of Vascular Access 22(1S) and the acoustic shadow of the clavicle make it a difficult artery to scan using ultrasound and it is extremely difficult to visualise it entirely. That is why it is usually impossible to evaluate the whole trajectory directly, except in very thin patients. Axillary artery This trunk is the continuation of the subclavian artery, from the first rib’s lateral edge to the pectoralis major mus- cle’s inferior border. As the subclavian artery, it is a short artery. Its location allows for better insonation. It can be visualised with ultrasound from the lower edge of the clav- Figure 2. B mode. (a) Arterial examination. Radial and icle anteriorly below both pectoral muscles and through ulnar arteries with their respective satellite veins. (b) Venous the axillary cavity, with the arm in abduction. examination. Diameter measurement. Brachial artery Palmar arch Greater in length, it continues to the axillary artery and This represents the terminal anastomoses between the paves a route along the whole arm’s inner face. It can be radial and ulnar arteries. The palmar arch shows great vari- located in an ultrasound-accessible position – with the arm ability. Usually, it consists of two arches: the deep palmar at 45° – between the arm’s biceps and triceps muscles arch, mainly dependent on the radial artery, which anasto- (bicipital groove). It bifurcates in the antecubital fossa, moses with the ulnar artery; and the superficial palmar giving two terminal branches: radial and ulnar artery. In up arch, tributary to the ulnar, which anastomoses with the to 15% of cases, it can present an anomaly consisting of a radial artery. Its morphology and patency can be explored proximal bifurcation, which will cause the existence of a using high-frequency ultrasound and the Allen Test. double artery in the arm. Palmar arch patency is crucial for hand perfusion when a distal arteriovenous fistula is implanted. In fact, after VA implantation, the hand’s entire vascularisation depends on Radial artery the palmar arch. The brachial artery’s terminal branch, which presents a relatively deep first segment, is placed in a more superfi- cial position. It approaches the hand and follows the radial Arterial mapping edge of the forearm (pulse channel). It is easily visible The arteries are examined morphologically, placing the throughout its trajectory using ultrasound. The radial probe first in a transverse plane, with the probe’s direc- artery can be identified from its origin because it is the tional mark towards the right site. The short axis helps most superficial artery after the brachial artery’s bifurca- achieve correct assessment of the arterial diameters and tion. As previously mentioned, it can sometimes originate explore in an ascending or descending direction. The oper- directly from the brachial artery in the proximal third of ator will note the diameters of the radial and brachial arter- the arm, in which case it travels the entire arm to the wrist. ies, calcifications and anomalies, such as the radial artery’s proximal bifurcation (Figure 2(a)). Subsequently, the arterial tree is studied dynamically on Ulnar artery the vessel’s long axis. Firstly, colour Doppler is used to This is the other terminal branch of the brachial artery, identify the areas with aliasing, where the flow velocity which, like the radial, follows a relatively deep path at the rate increases. This acceleration is quantified with the beginning but is located superficially in the wrist. Typically, spectral Doppler, which allows the determination of the it branches into a collateral at a short distance from its ori- peak systolic velocity (PSV) to assess the degree of exist- gin, the interosseous artery. As its name indicates, the lat- ing stenosis. The longitudinal study should be carried out ter follows the forearm’s deepest trajectory close to the ideally at an angle of 60° between the vessel’s major axis interosseous membrane, between the radius and ulna and the Doppler beam’s direction to avoid errors in the bones. However, it is a non-constant artery that may some- velocity measurement.14 times dominate the forearm, to the detriment of the radial Under normal conditions and in the absence of pathol- and ulnar arteries. The common initial trunk of the ulnar ogy, the Doppler wave’s morphology will typically be and interosseous arteries is often called the ulna-interosse- triphasic, with a positive initial peak followed by a negative ous trunk. wave and a positive end-diastolic wave. This waveform, Vallespin et al. 13 radial edge, external arm face and deltopectoral groove. It is the longest vein in the upper limb because it originates at the base of the thumb and empties into the axillary vein at the height of the lower edge of the clavicle. Its trajectory follows the most superficial path of all the trunk veins, so it is the first-choice vein to try to create vascular access. It often presents a dorsal branch at wrist level and may be appropriate for access creation. Basilic vein. This follows a trajectory in the ulnar portion in the forearm, while in the arm, it is located in the inner face, close to the brachial vascular sheath package. Despite being an epifascial vein, it is located in a deeper Figure 3. Doppler mode in arterial examination: (a) triphasic position than the cephalic vein throughout its entire morphology with high resistance flow and (b) reactive length. Besides, it perforates the brachial fascia from the hyperaemia. distal third of the arm, goes deep into this and drains into PSV: peak systolic velocity; EDV: end diastolic velocity. the brachial vein in the arm’s proximal third, close to the axilla; it is shorter than the previous one. Although its which corresponds to a high resistance flow, does not vary deeper location often preserves it from injuries due to iat- along the arterial tree and has the same morphology in the rogenic puncture, it is the second-choice vein for VA after proximal arteries (axillary and brachial) as in the distal the cephalic vein. arteries (radial and ulnar), with only small variations in width (Figure 3(a)). Communicating veins of antecubital fossa. This is a net- work of superficial veins that connect the cephalic vein system with that of the basilic. They are also very impor- Venous ultrasound examination tant in the development of the arteriovenous fistula since, It is well known that the prognosis of the new VA depends on the one hand, they determine the venous drainage of on the condition of the patient’s venous drainage system. the forearm towards the arm’s veins and, on the other That is why it is the most important part of mapping and hand, the forearm’s perforating vein is located in their will probably take up the most exploration time (Figure 1). midst. The perforating vein as well as the median cubital vein are of great surgical importance since are the veins used for the Gracz fistula and, in general, of all elbow Venous anatomy of the upper limb fistulas with open drainage towards the cephalic and In upper limbs, venous drainage occurs in two main sys- basilic veins in the arm. They present great anatomical tems: superficial and deep venous systems.12 variability and are most frequently laid out in the so- The deep venous system’s veins are located alongside the called ‘Y’ (with the prominence of the median vein) and main trunk arteries and bear the same corresponding names ‘M’ position (with the dominance of the cephalic median (radial, ulnar, brachial, axillary and subclavian veins), usu- and the basilic median veins). ally in even numbers, so that two veins accompany each artery. They are usually less developed in upper limbs than Venous mapping. Both the superficial and the deep venous in lower limbs, so they are seldom used to create an arterio- system should be explored, from the wrist to the central venous fistula since they are also at a deeper level; however, veins (axillary or subclavian), paying special attention to it is necessary to ensure their patency. In many cases, proxi- the superficial veins. mal veins (subclavian, brachiocephalic vein), as the accom- The study must be carried out with the probe placed in panying artery, cannot be seen directly using ultrasound. a transverse direction, which allows the precise morpho- The superficial venous system is usually well developed logical assessment of the wall’s diameter, compressibility and is therefore preferred in vascular access creation. It and characteristics (Figure 2(b)). differs from the deep one because it follows an epifascial The main qualities that must be determined in venous path, collects the venous drainage from superficial tissues mapping are: and drains into the deep venous system. It consists of two drainage systems: the cephalic vein and the basilic vein. •• Vessel patency. This characteristic checks vein com- pressibility after squeezing with the probe and venous Cephalic vein. This vein is responsible for superficial modulation, which appear on the spectral Doppler venous drainage and follows a path along the forearm’s trace after distal compression. A subcutaneous vein is 14 The Journal of Vascular Access 22(1S) easily compressible when applying external pressure with the transducer. Non-compressibility is a sign of endoluminal material, that is – thrombosis and sup- poses manual compression is performed in the distal territory. In that case, flow in the proximal veins must increase, causing a ‘surge’ that is easily detectable by CD. •• Distensibility. The vein’s ability to dilate as endolu- minal pressure increases can be assessed using B-mode to measure vein diameter through a trans- verse section before and after proximal cuff place- ment. The vessel should be measured without compression as a superficial vein easily collapses with the probe’s external pressure. Figure 4. Doppler mode in venous examination. Respiratory phasicity. In general, it is important to explore the entire path of the vein. Attention should be paid to wall thickening due to past phlebitis and significant changes in the vessel’s cali- bre. The value of the minimum diameter of the vein should also be determined, and attention paid to anomalies and tortuosity, which may hinder needling in the future. The sonographer must follow a series of recommenda- tions in the vein evaluation. •• Should be looked for venous stenosis (usually seg- mental thrombosis/thrombophlebitis after periph- eral indwelling catheters), for side branches (if many, the flow could be dissipated) and for the depth of the peripheral vein (as deep veins will cause problems with punctures). •• The basilic vein depth will have to be specifically noted throughout its path, helping us plan future Figure 5. Doppler mode in venous examination. Transmitted needling areas. This must be emphasised through- heart pulsatility. out the path in the case of deep veins to assess their possible superficialisation and/or transposition. •• It is important to determine vein position in the heartbeat modulations are detectable in the Doppler antecubital fossa since it will give us information on curve of central veins, and they are an indirect sign where the flow will go after the fistula is created. of patency (Figure 5). In the presence of stenosis or •• The operator can report the location and the calibre central venous occlusions, the flow in these veins of the antecubital perforating vein. becomes slow and continuous without any deflec- •• Stenosis in the proximal segment of subclavian and tion. Even so, it will lack variations with respiratory brachiocephalic veins may not be directly visible and cardiac movements, which will result in a flat using ultrasound modalities. Their patency and flow curve.11 functionality depend on the so-called indirect signs of patency. First of all, respiratory phasicity must Predictive maturation factors be checked: this is generated by negative pressure in the thorax during inspiration, which causes a Undoubtedly, ultrasound mapping places a large amount of ‘sucking’ effect in the proximal veins of the arm, in anatomical and functional information on the limb’s vascu- the form of an increase in flow with deep stimula- larisation at our disposal and offers us multiple criteria to tion if the drainage system has correct patency and help create a new VA. However, it adds uncertainty when functionality (Figure 4). Secondly, the closure of deciding on which type of fistula is the most convenient for the heart valves causes a pressure wave which, in each patient at all times. Multiple ultrasound variables the absence of central venous pathology, spreads associated, to a greater or lesser extent, with good access retrogradely through the blood column and is seen prognosis have been described in the literature. This does in the form of transmitted heart pulsatility. Small not prevent the most convenient access for each patient Vallespin et al. 15 from sometimes being a complex decision. Thus, all the It is important to remember the need for a warm envi- specialists should take the decision as a multidisciplinary ronment to prevent vessel spasm during exploration. Vein team, based on the patient’s personal preferences.3,15 diameter is measured through transverse scans with the probe placed in a perpendicular plane to the skin, and the inner diameter is always taken as the measurement. Vein diameter There is agreement among different authors that vein Analysis of the arterial Doppler curve: Peak diameter after proximal tourniquet placement is the ultra- sound parameter of greatest importance in access progno- systolic velocity (PSV) sis.16,17 On the other hand, although the differences are The arterial Doppler waveform of upper limbs has a tripha- small, there is no consensus on the minimum diameter that sic morphology at rest. A sudden systolic peak is followed can be considered a good prognosis.5,18–20 On the one hand, by a rapid fall in the flow and a reverse inflexion (reverse there is a risk of either discarding viable veins at the limit wave) due to the arterial wall’s elastic recoil in peripheral in diameter, or of creating accesses that may not function. arteries. Small anterograde modulation appears at the end Since most studies coincide that prognosis is poor in veins of diastole. This pattern corresponds to a high-resistance of diameter <1.5 mm, this diameter can be considered the vascular bed. In segmental stenosis, once the >50% diam- minimum from which the fistula is deemed to be viable. eter narrowing is detected, the PSV increases doubles at Most authors agree on a good prognosis for fistulas made the stenosis point in comparison to the upstream vascular in veins >2.0 mm, so it is reasonable to consider it a good tract. The spectral trace acquires a monophasic morphol- prognosis factor in daily practice.3 Diameters between 1.5 ogy with high-speed diastolic velocities. This pattern is and 2.0 mm can be considered suitable for creating the difficult to verify in presurgical mapping since limb distal access but have uncertain prognosis, so the decision must circulation is anastomotic. A post-stenotic pattern appears be taken based on other factors. downstream of the stenosis, with a flattened morphology, losing the triphasic component and acquiring a biphasic or Arterial diameter even monophasic form. These signs indicate poor arterial inflow and poor access prognosis.20 Some authors suggest The artery should be measured by determining the internal that a PSV value <50 cm/s in the radial artery is a sign of arterial diameter, which is the vessel’s adequate calibre. poor prognosis. But, as other factors, such as the stiffness However, this parameter is difficult to obtain in most and arterial calcification, can influence PSV, the absolute peripheral arteries with 7.5–10 MHz probes. This value value of PSV in the radial artery cannot be considered a has been shown to have important predictive value in reliable factor for fistula prognosis.24,25 Therefore, arterial access success.3 There is no agreement regarding the mini- Doppler curve assessment should be aimed at assessing a mum diameter that can be used in practice.5 However, the correct wave or a post stenotic pattern indicative of seg- opinion between authors and experts is that the larger the mentary stenosis. artery diameter, the better the prognosis. So, in this prac- tice, it is advisable to use the same values as with the vein, considering a minimum diameter of 2.0 mm to have good Response to reactive hyperaemia access prognosis,19,20 and below a minimum diameter of For the access to mature correctly, an increase in the feed- 1.5 mm considered to be a non-viable access.20–22 ing artery’s flow of 10–20 times versus the baseline value is necessary. This haemodynamic variation is achieved thanks to an adaptative response to wall shear stress, which per- Increase in the diameter of the vein mits vessel dilation. The arterial dilation process can be For the access to mature correctly, the fistula’s drain veins compromised if there are highly calcified arteries, as is the must be larger after surgery to drive the entire volume of case of patients with multiple cardiovascular risk factors flow to the central veins and to cannulate properly. This and diabetes. Therefore, it is essential to distinguish patients capability is known as distensibility and is defined as the in which there is insufficient dilation capacity in the vascu- vein’s ability to dilate as intraluminal pressure increases. lar bed and a high risk of maturation failure. The absolute This venous distensibility can be assessed directly by values of resting PSV have not demonstrated prognostic measuring vein diameter prior to and within 2 min of plac- utility in this regard.20 A hyperaemia test has been proposed ing a proximal tourniquet on the limb, and measuring the for this purpose – hand ischaemia is induced by making a percentage increase in the vessel’s diameter. Although an fist for 2 min. Opening the hand allows the operator to eval- increase of above 48% is considered a good prognosis,23 uate reperfusion time and resistance variation to hyperae- there is no minimum value required for creating access, mia using PWD. Normally, Doppler curve at the radial but the prognosis is better when there is a greater increase artery shows sudden vasodilation of vascular bed in in the vein diameter. response to ischaemia. We can evaluate haemodynamic 16 The Journal of Vascular Access 22(1S) response by calculating the increase in PSV26,27 and the decision-making, and allow greater agility and quality of decrease in Resistive Index (RI),3 obtained with the for- care. High-resolution check-ups can be performed. The mula: RI = [PSV − EDV]/PSV, where EDV (end diastolic vascularisation of the limb and venous capital can be velocity) is the lowest velocity value in the Doppler curve. examined accurately. Which access is most appropriate RI variations are the parameter most widely used in prac- can be decided according to the circumstances without tice: an RI value <0.7 after the hyperaemia test and is a having to do invasive radiological tests. But for this sign of good VA prognosis.3 RI determination is subject to improvement in diagnostic capacity to be turned into better significant variability in measurement. Some studies have patient care, greater and improved collaboration between not found a relationship between RI and fistula prognosis,22 the professionals involved is necessary, especially the so it is relatively helpful in deciding about the access to be nephrologist-vascular surgeon relationship.31 Joint check- created (Figure 3). ups between both specialities are desirable to offer the vas- cular access candidate an immediate and adequate proposal for individual treatment needs, without the need for delays Arterial wall thickness that may affect their morbidity and mortality. Arterial wall thickness, evaluated with the high-resolution That is why ultrasound should play a leading role in probe (10–20 MHz) by measuring the thickness of intima- decision-making regarding vascular access. However, at media layers (IMT), is a well-known marker of cardiovas- no time should incorporating such technology replace an cular risk factors in the general population. A clear adequate individual assessment of each patient, which relationship between carotid artery IMT and cardiovascu- must be performed jointly between the medical team, lar events has been suggested.28,29 Thus, IMT determina- nephrologist and vascular surgeon and the patient tion in the access-feeding artery can be used as a prognostic himself. factor of VA patency.30 Despite this, its true role in the decision taken on the vascular access to be created is not Acknowledgements described, so IMT determination is not usually part of rou- To Nuria Monill Raya, I3PT biomedical engineer, for the col- tine presurgical mapping. laboration in the creation of the vascular bed atlas based on real anatomical models. Central venous patency Declaration of conflicting interests The presence of central venous pathology is a known fac- The author(s) declared no potential conflicts of interest with tor of poor prognosis for creating the new vascular access.3 respect to the research, authorship, and/or publication of this Therefore, when clinical suspicion of central vein stenosis article. derives from clinical history, a careful analysis of the cen- tral vein’s spectral wave should be performed. A multipha- Funding sic flow detected from respiratory movements and heart The author(s) received no financial support for the research, pulsatility at the subclavian or jugular vein level is a sign authorship, and/or publication of this article. of venous patency11,25 (Figures 4 and 5). Prognostic ultrasound criteria in presurgical mapping ORCID iD Mario Meola https://orcid.org/0000-0002-1330-2820 Jose Ibeas https://orcid.org/0000-0002-1292-7271 Major factors Vein diameter. 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