Renal venous doppler ultrasonography in normal subjects and patients with diabetic nephropathy: value of venous impedance index measurements

Point-of-care ultrasonography spotlight: Could venous excess ultrasound serve as a shared language for internists and intensivists?

Point-of-care ultrasonography (POCUS), particularly venous excess ultrasound (VExUS) is emerging as a valuable bedside tool to gain real-time hemodynamic insights. This modality, derived from hepatic vein, portal vein, and intrarenal vessel Doppler patterns, offers a scoring system for dynamic venous congestion assessment. Such an assessment can be crucial in effective management of patients with heart failure exacerbation. It facilitates diagnosis, quantification of congestion, prognostication, and monitoring the efficacy of decongestive therapy. As such, it can effectively help to manage cardiorenal syndromes in various clinical settings. Extended or eVExUS explores additional veins, potentially broadening its applications. While VExUS demonstrates promising outcomes, challenges persist, particularly in cases involving renal and liver parenchymal disease, arrhythmias, and situations of pressure and volume overload overlap. Proficiency in utilizing spectral Doppler is pivotal for clinicians to effectively employ this tool. Hence, the integration of POCUS, especially advanced applications like VExUS, into routine clinical practice necessitates enhanced training across medical specialties.

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.

Hemodynamic Changes in Intrarenal Blood Flow are Associated With Poor Prognosis in Patients With Acute Decompensated Heart Failure

AIM

To evaluate a potential role of different patterns of intrarenal blood flow using Doppler ultrasound as a part of determining the severity of venous congestion, predicting impairment of renal function and an unfavorable prognosis in patients with acute decompensated chronic heart failure (ADCHF).

MATERIAL AND METHODS

This prospective observational single-site study included 75 patients admitted in the intensive care unit for ADCHF. Upon admission all patients underwent bedside renal venous Doppler ultrasound to determine the blood flow pattern (continuous, biphasic, monophasic). In one hour after the initiation of intravenous diuretic therapy, sodium concentration was measured in a urine sample. The primary endpoint was the development of acute kidney injury (AKI). The secondary endpoints were the development of diuretic resistance (a need to increase the furosemide daily dose by more than 2 times compared with the baseline), decreased natriuretic response (defined as urine sodium concentration less than 50-70 mmol/l), and in-hospital death.

RESULTS

According to the data of Doppler ultrasound, normal renal blood flow was observed in 40 (53%) patients, biphasic in 21 (28%) patients, and monophasic in 14 (19%) patients. The monophasic pattern of intrarenal blood flow was associated with the highest incidence of AKI: among 14 patients in this group, AKI developed in 100% of cases (OR 3.8, 95% CI: 2.5-5.8, p<0.01), while among patients with normal and moderate impairment of renal blood flow, there was no significant increase in the risk of developing AKI. The odds of in-hospital death were increased 25.77 times in patients with monophasic renal blood flow (95% CI: 5.35-123.99, p<0.001). Patients with a monophasic intrarenal blood flow pattern were also more likely to develop diuretic resistance compared to patients with other blood flow patterns (p<0.001) and had a decreased sodium concentration to less than 50 mmol/l (p<0.001) in a spot urine test obtained one hour after the initiation of furosemide administration.

CONCLUSION

Patients with monophasic intrarenal blood flow are at a higher risk of developing AKI, diuretic resistance with decreased natriuretic response, and in-hospital death.

Impact of Renal Congestion in Patients With Secondary Mitral Regurgitation After Mitral Transcatheter Edge-to-Edge Repair

BACKGROUND

Renal congestion is a potential prognostic factor in patients with heart failure and recently, assessment has become possible with intrarenal Doppler ultrasonography (IRD). The association between renal congestion assessed by IRD and outcomes after mitral transcatheter edge-to-edge repair (TEER) is unknown, so we aimed to clarify renal congestion and its prognostic implications in patients with mitral regurgitation (MR) who underwent TEER using MitraClip system.Methods and Results: Patients with secondary MR who underwent TEER and were assessed for intrarenal venous flow (IRVF) by IRD were classified according to their IRVF pattern as continuous or discontinuous. Of the 105 patients included, 78 patients (74%) formed the continuous group and 27 (26%) were the discontinuous group. Kaplan-Meier analysis revealed significant prognostic power of the IRVF pattern for predicting the composite outcome of all-cause death and heart failure rehospitalization (log-rank P=0.0257). On multivariate Cox regression analysis, the composite endpoint was independently associated with the discontinuous IRVF pattern (hazard ratio, 3.240; 95% confidence interval, 1.300-8.076; P=0.012) adjusted using inverse probability of treatment weighting.

CONCLUSIONS

IRVF patterns strongly correlated with clinical outcomes without changes in renal function. Thus, they may be useful for risk stratification after mitral TEER for patients with secondary MR.

Renal Congestion in Heart Failure: Insights in Novel Diagnostic Modalities

Heart failure is increasingly prevalent and is estimated to increase its burden in the following years. A well-reported comorbidity of heart failure is renal dysfunction, where predominantly changes in the patient's volume status, tubular necrosis or other mechanical and neurohormonal mechanisms seem to drive this impairment. Currently, there are established biomarkers evaluating the patient's clinical status solely regarding the cardiovascular or renal system. However, as the coexistence of heart and renal failure is common and related to increased mortality and hospitalization for heart failure, it is of major importance to establish novel diagnostic techniques, which could identify patients with or at risk for cardiorenal syndrome and assist in selecting the appropriate management for these patients. Such techniques include biomarkers and imaging. In regards to biomarkers, several peptides and miRNAs indicative of renal or tubular dysfunction seem to properly identify patients with cardiorenal syndrome early on in the course of the disease, while changes in their serum levels can also be helpful in identifying response to diuretic treatment. Current and novel imaging techniques can also identify heart failure patients with early renal insufficiency and assess the volume status and the effect of treatment of each patient. Furthermore, by assessing the renal morphology, these techniques could also help identify those at risk of kidney impairment. This review aims to present all relevant clinical and trial data available in order to provide an up-to-date summary of the modalities available to properly assess cardiorenal syndrome.

Central venous pressure combined with renal venous impedance index in predicting the acute kidney injury after thoracic and abdominal (non-cardiac) surgery

BACKGROUND

In the 21st century, 13% of patients undergoing open abdominal surgery, 25% of patients undergoing heart surgery, and 57% of patients admitted to the intensive care unit (ICU) are affected by acute kidney injury (AKI).

METHODS

This prospective observational study included patients admitted directly to the ICU between June 2021 and December 2021.

RESULTS

A total of 81 patients were enrolled after thoracic and abdominal (non-cardiac) surgery; 36 patients (44.4%) were diagnosed with AKI occurred within 7 days after surgery. Six-hour postoperative central venous pressure(CVP) was a risk factor for AKI in thoracic and abdominal (non-cardiac) postoperative patients (odds ratio [OR], 1.418; 95% confidence intervals [CI], 1.106-1.819; P = 0.006). Six-hour postoperative vein impedance index(VII) and CVP were significantly positively correlated (P = 0.031). The combination of 6-h postoperative VII with CVP (VII ≥0.34, CVP ≥7.5 mmHg) showed an area under the curve (AUC) of 0.787, In the subgroup analysis of patients with 6-h postoperative CVP <7.5 mmHg, there was a significant statistical difference in 6-h postoperative VII between the groups and those without AKI (P = 0.048). At 6-h postoperative CVP <7.5 mmHg, VII of ≥0.44 had a predictive value for AKI after thoracic and abdominal (non-cardiac) surgery, with an AUC of 0.669, a sensitivity of 41.2%, and a specificity of 94.4%.

CONCLUSION

Six-hour postoperative CVP combined with VII can better predict the occurrence of AKI occurred within 7 days after thoracic and abdominal (non-cardiac) surgery but cannot predict the severity of AKI.

Doppler-based evaluation of intrarenal venous flow as a new tool to predict acute kidney injury: A systematic review and meta-analysis

Congestion is a common complication in the critical care setting, these patients are at increased risk of developing acute kidney injury (AKI). Congestive nephropathy (CN) has recently been described as a mechanism of worsening renal function, and evaluation of renal venous flow by pulsed Doppler (PD) is a useful tool to assess the presence of renal vein congestion. We comprehensively explore the ability of the PD in the evaluation of the intrarenal venous flow (IRVF) to predict the development of AKI in critically ill patients. We searched Pubmed-MEDLINE, Scopus, Embase, and Cochrane Library of Systematic Reviews (to 31th December 2021). We evaluated the association between Doppler-based Intrarenal venous flow demodulation and AKI. CN was defined as the presence of a pulsatile pattern (biphasic or monophasic) in the PD. A total of 4 articles (660 patients) were included in our systematic review, three of these in the metanalysis (413 patients): one study was excluded because its data were inadequate for pooling. Two studies originated in Europe and the other two in the United States. AKI occurrence ranged between 34 and 68%. Patients who developed AKI had a significant difference in PD pattern (continuous vs. pulsatile) in the IRVF (RR=0.46; 95% CI 0.28-0.76). Nevertheless, a large heterogeneity was observed among the studies (I2=68.7%; p=0.04). Albeit preliminary, these findings suggest that the presence of a pulsatile pattern in the PD of the IRVF may be involved in the development of AKI in the critically ill patient. The effect of alterations in the IRVF and renal function warrant further investigation.

Phenotyping congestion in acute heart failure by renal flow and right heart to pulmonary circulation coupling

AIMS

In acute heart failure (AHF), kidney congestion is basic to treatment and prognosis. Its aetiology is manifold and quite unexplored in details mainly regarding the right heart to pulmonary circulation (Pc) coupling. We investigated the right heart to kidney interrelationship by Doppler renal flow pattern, right atrial dynamics, and right ventricular (RV) function to Pc coupling in AHF.

METHODS AND RESULTS

In 119 AHF patients, echocardiographic and renal Doppler data were analysed. Univariate and multivariate regression models were performed to define the determinants of a quantitative parameter of renal congestion, the renal venous stasis index (RVSI). When grouped according to different intra-renal venous flow patterns, no differences were observed in haemodynamics and baseline renal function. Nonetheless, patients with renal Doppler evidence of congestion showed a reduced RV function [tricuspid annular plane systolic excursion (TAPSE), S'-wave velocity, and fractional area change], impaired RV to Pc coupling [TAPSE/pulmonary artery systolic pressure (PASP) ratio], and right atrial peak longitudinal strain (RAPLS), along with signs of volume overload [increased inferior vena cava (IVC) diameters and estimated right atrial pressure]. Univariate and multivariate regression analyses confirmed TAPSE/PASP, RAPLS, and IVC diameter as independent determinants of the RVSI. RVSI was the only variable predicting the composite outcome (cardiac death, heart failure hospitalization, and haemodialysis). An easy-to-use echo-derived right heart score of four variables provided good accuracy in identifying kidney congestion.

CONCLUSIONS

In AHF, the renal venous flow pattern combined with a right heart study phenotypes congestion and clinical evolution. Keys to renal flow disruption are an impaired right atrial dynamics and RV-Pc uncoupling. Integration of four right heart echocardiographic variables may be an effective tool for scoring the renal congestive phenotype in AHF.

Renal hemodynamic evaluation protocol based on the pathophysiological mechanism of acute kidney injury: Critical Care UltraSound Guided-A(KI)BCDE

The multiple etiological characteristics of acute kidney injury (AKI) have brought great challenges to its clinical diagnosis and treatment. Renal injury in critically ill patients always indicates hemodynamic injury. The Critical Care UltraSound Guided (CCUSG)-A(KI)BCDE protocol developed by the Chinese Critical Ultrasound Study Group (CCUSG), respectively, includes A(KI) diagnosis and risk assessment and uses B-mode ultrasound, Color doppler ultrasound, spectral Doppler ultrasound, and contrast Enhanced ultrasound to obtain the hemodynamic characteristics of the kidney so that the pathophysiological mechanism of the occurrence and progression of AKI can be captured and the prognosis of AKI can be predicted combined with other clinical information; therefore, the corresponding intervention and treatment strategies can be formulated to achieve targeted, protocolized, and individualized therapy.

Clinical relevance and prognostic value of renal Doppler in acute decompensated precapillary pulmonary hypertension

AIMS

We aim to evaluate the clinical relevance and the prognostic value of arterial and venous renal Doppler in acute decompensated precapillary pulmonary hypertension (PH).

METHODS AND RESULTS

The renal resistance index (RRI) and the Doppler-derived renal venous stasis index (RVSI) were monitored at admission and on Day 3 in a prospective cohort of precapillary PH patients managed in intensive care unit for acute right heart failure (RHF). The primary composite endpoint included death, circulatory assistance, urgent transplantation, or rehospitalization for acute RHF within 90 days following inclusion. Ninety-one patients were enrolled (58% female, age 58 ± 16 years). The primary endpoint event occurred in 32 patients (33%). In univariate logistic regression analysis, variables associated with RRI higher than the median value were non-variable parameters (age and history of hypertension), congestion (right atrial pressure and renal pulse pressure), cardiac function [tricuspid annular plane systolic excursion (TAPSE) and left ventricular outflow tract- velocity time integral], systemic pressures and NT-proBNP. Variables associated with RVSI higher than the median value were congestion (high central venous pressure, right atrial pressure, and renal pulse pressure), right cardiac function (TAPSE), severe tricuspid regurgitation, and systemic pressures. Inotropic support was more frequently required in patients with high RRI (P = 0.01) or high RVSI (P = 0.003) at the time of admission. At Day 3, a RRI value <0.9 was associated with a better prognosis after adjusting to the estimated glomerular filtration rate.

CONCLUSION

Renal Doppler provides additional information to assess the severity of patients admitted to the intensive care unit for acute decompensated precapillary PH.

Proceedings of the 2022 UAB CRRT Academy: Non-Invasive Hemodynamic Monitoring to Guide Fluid Removal with CRRT and Proliferation of Extracorporeal Blood Purification Devices

In 2022, we celebrated the 15th anniversary of the University of Alabama at Birmingham (UAB) Continuous Renal Replacement Therapy (CRRT) Academy, a 2-day conference attended yearly by an international audience of over 100 nephrology, critical care, and multidisciplinary trainees and practitioners. This year, we introduce the proceedings of the UAB CRRT Academy, a yearly review of select emerging topics in the field of critical care nephrology that feature prominently in the conference. First, we review the rapidly evolving field of non-invasive hemodynamic monitoring and its potential to guide fluid removal by renal replacement therapy (RRT). We begin by summarizing the accumulating data associating fluid overload with harm in critical illness and the potential for harm from end-organ hypoperfusion caused by excessive fluid removal with RRT, underscoring the importance of accurate, dynamic assessment of volume status. We describe four applications of point-of-care ultrasound used to identify patients in need of urgent fluid removal or likely to tolerate fluid removal: lung ultrasound, inferior vena cava ultrasound, venous excess ultrasonography, and Doppler of the left ventricular outflow track to estimate stroke volume. We briefly introduce other minimally invasive hemodynamic monitoring technologies before concluding that additional prospective data are urgently needed to adapt these technologies to the specific task of fluid removal by RRT and to learn how best to integrate them into practical fluid-management strategies. Second, we focus on the growth of novel extracorporeal blood purification devices, starting with brief reviews of the inflammatory underpinnings of multiorgan dysfunction and the specific applications of pathogen, endotoxin, and/or cytokine removal and immunomodulation. Finally, we review a series of specific adsorptive technologies, several of which have seen substantial clinical use during the COVID-19 pandemic, describing their mechanisms of target removal, the limited existing data supporting their efficacy, ongoing and future studies, and the need for additional prospective trials.

The repeatability, reproducibility, and influencing factors of intrarenal Doppler ultrasonography in dogs without heart disease

Renal impairment is concurrent with adverse outcomes such as heart disease in humans and dogs. Intrarenal Doppler ultrasonography (IRD) is used to assess intrarenal hemodynamics, and resistance index (RI) and venous impedance index (VII) are used to evaluate intrarenal hemodynamics in humans with heart failure. However, only a few studies have assessed the efficacy of IRD, especially VII, in dogs, and the methods differ between studies. Additionally, repeatability, reproducibility, and factors influencing IRD values have not been validated in dogs. This prospective, analytical study aimed to assess repeatability and reproducibility of IRD, and to clarify influencing factors of IRD in dogs without heart disease. We enrolled 78 dogs without heart disease. The RI and VII were highly reproducible, and the reference intervals for VII were 0.13-0.37. Differences in transducer (sector and convex) and posture (right lateral and supine decubitus position) had no effect on the IRD values. In contrast, RI and VII were higher in the renal vessels than in interlobar vessels. Age affected RI values (r = 0.39, P < 0.001), but there was no correlation between age, body weight, and VII. In conclusion, IRD is a repeatable and reproducible method to assess intrarenal hemodynamics in dogs. The findings also suggest that age should be considered while interpreting RI.

Electrocardiographic Time-Intervals Waveforms as Potential Predictors for Severe Acute Kidney Injury in Critically Ill Patients

Background: Acute kidney injury (AKI) is common in critically ill patients admitted to intensive care units (ICU) and is frequently associated with poorer outcomes. Hence, if an indicator is available for predicting severe AKI within the first few hours of admission, management strategies can be put into place to improve outcomes. Materials and methods: This was a prospective, observational study, involving 63 critically ill patients, that aimed to explore the diagnostic accuracy of different Doppler parameters in predicting AKI in critically ill patients from a mixed ICU. Participants were enrolled at ICU admission. All underwent ultrasonographic examinations and hemodynamic assessment. Renal Doppler resistive index (RDRI), venous impedance index (VII), arterial systolic time intervals (a-STI), and venous systolic time intervals (v-STI) were measured within 2 h from ICU admission. Results: Cox proportional hazards models, including a-STI, v-STI, VII, and RDRI as independent variables, returned a-STI as the only putative predictor for the development of AKI or severe AKI. An overall statistically significant difference (p < 0.001) was observed in the Kaplan−Meier plots for cumulative AKI events between patients with a-STI higher or equal than 0.37 and for cumulative severe AKI-3 between patients with a-STI higher or equal than 0.63. As assessed by the area under the receiver operating curves (ROC) curves, a-STI performed best in diagnosing any AKI and/or severe AKI-3. Positive correlations were found between a-STI and the N-terminal brain natriuretic peptide precursor (NT-pro BNP) (ρ = 0.442, p < 0.001), the sequential organ failure assessment (SOFA) score (ρ: 0.361, p = 0.004), and baseline serum creatinine (ρ: 0.529, p < 0.001). Conclusions: Critically ill patients who developed AKI had statistically significant different a-STI (on admission to ICU), v-STI, and VII than those who did not. Moreover, a-STI was associated with the development of AKI at day 5 and provided the best diagnostic accuracy for the diagnosis of any AKI or severe AKI compared with RDRI, VII, and v-STI.

Venous Doppler to Assess Congestion: A Comprehensive Review of Current Evidence and Nomenclature

Organ congestion from venous hypertension is an important pathophysiological mechanism mediating organ injury in several clinical contexts including critical illness, congestive heart failure and end-stage chronic kidney disease. However, the practical evaluation of venous congestion is often challenging at the bedside because of the limitations of traditional methods. Point-of-care ultrasound (POCUS) enables the clinician to assess venous velocity profiles during the cardiac cycle using Doppler modalities. Venous Doppler profile abnormalities at multiple sites are detected when elevated venous pressure results in hemodynamic changes within the systemic venous circulation. The detection of these abnormal Doppler profiles may identify patients with clinically significant systemic venous congestion. These patients have been reported to be at increased risk of medical complications. Improving the evaluation of venous congestion may lead to individualized treatment and improved patient outcomes. In this review, we describe the physiologic principles necessary to understand venous Doppler assessment. We also propose a nomenclature for the description of venous Doppler profiles. Finally, we provide a narrative review of the current clinical evidence related to use of venous Doppler assessment in various clinical contexts.

How to Determine Fluid Management Goals during Continuous Kidney Replacement Therapy in Patients with AKI: Focus on POCUS

The utilization of kidney replacement therapies (KRT) for fluid management of patients who are critically ill has significantly increased over the last years. Clinical studies have suggested that both fluid accumulation and high fluid removal rates are associated with adverse outcomes in the critically ill population receiving KRT. Importantly, the ideal indications and/or fluid management strategies that could favorably affect these patients are unknown; however, differentiating clinical scenarios in which effective fluid removal may provide benefit to the patient by avoiding congestive organ injury, compared with other settings in which this intervention may result in harm, is direly needed in the critical care nephrology field. In this review, we describe observational data related to fluid management with KRT, and examine the role of point-of-care ultrasonography as a potential tool that could provide physiologic insights to better individualize decisions related to fluid management through KRT.

Intrarenal Doppler approaches in hemodynamics: A major application in critical care

The treatment of severe cases usually requires multimodality hemodynamic monitoring approaches, particularly for tissue and organ perfusion tracking. Currently, only a few studies have investigated renal perfusion status at the bedside. Ultrasound has become increasingly utilized to guide the hemodynamic management of severe patients. Similarly, intrarenal Doppler (IRD) is widely used to assess renal perfusion from both the intrarenal artery and vein perspectives. The renal resistive index (RRI), which reflects the renal arterial blood flow profile, is often applied to predict the reversibility of renal dysfunction and to titrate hemodynamic support. Intrarenal venous flow (IRVF) patterns and the renal venous stasis index (RVSI), which reflects the intrarenal vein blood flow profile, are now being used to assess intravenous congestion. They may also be useful in predicting the risk of acute kidney injury and avoiding fluid overload. IRD can provide diverse and supplemental information on renal perfusion and may help to establish the early diagnosis in severe patients. This review focused on the specific operational methods, influencing factors, and applications of IRD in hemodynamics.

Evaluation of Renal Blood Flow in Dogs during Short-Term Human-Dose Epoprostenol Administration Using Pulsed Doppler and Contrast-Enhanced Ultrasonography

Simple Summary

Since there is a lack of information regarding how epoprostenol, a prostacyclin, affects canine renal blood flow (RBF), we investigated the effects of short-term administration of epoprostenol at human doses of 2, 5, and 10 ng/kg/min intravenously for 20 min on RBF in six healthy dogs under anesthesia. The effects of short-term administration were investigated. As the dose of epoprostenol increased, peak systolic and end diastolic velocities of the renal arteries, maximum and minimum venous flow velocities of the interlobular and renal veins, and heart rate all tended to increase. However, these increases were not significant. These results indicate that the administration of human doses of epoprostenol to dogs does not produce significant changes in renal or systemic circulation.

Abstract

Prostacyclin is an in vivo bioactive substance that regulates renal blood flow (RBF). Information regarding how epoprostenol, a prostacyclin preparation, affects RBF in dogs is lacking. We investigated the effects of short-term epoprostenol administration on RBF in six healthy dogs under anesthesia by administering it intravenously at human doses—2, 5, and 10 ng/kg/min for 20 min. RBF was evaluated before and during epoprostenol administration using pulsed Doppler ultrasonography, and renal perfusion was evaluated using contrast-enhanced ultrasonography. Effects on renal and systemic circulation were evaluated by measuring systolic arterial, mean arterial, diastolic arterial, pulmonary arterial, mean right atrial, and pulmonary capillary wedge pressures; heart rate; and cardiac output. Kruskal–Wallis and Bonferroni multiple comparison tests and Spearman’s rank correlation coefficient were used for statistical analyses. As epoprostenol dosage increased, the peak systolic and end diastolic velocity of the renal artery, maximum and minimum venous flow velocities of the interlobular and renal veins, and heart rate all tended to increase, although not significantly. Our results indicate that human-dose epoprostenol administration in dogs does not cause significant changes in renal or systemic circulation. However, the human doses used may have been too low to produce a clinical effect in dogs.

The Intensivist's Perspective of Shock, Volume Management, and Hemodynamic Monitoring

One of the primary reasons for intensive care admission is shock. Identifying the underlying cause of shock (hypovolemic, distributive, cardiogenic, and obstructive) may lead to entirely different clinical pathways for management. Among patients with hypovolemic and distributive shock, fluid therapy is one of the leading management strategies. Although an appropriate amount of fluid administration might save a patient's life, inadequate (or excessive) fluid use could lead to more complications, including organ failure and mortality due to either hypovolemia or volume overload. Currently, intensivists have access to a wide variety of information sources and tools to monitor the underlying hemodynamic status, including medical history, physical examination, and specific hemodynamic monitoring devices. Although appropriate and timely assessment and interpretation of this information can promote adequate fluid resuscitation, misinterpretation of these data can also lead to additional mortality and morbidity. This article provides a narrative review of the most commonly used hemodynamic monitoring approaches to assessing fluid responsiveness and fluid tolerance. In addition, we describe the benefits and disadvantages of these tools.

Renal Venous Stasis Index Reflects Renal Congestion and Predicts Adverse Outcomes in Patients With Heart Failure

Background

It has been recently reported that the renal venous stasis index (RVSI) assessed by renal Doppler ultrasonography provides information to stratify pulmonary hypertension that can lead to right-sided heart failure (HF). However, the clinical significance of RVSI in HF patients has not been sufficiently examined. We aimed to examine the associations of RVSI with parameters of cardiac function and right heart catheterization (RHC), as well as with prognosis, in patients with HF.

Methods

We performed renal Doppler ultrasonography, echocardiography and RHC in hospitalized patients with HF (n = 388). RVSI was calculated as follows: RVSI = (cardiac cycle time-venous flow time)/cardiac cycle time. The patients were classified to three groups based on RVSI: control group (RVSI = 0, n = 260, 67%), low RVSI group (0 &lt; RVSI ≤ 0.21, n = 63, 16%) and high RVSI group (RVSI &gt; 0.21, n = 65, 17%). We examined associations of RVSI with parameters of cardiac function and RHC, and followed up for cardiac events defined as cardiac death or worsening HF.

Results

There were significant correlations of RVSI with mean right atrial pressure (mRAP; R = 0.253, P &lt; 0.001), right atrial area (R = 0.327, P &lt; 0.001) and inferior vena cava diameter (R = 0.327, P &lt; 0.001), but not with cardiac index (R = −0.019, P = 0.769). During the follow-up period (median 412 days), cardiac events occurred in 60 patients. In the Kaplan–Meier analysis, the cumulative cardiac event rate increased with increasing RVSI (log-rank, P = 0.001). In the multivariate Cox proportional hazard analysis, the cardiac event rate was independently associated with RVSI (high RVSI group vs. control group: hazard ratio, 1.908; 95% confidence interval, 1.046–3.479, P = 0.035).

Conclusion

RVSI assessed by renal Doppler ultrasonography reflects right-sided overload and is associated with adverse prognosis in HF patients.

Comprehensive Assessment of Fluid Status by Point-of-Care Ultrasonography

The management of complex fluid and electrolyte disorders is central to the practice of nephrologists. The sensitivity of physical examination alone to determine fluid status is limited, precluding accurate clinical decision making. Point-of-care ultrasonography (POCUS) is emerging as a valuable, noninvasive, bedside diagnostic tool for objective evaluation of physiologic and hemodynamic parameters related to fluid status, tolerance, and responsiveness. Rapid bedside sonographic evaluation can obtain qualitative data on cardiac function and quantitative data on pulmonary congestion. Advanced POCUS, including goal-directed Doppler echocardiography, provides additional quantitative information, including flow velocities and pressures across the cardiac structures. Recently, abnormal Doppler flow patterns in abdominal organs secondary to increased right atrial pressure have been linked to congestive organ damage, adding another component to the hemodynamic assessment. Integrating POCUS findings with clinical and laboratory data can further elucidate a patient's hemodynamic status. This drives decisions regarding crystalloid administration or, conversely, diuresis or ultrafiltration and allows tailored therapy for individual patients. In this article, we provide an overview of the focused assessment of cardiovascular function and pulmonary and venous congestion using POCUS and review relevant literature.

Comprehensive Assessment of Fluid Status by Point-of-Care Ultrasonography

The management of complex fluid and electrolyte disorders is central to the practice of nephrologists. The sensitivity of physical examination alone to determine fluid status is limited, precluding accurate clinical decision making. Point-of-care ultrasonography (POCUS) is emerging as a valuable, noninvasive, bedside diagnostic tool for objective evaluation of physiologic and hemodynamic parameters related to fluid status, tolerance, and responsiveness. Rapid bedside sonographic evaluation can obtain qualitative data on cardiac function and quantitative data on pulmonary congestion. Advanced POCUS, including goal-directed Doppler echocardiography, provides additional quantitative information, including flow velocities and pressures across the cardiac structures. Recently, abnormal Doppler flow patterns in abdominal organs secondary to increased right atrial pressure have been linked to congestive organ damage, adding another component to the hemodynamic assessment. Integrating POCUS findings with clinical and laboratory data can further elucidate a patient's hemodynamic status. This drives decisions regarding crystalloid administration or, conversely, diuresis or ultrafiltration and allows tailored therapy for individual patients. In this article, we provide an overview of the focused assessment of cardiovascular function and pulmonary and venous congestion using POCUS and review relevant literature.

Cardiorenal Syndrome: Emerging Role of Medical Imaging for Clinical Diagnosis and Management

Cardiorenal syndrome (CRS) concerns the interconnection between heart and kidneys in which the dysfunction of one organ leads to abnormalities of the other. The main clinical challenges associated with cardiorenal syndrome are the lack of tools for early diagnosis, prognosis, and evaluation of therapeutic effects. Ultrasound, computed tomography, nuclear medicine, and magnetic resonance imaging are increasingly used for clinical management of cardiovascular and renal diseases. In the last decade, rapid development of imaging techniques provides a number of promising biomarkers for functional evaluation and tissue characterization. This review summarizes the applicability as well as the future technological potential of each imaging modality in the assessment of CRS. Furthermore, opportunities for a comprehensive imaging approach for the evaluation of CRS are defined.

Clinical applications of the venous excess ultrasound (VExUS) score: conceptual review and case series

The importance of functional right ventricular failure and resultant splanchnic venous congestion has long been under-appreciated and is difficult to assess by traditional physical examination and standard diagnostic imaging. The recent development of the venous excess ultrasound score (VExUS) and growth of point-of-care ultrasound in the last decade has made for a potentially very useful clinical tool. We review the rationale for its use in several pathologies and illustrate with several clinical cases where VExUS was pivotal in clinical management.

VExUS Nexus: Bedside Assessment of Venous Congestion

Organ dysfunction in the setting of heart failure is mainly determined by backward transmission of increased right atrial pressure. Although traditional point-of-care ultrasound applications such as inferior vena cava and lung ultrasound have been increasingly incorporated in the clinical care of congestive heart failure, they do not directly evaluate the hemodynamic consequences of high right atrial pressure on organ blood flow. Congestion induces alterations in the venous flow patterns of abdominal organs that can be readily assessed using Doppler imaging. These alterations have been consistently associated with congestive organ dysfunction and adverse clinical outcomes. In this article, we provide a comprehensive overview of the bedside assessment of venous congestion using Doppler imaging. The review focuses mainly on the normal and abnormal Doppler patterns of the hepatic, portal, and intrarenal veins along with clinical examples of how to incorporate this tool in the management of patients with venous congestion.

Ultrasound imaging of congestion in heart failure: examinations beyond the heart

Congestion, related to pressure and/or fluid overload, plays a central role in the pathophysiology, presentation and prognosis of heart failure and is an important therapeutic target. While symptoms and physical signs of fluid overload are required to make a clinical diagnosis of heart failure, they lack both sensitivity and specificity, which might lead to diagnostic delay and uncertainty. Over the last decades, new ultrasound methods for the detection of elevated intracardiac pressures and/or fluid overload have been developed that are more sensitive and specific, thereby enabling earlier and more accurate diagnosis and facilitating treatment strategies. Accordingly, we considered that a state-of-the-art review of ultrasound methods for the detection and quantification of congestion was timely, including imaging of the heart, lungs (B-lines), kidneys (intrarenal venous flow), and venous system (inferior vena cava and internal jugular vein diameter).

Role of intrarenal resistive index and ElastPQ® renal shear modulus in early diagnosis and follow-up of diabetic nephropathy: A prospective study

Introduction

We aimed to establish baseline normal values of ElastPQ^® (Philips Healthcare, Bothell, Washington, USA) renal shear modulus, evaluate changes in intrarenal resistive index and renal shear modulus in various stages of diabetic nephropathy, their diagnostic potential and role in follow-up.

Methods

Our prospective observational study was performed over two years. In total, 130 adult cases with diabetic nephropathy and 130 normal adult controls were selected. Diabetic nephropathy was confirmed by persistent albuminuria on 24-hour urinary albumin testing at three month intervals and staged by albuminuria quantification. Measurement of intrarenal resistive index and renal shear modulus in all subjects was performed and their variation with stage of nephropathy was statistically analyzed using Pearson's correlation. Receiver operating characteristic curves were plotted and their individual and combined diagnostic potentials were assessed. Statistical significance was tested using t tests and analysis of variance. Interrater agreement was tested using Cohen's kappa coefficient.

Results

Mean intrarenal resistive index was significantly higher for cases (mean 0.72 ± 0.05) than controls (mean 0.62 ± 0.04) and showed significant age variation (p < 0.05). Normal values of ElastPQ^® renal shear modulus ranged from 3.87 to 4.72 kPa and was significantly higher for cases (mean 8.59 ± 1.77 kPa) than controls (mean 4.32 ± 0.45 kPa) and showed significant differences between each stage of nephropathy, being highest in stage 2. Maximum diagnostic accuracy was at 0.65 (sensitivity 90%, specificity 76.2%, area under curve 0.916) for intrarenal resistive index and at 5.31 kPa (sensitivity 90.8%, specificity 84.6%, area under curve 0.923) for renal shear modulus. Combination of the two further improved diagnostic performance (highest accuracy of 89%, sensitivity 81.7%, specificity 96.3%).

Conclusions

Normal range of ElastPQ^® renal shear modulus values could be established. Intrarenal resistive index and renal shear modulus can be used as imaging parameters for early diagnosis and follow-up of diabetic nephropathy.

Right Heart Failure and Cardiorenal Syndrome

Cardiorenal syndrome is a complex interplay of dysregulated heart and kidney interaction that leads to multiorgan system dysfunction, which is not an uncommon occurrence in the setting of right heart failure. The traditional concept of impaired perfusion and forward flow recently has been modified to include the recognition of systemic venous congestion as a contributor, with direct and indirect mechanisms, including elevated renal venous pressure, reduced renal perfusion pressure, increased renal interstitial pressure, tubular dysfunction, splanchnic congestion, and neurohormonal and inflammatory activation. Treatment options beyond diuretics and vasoactive drugs remain limited and lack supportive evidence.

Doppler-Derived Renal Venous Stasis Index in the Prognosis of Right Heart Failure

Background Persistent congestion with deteriorating renal function is an important cause of adverse outcomes in heart failure. We aimed to characterize new approaches to evaluate renal congestion using Doppler ultrasonography. Methods and Results We enrolled 205 patients with suspected or prediagnosed pulmonary hypertension (PH) undergoing right heart catheterization. Patients underwent renal Doppler ultrasonography and assessment of invasive cardiopulmonary hemodynamics, echocardiography, renal function, intra-abdominal pressure, and neurohormones and hydration status. Four spectral Doppler intrarenal venous flow patterns and a novel renal venous stasis index (RVSI) were defined. We evaluated PH-related morbidity using the Cox proportional hazards model for the composite end point of PH progression (hospitalization for worsening PH, lung transplantation, or PH-specific therapy escalation) and all-cause mortality for 1-year after discharge. The prognostic utility of RVSI and intrarenal venous flow patterns was compared using receiver operating characteristic curves. RVSI increased in a graded fashion across increasing severity of intrarenal venous flow patterns (P<0.0001) and was significantly associated with right heart and renal function, intra-abdominal pressure, and neurohormonal and hydration status. During follow-up, the morbidity/mortality end point occurred in 91 patients and was independently predicted by RVSI (RVSI in the third tertile versus referent: hazard ratio: 4.72 [95% CI, 2.10-10.59; P<0.0001]). Receiver operating characteristic curves suggested superiority of RVSI to individual intrarenal venous flow patterns in predicting outcome (areas under the curve: 0.789 and 0.761, respectively; P=0.038). Conclusions We propose RVSI as a conceptually new and integrative Doppler index of renal congestion. RVSI provides additional prognostic information to stratify PH for the propensity to develop right heart failure. Clinical Trial Registration URL: https://www.clinicaltrials.gov/. Unique identifier: NCT03039959.

Renal Venous Pattern: A New Parameter for Predicting Prognosis in Heart Failure Outpatients

Aim of the study: In chronic heart failure (CHF) patients, renal congestion plays a key role in determining the progression of renal dysfunction and a worse prognosis. The aim of this study was to define the role of Doppler venous patterns reflecting renal congestion that predict heart failure progression. Methods: We enrolled outpatients affected by CHF, in stable clinical conditions and in conventional therapy. All patients underwent a clinical evaluation, routine chemistry, an echocardiogram and a renal echo-Doppler. Pulsed Doppler flow recording was performed at the level of interlobular renal right veins in the tele-expiratory phase. The venous flow patterns were divided into five groups according to the fluctuations of the flow. Type A and B were characterized by a continuous flow, whereas type C was characterized by a short interruption or reversal flow during the end-diastolic or protosystolic phase. Type D and E were characterized by a wide interruption and/or reversal flow. The occurrence of death and/or of heart transplantation and/or of hospitalization due to heart failure worsening was considered an event during follow-up. Results: During a median follow-up of 38 months, 126 patients experienced the considered end-point. Venous pattern C (HR 4.04; 95% CI: 2.14–7.65; p < 0.001), pattern D (HR 7.16; 95% CI: 3.69–13.9; p < 0.001) and pattern E (HR 8.94; 95% CI: 4.65–17.2; p < 0.001) were all associated with events using an univariate Cox regression analysis. Moreover, both the presence of pattern C (HR: 1.79; 95% CI: 1.09–2.97; p: 0) and of pattern D or E (HR: 1.90; 95% CI: 1.16–3.12; p: 0.011) remained significantly associated to events using a multivariate Cox regression analysis after correction for a reference model with an improvement of the overall net reclassification index (0.46; 95% CI 0.24–0.68; p < 0.001). Conclusions: Our findings demonstrate the independent and incremental role of Doppler venous patterns reflecting renal congestion in predicting HF progression among CHF patients, thus suggesting its possible utility in daily clinical practice to better characterize patients with cardio-renal syndrome.

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.

Association of Renal Elasticity and Renal Function Progression in Patients with Chronic Kidney Disease Evaluated by Real-Time Ultrasound Elastography

Glomerulosclerosis and tubulointerstitial fibrosis are associated with lower renal parenchymal elasticity. This study was designed to evaluate the predictive ability of renal elasticity in patients with chronic kidney disease (CKD). 148 non-CKD patients and 227 patients with CKD were recruited. 145 (38.7%) were female, 166 (73.1%) had diabetes, the mean estimated glomerular filtration rate (eGFR) was 33.9 ± 15.8 ml/min/1.73 m² and the median urinary protein-to-creatinine ratio (UPCR) 502 (122–1491) mg/g. Patients with later stages of CKD had lower renal elasticity values, indicating stiffer kidneys (p < 0.001), and smaller kidney (p < 0.001). Renal elasticity correlated with log-transformed UPCR (β = −7.544, P < 0.001). Renal length correlated with age (β = −0.231, P < 0.001), sex (β = −3.730, P < 0.001), serum albumin level (β = −3.024, P = 0.001), body mass index (β = 0.390, P = 0.009) and eGFR (β = 0.146, P < 0.001). In fully-adjusted logistic regression model, the odds ratio (OR) per 10 unit change in renal elasticity for rapid renal deterioration was 0.928 (95% CI, 0.864–0.997; P = 0.042). The OR per 1 mm change in renal length for rapid renal deterioration was 1.022 (95% CI, 0.994–1.050; P = 0.125). Renal elasticity is associated with proteinuria and rapid renal deterioration in patients with CKD.

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.

The inability of an early post-transplantation intrarenal resistive index to predict renal allograft function at 12 weeks after engraftment in young adults

Background The intrarenal resistive index (RI) is a promising tool for predicting renal graft outcomes. Due to the complexity of graft function and the presence of diverse contributing factors, however, the available data are inconclusive. Purpose To examine the performance of the RI 1 week after transplant in predicting allograft function at week 12, with an emphasis on the type of intrarenal artery used in the examination. Material and Methods A total of 58 first-time living-donor kidney-allograft-transplantation patients aged less than 50 years underwent Doppler ultrasonography (US) of the intrarenal arteries 1 week after engraftment. The RI was calculated for both the segmental (RI-C) and interlobar-arcuate (RI-P) arteries. Serum creatinine level and the creatinine reduction ratio (CRR) were determined at weeks 1 and 12 post transplantation. Results While the RI did not correlate with serum creatinine level and CRR at week 1, significant correlations were present between the RI and serum creatinine level (r = 0.28, P = 0.03 for both RI-C and RI-P) and CRR (r = -0.25, P = 0.05 for both RI-C and RI-P) at week 12. The sensitivity, specificity, positive predictive value, and negative predictive value of using RI-C in predicting abnormal 12-week serum creatinine level were 51.2%, 52.9%, 72.4%, and 31.3%, respectively; and 53.7%, 47.1%, 70.9%, and 29.6% for RI-P, respectively ( P > 0.99 for all comparisons). Conclusion Early post-transplantation RI correlates significantly with both serum creatinine level and creatinine reduction ratio 12 weeks after engraftment with intermediate predictive accuracy.

Clinical Implications of Intrarenal Hemodynamic Evaluation by Doppler Ultrasonography in Heart Failure

OBJECTIVES

This study clarified the characteristics of intrarenal Doppler ultrasonography (IRD) profiles and their prognostic implications in heart failure (HF).

BACKGROUND

IRD can assess intrarenal hemodynamics.

METHODS

Initially, 224 patients with HF were prospectively enrolled; 151 inpatients were enrolled during hospitalization for HF, and 73 were outpatients in our institution. In IRD profiles of interlobar vessels, the arterial resistance index (RI), venous impedance index (VII), and intrarenal venous flow (IRVF) pattern were assessed. Patients were followed to evaluate the associations with 1-year prognosis. Primary endpoints included death from cardiovascular disease and unplanned hospitalization for HF.

RESULTS

Finally, 217 patients with adequate IRD images were enrolled. IRD profiles were associated with conventional risk factors for HF. In particular, IRVF was associated with mean right atrial pressure (RAP); 3 IRVF patterns were stratified by RAP (in a continuous pattern: 5.4 ± 2.5; in a biphasic pattern: 9.5 ± 3.5; and in a monophasic pattern: 14.9 ± 4.3 mm Hg; p < 0.001). In addition, the monophasic IRVF pattern had a poorer prognosis than the other patterns (log rank p < 0.001), and prognosis was poorer for the biphasic pattern than for the continuous flow pattern (log rank p = 0.01). Multivariate Cox proportional hazard model analysis revealed that IRVF patterns were associated with the endpoints, independent of other HF risk factors.

CONCLUSIONS

IRVF patterns, rather than RI, depended on RAP, suggesting a correlation with renal congestion. In addition, IRVF patterns strongly correlated with clinical outcomes independent of RAP and other risk factors and might provide additional information to stratify vulnerable HF patients.