Renal Arterial and Venous Doppler in Cardiorenal Syndrome: Pathophysiological and Clinical Insights.

In recent decades, there has been considerable effort in investigating the clinical utility of renal Doppler measurements in both cardiovascular and renal disorders. In particular, a measure of renal arterial resistance, the renal resistive index (RRI), has been demonstrated to predict chronic kidney disease progression and acute kidney injury in different clinical settings. Furthermore, it is linked to a poorer prognosis in individuals suffering from chronic heart failure. Examining the renal venous flow through pulsed Doppler can offer additional insights into renal congestion and cardiovascular outcomes for these patients. This review seeks to summarize the existing data concerning the clinical significance of arterial and venous renal Doppler measurements across various cardiovascular and renal disease contexts.

The clinical significance of renal resistance index (RRI) and renal oxygen saturation (RrSO2) in critically ill children with AKI: a prospective cohort study.

OBJECTIVE: The purpose of this study was to look into the clinical significance of the renal resistance index (RRI) and renal oxygen saturation (RrSO2) in predicting the development of acute kidney injury (AKI) in critically ill children. A new non-invasive method for the early detection and prediction of AKI needs to develop. METHODS: Patients admitted to the pediatric intensive care unit (PICU) affiliated with the capital institute of pediatrics from December 2020 to March 2021 were enrolled consecutively. Data of clinical information, renal Doppler ultrasound, RrSO2, and hemodynamic index within 24 h of admission were prospectively collected. Patients were divided into two groups: the study group was AKI occurred within 72 h, while the control group did not. SPSS (version 25.0) was used to analyze the data, and P < 0.05 was considered a statistical difference. RESULTS: 1) A total of 66 patients were included in this study, and the incidence of AKI was 19.70% (13/66). The presence of risk factors (shock, tumor, severe infection) increased the incidence of AKI by three times. 2) Univariate analysis showed significant differences in length of hospitalization, white blood cells (WBC), C-reactive protein (CRP), renal resistance index (RRI), and ejection fraction (EF) between the study and control groups (P < 0.05). There were no significant differences in renal perfusion semi-quantitative score (P = 0.053), pulsatility index (P = 0.051), pediatric critical illness score (PCIS), and peripheral vascular resistance index (P > 0.05). 3) Receiver operating characteristic (ROC) curve showed that if RRI > 0.635, the sensitivity, specificity, and AUC for predicting AKI were 0.889, 0.552, and 0.751, respectively; if RrSO2 < 43.95%, the values were 0.615, 0.719 and 0.609, respectively; if RRI and RrSO2 were united, they were 0.889, 0.552, and 0.766, respectively. CONCLUSIONS: The incidence of AKI is high in PICU patients. And infection, RRI, and EF are risk factors for AKI in PICU patients. RRI and RrSO2 have certain clinical significance in the early prediction of AKI and may provide a new non-invasive method for early diagnosis and prediction of AKI.

Renal resistance index independently predicts worsening of renal function after coronary angiography.

The renal resistance index (RRI) has been demonstrated to be a useful parameter that can detect patients at a high risk of worsening of renal function (WRF). This study was designed to evaluate the role of the RRI in predicting WRF mediated by the intravascular administration of contrast media. We enrolled patients who were referred for coronary angiography. Renal arterial echo-color Doppler was performed to calculate the RRI. WRF was defined as an increase of > 0.3 mg/dL and at least 25% of the baseline value in creatinine concentration 24-48 h after coronary angiography. Among the 148 patients enrolled in this study, 18 (12%) had WRF. In the multivariate logistic analysis, the RRI was independently associated with WRF (odds ratio [OR]: 1.22; 95% confidence interval [CI]: 1.09-1.36; p = 0.001). After angiography, the RRI significantly increased in both patients with and without WRF. In the receiver operating characteristic curve analyses for WRF, the RRI at baseline and after angiography showed similar accuracy, and the best cutoff value for predicting WRF was 70%. In patients undergoing coronary angiography, the RRI is independently associated with WRF, probably because it provides more accurate information about cardiorenal pathophysiological factors and reflects kidney hemodynamic status and flow reserve.

Cystatin C, renal resistance index, and kidney injury molecule-1 are potential early predictors of diabetic kidney disease in children with type 1 diabetes.

Background: Diabetic kidney disease (DKD) is the main cause of end-stage renal disease in patients with diabetes mellitus type I (DM-T1). Microalbuminuria and estimated glomerular filtration rate (eGFR) are standard predictors of DKD. However, these predictors have serious weaknesses. Our study aimed to analyze cystatin C, renal resistance index, and urinary kidney injury molecule-1 (KIM-1) as predictors of DKD. Methods: We conducted a cross-sectional study in 2019 on a consecutive sample of children and adolescents (10-18 years) diagnosed with DM-T1. The outcome was a risk for DKD estimated using standard predictors: age, urinary albumin, eGFR, serum creatinine, DM-T1 duration, HbA1c, blood pressure, and body mass index (BMI). We conducted the analysis using structural equation modeling. Results: We enrolled 75 children, 36 girls and 39 boys with the median interquartile range (IQR) age of 14 (11-16) years and a median (IQR) duration of DM-T1 of 6 (4-9) years. The three focal predictors (cystatin C, resistance index, and urinary KIM-1) were significantly associated with the estimated risk for DKD. Raw path coefficients for cystatin C were 3.16 [95% CI 0.78; 5.53; p = 0.009, false discovery rate (FDR) < 5%], for renal resistance index were -8.14 (95% CI -15.36; -0.92; p = 0.027; FDR < 5%), and for urinary KIM-1 were 0.47 (95% CI 0.02; 0.93; p = 0.040; FDR < 5%). Conclusion: Cystatin C, renal resistance index, and KIM-1 may be associated with the risk for DKD in children and adolescents diagnosed with DM-T1. We encourage further prospective cohort studies to test our results.

Effects of Sacubitril/Valsartan on the Renal Resistance Index.

BACKGROUND: Sacubitril/valsartan plays a key role in improving left ventricular remodeling and prognosis in patients with heart failure with a reduced ejection fraction (HFrEF). Moreover, some data support its role in preserving renal function. In order to better clarify the effects of sacubitril/valsartan in cardiorenal syndrome, this study evaluated its effects on the renal resistance index (RRI). METHODS: A group of patients with HFrEF was enrolled. The RRI was assessed with renal echo-color Doppler at enrollment and again after at least six months of sacubitril/valsartan treatment. In a subgroup of patients, the RRI was also evaluated at least six months before enrollment. The variations in echocardiographic parameters reflecting the left and right ventricular function, as well as creatinine and the estimated glomerular filtration rate, were also evaluated. RESULTS: After treatment with sacubitril/valsartan, significant improvements in the left ventricular ejection fraction, and a decrease in the left atrial and ventricular volumes were observed. The RRI also showed a significant decrease. No relationship was found between the improvements in the parameters reflecting cardiac function and changes in the RRI. CONCLUSIONS: Treatment with sacubitril/valsartan is associated with improvements in both left ventricular function and renal perfusion, through decreasing the renal resistance. These data help to clarify the effects of the drug on cardiorenal syndrome progression.

Elevated renal resistive index is independently predicted by older age, but not by the presence of chronic kidney disease: a retrospective cohort study.

BACKGROUND: Renal resistive index (RRI), which reflects intrarenal arterial impedance, is routinely measured when undertaking renal Doppler ultrasonography (RDU). Increased RRI has been suggested to reflect renal parenchymal disease and imply risk of kidney disease progression. But this has been disputed and extra-renal haemodynamic factors rather than intra-renal factors have been proposed to determine RRI. AIMS: To investigate the relationship between elevated RRI and presence of chronic kidney disease (CKD), and examine whether elevated RRI at baseline is associated with decline in estimated glomerular filtration rate (eGFR) on follow up. METHODS: This retrospective observational study examined the association of elevated RRI (>0.7) with the presence of CKD (eGFR < 60 mL/min for >3 months), demographic and clinical factors in multivariable models. We also examined the effect of elevated RRI on eGFR decline on follow up using mixed models. RESULTS: Of the 346 patients undergoing RDU (median age 69.7 years; 46.2% male), 180 had elevated RRI. There was a strong inverse association between RRI and eGFR at baseline, 1 and 2 years (rho = -0.53, -0.51, -0.53, all P < 001). Elevated RRI was independently predicted by older age (odds ratio 3.29; 95% confidence interval 2.25-4.8; P < 0.001) and diabetes (odds ratio 2.65; 95% confidence interval 1.21-5.80; P = 0.015), but not CKD using multivariate logistic regression. Decline of eGFR was not different between RRI categories on follow up. CONCLUSION: Elevated RRI was predicted by older age and diabetes, but not by the presence of CKD. Baseline RRI was not associated with eGFR decline.

The role of the renal resistance index in patients with heart failure with reduced or preserved ejection fraction.

BACKGROUND: Renal impairment is a common phenomenon that portends a poor prognosis of heart failure (HF). The renal arterial resistance index (RRI) can be useful for defining renal function and predicting outcomes in patients with HF. This study aimed to investigate the determining factors of the RRI in HF patients with preserved ejection fraction (HFpEF) and with reduced EF (HFrEF). METHODS: This retrospective study included 330 patients with HF. We investigated the determining factors for the RRI and the association between the RRI and 1-year composite outcome, comprising all-cause mortality and re-hospitalization for HF. RESULTS: The independent predictors of the RRI were tricuspid regurgitation peak gradient and estimated glomerular filtration rate in HFpEF, and pulse pressure and blood urea nitrogen in HFrEF. During the follow-up, 30 (9.1%) patients presented the composite outcome. Cox proportional hazard analysis revealed the association of the RRI with the composite outcome in both HFrEF (HR 1.08; 95% CI 1.03-1.14) and HFpEF (HR 1.07; 95% CI 1.03-1.12) without an interaction (p for interaction = 0.770). CONCLUSIONS: The RRI was a consistent prognosticator in patients with HFpEF and those with HFrEF, while factors defining RRI were different between these groups.

Fenoldopam and renal hemodynamics in shiga toxin-related hemolytic uremic syndrome.

BACKGROUND: Fenoldopam, a vasodilating agent, may represent a potential therapeutic opportunity to increase renal perfusion in those conditions where renal hemodynamics are severely impaired by vascular sub-occlusion, as, indeed, is the case in thrombotic microangiopathies. METHODS: The renal resistance index (RRI) was measured, on and off fenoldopam, in 27 children with STEC-HUS. RESULTS: A 12% decrease in RRI was observed on fenoldopam compared to off treatment without changes in the systemic hemodynamics and with no side effects. CONCLUSIONS: If confirmed in larger series, fenoldopam may become an important addition to supportive care to reduce ischemic damage in STEC-HUS and improve long-term outcomes.

Intrarenal hemodynamics and kidney function in pheochromocytoma and paraganglioma before and after surgical treatment.

PURPOSE: Current evidence regarding renal involvement in pheochromocytoma and paraganglioma (PPGL) is scant. More accurate diagnostic methods, such as renal Doppler ultrasound for intrarenal hemodynamic studies, may provide more detailed information on renal function. It might be postulated that renal function in PPGL patients might be altered by high blood pressure and excess secretion of catecholamines. The aim of this prospective study was to assess intrarenal blood flow parameters in PPGL patients included in the prospective monoamine-producing tumour (PMT) study and to evaluate the effects of normalisation of catecholamine production after surgical treatment on long-term renal function. MATERIALS AND METHODS: Seventy consecutive patients (aged 46.5 ± 14.0 years) with PPGL were included. Forty-eight patients from the PMT study cohort, matched for age, gender, blood pressure level and presence of hypertension, served as a control group. Renal artery doppler ultrasound spectral analysis included mean resistance index (RRI) and pulsatility index (PI). Forty-seven patients completed 12 months follow-up. RESULTS: There were no differences in renal parameters such as RRI, PI and kidney function between PPGL and non-PPGL patients as assessed by renal ultrasound, serum creatinine, eGFR and albumin excretion rate. No correlations between kidney function parameters, intrarenal doppler flow parameters and plasma catecholamines were observed in PPGL patients. At 12 months after surgery, no differences in creatinine level, eGFR, albumin excretion rate, RI and PI were found as compared to baseline results. CONCLUSIONS: In contrast to patients with other forms of secondary hypertension, our study did not show differences in intrarenal blood flow parameters and renal function between PPGL and non-PPGL subjects. Intrarenal hemodynamics and renal function did not change after normalisation of catecholamine levels by surgical treatment.

Research progress of renal resistive index in the evaluation of acute kidney injury / 中华危重病急救医学

Acute kidney injury (AKI) is common in critically ill patients and it is directly related to the patient's prognosis and survival. Despite remaining uncertainties regarding the prevalence of AKI in intensive care unit (ICU), the overall incidence of AKI is relatively high, and prompt recognition is necessary to ensure the risk assessment, early diagnosis, clinical outcome, and treatment of critically ill patients. Doppler-based renal resistive index (RRI) mainly reflects vascular bed resistance state, which can be indirect to the extent of the damage of renal parenchyma. It is a relatively objective and quantitative evaluation, and is widely used in clinical prognosis of acute or chronic renal damage evaluation and judgment. This paper reviews the definition of RRI, the measurement methods of RRI, the application and progress of RRI in the field of AKI, the advantages and disadvantages of ultrasonic measurement of RRI, the long-term application of RRI, the effectiveness of RRI in predicting AKI, and the progress in clinical application.

[The value of renal resistance index and urine oxygen pressure for prediction of acute kidney injury in patients with septic shock].

Objective: To explore the value of renal resistance index (RI) and urine oxygen pressure for early prediction of acute kidney injury (AKI) in patients with septic shock. Methods: Patients with septic shock were enrolled from August 2018 to November 2018 in intensive care unit (ICU) at Peking Union Medical College Hospital. Subjects' general information and AKI characteristics were assessed. Area under the receiver operating characteristic (ROC) curve was used to analyze the predictive value of RI, urine oxygen pressure, or combination of RI on the occurrence of AKI. Results: A total of 72 septic shock patients were enrolled including 29 patients with AKI and 43 without. Logistic regression analysis of AKI risk factors found that RI (OR=1.139, 95%CI 1.029-1.261, P=0.012) and urine oxygen pressure (OR=0.957, 95%CI 0.923-0.991, P=0.014) at admission were independent risk factors for AKI in patients with septic shock. The sensitivity and specificity of dual RI and urine oxygen pressure in predicting AKI were 65.5% and 76.7% respectively (AUCROC 0.772, Youden index 0.423). We selected the cut-off value of RI as 0.70,and urine oxygen pressure as 48 mmHg (1 mmHg=0.133 kPa). According to this two cut-off values patients were divided into four groups, those with RI≥0.70 and urine oxygen pressure≤48 mmHg showed the highest incidence of AKI (75%). There was no statistically difference in 28-day survival rate between the four groups (P=0.197). Conclusion: High RI and low urine oxygen pressure are independent risk factors for the development of AKI in patients with septic shock. The predictive cut-off values are 0.70 for RI and 48 mmHg for urine oxygen pressure. Combination of RI and urine oxygen pressure has a practical predictive value for AKI in patients with septic shock.

The value of renal resistance index and urine oxygen pressure for prediction of acute kidney injury in patients with septic shock / 中华内科杂志

Objective To explore the value of renal resistance index (RI) and urine oxygen pressure for early prediction of acute kidney injury (AKI) in patients with septic shock.Methods Patients with septic shock were enrolled from August 2018 to November 2018 in intensive care unit (ICU) at Peking Union Medical College Hospital.Subjects' general information and AKI characteristics were assessed.Area under the receiver operating characteristic (ROC) curve was used to analyze the predictive value of RI,urine oxygen pressure,or combination of RI on the occurrence of AKI.Results A total of 72 septic shock patients were enrolled including 29 patients with AKI and 43 without.Logistic regression analysis of AKI risk factors found that RI (OR=1.139,95％CI 1.029-1.261,P=0.012) and urine oxygen pressure (OR=0.957,95％CI 0.923-0.991,P=0.014) at admission were independent risk factors for AKI in patients with septic shock.The sensitivity and specificity of dual RI and urine oxygen pressure in predicting AKI were 65.5％and 76.7％ respectively (AUCROC 0.772,Youden index 0.423).We selected the cut-off value of RI as 0.70,and urine oxygen pressure as 48 mmHg (1 mmHg=0.133 kPa).According to this two cut-off values patients were divided into four groups,those with RI≥0.70 and urine oxygen pressure≤48 mmHg showed the highest incidence of AKI (75％).There was no statistically difference in 28-day survival rate between the four groups (P=0.197).Conclusion High RI and low urine oxygen pressure are independent risk factors for the development of AKI in patients with septic shock.The predictive cut-off values are 0.70 for RI and 48 mmHg for urine oxygen pressure.Combination of RI and urine oxygen pressure has a practical predictive value for AKI in patients with septic shock.

[Evaluation of renal function in the course of hypertension in the elderly]. / Ocena funkcji nerek w przebiegu nadcisnienia tetniczego u osób w podeszlym wieku.

Hypertension is one of the most common chronic diseases in Poland. It occurs in all age groups, but most often affects people over 65 years of age. The correct diagnosis of hypertension in older people includes documenting elevated blood pressure values, differentiating disease changes from physiologically related changes to aging, as well as assessing organ related complications. Detection of organ complications is also an important parameter of prognosis assessment. AIM: The aim of the study was evaluation of renal function in the course of hypertension in the elderly. MATERIALS AND METHODS: The study involved 63 women and 17 men, aged from 75 to 93 years, who were diagnosed with arterial hypertension in accordance with the guidelines of the Polish Society of Hypertension. Patients were divided into two groups. The first pair consisted of a group of 1 hypertensive patients (HA) lasting up to 10 years of age over 85 years and a group of 2 patients with HA lasting up to 10 years at the age of 75-85 years. The second pair is group I - patients with HA over 10 years of age over 85 years and group II - patients with HA lasting over 10 years at the age of 75-85. The assessment of glomerular filtration was made using the estimated glomerular filtration rate (GFR), which was calculated according to the mathematical formula of MDRD, while the renal resistance index was assessed using spectral Doppler after visualization of the flow in the renal arteries. RESULTS: The value of glomerular filtration in the examined groups divided by age was 55.1±15 (group 1) and 66.9±16 (group 2). The values of the kidney artery resistance index (depending on age) were in 1 group: 0.61±0.04 vs 0.60±0.05 and in the second group: 0.59±0.06 vs 0.58±0.05. The values of the renal artery resistance index (depending on the duration of HA) were 0.62±0.04 vs 0.61±0.03 (group I) and 0.61±0.04 vs 0.60±0.04 ( group II). CONCLUSIONS: GFR depends on the duration of hypertension. A relationship was found between the value of the kidney artery resistance index and age. There was no significant relationship between the value of the kidney artery resistance index and duration of hypertension.

Heart Failure and Kidney Disease.

Kidney disease is commonly found in heart failure (HF) patients. They share many risk factors and common pathophysiological pathways which often lead to mutual dysfunction. Both haemodynamic and non-haemodynamic mechanisms are involved in the development of renal impairment in heart failure patients. Moreover, the presence of a chronic kidney disease is a significant independent predictor of worse outcome in chronic as well as in acute decompensated HF. As a consequence, an accurate evaluation of renal function plays a key role in the management of HF patients. Serum creatinine levels and glomerular filtration rate (GFR) estimates are the corner stones of renal function evaluation in clinical practice. However, to overcome their limits, several emerging glomerular and tubular biomarkers have been proposed over the last years. Alongside the renal biomarkers, imaging techniques could complement the laboratory data exploring different pathophysiological pathways. In particular, Doppler evaluation of renal circulation is a highly feasible technique that can effectively identify HF patients prone to develop renal dysfunction and with a worse outcome. Finally, some classes of drugs currently used in heart failure treatment can affect renal function and their use can be influenced by the presence of chronic kidney disease.

Intrarenal Flow Alterations During Transition From Euvolemia to Intravascular Volume Expansion in Heart Failure Patients.

OBJECTIVES: The goal of this study was to assess: 1) the intrarenal flow in heart failure (HF) patients during the transition from euvolemia to intravascular volume overload; and 2) the relationship between intrarenal flow and diuretic efficiency. BACKGROUND: Intrarenal blood flow alterations may help to better understand impaired volume handling in HF. METHODS: Resistance index (RI) and venous impedance index (VII) were assessed in 6 healthy subjects, 40 euvolemic HF patients with reduced ejection fraction (HFrEF), and 10 HF patients with preserved ejection fraction (HFpEF). Assessments were performed by using Doppler ultrasonography at baseline, during 3 h of intravascular volume expansion with 1 l of hydroxyethyl starch 6%, and 1 h after the administration of a loop diuretic. Clinical parameters, echocardiography, and biochemistry were assessed. Urine output was collected after 3 and 24 h. RESULTS: In response to volume expansion, VII increased significantly in HFrEF patients (0.4 ± 0.3 to 0.7 ± 0.2; p < 0.001) and in HFpEF patients (0.4 ± 0.3 to 0.7 ± 0.2; p = 0.002) but not in healthy subjects (0.2 ± 0.2 to 0.3 ± 0.1; p = 0.622). This outcome was reversed after loop diuretic administration. In contrast, RI did not change significantly after volume expansion. Echocardiographic-estimated filling pressures did not change significantly. VII during volume expansion was significantly correlated with diuretic response in HF patients independent of baseline renal function (R2 = 0.35; p < 0.001). CONCLUSIONS: In HF patients, intravascular volume expansion resulted in significant blunting of venous flow before a significant increase in cardiac filling pressures could be demonstrated. The observed impaired renal venous flow is correlated with less diuretic efficiency. Intrarenal venous flow patterns may be of interest for evaluating renal congestion.

Role of imaging in the evaluation of renal dysfunction in heart failure patients.

Heart failure and kidney disease share common pathophysiological pathways which can lead to mutual dysfunction, known as cardiorenal syndrome. In heart failure patients, renal impairment is related to hemodynamic and non-hemodynamic factors. Both decreased renal blood flow and renal venous congestion due to heart failure could lead to impaired renal function. Kidney disease and worsening renal function are independently associated with poor prognosis in heart failure patients, both in acute and chronic clinical settings. The aim of this review is to assess the role of renal imaging modalities in the evaluation and management of heart failure patients. Renal imaging techniques could complete laboratory data, as estimated glomerular filtration rate, exploring different pathophysiological factors involved in kidney disease and adding valuable information about renal structure and function. In particular, Doppler examination of arterial and venous hemodynamics is a feasible and non invasive technique, which has proven to be a reliable method for prognostic stratification in patients with cardiorenal syndrome. The renal resistance index, a measure related to renal hemodynamics, can be calculated from the Doppler evaluation of arterial flow. Moreover, the analysis of Doppler venous flow patterns can integrate information from the arterial study and evaluate renal congestion. Other imaging modalities are promising, but still confined to research purposes.

Relationship Between Carotid Atherosclerosis and Pulse Pressure with Renal Hemodynamics in Hypertensive Patients.

BACKGROUND: Structural atherosclerotic damage, arterial stiffness, pulse pressure (PP), and renal hemodynamics may interact and influence each other. Renal resistance index (RRI) appears as a good indicator of systemic vascular changes. The aim of our study was to assess the independent relationships of carotid intima-media thickness (cIMT), aortic pulse wave velocity (aPWV), and peripheral PP with RRI in hypertensives with various degrees of renal function. METHODS: We enrolled 463 hypertensive patients (30-70 years) with normal renal function (group 0; n = 280) and with chronic kidney disease (groups I-V; n = 183). All subjects underwent ultrasonographic examination of intrarenal and carotid vasculature, as well as a 24-h ambulatory blood pressure monitoring. RESULTS: A statistically significant difference in RRI, cIMT, aPWV, and clinic PP was observed in the different 6 groups (all P < 0.001), even after adjustment for age. RRI correlated with cIMT (r = 0.460, P < 0.001), aPWV (r = 0.386, P < 0.001), clinic PP (r = 0.279, P < 0.001), and 24-h PP (r = 0.229, P < 0.001) in the entire study population. These correlations were similar in subjects with and without renal dysfunction. In the overall study population, the association between RRI, cIMT, and clinic PP remained statistically significant even after adjustment for various confounding factors, whereas the relationship between RRI and aPWV was lost in multivariate analysis. CONCLUSIONS: cIMT and clinic PP rather than directly aPWV are associated with intrarenal hemodynamics. Our results confirm that in hypertensives RRI not only detects derangement of intrarenal circulation but may also be considered as a sensor of systemic vascular changes, independently of level of renal function.

Intrarenal hemodynamic and oxidative stress in patients with obstructive sleep apnea syndrome.

BACKGROUND: Oxygen desaturation and reoxygenation, related to intermittent hypoxia cycles due to upper airway obstruction, are major pathophysiologic features of obstructive sleep apnea syndrome (OSAS) and are thought to be responsible for an increased risk of cardiovascular diseases. Continuous positive airway pressure (CPAP) is therefore considered the gold standard in the management of OSAS. Further data demonstrated a high prevalence of OSAS in patients with altered renal function despite the underlying pathophysiological mechanisms that have not been clarified. This study aims to provide evidence on the reported high prevalence of endothelial dysfunction and alterations of the intrarenal hemodynamic in patients affected by OSAS. Furthermore, we evaluated the effect of a CPAP therapy on these endpoints. METHODS: Twenty patients were enrolled in a prospective study and underwent ultrasound examination to assess endothelial dysfunction, by collecting brachial flow-mediated dilation (FMD) and intrarenal artery stiffness, pre- and post a 30-day treatment with CPAP. RESULTS: Endothelial dysfunction and intrarenal artery stiffness significantly improved in all patients after a month of CPAP. In particular, we observed a significant reduction in the renal resistance index (RI) (p < 0.001) and systolic/diastolic ratio (S/D) ratio (p < 0.001) and a significant increase of FMD (p < 0.001). The apnea-hypopnea index (AHI) showed a negative correlation with Δ FMD (p < 0.05, r = -0.46). Conversely, a positive correlation exists between Δ RI and the oxygen desaturation index (ODI) (specificare la sigla) (p < 0.05, r = 0.46). CONCLUSIONS: Our study firstly showed a significant effect of CPAP on renal perfusion and endothelial function in OSAS patients without concomitant cardiovascular comorbidities.

Evaluation of chronic kidney disease in chronic heart failure: From biomarkers to arterial renal resistances.

Chronic kidney disease and its worsening are recurring conditions in chronic heart failure (CHF) which are independently associated with poor patient outcome. The heart and kidney share many pathophysiological mechanisms which can determine dysfunction in each organ. Cardiorenal syndrome is the condition in which these two organs negatively affect each other, therefore an accurate evaluation of renal function in the clinical setting of CHF is essential. This review aims to revise the parameters currently used to evaluate renal dysfunction in CHF with particular reference to the usefulness and the limitations of biomarkers in evaluating glomerular dysfunction and tubular damage. Moreover, it is reported the possible utility of renal arterial resistance index (a parameter associated with abnormalities in renal vascular bed) for a better assesment of kidney disfunction.