Changes in renal microcirculation in patients with nephrotic and nephritic syndrome: The role of resistive index.

BACKGROUND: Renal Resistive Index (RRI) is an important and non-invasive parameter of renal damage and it is associated with abnormal microcirculation or to a parenchymal injury. The aim of our study was to compare the RRI in a cohort of patients with renal diseases categorized in three groups: nephrotic syndrome (NS), acute nephritic syndrome (ANS) and patients with urinary abnormalities (UA). METHODS: Four hundred eighty-two patients with median age of 48 years (IQR 34-62) with indications for kidney disease were included in the study. Biochemical analyses, clinical assessment with detection of NS, ANS and UA and comorbidities were reported. Renal Doppler ultrasound with RRI was evaluated in all patients at the time of enrolment. RESULTS: NS was present in 81 (16.8 %) patients while ANS in 81 (16.8 %) and UA in 228 (47.3 %) patients. Patients with ANS showed significant higher RRI compared to both patients with NS [0.71 (IQR 0.67-0.78) vs 0.68 (0.63-0.73), p < 0.001] and UA [0.71 (0.67-0.78) vs 0.65 (0.61-0.71), p < 0.001]; RRI was higher in NS patients than in patients with UA [0.68 (0.63-0.73) vs 0.65 (0.61-0.71), p < 0.001]. Patients with ANS had significantly lower median estimated glomerular filtration rate (eGFR) compared respectively to NS and UA patients [19.7 ml/min vs 54.8 ml/min and vs 72.3 ml/min, p < 0.001], while renal length was significantly higher in patients with NS compared to both patients with ANS and UA [111.88 mm vs 101.98 mm and vs 106.15, p < 0.001]. Patients with ANS had more frequently hematuria and RRI ≥ 0.70 (p < 0.001) compared to both patients with NS and patients with UA. The multiple regression analysis, weighted for age, showed that RRI inversely correlates with eGFR (ß coefficient = -0.430, p < 0.001). CONCLUSIONS: Higher and pathological RRI were found in ANS than NS and UA. Renal resistive index in ANS reflects changes in intrarenal perfusion and microvascular dysfunction related to disease characteristics.

Role of endogenous GLP-1 on arterial stiffness and renal haemodynamics following bariatric surgery.

BACKGROUND: Cardiovascular trials have revealed the positive impact of GLP-1 receptor agonists (GLP-1 RAs) on cardiovascular outcomes in type 2 diabetes (T2D). However, the specific effects of endogenous GLP-1 on arterial stiffness and renal function remain understudied. This study aimed to explore the influence of endogenous GLP-1 response post-bariatric surgery on arterial stiffness and renal haemodynamic. METHODS: Thirty individuals with morbid obesity and without T2D, scheduled for Roux-en-Y Gastric Bypass (RYGB), were included. Clinical parameters, 3-hour oral glucose tolerance test (OGTT) with serial sampling for glycaemia, GLP-1 and insulin, carotid-femoral pulse wave velocity (cf-PWV), carotid distensibility coefficient (carotid-DC) and renal resistive index (RRI) measurements were conducted pre-surgery and 1-year post-surgery. Participants were categorized into high-response and low-response groups based on their post-surgery increase in GLP-1 (median increase of 104% and 1%, respectively, pre- vs. post-surgery). RESULTS: Post-surgery, high-response group demonstrated a greater reduction in cf-PWV (p = .033) and a greater increase (p = .043) in carotid DC compared to low-response group. These enhancements were observed independently of weight loss or blood pressure changes. High-response group exhibited a reduction in RRI (p = .034), although this association was influenced by improvement in pulse pressure. Finally, a multivariate stepwise regression analysis indicated that the percentage increase of GLP1, Δ-GLP1(AUC)%, was the best predictor of percentage decrease in cf-PWV (p = .014). CONCLUSIONS: Elevated endogenous GLP-1 response following RYGB was associated with improved arterial stiffness and renal resistances, suggesting potential cardio-renal benefits. The findings underscore the potential role of endogenous GLP-1 in influencing vascular and renal haemodynamics independent of traditional weight loss.

The Relationship between Renal Resistive Index and Complexity of Coronary Lesions in Patients with Stable Coronary Artery Diseases.

Background: The most common cause of coronary artery diseases (CAD) is atherosclerosis. The synergy between percutaneous coronary intervention with TAXUS™ and cardiac surgery (SYNTAX) score was used to assess complex CAD lesions. The renal resistive index (RRI) is a Doppler ultrasound parameter calculated to assess renal haemodynamics. The direct relationship between CAD complexity and RRI was not yet investigated. The aim of our study was to investigate this relationship between RRI and SYNTAX score in stable CAD patients. Methods: This study included 214 patients with stable CAD and subsequent coronary angiography done at our institution. Regarding CAD complexity, these patients were classified into 166 patients with low SYNTAX score (SYNTAX ≤ 22), and 48 patients with high SYNTAX score (SYNTAX > 22). The demographic, laboratory, clinical, echocardiographic data and renal Doppler parameters; including RRI, were recorded. Results: Multivariate logistic regression analysis demonstrated that RRI (odds ratio, OR = 4.440, 95% (confidence interval) CI: 1.418-13.903, p = 0.010) was a novel independent predictor of high SYNTAX score in patients with stable CAD, in addition to other traditional predictors as diabetes mellitus (OR = 4.401, 95% CI: 1.081-17.923, p = 0.04), low-density lipoprotein cholesterol (LDL-C) (OR = 2.957, 95% CI: 1.920-8.995, p = 0.027), multi-vessel CAD (OR = 2.113, 95% CI: 1.241-2.280, p = 0.001) and Gensini score (OR = 6.539, 95% CI: 1.977-21.626, p = 0.002). Receiver operator characteristic curve analysis showed that RRI > 0.655 (sensitivity of 80%, specificity of 73.6%) was the best cut-off value for predicting high SYNTAX score. Conclusions: The non-invasively measured RRI is closely associated with high SYNTAX score in stable CAD patients.

Contrast-enhanced ultrasonography reveals a lower cortical perfusion and a decreased renal flow reserve in hypertensive patients.

BACKGROUND: Microvascular structural alteration and dysfunction is a hallmark of arterial hypertension. So far, the visualization and the quantification of renal microcirculation in humans has been hampered by the lack of non-nephrotoxic and non-invasive radiologic techniques. Contrast-enhanced ultrasonography (CEUS) is an appealing method to investigate renal microcirculation and has not been investigated in this setting. We aimed to compare renal microcirculation in normotensive (NT) and hypertensive (HT) participants using CEUS at rest and during a sympathetic stress test. METHODS: We measured the renal perfusion index (PI, primary outcome), the renal resistive index (RRI), beat-to-beat systemic hemodynamics and plasma catecholamines before and during a 2-min cold pressor test (CPT) in NT and HT participants. Linear mixed model analysis was used to compare the effect of the CPT on the variables of interest. RESULTS: Seventy-three participants (32 HT) with normal kidney function were included. HT participants had a lower baseline PI compared with NT participants [median (interquartile range) 1476 (959-2155) arbitrary units (a.u.) vs 2062 (1438-3318) a.u., P < .001]. The CPT increased blood pressure, heart rate and catecholamines in all participants. The increase in PI observed in NT during the CPT was blunted in HT [+504 (117-920) a.u. vs +1159 (678-2352) a.u in NT, interaction P = .013]. Age, sex and body mass index did not modify these results. CONCLUSIONS: HT patients had a lower basal renal cortical perfusion. During the cold pressor test, HT participants had a smaller increase in the PI, suggesting that renal cortical flow reserve is impaired.

Kidney Doppler Ultrasonography in Critical Care Nephrology.

Color pulsed-wave Doppler ultrasound (CPWD-US) emerges as a pivotal tool in intensive care units (ICUs) for diagnosing acute kidney injury (AKI) swiftly and non-invasively. Its bedside accessibility allows for rapid assessments, making it a primary imaging modality for AKI characterization. Furthermore, CPWD-US serves as a guiding instrument for key diagnostic-interventional procedures such as renal needle biopsy and percutaneous nephrostomy, while also facilitating therapy response monitoring and AKI progression tracking. This review shifts focus towards the integration of renal ultrasound into ICU workflows, offering contemporary insights into its utilization through a diagnostic-standard-oriented approach. By presenting a flow chart, this review aims to provide practical guidance on the appropriate use of point-of-care ultrasound (POC-US) in critical care scenarios, enhancing diagnostic precision, patient management, and safety, albeit amidst a backdrop of limited evidence regarding long-term outcomes.

Renal resistive index by point of care ultrasound to predict sepsis associated acute kidney injury in critically ill children.

BACKGROUND: Sepsis associated acute kidney injury (AKI) is linked with adverse outcomes in the PICU. Doppler-based renal resistive index (RRI) has shown promising results in adults for prediction of AKI. We aimed to explore the performance of RRI in children with sepsis. METHODS: This prospective observational study (March - November 2022) included children aged 1-12 years with sepsis admitted to the PICU. RRI and urine neutrophil gelatinase associated lipocalin (NGAL) were measured within 12 h of admission. Children were followed up for 3 days. AKI (new and persistent) was defined as any child with KDIGO stage 2 or 3 AKI on day 3. RESULTS: We enrolled 90 children but included 79 in final analysis. Two thirds (n = 53, 67%) had septic shock. Median (IQR) age was 6.2 years (4.1-9.2). RRI decreased with increasing age. Twenty-six (33%) children had AKI on day 3. Mean (SD) RRI was higher in the AKI group [0.72 (0.08) vs. 0.65 (0.07), p < 0.001].The area under ROC curve for RRI to detect AKI among the 1-4 year old group was 0.75 (95% CI:0.51, 0.98; p = 0.05) and among the 5-12 year old group was 0.76 (0.62, 0.89; p = 0.001). An RRI 0.71 predicted AKI with 100% sensitivity and 46.2% specificity among the 1-4-year-old group and RRI 0.69 predicted it with 70% sensitivity and 77.5% specificity in the 5-12-year-old group. RRI and eGFR at admission were independent predictors of AKI on multivariable analysis. Urine NGAL 94.8 ng/ml predicted AKI with 76.9% sensitivity and 77.4% specificity and AUROC was 0.74 (0.62, 0.86) among the 1-12-year-old group. CONCLUSIONS: RRI values varied with age. RRI showed good diagnostic accuracy to detect new/persistent AKI on day 3 in children with sepsis; however, it was less precise as an independent predictor.

Ultrasound-based quantitative tools in predicting renal involvement in asymptomatic primary hyperparathyroidism.

PURPOSE: Asymptomatic primary hyperparathyroidism (aPHPT) has been recognized as a condition that can lead to renal complications. Timely identification of prognostic indicators for renal impairment holds the potential to facilitate proactive monitoring and treatment strategies in these patients. This study aims to investigate the utility of acoustic radiation force impulse (ARFI) imaging and renal resistive index (RRI), in identifying renal parenchymal and vascular changes in patients with aPHPT. METHODS: Forty-two patients with aPHPT and 42 controls matched for age, sex, and body mass index were included in the study. The presence of renovascular changes was evaluated by RRI measurement with Doppler ultrasonography, and the presence of renal parenchymal involvement was evaluated by ARFI quantification, given as shear wave velocity (SWV). RESULTS: In aPHPT patients, both the mean RRI and mean SWV values exhibited substantial elevation compared to the control group (P < 0.001 for both). Significant associations were observed between SWV values and serum calcium, parathyroid hormone (PTH), and adenoma size within the patient group (P < 0.001, P < 0.001, P = 0.016, respectively). Similarly, the mean RRI demonstrated positive correlations with serum calcium and PTH levels in the patient group (P< 0.001, P = 0.011, respectively). Multivariate linear regression analysis underscored the connection between mean RRI and mean SWV values with serum calcium levels within the patient group. In addition, serum PTH levels affected mean SWV positively and significantly. CONCLUSION: The use of ARFI imaging and RRI measurements appears to hold potential in identifying renal involvement in patients with aPHPT.

Elevated Renal-Resistive Index as an Indicator of Acute Kidney Injury Associated With Neonatal Extracorporeal Membrane Oxygenation.

OBJECTIVE: The authors aimed to assess the relationship between elevated renal-resistive index (RRI) and acute kidney injury (AKI) related to extracorporeal membrane oxygenation (ECMO) in neonatal patients. DESIGN: This was a retrospective study. SETTING: The study was conducted at a teaching hospital. PARTICIPANTS: Sixteen neonates treated with ECMO at the authors' hospital between June 2021 and December 2022 were included in this study. INTERVENTIONS: Demographic and clinical data of patients were collected from the computer database. The RRI of patients before and during ECMO treatment was measured by bedside ultrasound. A receiver operating characteristic (ROC) curve was constructed to evaluate the diagnostic value of elevation of RRI as evidence of neonatal ECMO-related AKI. Logistic regression analysis was utilized to calculate the odds ratio (OR) with a 95% CI. MEASUREMENTS AND MAIN RESULTS: A total of 16 patients met the inclusion criteria. For the primary outcome, the authors observed that the RRI during ECMO therapy was significantly elevated in patients with AKI compared to those without AKI. As for the secondary outcome, ROC curve analysis revealed an optimal RRI cutoff of 0.797, with an area under the curve of 0.855 (95% CI, 0.664-1, p = 0.027). The sensitivity and specificity of RRI values >0.797 for diagnosing AKI were 72.7% and 80%, respectively. Univariate logistic regression analysis indicated an OR of 1.433 (95% CI 1.192-1.873, p < 0.05) for RRI values above 0.797. This association remained statistically significant even after adjusting for serum cystatin C and Sequential Organ Failure Assessment score, with an adjusted OR of 1.352 (95% CI 1.108-1.612, p < 0.05). CONCLUSION: The elevation of the RRI demonstrated a strong correlation with the onset of neonatal ECMO-related AKI, which may offer valuable support for diagnosing neonatal ECMO-related AKI.

Association of Preoperative Renal-Resistive Index With Long-term Renal and Cardiovascular Outcomes After Cardiac Surgery.

OBJECTIVE: To investigate the association of elevated preoperative renal-resistive index (RRI) with persistent renal dysfunction, major adverse kidney events (MAKE), and major adverse cardiovascular events (MACE) after cardiac surgery. DESIGN: Observational cohort study. SETTING: University hospital. PARTICIPANTS: Ninety-six adult patients undergoing cardiac surgery. INTERVENTIONS: RRI measurement the day before surgery. MEASUREMENTS AND MAIN RESULTS: Fifty-eight patients (60%) had elevated RRI ≥0.70. Five years after surgery, persistent renal dysfunction (sustained decline in estimated glomerular filtration rate ≥25%) had occurred in 25 patients (26%), MAKE (persistent renal dysfunction, renal replacement therapy, or death) in 34 (35%), and MACE (myocardial infarction, unstable angina, decompensated heart failure, stroke, or cardiovascular death) in 28 (29%). RRI was higher in patients who developed persistent renal dysfunction (median, 0.78 [IQR, 0.74-0.82] v 0.70 [0.66-0.77], p = 0.001), MAKE (0.77 [0.72-0.81] v 0.68 [0.65-0.76], p = 0.002), and MACE (0.77 [0.72-0.81] v 0.70 [0.66-0.77], p = 0.006). Patients with elevated RRI had a significantly higher cumulative incidence of all long-term outcomes. After adjustment for baseline renal function and heart failure, elevated RRI was associated with persistent renal dysfunction (hazard ratio [HR], 5.82 [95% CI, 1.71-19.9]), MAKE (HR, 4.21 [1.59-11.1]), and MACE (HR, 2.81 [1.03-7.65]). CONCLUSIONS: Elevated preoperative RRI is associated with persistent renal dysfunction, MAKE, and MACE after cardiac surgery. Preoperative RRI may be used for long-term risk assessment in patients undergoing cardiac surgery.

Cardiovascular risk and renal injury profile in subjects with type 2 diabetes and non-albuminuric diabetic kidney disease.

BACKGROUND: In the last years, the classical pattern of diabetic kidney disease (DKD) has been partially overcome, because of the uncovering of a new DKD phenotype with significant renal dysfunction without presence of albuminuria: the non-albuminuric DKD (NA-DKD). To date, the cardiovascular risk associated with this phenotype is still debated. We investigated the cardiovascular risk and renal injury profile of NA-DKD subjects in comparison with other DKD phenotypes. METHODS: Pulse wave velocity (PWV), intima-media thickness, presence of carotid atherosclerotic plaque, renal resistive index (RRI), and a panel of urinary biomarkers of kidney injury were evaluated in 160 subjects with type 2 diabetes, stratified according to estimated glomerular filtration rate (eGFR) and urinary albumin to creatinine ratio (UACR) into four groups: controls (UACR < 30 mg/g and eGFR ≥ 60 mL/min/1.73 m2), A-DKD (Albuminuric-DKD, UACR ≥ 30 mg/g and eGFR ≥ 60 mL/min/1.73 m2), NA-DKD (UACR < 30 mg/g and eGFR < 60 mL/min/1.73 m2), AL-DKD (Albuminuric and Low eGFR-DKD; UACR ≥ 30 mg/g and eGFR < 60 mL/min/1.73 m2). RESULTS: Subjects with NA-DKD showed a higher PWV (11.83 ± 3.74 m/s vs. 10.24 ± 2.67 m/s, P = 0.045), RRI (0.76 ± 0.11 vs. 0.71 ± 0.09, P = 0.04), and prevalence of carotid atherosclerotic plaque (59% vs. 31%, P = 0.009) compared with controls. These characteristics were similar to those of subjects with AL-DKD, whereas the profile of A-DKD subjects was closer to controls. After multiple regression analyses, we found that RRI, that is in turn influenced by eGFR (ß = - 0.01, P = 0.01), was one of the major determinants of PWV (ß = 9.4, P = 0.02). Urinary TreFoil Factor 3, a marker of tubular damage, was higher in NA-DKD subjects vs. controls (1533.14 ± 878.31 ng/mL vs. 1253.84 ± 682.17 ng/mL, P = 0.047). Furthermore, after multiple regression analyses, we found that urinary osteopontin was independently associated with PWV (ß = 2.6, P = 0.049) and RRI (ß = 0.09, P = 0.006). CONCLUSIONS: Our data showed a worse cardiovascular and renal injury profile in NA-DKD subjects. This finding emphasizes the central role of eGFR in the definition of cardiovascular risk profile of diabetic subjects together with albuminuria.

Influence of hyperthermic intraperitoneal chemotherapy on renal blood perfusion.

PURPOSE: Hyperthermic intraperitoneal chemotherapy (HIPEC) is accompanied with an increased risk of acute kidney injury (AKI). Whether AKI is induced by chemotoxicity or hyperthermia-related changes in renal perfusion remains controversial. The influence of HIPEC on renal perfusion has not been evaluated in patients yet. METHODS: Renal blood perfusion was assessed in ten patients treated with HIPEC by intraoperative renal Doppler pulse-wave ultrasound. Ultrasound (US) examinations were performed pre-, intra-, and postoperative with analyses of time-velocity curves. Patient demographics, surgical details, and data regarding renal function were recorded perioperatively. For evaluation of renal Doppler US to predict AKI, patients were divided in two groups with (AKI +) and without (AKI -) kidney injury. RESULTS: Throughout HIPEC perfusion, neither significant nor consistent changes in renal perfusion could be observed. Postoperative AKI occurred in 6 of 10 participating patients. Intraoperative renal resistive index (RRI) values > 0.8 were observed in one patient developing stage 3 AKI according KDIGO criteria. At 30 min in perfusion, RRI values were significantly higher in AKI + patients. CONCLUSION: AKI is a common and frequent complication after HIPEC, but underlying pathophysiology remains elusive. High intraoperative RRI values may indicate an increased risk of postoperative AKI. Present data challenges the relevance of hyperthermia-derived hypothesis of renal hypoperfusion with prerenal injury during HIPEC. More attention should be drawn towards chemotoxic-induced hypothesis of HIPEC-induced AKI and caution applying regimens containing nephrotoxic agents in patients. Further confirmatory and complementary studies on renal perfusion as well as pharmacokinetic HIPEC studies are required.

Association of renal resistive indices with kidney disease progression and mortality.

BACKGROUND: Renal resistive indices (RRI) have been shown to predict the progression of kidney disease. This study aims to evaluate the association of RRI with mortality and dialysis initiation after adjustment to therapeutic and life style interventions. METHODS: This is a retrospective study that included all chronic kidney disease patients followed for at least two years in three nephrology clinics between 2006 and 2019 and who had a RRI level in their files. Kaplan Meier and log rank test compared the survival of patients with normal versus high RRI. Cox regression analysis evaluated the association between RRI and death or dialysis initiation after adjustment to treatments and life style modifications. RESULTS: A total of 192 patients were analyzed: 68 had RRI < 0.7 and 124 had RRI ≥ 0.7. Their mean age was 66.5 ± 13.1 years at first visit, 78.1% were males. There was a negative correlation between baseline eGFR and RRI (p < 0.001; Spearman correlation coefficient = -0.521). The survival was significantly better in patients with RRI < 0.7 with a Log Rank test < 0.001. The univariate cox regression analysis showed a significant association between RRI and mortality (HR = 1.08; 95%CI: 1.04-1.11; p < 0.001) that remained significant after adjustment to cardiovascular risk factors and interventions such as salt reduction, blood pressure control, statins and RAAS inhibitors (HR = 1.04; 95%CI: 1.00-1.08; p = 0.036). Cox regression analysis showed a significant association between RRI and dialysis initiation (HR = 1.06; 95%CI 1.01-1.10; p = 0.011). CONCLUSION: Our study revealed that patients with an elevated RRI ≥ 0.7 are at a higher risk of mortality after adjustment to medications and lifestyle modifications. RRI can, according to this study, be considered as an independent prognostic factor in CKD patients.

The Relationship of Renal Augmented Velocity Index With Ventricular-Arterial Coupling in Comparison to Renal Resistive Index: Analysis by Means of Arterial and Ventricular Elastances in Hypertensive Patients.

OBJECTIVE: It's a well-known scientific statement that the heart and kidney functions are frequently tied together and the impairment of one directly alters the other. However, there exist knowledge gaps about this intricate pathophysiologic link and the exact unifying mechanism is not established. Herein, we aimed to investigate the presence of cardiorenal interaction at subclinical level while the conventional cardiac and renal clinical parameters are not disrupted yet in patients with hypertension. METHODS: We chose a novel renal Doppler ultrasonographic parameter-augmented velocity index (Avi)-and an echocardiographic measure-ventriculoarterial coupling-which is complex to analyze but increasingly used after its acceptance about being a key determinant of cardiovascular efficiency. We recruited 137 patients without a previous history of antihypertensive medication use (47.4% women; median age, 49 years). Renal Avi, renal resistive index (RI), arterial elastance (Ea ), ventricular elastance (Ees ) and Ea /Ees (ventriculoarterial coupling) parameters were all examined. RESULTS: Renal Avi, Ea , and Ea /Ees values were higher in females. Correlation analysis revealed that renal Avi was correlated with many hemodynamic variables including Ea and Ea /Ees . On multiple linear regression analysis, Ea and Ea /Ees remained as significant independent predictors of renal Avi but not of renal RI after adjustments for co-variables (ß = 0.488, P < .001 for Ea ; ß = 0.380, P < .001 for Ea /Ees ). CONCLUSIONS: In comparison to renal RI, we suggest that renal Avi is a more reliable and promising index that can even measure subclinical changes in the cardiorenal circulation which needs to be elucidated.

Research on the correlation between the renal resistive index, renal microvessel density, and fibrosis.

BACKGROUND: This study was designed to investigate the relationship between the renal resistive index (RRI), renal microvessel density (RMD), and fibrosis in patients with chronic kidney disease (CKD). METHODS: A total of 73 CKD patients were included in the study. Prior to kidney biopsy, we recorded the RRI of the interlobar artery and the estimated glomerular filtration rate (eGFR). Immunohistochemical analysis was performed to assess CD34 expression, and Masson staining was used to evaluate histopathological specimens for RMD and the degree of fibrosis. The percentage of the positive area (PPA) was recorded. Subsequently, we investigated the correlation between RRI, RMD, and kidney fibrosis. RESULTS: RMD (CD34 PPA-total and CD34 PPA-peritubular capillary) showed a slight increase in early CKD stages (1-2) and gradually declined from CKD stages 2 to 5. No correlation was observed between the RRI and RMD or between the RRI and fibrosis across CKD stages 1 to 5. However, across CKD stages 2 to 5, RRI negatively correlated with CD34 PPA-glomerulus (r = -0.353, p = 0.022), but no correlation was found with CD34 PPA-total, CD34 PPA-peritubular capillary, or kidney fibrosis. eGFR showed a positive correlation with RMD (CD34 PPA-total, CD34 PPA-peritubular capillary, and CD34 PPA-glomerulus) across CKD stages 2 to 5, while no correlation was found from CKD stages 1 to 5. CONCLUSION: There was no correlation between RRI and RMD or between RRI and fibrosis across CKD stages 1 to 5 (RRI ≤ 0.7).

Predictive performance of renal resistive index, semiquantitative power Doppler ultrasound score and renal venous Doppler waveform pattern for acute kidney injury in critically ill patients and prediction model establishment: a prospective observational study.

BACKGROUND: This study aimed to explore the performance of renal resistive index (RRI), semiquantitative power Doppler ultrasound (PDU) score and renal venous Doppler waveform (RVDW) pattern in predicting acute kidney injury (AKI) in critically ill patients and establish prediction models. METHODS: This prospective observational study included 234 critically ill patients. Renal ultrasound was measured within 24 h after intensive care unit admission. The main outcome was the highest AKI stage within 5 days after admission according to the Kidney Disease Improving Global Outcomes criteria. RESULTS: Patients in the AKI stage 3 group had significantly higher RRI, RVDW pattern and lower PDU score (p < 0.05). Only lactate, urine volume, serum creatinine (SCr) on admission, PDU score and RVDW pattern were statistically significant predictors (p < 0.05). Model 1 based on these five variables (area under the curve [AUC] = 0.938, 95% confidence interval [CI] 0.899-0.965, p < 0.05) showed the best performance in predicting AKI stage 3, and difference in AUC between it and the clinical model including lactate, urine volume and SCr (AUC = 0.901, 95% CI 0.855-0.936, p < 0.05) was statistically significant (z statistic = 2.224, p = 0.0261). The optimal cut-off point for a nomogram based on Model 1 was ≤127.67 (sensitivity: 95.8%, specificity: 82.3%, Youden's index: 0.781). CONCLUSIONS: The nomogram model including SCr, urine volume, lactate, PDU score and RVDW pattern upon admission exhibited a significantly stronger capability for AKI stage 3 than each single indicator and clinical model including SCr, urine volume and lactate.

Shear wave elastography: usefulness in chronic kidney disease.

Purpose: Chronic kidney disease (CKD) is recognized as a major worldwide health problem. For all CKD, intra-renal fibrosis is a final common pathway that can be correlated with disease severity. Tissue stiffness can be measured non-invasively using shear wave elastography. This study evaluates the use of Young's modulus derived by SWE as a biomarker that can distinguish normal from diseased kidneys. Also, Young's modulus was correlated with Doppler findings and estimated glomerular filtration rate (eGFR). Material and methods: This prospective study was performed in 2 phases, in which initially 50 CKD patients and 50 controls were studied to arrive at a median Young's modulus value in both the groups. In the later phase, a cross-sectional comparative study was conducted on 58 diabetic and 56 non-diabetic patients with SWE and renal Doppler, and the findings were correlated in various stages of CKD. Results: Using Young's modulus, the renal cortex elasticity of CKD patients was shown to be considerably reduced as compared to normal kidneys. There was significant correlation between Young's modulus, eGFR, and renal resistive index. Young's modulus values did not show significant differences between diabetic and non-diabetic groups, revealing its inability to arrive at the aetiopathogenesis of CKD. Conclusions: Correlation of renal tissue Young's modulus with eGFR suggests that SWE may be used as an indicator of renal tissue injuries in CKD patients. SWE can never replace the gold standard biopsy, but it can be used for staging of CKD. Even though SWE cannot predict the aetiopathogenesis of CKD, it may be a low-cost way to provide additional diagnostic information in CKD.

Assessment of renal microcirculation in biopsy-proven tubulointerstitial nephritis in patients with and without glomerular disease: the role of resistive index.

BACKGROUND: Renal resistive index (RRI) measured by Doppler sonography is a marker of microvascular status and it is associated with changes in renal function. Aim of the study was to assess RRI in biopsy-proven tubulointerstitial nephritis (TIN) in patients with and without glomerular disease. METHODS: 132 consecutive patients underwent to native renal biopsy with diagnosis of isolated TIN or in association with glomerulonephritis. Estimated glomerular filtration rate (eGFR), 24-hour urinary protein excretion and renal ecocolorDoppler ultrasonography with RRI assessment were performed at time of enrollment. RESULTS: Patients with isolated-TIN had significantly higher RRI than both patients with non-immunoglobulin A glomerulonephritis (non-IgA-TIN) [0.73 (0.68-0.77) vs 0.64 (0.60-0.67), p < 0.001] and patients with IgA nephropathy (IgAN) [0.73 (0.68-0.77) vs 0.66 (0.60-0.71), p < 0.01]. Patients with isolated-TIN had mainly RRI ≥ 0.70 (n = 15, 65.2%) with the respect to patients with non-IgA-TIN (n = 7, 12.3%) and patients with IgAN (n = 17, 32.7%). A negative linear correlation was found between RRI and hemoglobin (r = 0.233, p < 0.01) and between RRI and eGFR (r = 0.537, p < 0.001). CONCLUSION: Tubulointerstitial damage is the most accurate histological lesion that correlates with eGFR and renal impairment. RRI can be a useful parameter to detect tubulointerstitial lesions.

IL33 and sST2 serum level in systemic sclerosis microvascular involvement.

AIM: Endothelial dysfunction and microvascular damage are hallmarks of systemic sclerosis (SSc). Objective of this study was to evaluate IL33 and ST2 serum levels in SSc patients and healthy controls (HC). Secondary aim was to evaluate the IL33 axis in the SSc microvascular manifestation. METHODS: IL33 and sST2 have been assessed in 46 SSc patients and 24 HC matched for sex and age. Main clinimetric indexes were assessed. Skin perfusion of hands was evaluated by Laser Speckle Contrast Analysis (LASCA) and echocolordoppler ultrasound of renal arteries was performed to evaluate subclinical renal involvement. RESULTS: SSc patients had higher serum level of IL33 and sST2 than HC. IL33 and sST2 were significantly higher in SSc patient with digital ulcers (DUs) compared to SSc patients without DUs. SSc patients with late nailfold videocapillaroscopy (NVC) pattern had higher serum levels of sST2 than SSc patients with active NVC pattern. SSc patients without proximal-distal gradient (PDG) at LASCA had significantly higher sST2 serum level compared to SSc patients with PDG. SSc patients with renal resistive index (RRI) ≥ 0.70 had higher serum levels of sST2 than SSc patients with RRI < 0.70. A positive linear correlation was shown between sST2 and RRI, between sST2 and intrarenal S/D and between sST2 and PI. Kaplan-Meier curves show a significantly reduced free survival from DUs in patients with increased sST2 (p = 0.025). In multivariate analysis, sST2 is associated with the development of new DUs. CONCLUSION: IL33 and sST2 are increased in SSc patients and ST2 might be a marker of microvascular damage.

The role of renal resistive index as a prognostic tool in kidney transplantation: a systematic review.

BACKGROUND: In kidney transplant recipients (KTRs), observational data have reported conflicting findings about the utility of renal resistive index (RRI) in determining outcomes. This study aimed to synthesize the current literature and determine the prognostic role of RRI in KTRs. METHODS: The authors conducted a systematic review to assess the role of RRI in predicting death, graft failure, graft function and proteinuria. Of the 934 titles/abstracts reviewed, 26 studies were included. There was significant heterogeneity in RRI measurements and thresholds as well as in analytical methods, and a meta-analysis could not be performed. RESULTS: All included studies were observational and included 7049 KTRs. Eight studies analyzed death, of which five reported a significant association with higher RRI. In the remaining three, small sample sizes and lower/multiple RRI thresholds may have limited detection of a statistically significant difference. Three studies investigated all-cause graft failure, and an association with RRI was reported but varied by time of RRI measurement. Three out of five studies that analyzed a composite of patient and graft outcomes reported an association with RRI. Evidence analyzing death-censored graft failure, graft failure (unclear whether death-censored or all-cause), measures of graft function and proteinuria was conflicting. Most studies had a moderate to high risk of bias. CONCLUSIONS: RRI likely has a prognostic role in predicting patient outcomes, reflecting patient systemic vascular disease burden rather than graft hemodynamics. Since cardiovascular diseases are a major cause of death and graft loss, RRI may be explored as a noninvasive tool to risk-stratify KTRs.

Doppler ultrasound in the assessment of renal perfusion before and during continuous kidney replacement therapy in the pediatric intensive care unit.

BACKGROUND: This study aimed to assess observer variability and describe renal resistive index (RRI) and pulsatility index (PI) before and after onset of continuous kidney replacement therapy (CKRT). A secondary objective was to correlate Doppler ultrasound findings with those from direct measurement of renal blood flow (RBF). METHODS: This is a prospective observational study in hemodynamically stable Maryland piglets with and without acute kidney injury (AKI) and in hemodynamically unstable critically ill children requiring CKRT. Doppler-based RRI and PI were assessed for each subject. Measurements were made by two different operators (pediatric intensivists) before and after CKRT onset. RESULTS: Observer variability assessment in the measurement of RRI and PI rendered a moderate correlation for both RRI (ICC 0.65, IQR 0.51-0.76) and PI (ICC 0.63, IQR 0.47-0.75). RRI and PI showed no correlation with RBF or urine output. Baseline RRI and PI were normal in control piglets [RRI 0.68 (SD 0.02), PI 1.25 (SD 0.09)] and those with AKI [RRI 0.68 (SD 0.03), PI 1.20 (SD 0.13)]. Baseline RRI and PI were elevated in critically ill children (RRI 0.85, PI 2.0). PI and RRI did not change with CKRT in any study group. CONCLUSIONS: Observer variability between inexperienced pediatric intensivists was comparable with that between senior and junior operators. Doppler-based calculations did not correlate with invasive measurements of RBF. RRI and PI were normal in hemodynamically stable piglets with and without AKI. RRI and PI were high in hemodynamically unstable patients requiring CKRT. RRI and PI did not change after CKRT onset, despite changes in hemodynamic status. A higher resolution version of the Graphical abstract is available as Supplementary information.