Native arteriovenous fistula (AVF) is the vascular access of choice for hemodialysis patients. Compared with grafts and central venous catheters, AVFs last longer and are associated with fewer complications. The widespread use of the Doppler ultrasound (DUS) has increased the number of patients who are eligible for AVF by facilitating the identification of vessels that are suitable for fistula construction (preoperative vascular mapping). DUS can also extend native AVF survival by improving the early detection of complications (post-operative surveillance). It is the only imaging modality that furnishes both morphological and functional data on the native vascular access, and it is also the only imaging tool that can be used directly by the surgeon, an indisputable advantage. This review examines the numerous roles played by DUS in the construction and postoperative follow-up of AVFs, including preoperative vascular mapping, AVF maturation, and surveillance.Keywords Doppler ultrasound (DUS) Á Arteriovenous fistula (AVF) Á Preoperative vascular mapping Á Access flow volume measurement Á AVF monitoring and surveillance Riassunto La FAV confezionata con vasi nativi rappresenta l'accesso vascolare di scelta per il paziente emodializzato in quanto, a parità di flusso, presenta minore incidenza di complicanze e più lunga sopravvivenza rispetto alle protesi ed ai cateteri venosi centrali. L'avvento del DUS nell'armamentario di chi si occupa di chirurgia degli accessi vascolari ha, da un lato, aumentato il numero di pazienti in cui si riesce a confezionare una FAV con vasi nativi (grazie all'individuazione di vasi idonei all'intervento mediante il mapping pre-chirurgico), e, dall'altro, ha migliorato la sopravvivenza delle FAV grazie alla diagnosi precoce (monitoraggio post-operatorio) delle complicanze dell'accesso vascolare. L'eco-color-Doppler è l'unica tecnica in grado di dare informazioni sia morfologiche che di funzionalità (flusso) dell'accesso vascolare; inoltre, è l'unica tecnica (tra quelle di diagnostica per immagini) direttamente gestibile dal chirurgo e ciò rappresenta sicuramente un valore aggiunto. Questa review fornisce una panoramica sulle possibili applicazioni del DUS nell'ambito del confezionamento e del follow-up delle FAV, con particolare riferimento al mapping pre-chirurgico, alla maturazione della FAV e al monitoraggio/sorveglianza della FAV.

The term cardiorenal syndrome (CRS) describes a broad spectrum of clinical conditions with four combinations of acute and chronic heart and kidney failure. Based on the pathophysiological primum movens, the actual classification recognizes five CRS types: in type I and II CRS, the initiating event is heart failure (acute or chronic), while it is kidney failure in type III and IV CRS; type V is linked to systemic diseases. Ultrasound techniques (echocardiography and ultrasonography of the kidney, inferior vena cava and chest) can be extremely helpful in establishing a prompt diagnosis and a correct CRS classification. Basic echocardiography allows evaluation of ventricular diastolic and systolic functions, investigates pulmonary congestion and pericardial effusion, and describes volume overload. On the other hand, renal ultrasound helps clinicians to distinguish between acute and chronic renal failure, excludes urinary tract dilation or pathological bladder repletion, and provides crucial information regarding kidney volume or echogenicity. Applying basic knowledge of echocardiography and renal ultrasound, nephrologists may be in a better position for patient treatment and management, bearing in mind that doctors can properly use a stethoscope although not being a cardiologist.

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During the past 10 years the type of vascular access for haemodialysis procedures have changed markedly in our centre: more elbow AV fistulae and more central venous catheters are now used. Nevertheless, early referral to nephrologists and availability of central venous catheters and peritoneal dialysis allow elderly people to be admitted for dialysis treatment. Since vascular access for haemodialysis plays a key role in patient well-being, it is mandatory to apply quality assurance criteria to vascular access for haemodialysis surgery. Based on the results of a national survey, in Italy this policy is still in its early stages: monitoring of vascular access differs amongst centres, interventional radiology is used in a differing way, planning of vascular access for haemodialysis in pre-dialysis patients often remains an unsolved problem. According to our initial experience, we propose the use and validation of a quality-index [(minimum success rate) in elective vascular access for haemodialysis surgery], allowing accreditation of a department and a single surgeon for access management. Prevalence of central venous catheters at first dialysis of chronic renal failure patients is also proposed to evaluate the efficiency in access planning. Better knowledge of vascular access management by different teams could eventually lead to definition of guidelines for this 'Cinderella of dialysis'.

Achievement of a normal hydration status is one of the major targets of hemodialysis. It is based on the estimation of "dry weight", the term used to define normal body fluid content. The concept of dry weight in hemodialysis patients is clinically undisputed, but it is not always easy to achieve in this population. Assessment of hydration status by clinical evaluation is imprecise and often unreliable. Measurement of the inferior vena cava (IVC) diameter has been shown to reflect individual fluid status. The relationship between variation in IVC diameter before and after hemodialysis session and weight loss has been investigated. Ultrasound (US) measurement of the IVC diameter is considered a valid measure of the hydration status and is routinely used in hemodialysis patients. Moreover, a relationship between IVC diameter, respiratory activity and hydration status, evaluated by considering both plasma volume and central venous pressure, has been demonstrated. In conclusion, assessment of hydration status based on blood pressure and central venous pressure can be considered reliable only in patients without signs of heart failure.