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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.

In the last years, the systematic use of ultrasound mapping of the upper limb vascular network before the arteriovenous fistula (AVF) implantation, access maturation, and clinical management of late complications is widespread and expanding. Therefore, a good knowledge of theoretical outlines, instrumentation, and operative settings is undoubtedly required for a thorough examination. In this review, the essential Doppler parameters, B-Mode setting, and Doppler applications are considered. Basic concepts on the Doppler shift equation, angle correction, settings on pulse repetition frequency, operative Doppler frequency, gain are reported to ensure adequate and correct sampling of blood flow velocity. A brief analysis of the Doppler inherent artefacts (as random noise, blooming, aliasing, and motion artefacts) and the adjustment setting to minimize or eliminate the confounding artefacts are also considered. Doppler aliasing occurs when the pulse repetition frequency is set too low. This artefact is particularly frequent in vascular access sampling due to the high velocities range registered in the fistula’s different segments. Aliasing should be recognized because its correction is crucial to analyse the Doppler signals correctly. Recent advances in instrumentation are also considered about a potential purchase of a portable ultrasound machine or a top-of-line, high-end, or mid-range ultrasound system. Last, the pulse wave Doppler setting for vascular access B-Mode and Doppler assessment is summarized.

Arteriovenous fistula (AVF) complications are classified based on fistula outcomes. This review aims to update colour Doppler (CD) and pulse wave Doppler (PWD) roles in managing early and late complications of the native and prosthetic AVF. Vascular access (VA) failure occurs because inflow or outflow stenosis activates Wirchow’s triad inducing thrombosis. Therefore, the diagnosis of the tributary artery and outgoing vein stenosis will be the first topic considered. Post-implantation complications occur from the inability to achieve AVF maturation and dialysis suitability due to inflow/outflow stenosis. Late stenosis is usually a sequence of early defects repaired to maintain patency. Less frequently, in the mature AVF or graft, complications are acquired ‘de novo’. They derive either from incorrect management of vascular access (haematoma, pseudoaneurysm, prosthesis infection) or wall pathologies (aneurysm, myxoid valve degeneration, kinking, coiling, abnormal dilation from defects of elastic structures). High-resolution transducers (10–20 MHz) allow the characterization of the wall damage, haemodynamic dysfunctions, early and late complications even if phlebography remains the gold standard for the diagnosis for its sensitivity and specificity.

Chronic hemodialysis therapy required regular entry into the patient’s blood stream with adequate flow. The use of arteriovenous fistulas and grafts is linked with lower morbidity and mortality than the use of catheters. However, these types of accesses are frequently affected by stenoses, which decrease the flow and lead to both inadequate dialysis and access thrombosis. The idea of duplex Doppler ultrasound surveillance is based on the presumption that in-time diagnosis of an asymptomatic significant stenosis and its treatment prolongs access patency. Details of performed trials are conflicting, and current guidelines do not support ultrasound surveillance. This review article summarizes the trials performed and focuses on the reasons of conflicting results. We stress the need of precise standardized criteria of significant access stenosis and the weakness of the metaanalyses performed.

Introduction: Cardiac surgery-associated acute kidney injury (CSA-AKI) is a common complication in patients undergoing cardiac surgery. Preoperative renal functional reserve (RFR) has been demonstrated to be highly predictive of CSA-AKI. We have previously demonstrated that intraparenchymal renal resistive index variation (IRRIV) measured by ultrasound (US) can identify the presence of RFR in healthy individuals. This study aimed (1) to examine the correlation between the US IRRIV test and RFR measured through the protein loading test in patients undergoing elective cardiac surgery and (2) to determine the value of the 2 methods for predicting occurrence of AKI or subclinical AKI after cardiac surgery. Methods: Consecutive patients scheduled for cardiac surgery were enrolled for this pilot study. The protein loading test and the IRRIV test were performed in all patients 2 days before cardiac surgery. Correlation between IRRIV and RFR was tested using Pearson correlation analysis. Association between presence of RFR and positive IRRIV test, presence of RFR and AKI and subclinical AKI, and positive IRRIV test and AKI and subclinical AKI was evaluated using logistic regression analysis. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the values of IRRIV for predicting RFR, RFR for predicting AKI and subclinical AKI, and IRRIV for predicting AKI and subclinical AKI. Results: Among the 31 patients enrolled, significant association was found between IRRIV and RFR (r = 0.81; 95% CI: 0.63–0.90; p < 0.01). The association between RFR and IRRIV was described in 27/31 (87.1%) patients. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the IRRIV test were 100, 84, 60, and 100%, respectively. In ROC curve analysis, the area under the curve (AUC) was 0.80 (95% CI: 0.64–0.96). After cardiac surgery, 1/31 (3.2%) patient had AKI and 12/31 (38.7%) had subclinical AKI. RFR predicted subclinical AKI (odds ratio [OR] = 0.93; 95% CI: 0.87–0.98; p = 0.02). The sensitivity, specificity, PPV, and NPV of the RFR were 61, 88.8, 80, and 76%, respectively; the AUC was 0.75 (95% CI: 0.59–0.91). IRRIV predicts subclinical AKI (OR = 0.79; 95% CI: 0.67–0.93; p = 0.005). The sensitivity, specificity, PPV, and NPV of the IRRIV test were 46.1, 100, 100, and 72%, respectively; the AUC was 0.73 (95% CI: 0.58–0.87). Conclusion: This pilot study suggests that a positive IRRIV test can significantly predict the presence of RFR in patients scheduled for cardiac surgery. RFR measured by the protein loading test or by the US IRRIV test can predict the occurrence of subclinical postoperative AKI. The findings of this study need to be confirmed in large patient cohorts.

Introduction: Renal allograft biopsy is the gold standard for the detection of histological lesions of chronic allograft dysfunction. The identification of a noninvasive routine test would be desirable. Elastosonography is used to assess tissue stiffness according to viscosity, and no data are available on the use of point quantification shear-wave elastography (ElastPQ) for the evaluation of renal chronic lesions. Research Question: To evaluate the feasibility of ElastPQ to assess cortical allograft stiffness and to determine the correlation of clinical, biological, and pathological factors with the diagnostic accuracy of kidney stiffness values in patients with histological lesions. Design: Forty-two patients underwent kidney transplant biopsy and 10 valid measurements of ElastPQ, blindly performed by 2 operators. The interobserver reproducibility was assessed according to intraclass correlation coefficient. The ElastPQ measurements and the clinical data were compared using the Spearman correlation analysis. Results: 97.6% reliable measurements were obtained using ElastPQ, with an excellent interobserver agreement. The kidney stiffness was significantly higher in the patients with a time since transplantation >12 months and was correlated with chronic lesions (interstitial fibrosis, tubular atrophy transplant glomerulopathy, and mesangial matrix), with the interstitial fibrosis/tubular atrophy, score and with the sum of the scores of the chronic lesions. Mesangial matrix increase is the only independent determinant of kidney stiffness. Discussion: ElastPQ is a noninvasive, reproducible, and sensitive diagnostic tool able to detect moderate/severe chronic lesions. Its routine use during follow-up can identify patients eligible for biopsy, which remains the gold standard exam for detecting chronic allograft dysfunction.

Acute kidney injury (AKI) is characterized by a rapid loss of kidney excretory function. Ultrasound (US) helps nephrologists in AKI diagnosis, in order to describe and follow kidney alterations and find possible causes of AKI. US is a safe, non-invasive, and repeatable imaging technique. Approximately 70% of community-acquired cases of AKI are due to pre-renal causes. Acute tubular necrosis (ATN) is the most common type of AKI related to parenchymal damage. Conventional US shows enlarged kidneys with hypoechoic pyramids. Although the role of color Doppler in AKI is still debated, many studies demonstrate that renal resistive indexes (RI) vary on the basis of primary disease. Moreover, several studies assessed that higher RI values are predictive of persistent AKI. Acute interstitial nephritis is also a frequent cause of AKI and conventional US does not allow a definitive diagnosis. Kidneys appear enlarged and widely hyperechoic. Also in this condition, hemodynamic changes are closely correlated to the severity and the progression of the anatomical damage. Renal artery and vein thrombosis may also cause parenchymal AKI. Acute renal infarction is a rare pathological condition due to clots or cholesterol aggregates that occlude renal artery or its branches. Renal vein thrombosis may be primary or secondary to retroperitoneal neoplasm or inflammatory diseases. Color Doppler US can detect thrombus within the lumen and document the absence of venous flow. The incidence of AKI related to urinary tract obstruction is low. It occurs in bilateral renal or lower urinary tract obstruction or in ureter obstruction in patients with a single functioning kidney or with pre-existing chronic kidney disease. Conventional US has a high sensitivity (>95%), but low specificity (

Purpose Dialysis settings have generally improved over the last decades, but the vascular access setting did not see significant advances and experienced a progressive worsening in epidemiology and clinical features. The aim of the study was to describe and compare evolution of vascular access in Italy over time. Methods A national survey implemented in Italy last year is presented and compared to a previous survey performed in 1998. Present survey collected data from almost 50% of centers involved in vascular access. Results The nephrologist participates in the management of vascular access in 97% of centers. Almost 40% of centers declare more than 40% of central venous catheters (CVCs) at first dialysis with maximum value being 60%. Prevalence of CVCs is greater than 20% in chronic prevalent patients in 38.8% of centers. According to the 2013 survey, CVCs account for 51.6% of procedures, while arteriovenous fistulae (AVF) and prostheses represent 42.4% and 6%, respectively. Nephrologists perform 73% of procedures on CVCs. From 1998 to 2013, a sharp increase in CVC prevalence was seen, in both incident and prevalent dialysis patients. This activity, mostly due to CVC management, is almost completely carried by nephrologists. Discussion The variability in CVC utilization among centers suggests the lack of a shared policy in patients and access coupling. Quantitative criteria should be used to reduce inappropriate strategy in vascular access creation. Since this activity in Italy is organized at a local level without a shared organizational model, we should inquire whether a system managed so well in the past should now be rebuilt on the model of organ transplantation.

Chronic kidney disease (CKD) includes all clinical features and complications during the progression of various kidney conditions towards end-stage renal disease (ESRD). These conditions include immune and inflammatory disease such as: primary and hepatitis C virus (HCV)-related glomerulonephritis; infectious disease such as pyelonephritis with or without reflux and tuberculosis; vascular disease such as chronic ischemic nephropathy; hereditary and congenital disease such as polycystic disease and congenital cystic dysplasia; metabolic disease including diabetes and hyperuricemia; and systemic disease (collagen disease, vasculitis, myeloma). During the progression of CKD, ultrasound imaging and color Doppler imaging (US–CDI) can differentiate the etiology of the renal damage in only 50–70% of cases. Indeed, the end-stage kidney appears shrunken, reduced in volume (O < 9 cm), unstructured, amorphous, and with acquired cystic degeneration (small and multiple cysts involving the cortex and medulla) or nephrocalcinosis, but there are rare exceptions, such as polycystic kidney disease, diabetic nephropathy, and secondary inflammatory nephropathies. The main difficulties in the differential diagnosis are encountered in multifactorial CKD, which is commonly presented to the nephrologist at stage 4–5, when the kidney is shrunken, unstructured and amorphous. As in acute renal injury and despite the lack of sensitivity, US–CDI is essential for assessing the progression of renal damage and related complications, and for evaluating all conditions that increase the risk of CKD, such as lithiasis, recurrent urinary tract infections, vesicoureteral reflux, polycystic kidney disease and obstructive nephropathy. The timing and frequency of ultrasound scans in CKD patients should be evaluated case by case. In this review, we will consider the morpho-functional features of the kidney in all nephropathies that may lead to progressive CKD.

Introduction: Ultrasound and colorDoppler technique, which is relatively inexpensive, rapid, non-invasive and repeatable is a powerful tool used for early diagnosis of vascular access (VA) complications in hemodialysis patients. To date a standard and widely comprehensible echocolorDoppler (ECD) protocol is not available. Materials and Methods: A simple step-by-step protocol based on anatomical and hemodynamic parameters of VA has been developed during a 3-years VA ECD follow-up. It consists of an ECD study scheme. The algorithm created involves the calculation of brachial artery flow, description of artero-venous and/or graft-vascular anastomosis and efferent vessel and/or graft. Results: The algorithm allows to formulate a medical report that takes into account both anatomic and hemodynamic parameters of the VA. Reduction of complications and the prevention of chronic complications as well as the early detection of acute problems were achieved. Discussion and Conclusion: The creation of a step-by-step protocol may simplify the multidisciplinary management of VA, its monitoring and the early diagnosis of its complications.

In diabetes, kidneys' morphological changes are non-specific at ultrasound (US) and they vary according to disease stage. In the earlier stages, kidneys are enlarged and diffusely hypoechoic due to hyperfiltration. Kidneys size decreases only in advanced stages whereas renal cortical echogenicity progressively increases due to glomerulosclerosis. Nephromegaly, as well as discrepancy between size and renal function, are typical features of diabetic nephropathy either in early or in advanced stages of the disease. Resistive indexes progressively increase together with serum creatinine levels and macro/microcirculation damage. Chronic glomerulonephritis (CGN) is the third leading cause of chronic kidney disease and it represents the clinical evolution of a variety of primary or secondary glomerular diseases. Kidneys in CGN are gradually reduced in volume, but remain symmetric, easily recognizable in renal space until the disease's later stages.

Acute tubular necrosis (ATN) is the most common type of acute kidney injury (AKI) related to parenchymal damage (90% of cases). It may be due to a direct kidney injury, such as sepsis, drugs, toxins, contrast media, hemoglobinuria and myoglobinuria, or it may be the consequence of a prolonged systemic ischemic injury. Conventional ultrasound (US) shows enlarged kidneys with hypoechoic pyramids. Increased volume is largely sustained by the increase of anteroposterior diameter, while longitudinal axis usually maintains its normal length. Despite the role of color Doppler in AKI still being debated, many studies demonstrate that renal resistive indexes (RIs) vary on the basis of primary disease. Moreover, several studies assessed that higher RI values are predictive of persistent AKI. Nevertheless, due to the marked heterogeneity among the studies, further investigations focused on timing of RI measurement and test performances are needed. Acute interstitial nephritis is also a frequent cause of AKI, mainly due to non-steroidal anti-inflammatory drugs and antibiotics administration. The development of acute interstitial nephritis is due to an immunological reaction against nephritogenic exogenous antigens, processed by tubular cells. In acute interstitial nephritis, as well as in ATN, conventional US does not allow a definitive diagnosis. Kidneys appear enlarged and widely hyperechoic due to interstitial edema and inflammatory infiltration. Also, in this condition, hemodynamic changes are closely correlated to the severity and the progression of the anatomical damage.

Chronic kidney disease (CKD) diagnosis and staging are based on estimated or calculated glomerular filtration rate (GFR), urinalysis and kidney structure at renal imaging techniques. Ultrasound (US) has a key role in evaluating both morphological changes (by means of B-Mode) and patterns of vascularization (by means of color-Doppler and contrast-enhanced US), thus contributing to CKD diagnosis and to the follow-up of its progression. In CKD, conventional US allows measuring longitudinal diameter and cortical thickness and evaluating renal echogenicity and urinary tract status. Maximum renal length is usually considered a morphological marker of CKD, as it decreases contemporarily to GFR, and should be systematically recorded in US reports. More recently, it has been found to be a significant correlation of both renal longitudinal diameter and cortical thickness with renal function. Conventional US should be integrated by color Doppler, which shows parenchymal perfusion and patency of veins and arteries, and by spectral Doppler, which is crucial for the diagnosis of renal artery stenosis and provides important information about intrarenal microcirculation. Different values of renal resistive indexes (RIs) have been associated with different primary diseases, as they reflect vascular compliance. Since RIs significantly correlate with renal function, they have been proposed to be independent risk factors for CKD progression, besides proteinuria, low GFR and arterial hypertension. Despite several new applications, US and color Doppler contribute to a definite diagnosis in50% of cases of CKD, because of the lack of specific US patterns, especially in cases of advanced CKD. However, US is useful to evaluate CKD progression and to screen patients at risk for CKD. The indications and the recommended frequency of color Doppler US could differ in each case and the follow-up should be tailored.

Cysts are frequently found in chronic kidney disease (CKD) and they have a different prognostic significance depending on the clinical context. Simple solitary parenchymal cysts and peripelvic cysts are very common and they have no clinical significance. At US, simple cyst appears as a round anechoic pouch with regular and thin profiles. On the other hand, hereditary polycystic disease is a frequent cause of CKD in children and adults. Autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD) are the best known cystic hereditary diseases. ADPKD and ARPKD show a diffused cystic degeneration with cysts of different diameters derived from tubular epithelium. Medullary cystic disease may be associated with tubular defects, acidosis and lithiasis and can lead to CKD. Acquired cystic kidney disease, finally, is secondary to progressive structural end-stage kidney remodelling and may be associated with renal cell carcinoma.

Acute cortical necrosis and hemolytic uremic syndrome (HUS) are 2 clinical scenarios of parenchymal acute kidney injury (AKI) related to renal microvascular injury. Acute cortical necrosis is a rare condition related to an ischemic necrosis of renal cortex. Necrotic lesions can be due to several injuries and may be focal, multifocal or diffuse. Renal necrotic lesions become visible with ultrasound only after renal recovery. HUS is a rare disease characterized by hemolytic anemia, thrombocytopenia and AKI. Color Doppler ultrasound is useful during diagnostic and follow-up phase. Renal artery thrombosis and renal vein thrombosis may also cause parenchymal AKI. Acute renal infarction is a rare pathological condition that occurs due to clots or cholesterol aggregates occluding renal artery or its branches. Several causes may lead to partial or massive kidney ischemic necrosis. Contrast-enhanced CT allows definitive diagnosis in 80% of cases and, at present, it is the first imaging technique used. Ultrasound (US) sensitivity and specificity significantly increases with color Doppler and contrast-enhanced US (CEUS). In AKI patients, in whom the use of iodinated contrast media is contraindicated, color Doppler and CEUS may be valid alternatives for the diagnosis of acute renal infarction. Renal vein thrombosis may be primary or secondary to retroperitoneal neoplasm or inflammatory diseases. It rarely causes an acute worsening of renal function because of the presence of several anastomosis that prevent parenchymal necrosis due to venous congestion. Color Doppler US could detect thrombus within the lumen and document the absence of venous flow.

Acquired cystic kidney disease (ACKD) and renal cell carcinoma (RCC) are the most important manifestations of end-stage kidneys' structural changes. ACKD is caused by kidney damage or scarring and it is characterized by the presence of small, multiple cortical and medullary cysts filled with a fluid similar to preurine. ACKD prevalence varies according to predialysis and dialysis age and its pathogenesis is unknown, although it is stated that progressive destruction of renal tissue induces hypertrophy/compensatory hyperplasia of residual nephrons and may trigger the degenerative process. ACKD is almost asymptomatic, but it can lead to several complications (bleeding, rupture, infections, RCC). Ultrasound (US) is the first level imaging technique in ACKD, because of its sensitivity and reliability. The most serious complication of ACKD is RCC, which is stimulated by the same growth factors and proto-oncogenes that lead to the genesis of cysts. Two different histological types of RCC have been identified: (1) RCC associated with ACKD and (2) papillary renal clear cell carcinoma. Tumors in end-stage kidneys are mainly small, multifocal and bilateral, with a papillary structure and a low degree of malignancy. At US, RCC appears as a small inhomogeneous nodule (3 cm), clearly outlined from the renal profile and hypoechoic if compared with sclerotic parenchyma. In some cases, tumor appears as a homogeneous and hyperechoic multifocal mass. The most specific US sign of a small tumor in end-stage kidney is the important arterial vascularization, in contrast with renal parenchymal vascular sclerosis.

Chronic tubulointerstitial diseases are a common final pathway toward chronic renal failure regardless the primary damage (glomerular, vascular or directly the tubulointerstitium). Chronic tubulointerstitial nephritis (CTN) is characterized by interstitial scarring, fibrosis and tubule atrophy, resulting in progressive chronic kidney disease. Most frequent causes of CTN are drugs, heavy metals, obstructive uropathy, nephrolithiasis, reflux disease, immunologic diseases, neoplasia, ischemia, metabolic diseases, genetics and miscellaneous. At ultrasound (US), kidneys' morphological aspect is similar in all forms of chronic interstitial nephropathy and only chronic pyelonephritis with or without reflux shows distinguishing characteristics. In interstitial nephropathy, kidneys' profiles are finely irregular and corticomedullary differentiation is altered because of a diffused hyperechogenicity. The only indirect sign of chronic interstitial damage can be derived from the value of intrarenal resistive indexes that hardly overcome 0.75. US is mandatory in clinical chronic pyelonephritis work-up because it provides information on kidney's diameter and on growth nomogram in children. Renal profiles can be more or less altered depending on the number of cortical scars and the presence of pseudonodular areas of segmental compensatory hypertrophy. In the early stages, US diagnosis of renal tuberculosis is difficult because parenchymal lesions are non-specific. US sensitivity in the diagnosis of hydronephrosis is very high, close to 100% and, finally, US is the first choice imaging technique in the diagnosis of urinary lithiasis.

Secondary nephropathies can be associated with disreactive immunological disorders or with a non-inflammatory glomerular damage. In systemic lupus erythematosus (SLE), scleroderma and rheumatoid arthritis as in other connective tissue diseases, kidney volume and cortex echogenicity are the parameters that best correlate with clinical severity of the disease, even if the morphological aspect is generally non-specific. Doppler studies in SLE document the correlation between resistance indexes (RIs) values and renal function. Acquired immunodeficiency syndrome (HIV) causes different types of renal damage. At ultrasound (US), kidneys have almost a normal volume, while during superinfection they enlarge (coronal diameter13 cm) and become globular, loosing their normal aspect. Cortex appears highly hyperechoic, uniform or patchy. Microcalcifications of renal cortex and medulla are a US sign that can suggest HIV. In amyloidosis, kidneys appear normal or increased in volume in the early stages of disease. Renal cortex is diffusely hyperechoic and pyramids can show normal size and morphology, but more often they appear poorly defined and hyperechoic. RIs are very high since the early stages of the disease. Nephromegaly with normal kidney shape is the first sign of lymphoma or multiple myeloma. In systemic vasculitis, renal cortex is diffusely hyperechoic, while pyramids appear hypoechoic and globular due to interstitial edema. When vasculitis determines advanced chronic kidney disease stages, kidneys show no specific signs. Microcirculation damage is highlighted by increased RIs values0.70 in the chronic phase.

The incidence of acute kidney injury related to urinary tract obstruction is low (1-10%). It occurs in bilateral renal or lower urinary tract obstruction or in ureter obstruction in patients with a single functioning kidney or with pre-existing chronic kidney disease. The etiology and the incidence of obstruction vary on the basis of age and gender. Conventional ultrasound has a high sensitivity (95%), but low specificity (70%) in the diagnosis of urinary tract obstruction. Nevertheless, color Doppler is used through the evaluation of renal resistive indexes, ureteral jet and twinkling artifact.

Acute kidney injury (AKI), also known in the past as acute renal failure, is a syndrome characterized by the rapid loss of kidney excretory function. It is usually diagnosed by the accumulation of end products of nitrogen metabolism (urea and creatinine) or decreased urine output or both. AKI is the clinical consequence of several disorders that acutely affect the kidney, causing electrolytes and acid-base imbalance, hyperhydration and loss of depurative function. AKI is common in critical care patients in whom it is often secondary to extrarenal events. No specific therapies can attenuate AKI or accelerate renal function recovery; thus, the only treatment is supportive. New diagnostic techniques such as renal biomarkers might improve early diagnosis. Also ultrasonography helps nephrologists in AKI diagnosis, in order to describe and follow kidney alterations and find possible causes of AKI. Renal replacement therapy is a life-saving treatment if AKI is severe. If patients survive to AKI, and did not have previous chronic kidney disease (CKD), they typically recover to dialysis independence. However, evidence suggests that patients who have had AKI are at increased risk of subsequent CKD.

Vascular chronic diseases represent one of the leading causes of end-stage renal disease in incident dialysis patients. B-Mode ultrasound (US) and color Doppler (CD) have a high sensitivity and specificity in the diagnosis of vascular chronic diseases. US and CD should be used to identify subjects in the high risk population who are affected by main renal artery stenosis (RAS) and to identify and characterize patients without RAS who have chronic ischemic nephropathy caused by nephroangiosclerosis and/or atheroembolic disease. The most important CD parameters in the work-up of suspected RAS are increased peak systolic velocity and diastolic velocity, spectral broadening, high renal:aortic ratio and lateralization of renal resistive indexes (RIs). In the absence of direct or indirect signs of RAS, increases in intraparenchymal RIs, associated with systemic atherosclerotic disease, are indicative of microcirculation damage related to nephroangiosclerosis or atheroembolic disease.

Acute cortical necrosis and hemolytic uremic syndrome (HUS) are 2 clinical scenarios of parenchymal acute kidney injury (AKI) related to renal microvascular injury. Acute cortical necrosis is a rare condition related to an ischemic necrosis of renal cortex. Necrotic lesions can be due to several injuries and may be focal, multifocal or diffuse. Renal necrotic lesions become visible with ultrasound only after renal recovery. HUS is a rare disease characterized by hemolytic anemia, thrombocytopenia and AKI. Color Doppler ultrasound is useful during diagnostic and follow-up phase. Renal artery thrombosis and renal vein thrombosis may also cause parenchymal AKI. Acute renal infarction is a rare pathological condition that occurs due to clots or cholesterol aggregates occluding renal artery or its branches. Several causes may lead to partial or massive kidney ischemic necrosis. Contrast-enhanced CT allows definitive diagnosis in 80% of cases and, at present, it is the first imaging technique used. Ultrasound (US) sensitivity and specificity significantly increases with color Doppler and contrast-enhanced US (CEUS). In AKI patients, in whom the use of iodinated contrast media is contraindicated, color Doppler and CEUS may be valid alternatives for the diagnosis of acute renal infarction. Renal vein thrombosis may be primary or secondary to retroperitoneal neoplasm or inflammatory diseases. It rarely causes an acute worsening of renal function because of the presence of several anastomosis that prevent parenchymal necrosis due to venous congestion. Color Doppler US could detect thrombus within the lumen and document the absence of venous flow.

The incident hemodialysis (HD) population is aging, and the elderly group is the one with the most rapid increase. In this context it is important to define the factors associated with outcomes in elderly patients. The high prevalence of comorbidities, particularly diabetes mellitus, peripheral vascular disease and congestive heart failure, usually make vascular access (VA) creation more difficult. Furthermore, many of these patients may have an insufficient vasculature for fistula maturation. Finally, many fistulas may never be used due to the competing risk of death before dialysis initiation. In these cases, an arteriovenous graft and in some cases a central venous catheter become a valid alternative form of VA. Nephrologists need to know what is the most appropriate VA option in these patients. Age should not be a limiting factor when determining candidacy for arteriovenous fistula creation. The aim of this position statement, prepared by experts of the Vascular Access Working Group of the Italian Society of Nephrology, is to critically review the current evidence on VA in elderly HD patients. To this end, relevant clinical studies and recent guidelines on VA are reviewed and commented. The main advantages and potential drawbacks of the different VA modalities in the elderly patients are discussed.

Secondary nephropathies can be associated with disreactive immunological disorders or with a non-inflammatory glomerular damage. In systemic lupus erythematosus (SLE), scleroderma and rheumatoid arthritis as in other connective tissue diseases, kidney volume and cortex echogenicity are the parameters that best correlate with clinical severity of the disease, even if the morphological aspect is generally non-specific. Doppler studies in SLE document the correlation between resistance indexes (RIs) values and renal function. Acquired immunodeficiency syndrome (HIV) causes different types of renal damage. At ultrasound (US), kidneys have almost a normal volume, while during superinfection they enlarge (coronal diameter >13 cm) and become globular, loosing their normal aspect. Cortex appears highly hyperechoic, uniform or patchy. Microcalcifications of renal cortex and medulla are a US sign that can suggest HIV. In amyloidosis, kidneys appear normal or increased in volume in the early stages of disease. Renal cortex is diffusely hyperechoic and pyramids can show normal size and morphology, but more often they appear poorly defined and hyperechoic. RIs are very high since the early stages of the disease. Nephromegaly with normal kidney shape is the first sign of lymphoma or multiple myeloma. In systemic vasculitis, renal cortex is diffusely hyperechoic, while pyramids appear hypoechoic and globular due to interstitial edema. When vasculitis determines advanced chronic kidney disease stages, kidneys show no specific signs. Microcirculation damage is highlighted by increased RIs values >0.70 in the chronic phase.

Acute tubular necrosis (ATN) is the most common type of acute kidney injury (AKI) related to parenchymal damage (90% of cases). It may be due to a direct kidney injury, such as sepsis, drugs, toxins, contrast media, hemoglobinuria and myoglobinuria, or it may be the consequence of a prolonged systemic ischemic injury. Conventional ultrasound (US) shows enlarged kidneys with hypoechoic pyramids. Increased volume is largely sustained by the increase of anteroposterior diameter, while longitudinal axis usually maintains its normal length. Despite the role of color Doppler in AKI still being debated, many studies demonstrate that renal resistive indexes (RIs) vary on the basis of primary disease. Moreover, several studies assessed that higher RI values are predictive of persistent AKI. Nevertheless, due to the marked heterogeneity among the studies, further investigations focused on timing of RI measurement and test performances are needed. Acute interstitial nephritis is also a frequent cause of AKI, mainly due to non-steroidal anti-inflammatory drugs and antibiotics administration. The development of acute interstitial nephritis is due to an immunological reaction against nephritogenic exogenous antigens, processed by tubular cells. In acute interstitial nephritis, as well as in ATN, conventional US does not allow a definitive diagnosis. Kidneys appear enlarged and widely hyperechoic due to interstitial edema and inflammatory infiltration. Also, in this condition, hemodynamic changes are closely correlated to the severity and the progression of the anatomical damage.

BK polyomavirus (BKV) is an emerging pathogen in immunocompromised patients. BKV infection occurs in 1-9 % of renal transplants and causes chronic nephropathy or graft loss. Diagnosis of BKV-associated nephropathy (BKVAN) is based on detection of viruria then viremia and at least a tubule-interstitial nephritis at renal biopsy. This paper describes the ultrasound and color Doppler (US-CD) features of BKVAN. Seventeen patients affected by BKVAN were studied using a linear bandwidth 7-12 MHz probe. Ultrasound showed a widespread streak-like pattern with alternating normal echoic and hypoechoic streaks with irregular edges from the papilla to the cortex. Renal biopsy performed in hypoechoic areas highlighted the typical viral inclusions in tubular epithelial cells. Our experience suggests a possible role for US-CD in the non-invasive diagnosis of BKVAN when combined with blood and urine screening tests. US-CD must be performed with a high-frequency linear probe to highlight the streak-like pattern of the renal parenchyma.

Vascular chronic diseases represent one of the leading causes of end-stage renal disease in incident dialysis patients. B-Mode ultrasound (US) and color Doppler (CD) have a high sensitivity and specificity in the diagnosis of vascular chronic diseases. US and CD should be used to identify subjects in the high risk population who are affected by main renal artery stenosis (RAS) and to identify and characterize patients without RAS who have chronic ischemic nephropathy caused by nephroangiosclerosis and/or atheroembolic disease. The most important CD parameters in the work-up of suspected RAS are increased peak systolic velocity and diastolic velocity, spectral broadening, high renal:aortic ratio and lateralization of renal resistive indexes (RIs). In the absence of direct or indirect signs of RAS, increases in intraparenchymal RIs, associated with systemic atherosclerotic disease, are indicative of microcirculation damage related to nephroangiosclerosis or atheroembolic disease.

Chronic kidney disease (CKD) diagnosis and staging are based on estimated or calculated glomerular filtration rate (GFR), urinalysis and kidney structure at renal imaging techniques. Ultrasound (US) has a key role in evaluating both morphological changes (by means of B-Mode) and patterns of vascularization (by means of color-Doppler and contrast-enhanced US), thus contributing to CKD diagnosis and to the follow-up of its progression. In CKD, conventional US allows measuring longitudinal diameter and cortical thickness and evaluating renal echogenicity and urinary tract status. Maximum renal length is usually considered a morphological marker of CKD, as it decreases contemporarily to GFR, and should be systematically recorded in US reports. More recently, it has been found to be a significant correlation of both renal longitudinal diameter and cortical thickness with renal function. Conventional US should be integrated by color Doppler, which shows parenchymal perfusion and patency of veins and arteries, and by spectral Doppler, which is crucial for the diagnosis of renal artery stenosis and provides important information about intrarenal microcirculation. Different values of renal resistive indexes (RIs) have been associated with different primary diseases, as they reflect vascular compliance. Since RIs significantly correlate with renal function, they have been proposed to be independent risk factors for CKD progression, besides proteinuria, low GFR and arterial hypertension. Despite several new applications, US and color Doppler contribute to a definite diagnosis in

Acquired cystic kidney disease (ACKD) and renal cell carcinoma (RCC) are the most important manifestations of end-stage kidneys' structural changes. ACKD is caused by kidney damage or scarring and it is characterized by the presence of small, multiple cortical and medullary cysts filled with a fluid similar to preurine. ACKD prevalence varies according to predialysis and dialysis age and its pathogenesis is unknown, although it is stated that progressive destruction of renal tissue induces hypertrophy/compensatory hyperplasia of residual nephrons and may trigger the degenerative process. ACKD is almost asymptomatic, but it can lead to several complications (bleeding, rupture, infections, RCC). Ultrasound (US) is the first level imaging technique in ACKD, because of its sensitivity and reliability. The most serious complication of ACKD is RCC, which is stimulated by the same growth factors and proto-oncogenes that lead to the genesis of cysts. Two different histological types of RCC have been identified: (1) RCC associated with ACKD and (2) papillary renal clear cell carcinoma. Tumors in end-stage kidneys are mainly small, multifocal and bilateral, with a papillary structure and a low degree of malignancy. At US, RCC appears as a small inhomogeneous nodule (

Kidneys' imaging provides useful information in acute kidney injury (AKI) diagnosis and management. Today, several imaging techniques give information on kidneys anatomy, urinary obstruction, differential diagnosis between AKI and chronic kidney disease (CKD), renal blood flow and glomerular filtration rate. Ultrasound is a safe, non-invasive and repeatable imaging technique so it is widely used in the first level work-up of AKI. The utility of contrast-enhanced computed tomography and magnetic resonance imaging in AKI or in AKI during CKD is limited because of renal toxicity associated with contrast agents used.

Chronic tubulointerstitial diseases are a common final pathway toward chronic renal failure regardless the primary damage (glomerular, vascular or directly the tubulointerstitium). Chronic tubulointerstitial nephritis (CTN) is characterized by interstitial scarring, fibrosis and tubule atrophy, resulting in progressive chronic kidney disease. Most frequent causes of CTN are drugs, heavy metals, obstructive uropathy, nephrolithiasis, reflux disease, immunologic diseases, neoplasia, ischemia, metabolic diseases, genetics and miscellaneous. At ultrasound (US), kidneys' morphological aspect is similar in all forms of chronic interstitial nephropathy and only chronic pyelonephritis with or without reflux shows distinguishing characteristics. In interstitial nephropathy, kidneys' profiles are finely irregular and corticomedullary differentiation is altered because of a diffused hyperechogenicity. The only indirect sign of chronic interstitial damage can be derived from the value of intrarenal resistive indexes that hardly overcome 0.75. US is mandatory in clinical chronic pyelonephritis work-up because it provides information on kidney's diameter and on growth nomogram in children. Renal profiles can be more or less altered depending on the number of cortical scars and the presence of pseudonodular areas of segmental compensatory hypertrophy. In the early stages, US diagnosis of renal tuberculosis is difficult because parenchymal lesions are non-specific. US sensitivity in the diagnosis of hydronephrosis is very high, close to 100% and, finally, US is the first choice imaging technique in the diagnosis of urinary lithiasis.

Renal failure commonly occurs in patients affected by cirrhosis, especially when there is ascites. It is typically secondary to intercurrent events that can further compromise blood flow in conditions of relatively decreased renal perfusion. Hepatorenal syndrome (HRS) is a particular and common type of kidney failure that affects patients with liver cirrhosis or, less frequently, with fulminant hepatic failure. The syndrome is characterized by splanchnic vasodilation and renal vasoconstriction. The classification of HRS identifies 2 categories of kidney failure, known as type 1 and type 2 HRS, that occur in patients with either cirrhosis or fulminant hepatic failure.

Acute kidney injury (AKI), also known in the past as acute renal failure, is a syndrome characterized by the rapid loss of kidney excretory function. It is usually diagnosed by the accumulation of end products of nitrogen metabolism (urea and creatinine) or decreased urine output or both. AKI is the clinical consequence of several disorders that acutely affect the kidney, causing electrolytes and acid-base imbalance, hyperhydration and loss of depurative function. AKI is common in critical care patients in whom it is often secondary to extrarenal events. No specific therapies can attenuate AKI or accelerate renal function recovery; thus, the only treatment is supportive. New diagnostic techniques such as renal biomarkers might improve early diagnosis. Also ultrasonography helps nephrologists in AKI diagnosis, in order to describe and follow kidney alterations and find possible causes of AKI. Renal replacement therapy is a life-saving treatment if AKI is severe. If patients survive to AKI, and did not have previous chronic kidney disease (CKD), they typically recover to dialysis independence. However, evidence suggests that patients who have had AKI are at increased risk of subsequent CKD.

Cysts are frequently found in chronic kidney disease (CKD) and they have a different prognostic significance depending on the clinical context. Simple solitary parenchymal cysts and peripelvic cysts are very common and they have no clinical significance. At US, simple cyst appears as a round anechoic pouch with regular and thin profiles. On the other hand, hereditary polycystic disease is a frequent cause of CKD in children and adults. Autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD) are the best known cystic hereditary diseases. ADPKD and ARPKD show a diffused cystic degeneration with cysts of different diameters derived from tubular epithelium. Medullary cystic disease may be associated with tubular defects, acidosis and lithiasis and can lead to CKD. Acquired cystic kidney disease, finally, is secondary to progressive structural end-stage kidney remodelling and may be associated with renal cell carcinoma.

In diabetes, kidneys' morphological changes are non-specific at ultrasound (US) and they vary according to disease stage. In the earlier stages, kidneys are enlarged and diffusely hypoechoic due to hyperfiltration. Kidneys size decreases only in advanced stages whereas renal cortical echogenicity progressively increases due to glomerulosclerosis. Nephromegaly, as well as discrepancy between size and renal function, are typical features of diabetic nephropathy either in early or in advanced stages of the disease. Resistive indexes progressively increase together with serum creatinine levels and macro/microcirculation damage. Chronic glomerulonephritis (CGN) is the third leading cause of chronic kidney disease and it represents the clinical evolution of a variety of primary or secondary glomerular diseases. Kidneys in CGN are gradually reduced in volume, but remain symmetric, easily recognizable in renal space until the disease's later stages.

An increase of glomerular filtration rate after protein load represents renal functional reserve (RFR) and is due to afferent arteriolar vasodilation. Lack of RFR may be a risk factor for acute kidney injury (AKI), but is cumbersome to measure. We sought to develop a non-invasive, bedside method that would indirectly measure RFR. Mechanical abdominal pressure, through compression of renal vessels, decreases blood flow and activates the auto-regulatory mechanism which can be measured by a fall in renal resistive index (RRI). The study aims at elucidating the relationship between intra-parenchymal renal resistive index variation (IRRIV) during abdominal pressure and RFR. In healthy volunteers, pressure was applied by a weight on the abdomen (fluid-bag 10% of subject's body weight) while RFR was measured through a protein loading test. We recorded RRI in an interlobular artery after application of pressure using ultrasound. The maximum percentage reduction of RRI from baseline was compared in the same subject to RFR. We enrolled 14 male and 16 female subjects (mean age 38 ± 14 years). Mean creatinine clearance was 106.2 ± 16.4 ml/min/1.73 m(2). RFR ranged between -1.9 and 59.7 with a mean value of 28.9 ± 13.1 ml/min/1.73 m(2). Mean baseline RRI was 0.61 ± 0.05, compared to 0.49 ± 0.06 during abdominal pressure; IRRIV was 19.6 ± 6.7%, ranging between 3.1% and 29.2%. Pearson's coefficient between RFR and IRRIV was 74.16% (p < 0.001). Our data show the correlation between IRRIV and RFR. Our results can lead to the development of a "stress test" for a rapid screen of RFR to establish renal susceptibility to different exposures and the consequent risk for AKI.

Renal failure commonly occurs in patients affected by cirrhosis, especially when there is ascites. It is typically secondary to intercurrent events that can further compromise blood flow in conditions of relatively decreased renal perfusion. Hepatorenal syndrome (HRS) is a particular and common type of kidney failure that affects patients with liver cirrhosis or, less frequently, with fulminant hepatic failure. The syndrome is characterized by splanchnic vasodilation and renal vasoconstriction. The classification of HRS identifies 2 categories of kidney failure, known as type 1 and type 2 HRS, that occur in patients with either cirrhosis or fulminant hepatic failure.

To assess the knowledge of adult hemodialysis patients and nurses working in dialysis units, specifically with regard to knowledge of phosphorus and other nutrients related to dietary management of end-stage renal disease.Cross-sectional cohort study.Hemodialysis unit.One hundred ninety-one hemodialysis patients and 105 dialysis nurses, as well as 86 control hospital employees who are not health professionals.Nutritional knowledge was assessed by a 25-item chronic kidney disease knowledge assessment tool for nutrition, which includes 15 questions on phosphorus and 10 questions on protein, sodium, and potassium knowledge.The scores obtained by patients were much lower than those of nurses (11.6 ± 3.9 vs. 16.0 ± 2.2, P.001) but slightly higher than those of controls (10.6 ± 3.2, P.05). Patients with phosphorus serum level5.5 mg/dL showed chronic kidney disease knowledge assessment tool for nutrition scores similar to those of patients with a serum phosphorus level5.5 mg/dL. The prevalence of right answers to questions regarding knowledge of phosphorus was lower than that regarding knowledge of the other nutrients, both for patients (38.4% ± 17.8% vs. 57.3% ± 19.9%, P.001) and nurses (55.6% ± 11.1% vs. 74.8% ± 11.7%, P.001) as well as for controls (30.7% ± 14.5% vs. 60.1% ± 17.4%, P.001).Our study suggests that nutritional knowledge of hemodialysis patients, although higher than the general population, is lower for phosphorus with respect to the other nutrients, such as protein, sodium, and potassium. This occurs even in patients with hyperphosphatemia or those taking phosphate binder medications. Nurses showed the best scores; however, improvement is necessary, especially with regard to knowledge of phosphorus. Training programs on nutrition for nurses and on information for patients should be implemented. They can contribute to achievement of a more effective control of phosphate balance, reduction of costs, and improvement of the quality of care for hemodialysis patients.

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