Cardiomyocyte substructure reverts to an immature phenotype during heart failure.

KEY POINTS: As reactivation of the fetal gene program has been implicated in pathological remodelling during heart failure (HF), we examined whether cardiomyocyte subcellular structure and function revert to an immature phenotype during this disease. Surface and internal membrane structures appeared gradually during development, and returned to a juvenile state during HF. Similarly, dyadic junctions between the cell membrane and sarcoplasmic reticulum were progressively 'packed' with L-type Ca2+ channels and ryanodine receptors during development, and 'unpacked' during HF. Despite similarities in subcellular structure, dyads were observed to be functional from early developmental stages, but exhibited an impaired ability to release Ca2+ in failing cardiomyocytes. Thus, while immature and failing cardiomyocytes share similarities in subcellular structure, these do not fully account for the marked impairment of Ca2+ homeostasis observed in HF. ABSTRACT: Reactivation of the fetal gene programme has been implicated as a driver of pathological cardiac remodelling. Here we examined whether pathological remodelling of cardiomyocyte substructure and function during heart failure (HF) reflects a reversion to an immature phenotype. Using scanning electron microscopy, we observed that Z-grooves and t-tubule openings at the cell surface appeared gradually during cardiac development, and disappeared during HF. Confocal and super-resolution imaging within the cell interior revealed similar structural parallels; disorganization of t-tubules in failing cells was strikingly reminiscent of the late stages of postnatal development, with fewer transverse elements and a high proportion of longitudinal tubules. Ryanodine receptors (RyRs) were observed to be laid down in advance of developing t-tubules and similarly 'orphaned' in HF, although RyR distribution along Z-lines was relatively sparse. Indeed, nanoscale imaging revealed coordinated packing of L-type Ca2+ channels and RyRs into dyadic junctions during development, and orderly unpacking during HF. These findings support a 'last in, first out' paradigm, as the latest stages of dyadic structural development are reversed during disease. Paired imaging of t-tubules and Ca2+ showed that the disorganized arrangement of dyads in immature and failing cells promoted desynchronized and slowed Ca2+ release in these two states. However, while developing cells exhibited efficient triggering of Ca2+ release at newly formed dyads, dyadic function was impaired in failing cells despite similar organization of Ca2+ handling proteins. Thus, pathologically deficient Ca2+ homeostasis during HF is only partly linked to the re-emergence of immature subcellular structure, and additionally reflects lost dyadic functionality.

Prenatal diagnosis of androgen insensitivity syndrome.

Androgen insensitivity syndrome (AIS) (OMIM 300068) is an X-linked recessive genetic disorder with an XY karyotype that is caused by androgen receptor (AR) defects. We report a prenatal diagnosis case with clinical and molecular findings. The fetal phenotype was female, moreover the autopsy revealed the presence of abdominal testes confirmed by histopathological examination. The AR gene molecular analysis performed on the fetal DNA showed the presence of a c.2493C>T change in exon 4. The single nucleotide change resulted in a Q711X amino acid substitution within the AR ligand-binding domain of the protein that has never been described before in the literature. AIS is an important consideration in pregnancies that show sex discordance in ultrasonography and karyotype results with the opportunity to perform molecular analysis of the AR gene in order to confirm the diagnosis.

Low-dose nesiritide in human anterior myocardial infarction suppresses aldosterone and preserves ventricular function and structure: a proof of concept study.

BACKGROUND: B-type natriuretic peptide (BNP, nesiritide) has anti-fibrotic, anti-hypertrophic, anti-inflammatory, vasodilating, lusitropic and aldosterone-inhibiting properties but conventional doses of BNP cause hypotension, limiting its use in heart failure. OBJECTIVE: To determine whether infusion of low-dose BNP within 24 h of successful reperfusion for anterior acute myocardial infarction (AMI) would prevent adverse left ventricular (LV) remodelling and suppress aldosterone. METHODS: A translational proof-of-concept study was carried out to determine tolerability and biological activity of intravenous BNP at 0.003 and 0.006 microg/kg/min, without bolus started within 24 h of successful reperfusion for anterior AMI. 24 patients with first anterior wall ST elevation AMI and successful revascularisation were randomly assigned to receive 0.003 (n = 12) or 0.006 (n = 12) microg/kg/min of IV BNP for 72 h in addition to standard care during hospitalisation for anterior AMI. RESULTS: Baseline characteristics, drugs and peak cardiac biomarkers for myocardial damage were similar between both groups. Infusion of BNP at 0.006 microg/kg/min resulted in greater biological activity than infusion at 0.003 microg/kg/min as measured by higher mean (SEM) plasma cGMP levels (8.6 (1) vs 5.5 (1) pmol/ml, p<0.05) and suppression of plasma aldosterone (8.0 (2) to 4.6 (1) ng/dl, p<0.05), which was not seen in the 0.003 microg/kg/min group. LV ejection fraction (LVEF) improved significantly from baseline to 1 month (40 (4)% to 54 (5)%, p<0.05) in the 0.006 group but not in the 0.003 group. Infusion of BNP at 0.006 microg/kg/min was associated with a decrease of LV end-systolic volume index (61 (9) to 43 (8) ml/m(2), p<0.05) at 1 month, which was not seen in the 0.003 group. No drug-related serious adverse events occurred in either group. CONCLUSIONS: 72 h infusion of low BNP at the time of anterior AMI is well tolerated and biologically active. Patients treated with low-dose BNP had improved LVEF and smaller LV end-systolic volume at 1 month.

Circulating E-selectin as a risk marker in patients with end-stage renal disease.

BACKGROUND: E-selectin is a key adhesion molecule which plays a fundamental role in endothelial progenitor cell-dependent reparative mechanisms in experimental ischaemia and it serves to anchor leucocytes to the endothelium in inflammatory processes. Inflammation is one of the strongest risk factors for death and cardiovascular (CV) events in end-stage renal disease (ESRD). OBJECTIVE: The objective of the current study was to evaluate whether E-selectin is a useful biomarker of clinical outcome in ESRD patients. We tested the prediction power of circulating E-selectin for mortality and CV events in a cohort of 265 ESRD patients. RESULTS: During the follow-up, 59 patients died and 58 had CV events. All-cause mortality was inversely related to serum E-selectin, the risk of death being the lowest in patients in the third E-selectin tertile (HR: 1, reference group), intermediate in those in the second tertile (HR: 1.30) and the highest in patients in the first tertile (HR: 2.02, P = 0.01). Similarly, the risk of fatal and nonfatal CV events followed an inverse pattern being lowest in the third tertile (reference group) and highest in the first tertile (HR: 1.73, P = 0.03). The prediction power of E-selectin for death and CV events was confirmed in a Cox regression analysis where E-selectin emerged as an inverse predictor of these outcomes, particularly so in patients with severe inflammation. CONCLUSIONS: These data are in keeping with the hypothesis that in systemic inflammation altered E-selectin shedding may play a role in arterial damage and implicates this adhesion molecule in atherosclerotic complications in a high-risk condition like ESRD.

New intrarenal echo-Doppler velocimetric indices for the diagnosis of renal artery stenosis.

We aimed at comparing the positive and negative predictive values (PPV, NPV) of several intrarenal velocimetric indices for revealing the presence of renal artery stenosis (RAS) among hypertensive patients who underwent a renal angiography for the clinical suspicion of renovascular hypertension. In 106 patients (200 kidneys), the pulsatility index (PI) and resistive index (RI), the acceleration time (AT), and the mean systolic acceleration (ACC(sys)) were evaluated. In addition, the maximal systolic acceleration (ACC(max)), that is, the maximal slope of the acceleration phase, and the maximal acceleration index (AI(max)), that is, the ratio between ACC(max) and the relative peak systolic velocity, were calculated. On angiography, we found that 56 (28%) of the 200 arteries had a greater than 60% RAS. PI and RI had an NPV below 75%, whereas AT, ACC(sys), ACC(max), and AI(max) had an NPV always above 95%. However, ACC(max), and AI(max), at their best cutoff limits, had higher PPV than ACC(sys) and AT (60 and 70% vs 45 and 51%, respectively). Thus, in a cohort of patients with a high prevalence of RAS, PI and RI failed to reach an NPV adequate for a screening test. In contrast, all the acceleration indices we tested had a sufficiently high NPV but AI(max) appears superior to the others because of higher PPV. We propose the evaluation of AI(max) as an additional screening test in patients with hypertension and the clinical suspicion of RAS.

Circulating natriuretic peptide concentrations in patients with end-stage renal disease: role of brain natriuretic peptide as a biomarker for ventricular remodeling.

OBJECTIVES: To determine levels of natriuretic peptides (NPs) in patients with end-stage renal disease (ESRD) and to examine the relationship of these cardiovascular peptides to left ventricular hypertrophy (LVH) and to cardiac mortality. PATIENTS AND METHODS: One hundred twelve dialysis patients without clinical evidence of congestive heart failure underwent plasma measurement of NP concentrations and echocardiographic investigation for left ventricular mass index (LVMI). RESULTS: Plasma atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) concentrations correlated positively with LVMI and inversely with left ventricular ejection fraction, whereas C-type NP and Dendroaspis NP levels did not correlate with LVMI. In dialysis patients with LVH (LVMI >125 g/m2), plasma ANP and BNP concentrations were increased compared with those in dialysis patients without LVH (both P<001). In a subset of 15 dialysis patients without LVH or other concomitant diseases, plasma BNP concentrations were not significantly increased compared with those in 35 controls (mean +/- SD, 20.1+/-13.4 vs 13.5+/-9.6 pg/mL; P=.06), demonstrating that the BNP concentration was not increased by renal dysfunction alone. Furthermore, the BNP level was significantly higher in the 16 patients who died from cardiovascular causes compared with survivors (mean +/- SD, 129+/-13 vs 57+/-7 pg/mL; P<.003) and was significantly associated with greater risk of cardiovascular death in Cox regression analysis (P<.001), as was the ANP level (P=.002). CONCLUSIONS: Elevation of the plasma BNP concentration is more specifically related to LVH compared with the other NP levels in patients with ESRD independent of congestive heart failure. Thus, BNP serves as an important plasma biomarker for ventricular hypertrophy in dialysis patients with ESRD.

Role of the natriuretic peptides in the cardiorenal and humoral actions of omapatrilat: insights from experimental heart failure.

Vasopeptidase (VP) inhibitors are novel molecules that co-inhibit neutral endopeptidase 24.11 (NEP), which degrades natriuretic peptides and angiotensin-converting enzyme (ACE). We review the biology of the natriuretic peptide system and a recent study of the role for the natriuretic peptide system in the mechanism of action of omapatrilat (the most clinically advanced VP inhibitor). This study compared the cardiorenal and humoral actions of omapatrilat with those of ACE inhibition. The actions of omapatrilat were further defined in the presence and absence of a natriuretic peptide receptor antagonist. This investigation provided insight into a unique new pharmacologic agent that has beneficial renal actions in experimental mild heart failure that exceed those seen with ACE inhibition alone and that are linked to the natriuretic peptide system.

Urinary adrenomedullin is related to ET-1 and salt intake in patients with mild essential hypertension. Salt Sensitivity Group of Italian Society of Hypertension.

Adrenomedullin (ADM) infusion increases salt excretion in the rat. However, there is no evidence that this substance is related to changes in salt intake in humans. In this study we sought whether the urinary excretion rate of this autacoid is related to salt intake and by the expected changes in arterial pressure in patients with mild essential hypertension. The influence of salt intake on the renal excretion of ADM was investigated in 55 hypertensive patients in a double blind, randomized and crossover study comparing a 2-week 50 mmol/day salt intake period with a 150 mmol/day salt intake period. Twenty-four-hour ADM and endothelin-1 (ET-1) excretion rate were measured by radioimmunoassay on preextracted urinary samples (intraassay confidence variable <8%). The antibodies used in these assays had minimal ADM-ET-1 cross-reactivity (<1%). Twenty-four-hour microalbuminuria was measured by nephelometry. On univariate analysis changes in urinary ADM were significantly related to those in salt excretion (r = 0.33, P = .01) as well as to changes in urinary ET-1 (r = 0.56, P = .0001). Furthermore, changes in urinary albumin excretion were related to those in urinary ET-1 (r = 0.26, P = .05), but were independent of those in urinary ADM (P = .19). In a multiple regression model including age, sex, body mass index, and changes in systolic pressure, plasma renin activity and plasma aldosterone and urine volume, salt excretion resulted as the stronger independent predictor of urinary ADM (r = 0.33, P = .01). However, changes in urinary salt lost prediction power (P = .11) for urinary ADM when urinary ET-1 was introduced into the model. In this model (multiple r = 0.31) urinary ET-1 resulted to be the only independent predictor of urinary ADM (beta = 0.56, P = .0001). This study is the first to show that the renal excretion of ADM is related to changes in salt intake and that it is tightly linked to that of ET-1. The data support the notion that these autacoids play a role in the regulation of sodium metabolism in patients with mild hypertension. The intercorrelations between ET-1, ADM, and microalbuminuria are compatible with the hypothesis that ET-1 is involved in a salt-induced increase in glomerular pressure and suggest that ADM may act as a counterregulatory factor in this situation.

Diagnostic potential of cardiac natriuretic peptides in dialysis patients.

BACKGROUND: In the general population, the plasma concentrations of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are useful to predict left ventricular hypertrophy (LVH) and LV systolic dysfunction. Whether these cardiac hormones have a similar diagnostic potential in dialysis patients is unknown. METHODS: We studied the diagnostic value of ANP and BNP for alterations in LV mass and function in a cohort of 246 dialysis patients without clinical evidence of heart failure. RESULTS: Both ANP and BNP were independently related to left ventricular mass (P < 0.0001) as well as to ejection fraction (P < 0.0001). In an analysis based on a prospectively defined threshold (95th percentile of the normal range), BNP had a significantly higher (P < 0.01) sensitivity (88%) than ANP (51%) for the diagnosis of LVH, but the positive predictive value of the two peptides was very similar (92 and 87%, respectively, P = NS). However, the negative predictive value of BNP for excluding LVH was 22% higher than that of ANP (53 vs. 31%, P = 0.05). Both natriuretic peptides had a high sensitivity for the detection of LV dysfunction (87 and 94%), but their positive predictive value was low (25 and 15%). Importantly, both ANP and BNP proved to be very useful for excluding this alteration (negative predictive value 97 and 96%, respectively). An analysis based on the "best cut-offs" of each peptide as identified on the basis of the ROC curves augmented the positive and negative prediction values of BNP for the diagnosis of LVH to 95 and 61%, respectively. This approach also raised the BNP-positive prediction value for the identification of LV dysfunction to 31% but did not modify the diagnostic potential of ANP (either for LVH or for LV dysfunction). CONCLUSIONS: Measuring the plasma concentration of cardiac natriuretic hormones, particularly BNP, may be useful for the identification of dialysis patients with LVH or for excluding systolic dysfunction.

Plasma concentration of asymmetrical dimethylarginine and mortality in patients with end-stage renal disease: a prospective study.

BACKGROUND: The plasma concentration of asymmetrical dimethylarginine (ADMA), an inhibitor of nitric-oxide synthase, which has been linked to endothelial dysfunction and atherosclerosis in the general population, is raised in patients with end-stage renal disease and could contribute to the high cardiovascular risk in patients with chronic renal failure. We investigated the relation between cardiovascular risk factors and plasma ADMA concentration in a cohort of haemodialysis patients (n=225), and tested the predictive power of ADMA for mortality and cardiovascular outcomes. METHODS: Patients had standard dialysis three times a week. We accurately recorded cardiovascular events over a mean follow-up of 33.4 months (SD 14.6); these events were reviewed by a panel of physicians. We identified correlates of plasma ADMA by univariate and multivariate analyses. FINDINGS: On univariate analysis, ADMA concentration in plasma was directly related to concentrations of fibrinogen and L-arginine in plasma, duration of dialysis treatment, and serum cholesterol concentration, and was inversely related to serum albumin concentration. On multivariate analysis, only plasma fibrinogen (p=0.0001) and serum albumin (p=0.04) concentrations were independently related to plasma ADMA concentration (multiple r=0.44, p=0.0001). 83 patients died, 53 (64%) by cardiovascular causes. In a Cox's proportional-hazards model, plasma ADMA ranked as the second factor predicting overall mortality (hazard ratio 1.26, 95% Cl 1.11-1.41, p=0.0001) and cardiovascular events (1.17, 1.04-1.33, p=0.008). INTERPRETATION: In haemodialysis patients, plasma ADMA is a strong and independent predictor of overall mortality and cardiovascular outcome. These findings lend support to the hypothesis that accumulation of ADMA is an important risk factor for cardiovascular disease in chronic renal failure.

Hepatocyte growth factor predicts survival and relates to inflammation and intima media thickness in end-stage renal disease.

Hepatocyte growth factor (HGF) is a pleiotropic cytokine involved in tissue protection and repair in the endothelium and various organ systems. The serum concentration of this protein is markedly increased in patients with chronic renal diseases, but the clinical and pathophysiological correlates of this substance in renal failure are scarcely understood. Serum HGF, lipid, albumin, hemoglobin, C-reactive protein (CRP), and immunoglobulin G (IgG) were measured in fasting conditions in a cohort of 244 dialysis patients. In addition, the relationship between HGF and severity of carotid atherosclerosis was studied in a subgroup of 105 patients. The entire cohort was followed up for a median of 31 months (interquartile range, 21 to 34 months). Serum HGF level was directly related to duration of dialysis treatment, CRP level, age, IgG level, and hemoglobin level and inversely related to systolic and diastolic arterial blood pressure. In a multiple regression model, only duration of dialysis treatment (r = 0.38), age (r = 0.26), hemoglobin level (r = 0.17), IgG level (r = 0.15), and CRP level (r = 0.14) were independent correlates of serum HGF level (R = 0.54; P < 0.0001), suggesting that increased levels of serum HGF may be the expression of a chronic inflammatory process. HGF levels were greater in hemodialysis than continuous ambulatory peritoneal dialysis patients, independent of the type of dialysis membrane, and slightly increased in patients seropositive for hepatitis C virus. In the subgroup of patients who underwent echo color Doppler studies, serum HGF level was an independent correlate of intima media thickness (IMT; partial r = 0.23; P = 0.02). In the entire cohort, increased HGF levels predicted shorter survival in a multivariate Cox regression model. These results support the hypothesis that in patients with chronic renal failure, increased serum HGF level is linked to an inflammatory state. The relationships between HGF level and survival and IMT suggest that this cytokine might be a marker of a process that has a major impact in the high mortality and morbidity of the dialysis population.

Renal endothelin-1 is linked to changes in urinary salt and volume in essential hypertension. Salt Sensitivity Group of the Italian Society of Hypertension.

METHODS: We investigated the influence of salt intake on urinary and plasma endothelin-1 (ET-1) in 55 patients who entered a two-week double-blind, randomised, crossover study comparing a 50 mMol/day salt intake and 150 mMol/day. Twenty-four-hour ET-1 excretion and plasma ET-1 were measured by RIA on pre-extracted samples. RESULTS: In the whole cohort (n=55), changes in urinary ET-1 were related to salt excretion (r=0.28, P=0.04) and urinary volume (r=0.47, P=0.0001). In a multivariable model, changes in PRA, plasma aldosterone, blood pressure and heart rate did not add any predictive power to salt excretion with regard to urinary ET-1 variations. The relationship between urinary volume and urinary ET-1 was stronger than that of urinary sodium with ET-1 excretion because sodium was excluded from the multivariable model when urinary volume was introduced. Changes in urinary ET-1 were unrelated to mean blood pressure changes (P=0.66). Changes in plasma ET-1 were unaffected by changes in salt intake (P=0.58) but were strongly related to those in PRA (r= -0.45, P=0.01) and plasma aldosterone (r= -0.53, P=0.002). CONCLUSIONS: The renal excretion of ET-1 is influenced by changes in salt intake and appears largely independent of the blood pressure response to salt. Changes in urinary volume which accompany variations in salt excretion play an important role in this response. Since urinary ET-1 reflects its renal synthesis, our data support the notion that renal ET-1 plays a role in the regulation of sodium balance in patients with mild hypertension.

Smoking, blood pressure and serum albumin are major determinants of carotid atherosclerosis in dialysis patients. CREED Investigators. Cardiovascular Risk Extended Evaluation in Dialysis patients.

AIM: To investigate the relationship between carotid atherosclerosis and some major cardiovascular risk factors in uremic patients on chronic dialysis. METHODS: A cross-sectional study was carried out in 119 unselected dialysis patients (89 on hemodialysis and 30 on chronic ambulatory peritoneal dialysis, CAPD). Fasting blood sampling for serum lipids, albumin, hemoglobin, and echo-colour-Doppler evaluation of common carotid arteries were performed in all patients (during the non-dialysis day in hemodialysis patients). In hemodialysis patients BP was measured before and after dialysis; in CAPD patients home BP values were recorded during the month before the study day. RESULTS: Ninety-five patients had at least one plaque and 57 had at least four plaques. Thirty-eight had mild and eleven severe carotid stenosis. In multiple regression models, the mean internal diameter of carotid arteries was explained (R=0.52, P=0.0001) by systolic pressure (r=0.39), serum cholesterol (r=-0.28), age (r=0.27) and smoking (r=0.24) while the degree of carotid stenosis was predicted (R=0.39, P=0.0001) by age (r=0.36) and smoking (r=0.25). The number of atherosclerotic plaques was explained (R=0.51, P=0.0001) by age (r=0.36), smoking (r=0.25) and pulse pressure (r=0.20), serum albumin just failing to reach statistical significance (P = 0.06). However, serum albumin was a significant and independent predictor of the number of atherosclerotic plaques (r=-0.26) in hemodialysis patients (n=89). Sex, diabetes, Kt/V, duration of dialysis treatment, hemoglobin, serum calcium and phosphate did not add any predictive power to the models. CONCLUSIONS: In dialysis patients arterial pressure and smoking are associated with carotid atherosclerosis. Serum albumin appears to serve as an independent predictor of carotid atherosclerosis.

The relationship between cardiac output and posthyperventilation hyperpnoea in patients with essential hypertension.

Posthyperventilation hyperpnoea (PHVH) is the progressive decline in minute ventilation (V'E) that follows abrupt cessation of voluntary hyperventilation. It has been hypothesized that the increase in cardiac output (CO) during hyperventilation could contribute to the duration of PHVH. This hypothesis was tested by measuring the duration of PHVH in patients with essential hypertension, in whom the increase in CO as a result of various stimuli is less pronounced. Twenty male hypertensives (mean arterial blood pressure+/-SEM: 178/ 107+/-3/1 mmHg), and 12 age-matched male healthy subjects were studied. The study consisted of three periods: control (5 min), voluntary hyperventilation (2 min), and recovery (3 min). V'E, CO, end-tidal CO2 and O2 tensions were measured, and the time constant (tau) of the V'E decay during recovery calculated. The V'E decay was faster in hypertensives (tau: 0-8.4 s) than in healthy subjects (tau: 12-59 s; p<0.01). During voluntary hyperventilation, CO increased to a lesser extent in hypertensives (6.8+0.7 L.min(-1)) than in healthy subjects (12.9+/-1.1 L.min(-1); p<0.01). In hypertensives, changes in CO during voluntary hyperventilation were significantly related to tau (r=0.646; n=20; p=0.002). The less pronounced rise in cardiac output during hyperventilation in hypertensives could account for the shorter duration of posthyperventilation hyperpnoea.

Diagnosis of renovascular disease by extra- and intrarenal Doppler parameters.

It is still a matter of debate as to which parameters should be used for noninvasive diagnosis of renovascular disease by renal Doppler sonography (RDS). The accuracy of RDS in the detection of renal artery stenosis (RAS) was tested in 95 consecutive, moderate to severe hypertensive patients (I-II World Health Organization [WHO] stages). Reno-aortic ratio (RAR) for peak systolic velocity (PSV) was also calculated to assist in the diagnosis of significant (>50%) RAS. Paired receiver-operating characteristic (ROC) analysis was plotted for evaluating the relationship between sensitivity and specificity for each parameter. In a subset of 57 kidneys, the influence of blood pressure and age on intraparenchymal parameters was evaluated. Measurements of maximal peak systolic velocity (PSV) at the site of stenosis, RAR for PSV, and minimum acceleration index in the main renal artery showed high accuracy (areas under the ROC curve 0.97, 0.88, and 0.80, respectively). Among intraparenchymal parameters, early systolic acceleration showed the best area under the ROC curve (0.90), but provided a low positive predictive value (29%) and was significantly influenced by blood pressure (multiple r=0.56; p=0.001). Pulsatility and resistive indices were found to be less powerful as absolute values, and both significantly influenced by blood pressure and age (multiple r=0.60 and 0.50; p=0.001, p=0.02, respectively). However, interindividual variance of intrarenal indices should be minimized by calculation of side difference, although this procedure would become misleading or impossible in patients with bilateral RAS or a single kidney, respectively. These results support the use of extraparenchymal parameters for noninvasive detection of RAS, and emphasize that intrarenal parameters cannot be considered as absolute values.