Search

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.

The purpose of this study was to investigate the relationship between preoperative psychological factors and percentage of total weight loss (%TWL) after laparoscopic Roux-en-Y gastric bypass (LRYGB) to identify possible psychological therapy targets to improve the outcome of bariatric surgery. Seventy-six patients completed the Hamilton's Anxiety and Depression Scales (HAM-A, HAM-D) and Toronto Alexithymia Scale (TAS-20) the day before surgery (T0). The pre-operative body weight and the %TWL at 3 (T1), 6 (T2), and 24–30 (T3) months were collected. At T3, depressed and alexithymic patients showed a lower %TWL compared to non-depressed patients (p = 0.03) and to non-alexithymic patients (p = 0.02), respectively. Finally, patients who had at least one of the three analyzed psychological factors showed less weight loss, at T2 (p = 0.02) and T3 (p = 0.0004). Psychological factors may also affect long-term outcome of bariatric surgery. This study shows an association between alexithymia/depression pre-operative levels and the weight loss at 30 months’follow-up after bariatric surgery. Level III, longitudinal cohort study.

Current literature suggests a higher risk of pregnancy-related complications in patients with renal fibromuscular dysplasia (FMD). The aim of our study was to assess the nature and prevalence of pregnancy-related complications in patients subsequently diagnosed with FMD. A call for participation was sent to centers contributing to the European/International FMD Registry. Patients with at least 1 pregnancy were included. Data on pregnancy were collected through medical files and FMD characteristics through the European/International FMD Registry. Data from 534 pregnancies were obtained in 237 patients. Despite the fact that, in 96% of cases, FMD was not diagnosed before pregnancy, 40% of women (n=93) experienced pregnancy-related complications, mostly gestational hypertension (25%) and preterm birth (20%), while preeclampsia was reported in only 7.5%. Only 1 patient experienced arterial dissection and another patient an aneurysm rupture. When compared with patients without pregnancy-related complications, patients with complicated pregnancies were younger at FMD diagnosis (43 versus 51 years old; P P =0.003) but underwent more often renal revascularization (63% versus 40%, P

AIMS: Since December 2015, the European/International Fibromuscular Dysplasia (FMD) Registry enrolled 1022 patients from 22 countries. We present their characteristics according to disease subtype, age and gender, as well as predictors of widespread disease, aneurysms and dissections. METHODS AND RESULTS: All patients diagnosed with FMD (string-of-beads or focal stenosis in at least one vascular bed) based on CTA, MRA and/or catheter-based angiography were eligible.Patients were predominantly women (82%) and Caucasians (88%). Age at diagnosis was 46±16 years (12% ≥65yo), 86% were hypertensive, 72% had multifocal and 57% multivessel FMD. Compared to patients with multifocal FMD, patients with focal FMD were younger, more often men, had less often multivessel FMD but more revascularizations. Compared to women with FMD, men were younger, had more often focal FMD and arterial dissections. Compared to younger patients with FMD, patients ≥65yo had more often multifocal FMD, lower eGFR and more atherosclerotic lesions. Independent predictors of multivessel FMD were age at FMD diagnosis, stroke, multifocal subtype, presence of aneurysm or dissection and family history of FMD. Predictors of aneurysms were multivessel and multifocal FMD. Predictors of dissections were age at FMD diagnosis, male gender, stroke and multivessel FMD. CONCLUSIONS: The European/International FMD Registry allowed large-scale characterization of distinct profiles of patients with FMD and, more importantly, identification of a unique set of independent predictors of widespread disease, aneurysms and dissections, paving the way for targeted screening, management and follow-up of FMD. TRANSLATIONAL PERSPECTIVE: Fibromuscular dysplasia (FMD) is nowadays considered as a systemic arterial disease, warranting brain-to-pelvis vascular imaging in all patients. However, most current evidence is derived from a limited number of expert centres. Furthermore, one size may not fit all. Based on analysis of the first thousand patients enrolled in the European/International FMD registry (46 centres; 22 countries) we characterized distinct patient profiles according to FMD subtype, age and gender and identified predictors of widespread disease, aneurysms and dissections, paving the way for individualized management and follow-up. Further studies will allow refining patient characterization according to ethnicity, genetic profile and imaging biomarkers.

Aim of this study was to investigate relationship between preoperative psychological factors and % total weight loss after gastric bypass. 76 adult patients scheduled for bariatric surgery were preoperatively asked to complete anxiety and depression Hamilton scales and Toronto Alexithymia Scale. At 3- and 6-month follow-up, body weight was assessed. At 6-month follow-up, alexithymic patients showed a poorer % total weight loss compared with non-alexithymic patients ( p = .017), and moderately depressed patients showed a lower % total weight loss compared with non-depressed patients ( p = .011). Focused pre- and postoperative psychological support could be useful in bariatric patients in order to improve surgical outcome.

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 (

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.

non disponibile

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.

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.

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.

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.

Vascular access (VA) is the lifeline for the hemodialysis patient and the native arterio-venous fistula (AVF) is the first-choice access. Among the different tests used in the VA domain, color Doppler ultrasound (CD-US) plays a key role in the clinical work-up. At the present time, three are the main fields of CD-US application: (i) evaluation of forearm arteries and veins in surgical planning; (ii) testing of AVF maturation; (iii) VA complications. Specifically, during the AVF maturation, CD-US allows to measure the diameter and flow volume in the brachial artery and calculate the peak systolic velocity (PSV) of the arterial axis, anastomosis and efferent vein, to detect critical stenosis. The borderline stenosis, revealed by the discrepancies between access flow rate and PSV, should be followed up with subsequent tests to detect progression of stenosis; the cases with significant changes in brachial flow should be referred to angiography. In conclusion, clinical monitoring remains the backbone of any VA program. CD-US is of utmost importance in a patient-centered VA evaluation, because it allows the appropriate management of all aspects of VA care. These are the main reasons why we strongly advocate the adoption of a VA surveillance program based on CD-US.

Lesson This case offers a starting point for a literature review on peritoneal ultrafiltration in refractory heart failure.

Chronic kidney disease (CKD) encompasses all clinical features and complications during the progression of various kidney conditions towards end-stage renal disease. These conditions include immune and inflammatory diseases such as primary and HCV-related glomerulonephritis; infectious diseases such as pyelonephritis with or without reflux and tuberculosis; vascular diseases such as chronic ischemic nephropathy; hereditary and congenital diseases such as polycystic disease and congenital cystic dysplasia; metabolic diseases including diabetes and hyperuricemia; and systemic diseases (collagen disease, vasculitis, myeloma). During the progression of CKD, ultrasound imaging can differentiate the nature of the renal damage in only 50-70% of cases. Infact, the end-stage kidney appears shrunken, reduced in volume (Ø9 cm), unstructured, amorphous, 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, ultrasonography is essential for assessing the progression of the 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 morphofunctional features of the kidney in all nephropathies that may lead to progressive CKD.

At present, ultrasonography (US) is not able to define the type of renal damage and therefore cannot replace percutaneous renal biopsy in the diagnosis of acute kidney disease. It is, however, the most immediate and safest imaging technique for the evaluation of patients with acute kidney injury (AKI) in order to exclude urinary tract obstruction or chronic kidney disease and guide clinical decision-making. In prerenal AKI caused by cardiorenal syndrome type 1, US does not show specific signs. However, in these patients, pleuropulmonary US is the first-choice imaging technique to evaluate the congestion of subpleural interlobular septa and to identify and count lung comet tails. In cardiorenal syndrome type 2, US visualizes signs of systemic overload (right pleural effusion, liver stasis, overdistention and rigidity of the inferior vena cava and suprahepatic veins). In acute tubular necrosis (ATN), the most common type of AKI, gray-scale US is nonspecific and shows enlarged kidneys with hypoechoic pyramids due to medullary edema. The resistance index (RI) is a very useful marker to establish the severity of ATN and the required follow-up, and to evaluate functional recovery, since its reduction precedes the normalization of serum creatinine. US is the technique of choice in the diagnosis of obstructive nephropathy, where it is highly sensitive (95%) but less specific (70%). The primary objective of this review is to analyze the applications of US in the diagnosis of prerenal, renal and postrenal AKI.

Secondary hyperparathyroidism (sHPT) is one of the most common and serious complications of chronic kidney disease (CKD) and maintenance hemodialysis (MHD). In sHPT, the biology of parathyroid cells changes significantly toward diffuse and nodular hyperplasia. Diagnosis and treatment of sHPT are based on intact parathyroid hormone (i-PTH) serum levels and on the parameters of mineral metabolism. The morphological diagnosis of sHPT relies on 2 complementary imaging techniques: high-resolution ultrasonography with color Doppler imaging (US/CD) and 99mTc-methoxyisobutylisonitrile (MIBI) scintigraphy. The main objective of this review is to stimulate nephrologists to use US/CD of the parathyroid glands during the progression of CKD in order to aid clinical, pharmacological and surgical strategies. The primary role of US/CD in sHPT should be to integrate the clinical diagnosis by defining the number and volume of hyperplastic glands, although the international guidelines do not state when and why to perform US/CD. This review also evaluates the role of US/CD in clinical follow-up and assessment of therapeutic response of sHPT, and it highlights how US/CD can evaluate the effect of therapy with phosphate binders, vitamin D or its analogues and calcimimetics, which are changing the natural history of sHPT and the frequency of parathyroidectomy. Evaluation of the morphological and vascular changes of hyperplastic parathyroids is useful to guide percutaneous ethanol injection therapy and to support clinical, pharmacological and surgical strategies. Epidemiological studies are needed to establish how US/CD could change the management of sHPT and why it should be repeated in patients with high levels of serum i-PTH.

When a renal mass is suspected, conventional ultrasound and color Doppler imaging are often used for initial assessment. Ultrasound screening has many advantages over contrast-enhanced CT and MRI, such as accessibility, low costs, and no need for intravenous iodine contrast administration or ionizing radiation. Sonography is very helpful to distinguish cystic from solid lesions and to monitor the growth and structural pattern of cysts. Detection of small renal carcinoma of less than 3 cm in diameter is limited, however, and small tumors are detected by conventional ultrasound only in 67-79% of cases. In fact, small renal malignancies may have an echogenicity similar to the normal renal parenchyma. In these cases it is very hard to distinguish the tumor, particularly when there is no evident disarrangement of the normal renal contours and no extension into the central renal complex. Renal cell carcinoma can also be hypo- or hyperechoic and indistinguishable from renal adenoma/oncocytoma or angiomyolipomas, which are commonly described as hyperechoic masses. In other words, the pattern and ultrasound characteristics of renal masses often overlap between benign and malignant tumors. A diagnosis of a malignant cystic lesion requires evidence of multiple, thickened internal septa, calcifications, vascularity, and parietal nodularity. When a solid lesion does not show the typical appearance of a simple cyst (a round anechoic lesion with a smooth well-defined wall, without internal debris, and showing increased through-transmission), further evaluation with contrast-enhanced CT or MRI is necessary. Contrast-enhanced ultrasound (CEUS) improves the sensitivity for detection of small renal masses. Compared to CT, CEUS is able to better visualize the number of septa, the septum and wall thickness, the presence of a solid component, and enhancement in some cases, resulting in upgrading of the Bosniak classification and affecting treatment planning.

Gray-scale ultrasound is the diagnostic technique of choice in patients with suspected or known renal disease. Knowledge of the normal and abnormal sonographic morphology of the kidney and urinary tract is essential for a successful diagnosis. Conventional sonography must always be complemented by Doppler sampling of the principal arterial and venous vessels. B-mode scanning is performed with the patient in supine, prone or side position. The kidney can be imaged by the anterior, lateral or posterior approach using coronal, transverse and oblique scanning planes. Morphological parameters that must be evaluated are the coronal diameter, the parenchymal thickness and echogenicity, the structure and state of the urinary tract, and the presence of congenital anomalies that may mimic a pseudomass. The main renal artery and the hilar-intraparenchymal branches of the arterial and venous vessels should be accurately evaluated using color Doppler. Measurement of intraparenchymal resistance indices (IP, IR) provides an indirect and quantitative parameter of the stiffness and eutrophic or dystrophic remodeling of the intrarenal microvasculature. These parameters differ depending on age, diabetic and hypertensive disease, chronic renal glomerular disease, and interstitial, vascular and obstructive nephropathy.

Advances in digital technology in the last decades have led to a fast development of ultrasound technology. Ultrasound information originating from stationary structures or red blood cells moving into the vessels can be visualized with different imaging modalities. Conventional B-mode sonography provides anatomical details based on acoustic impedance differences. Gray-scale sonography represents the structural echoes as brightness points. Based on the Doppler effect, vascular scattering can be represented as spectral wave velocity depending on time (velocity/time curve), or as dual-scale color mapping depending on the changes in average blood velocity. The flow-in is depicted in red and the flow-out in blue. The analysis of the vascular scattering enhanced by infusion of contrast agents is the basis of contrast-enhanced harmonic imaging. The perfusional pattern of tissues allows the differential diagnosis of expansive lesions. Tissue strain analysis provides a new dimension of diagnostic information. It is used in elastographic imaging to describe relative physical tissue stiffness properties. Tissue stiffness information is complementary to and independent of the acoustic impedance information provided by B-mode imaging as well as the vascular flow information provided by Doppler imaging. Adjacent tissue elements may appear identical using conventional B-mode or Doppler imaging. When stress (axial force) is applied to tissues, they show different degrees of deformation. Comparing the baseline and stress image information, each tissue element may be labeled by its relative stiffness. A lighter shade indicates relatively soft tissue (elastic), while a darker shade indicates relatively stiff tissue (non-elastic).

Sonography is an imaging technique that generates tomographic images using ultrasound. The sound constitutes mechanical energy transmitted in a medium by pressure waves. Sound waves with frequencies greater than 20 kHz are called ultrasounds. Diagnostic ultrasounds use frequencies from 1 to 20 MHz. Ultrasound equipment is composed of a scanner, an image monitor, and different transducers that transform acoustic energy into electrical signals and electrical energy into acoustic energy (piezoelectric effect). The spatial resolution defines the minimum distance between two reflectors or echogenic regions that can be imaged as separate reflectors. The spatial resolution is mainly determined by the array design (linear, curved and sectorial) and by the operative system of the transducer. Modern ultrasound machines are very sophisticated medical devices that often support many transducers, imaging modes and display devices. The scan converter memory is the device in which images are formed and then presented to the monitor and to the hard copy devices.