Renal vein Doppler sonography of obstructive uropathy

Assessment of renal congestion in a rat model with congestive heart failure using superb microvascular imaging

PURPOSE

Renal congestion is a therapeutic target in congestive heart failure. However, its detailed evaluation in a clinical setting is challenging. This study sought to assess renal congestion impairment using superb microvascular imaging (SMI), a simple and accessible method.

METHODS

Dahl salt-sensitive rats, used as a model for congestive heart failure, underwent central venous pressure (CVP) measurements. Renal congestion was evaluated through measurements of renal medullary pressure (RMP) and assessment of renal perfusion using contrast-enhanced ultrasonography at both the early (control group) and heart failure phases (HF group). All rats were assessed with SMI. The region of interest (ROI) was set in interlobular vessels, interlobar vessels, and a combination of these areas. The area ratio was calculated from the color pixel count in the ROI divided by the total pixel count in the ROI. Intrarenal perfusion index (IRPI) was defined as (maximum area ratio-minimum area ratio) / maximum area ratio.

RESULTS

There were no significant differences in renal function and left ventricular ejection fraction between the two groups. CVP, time-to-peak (TTP) in the medulla, and RMP were higher in the HF group than in the control group. In the HF group, IRPI, evaluated in the interlobular vessels, was significantly higher than in the control group. IRPI was positively correlated with TTP in the medulla (p = 0.028, R = 0.60) and RMP (p < 0.001, R = 0.84), indicating that IRPI reflected renal congestion.

CONCLUSIONS

IRPI is a useful tool for assessing renal congestion in rats with congestive heart failure.

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.

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.

Kidney function changes in acute heart failure: a practical approach to interpretation and management

Worsening kidney function (WKF) is common in patients with acute heart failure (AHF) syndromes. Although WKF has traditionally been associated with worse outcomes on a population level, serum creatinine concentrations vary greatly during episodes of worsening heart failure, with substantial individual heterogeneity in terms of their clinical meaning. Consequently, interpreting such changes within the appropriate clinical context is essential to unravel the pathophysiology of kidney function changes and appropriately interpret their clinical meaning. This article aims to provide a critical overview of WKF in AHF, aiming to provide physicians with some tips and tricks to appropriately interpret kidney function changes in the context of AHF.

Association between intrarenal venous flow from Doppler ultrasonography and acute kidney injury in patients with sepsis in critical care: a prospective, exploratory observational study

BACKGROUND

Intrarenal venous flow (IRVF) patterns assessed using Doppler renal ultrasonography are real-time bedside visualizations of renal vein hemodynamics. Although this technique has the potential to detect renal congestion during sepsis resuscitation, there have been few studies on this method. We aimed to examine the relationship between IRVF patterns, clinical parameters, and outcomes in critically ill adult patients with sepsis. We hypothesized that discontinuous IRVF was associated with elevated central venous pressure (CVP) and subsequent acute kidney injury (AKI) or death.

METHODS

We conducted a prospective observational study in two tertiary-care hospitals, enrolling adult patients with sepsis who stayed in the intensive care unit for at least 24 h, had central venous catheters placed, and received invasive mechanical ventilation. Renal ultrasonography was performed at a single time point at the bedside after sepsis resuscitation, and IRVF patterns (discontinuous vs. continuous) were confirmed by a blinded assessor. The primary outcome was CVP obtained at the time of renal ultrasonography. We also repeatedly assessed a composite of Kidney Disease Improving Global Outcomes of Stage 3 AKI or death over the course of a week as a secondary outcome. The association of IRVF patterns with CVP was examined using Student's t-test (primary analysis) and that with composite outcomes was assessed using a generalized estimating equation analysis, to account for intra-individual correlations. A sample size of 32 was set in order to detect a 5-mmHg difference in CVP between IRVF patterns.

RESULTS

Of the 38 patients who met the eligibility criteria, 22 (57.9%) showed discontinuous IRVF patterns that suggested blunted renal venous flow. IRVF patterns were not associated with CVP (discontinuous flow group: mean 9.24 cm H2O [standard deviation: 3.19], continuous flow group: 10.65 cm H2O [standard deviation: 2.53], p = 0.154). By contrast, the composite outcome incidence was significantly higher in the discontinuous IRVF pattern group (odds ratio: 9.67; 95% confidence interval: 2.13-44.03, p = 0.003).

CONCLUSIONS

IRVF patterns were not associated with CVP but were associated with subsequent AKI in critically ill adult patients with sepsis. IRVF may be useful for capturing renal congestion at the bedside that is related to clinical patient outcomes.

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.

Early-onset preeclampsia is characterised by an increased vascular tone in internal jugular veins

Purpose

This study aimed to investigate Doppler characteristics of maternal internal jugular veins in uncomplicated pregnancies vs. those affected by hypertensive disorders.

Materials and methods

Venous pulse transit time and venous impedance index were measured at three different locations (right proximal, right distal, left proximal) of internal jugular veins according to a standardised combined Doppler-Electrocardiogram protocol in five different groups of pregnant women: uncomplicated pregnancy, early-onset preeclampsia, late-onset preeclampsia, gestational hypertension, and normotensive pregnancies with a small for gestational age foetus. Values of both parameters of the latter four groups were plotted against the reference range of uncomplicated pregnancies at corresponding gestation. Linear mixed models with random intercept were used to investigate gestational changes in venous pulse transit time and venous impedance index at the three internal jugular vein locations within and between the different groups.

Results

A total of 127 women were included: 41 had uncomplicated pregnancies, 13 had early-onset preeclampsia, 25 had late-onset preeclampsia, 22 had gestational hypertension, and 26 had normotensive pregnancies with a small for gestational age foetus. Venous pulse transit time values were lower than uncomplicated pregnancy (p ≤ 0.001) at all three locations in the third trimester of early-onset preeclampsia.

Conclusion

Contrary to late-onset preeclampsia and gestational hypertension, early-onset preeclampsia is characterised by a lower venous pulse transit time at internal jugular veins compared to uncomplicated pregnancy, suggesting increased venous vascular tone.

Characteristics of the Maternal Jugular Venous Pulse Waveform by Combined Doppler-Electrocardiogram Assessment

Standardized combined Doppler-electrocardiogram assessment was performed longitudinally at three different locations of internal jugular veins between 12 wk of gestation and 6 wk postnatally in 24 uncomplicated pregnancies. All images were classified as typical or non-typical based on the presence of the physiologic deflections A, X, H and C. Linear mixed models with random intercepts of typical images were used to investigate gestational changes in venous pulse transit time and venous impedance index. Unequivocal identification of venous pulse transit time and venous impedance index was possible in 2617 of 3798 (69%) and 2234 of 3798 (59%) images, respectively. The best identification rate (80%, 1018/1266) was at the right distal internal jugular vein. Venous pulse transit time increased with gestational age at all locations; venous impedance index decreased at the right sided internal jugular vein. Maternal jugular venous pulse waveform by combined Doppler-electrocardiogram allows unequivocal identification of A-deflection and calculation of venous pulse transit time and venous impedance index in around two-thirds of assessments, with the highest success rate at the right distal internal jugular vein. Gestational evolutions of venous pulse transit time and venous impedance index are similar to those reported at the level of renal interlobar and hepatic veins.

Non-Invasive Assessment of Congestion by Cardiovascular and Pulmonary Ultrasound and Biomarkers in Heart Failure

Worsening chronic heart failure (HF) is responsible for recurrent hospitalization and increased mortality risk after discharge, irrespective to the ejection fraction. Symptoms and signs of pulmonary and systemic congestion are the most common cause for hospitalization of acute decompensated HF, as a consequence of increased cardiac filling pressures. The elevated cardiac filling pressures, also called hemodynamic congestion, may precede the occurrence of clinical congestion by days or weeks. Since HF patients often have comorbidities, dyspnoea, the main symptom of HF, may be also caused by respiratory or other illnesses. Recent studies underline the importance of the diagnosis and treatment of hemodynamic congestion before HF symptoms worsen, reducing hospitalization and improving prognosis. In this paper we review the role of integrated evaluation of biomarkers and imaging technics, i.e., echocardiography and pulmonary ultrasound, for the diagnosis, prognosis and treatment of congestion in HF patients.

Usefulness of Serial Multiorgan Point-of-Care Ultrasound in Acute Heart Failure: Results from a Prospective Observational Cohort

Background and Objectives: Acute heart failure (AHF) is a common disease and a cause of high morbidity and mortality, constituting a major health problem. The main purpose of this study was to determine the impact of multiorgan ultrasound in identifying pulmonary hypertension (PH), a major prognostic factor in patients admitted due to AHF, and assess whether there are significant changes in the venous excess ultrasonography (VE × US) score or femoral vein Doppler at discharge. Materials and Methods: Patients were evaluated with a standard protocol of lung ultrasound, echocardiography, inferior vena cava (IVC) and hepatic, portal, intra-renal and femoral vein Doppler flow patterns at admission and on the day of discharge. Results: Thirty patients were enrolled during November 2021. The mean age was seventy-nine years (Standard Deviation-SD 13.4). Seven patients (23.3%) had a worsening renal function during hospitalization. Regarding ultrasound findings, VE × US score was calculated at admission and at discharge, unexpectedly remaining unchanged or even worsened (21 patients, 70.0%). The area under the curve for the lung score was 83.9% (p = 0.008), obtaining a cutoff value of 10 that showed a sensitivity of 82.6% and a specificity of 71.4% in the identification of intermediate and high PH. It was possible to monitor significant changes between both exams on the lung score (16.5 vs. 9.3; p < 0.001), improvement in the hepatic vein Doppler pattern (2.4 vs. 2.1; p = 0.002), improvement in portal vein Doppler pattern (1.7 vs. 1.4; p = 0.023), without significant changes in the intra-renal vein Doppler pattern (1.70 vs. 1.57; p = 0.293), VE × US score (1.3 vs. 1.1; p = 0.501), femoral vein Doppler pattern (2.4 vs. 2.1; p = 0.161) and IVC collapsibility (2.0 vs. 2.1; p = 0.420). Conclusions: Our study results suggest that performing serial multiorgan Point-of-Care ultrasound can help us to better identify high and intermediate probability of PH patients with AHF. Currently proposed multi-organ, venous Doppler scanning protocols, such as the VE × US score, should be further studied before expanding its use in AHF patients.

Intrarenal Doppler Ultrasound Renal Venous Stasis Index Correlates With Acute Cardiorenal Syndrome in Patients With Acute Decompensated Heart Failure

Background

Acute cardiorenal syndrome (ACRS) is associated with adverse outcomes in patients with acute decompensated heart failure (ADHF). Intrarenal venous blood flow can be assessed using Doppler ultrasound and has prognostic significance in ADHF. Although intrarenal Doppler (IRD) may be sensitive to renal congestion, an association between IRD parameters and ACRS has not been demonstrated in an ADHF population.

Methods

Hospitalized patients with ADHF (n = 21) or acute coronary syndrome (ACS; n = 21) were prospectively enrolled. Patients underwent echocardiography, including IRD, using a standard cardiac ultrasound transducer. Intrarenal venous flow was quantified with the renal venous stasis index (RVSI), defined as the duration of absent venous flow time divided by cardiac cycle duration. The primary outcome was acute kidney injury (AKI) as assessed using the Kidney Disease: Improving Global Outcomes (KDIGO) criteria.

Results

ADHF patients had a similar cardiac index (2.0 ± 0.6 vs 2.1 ± 0.4 L/min per m², P = 0.91) but higher estimated central venous pressure (13.0 ± 3.2 vs 4.6 ± 2.4 mm Hg, P < 0.001) measured using echocardiography, compared with ACS patients. IRD was abnormal in all ADHF patients and normal in all ACS patients (RVSI 0.62 ± 0.20 vs 0.0 ± 0, P < 0.001). AKI stage II/III occurred in 10 of 21 ADHF patients (48%) vs 0 of 21 ACS patients (P < 0.001), with a mean rise in serum creatinine of 97.7 ± 79.3 vs 16.8 ± 10.9 μmol/L (P < 0.001), respectively. RVSI was correlated with AKI severity in ADHF patients (r = 0.57; P = 0.004).

Conclusions

RVSI is associated with AKI among ADHF patients and may be a useful diagnostic biomarker for ACRS in this setting. Further studies are needed to validate this finding and evaluate the potential efficacy of IRD-guided decongestive therapy in this setting.

Point of care venous Doppler ultrasound: Exploring the missing piece of bedside hemodynamic assessment

Accurate assessment of the hemodynamic status is vital for appropriate management of patients with critical illness. As such, there has been a constant quest for reliable and non-invasive bedside tools to assess and monitor circulatory status in order to ensure end-organ perfusion. In the recent past, point of care ultrasonography (POCUS) has emerged as a valuable adjunct to physical examination in various specialties, which basically is a clinician-performed bedside ultrasound to answer focused questions. POCUS allows visualization of the internal anatomy and flow dynamics in real time, guiding apt interventions. While both arterial (forward flow) and venous (organ outflow or afterload) limbs of hemodynamic circuit are important for tissue perfusion, the venous side remains relatively under-explored. With recent data underscoring the deleterious consequences of iatrogenic volume overload, objective evaluation of venous congestion is gaining attention. Bedside Doppler ultrasound serves this purpose and aids in diagnosing and monitoring the congestion/venous blood flow pattern. In this article, we summarize the rationale for integrating this technology into routine care of patients with volume-related disorders, discuss the normal and abnormal waveforms, limitations, and future directions.

Diagnostic value of doppler ultrasound indices of maternal renal interlobar vasculature in the prediction of preeclampsia

We aimed to determine the diagnostic accuracy of maternal renal vasculature Doppler ultrasound indices in the prediction of preeclampsia. A total of 40 pregnant women with a gestational age of more than 20 weeks were included and followed. The pregnant women underwent a Doppler ultrasound examination to measure the resistance index (RI) of the interlobar arteries of right and left kidneys and the renal interlobar vein impedance index (RIVI). Of the included women, 15 patients developed preeclampsia based on clinical and laboratory criteria. The renal vascular Doppler ultrasound indices were compared between the two groups. Then, using the Receiver Operating Characteristic (ROC) analysis, the diagnostic accuracy of interlobar artery RI and RIVI were investigated in the prediction of preeclampsia occurrence. RIVI values of right and left kidneys were significantly higher in the preeclampsia group compared to the normal pregnancy group. The left kidney interlobar artery RI at a cut-point of 0.59 had a sensitivity of 100% and a specificity of 40% (area under curve=0.7, P-0.03) in the prediction of preeclampsia. The RIVI of the left kidney (adjusted odds ratio=17.14, 95% CI = 3.46 to 47.28) was statistically significant in predicting preeclampsia (P-0.006). We found that, besides other routine methods, using Doppler ultrasound and measuring RIVI can be reliable in the prediction of preeclampsia.

Maternal microvascular dysfunction during preeclamptic pregnancy

Preeclampsia is a hypertensive disorder of pregnancy effecting ∼5-8% of pregnancies in the United States, and ∼8 million pregnancies worldwide. Preeclampsia is clinically diagnosed after the 20th week of gestation and is characterized by new onset hypertension accompanied by proteinuria and/or thrombocytopenia, renal insufficiency, impaired liver function, pulmonary edema, or cerebral or visual symptoms. This broad definition emphasizes the heterogeneity of the clinical presentation of preeclampsia, but also underscores the role of the microvascular beds, specifically the renal, cerebral, and hepatic circulations, in the pathophysiology of the disease. While the diagnostic criteria for preeclampsia relies on the development of de novo hypertension and accompanying clinical symptoms after 20-week gestation, it is likely that subclinical dysfunction of the maternal microvascular beds occurs in parallel and may even precede the development of overt cardiovascular symptoms in these women. However, little is known about the physiology of the non-reproductive maternal microvascular beds during preeclampsia, and the mechanism(s) mediating microvascular dysfunction during preeclamptic pregnancy are largely unexplored in humans despite their integral role in the pathophysiology of the disease. Therefore, the purpose of this review is to provide a summary of the existing literature on maternal microvascular dysfunction during preeclamptic pregnancy by reviewing the functional evidence in humans, highlighting potential mechanisms, and providing recommendations for future work in this area.

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.

Congestive nephropathy: a neglected entity? Proposal for diagnostic criteria and future perspectives

Venous congestion has emerged as an important cause of renal dysfunction in patients with cardiorenal syndrome. However, only limited progress has been made in differentiating this haemodynamic phenotype of renal dysfunction, because of a significant overlap with pre-existing renal impairment due to long-term hypertension, diabetes, and renovascular disease. We propose congestive nephropathy (CN) as this neglected clinical entity. CN is a potentially reversible subtype of renal dysfunction associated with declining renal venous outflow and progressively increasing renal interstitial pressure. Venous congestion may lead to a vicious cycle of hormonal activation, increased intra-abdominal pressure, excessive renal tubular sodium reabsorption, and volume overload, leading to further right ventricular (RV) stress. Ultimately, renal replacement therapy may be required to relieve diuretic-resistant congestion. Effective decongestion could preserve or improve renal function. Congestive acute kidney injury may not be associated with cellular damage, and complete renal function restoration may be a confirmatory diagnostic criterion. In contrast, a persistently low renal perfusion pressure might induce renal dysfunction and histopathological lesions with time. Thus, urinary markers may differ. CN is mostly seen in biventricular heart failure but may also occur secondary to pulmonary arterial hypertension and elevated intra-abdominal pressure. An increase in central venous pressure to >6 mmHg is associated with a steep decrease in glomerular filtration rate. However, the central venous pressure range that can provide an optimal balance of RV and renal function remains to be determined. We propose criteria to identify cardiorenal syndrome subgroups likely to benefit from decongestive or pulmonary hypertension-specific therapies and suggest areas for future research.

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).

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 intraparenchymal resistive index: the ultrasonographic answer to many clinical questions

The use of renal resistive indices (RRIs) for the study of renal microcirculation has in the past been proposed for the identification of renal organ damage or even to specifically identify injury to some areas of the renal parenchyma. Nevertheless, according to the most recent evidences from literature this organ-based conception of RRIs has been proven to be partial and unable to explain the RRIs variations in clinical settings of sepsis or combined organ failure of primitively extrarenal origin or, more generally, the deep connection between RRIs and hemodynamic factors such as compliance and pulsatility of the large vessels. The aim of this review is to explain the physiopathological basis of RRIs determination and the most common interpretative errors in their analysis. Moreover, through a comprehensive vision of these Doppler indices, the traditional and emerging clinical application fields for RRIs are discussed.

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.

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.

Renal Venous Doppler Study in Obstructive Uropathy

INTRODUCTION

Obstructive uropathy is very common cause of pain abdomen. Recognition of the cause of the pain and level of obstruction is the goal. Ultrasound is the primary modality used for detection and characterization of obstructive uropathy along with conventional radiographs. Obstructive uropathy in early stages can be difficult to diagnose using standard B-mode USG or arterial sensitive index.

AIM

The purpose of this study is to evaluate the diagnostic accuracy of renal venous doppler ultrasound in diagnosing acute obstructive uropathy either alone or in addition to arterial doppler study of inter lobar arteries. As there is limited literature available till date on Indian population regarding renal venous doppler in obstructive uropathy, this study can be useful.

MATERIALS AND METHODS

Fifty patients presenting with features suggestive of obstructive uropathy were studied and compared with non-obstructed kidney of the same patient. Fifty normal individuals were studied and taken as controls.

RESULTS

The mean venous impedance index on the obstructed side (0.26 ± 0.07) was less than the mean venous impedance index on the unobstructed side (0.41 ± 0.08) and was statistically highly significant. There was no statistically significant difference in mean arterial Resistivity Index (RI).

CONCLUSION

Thus renal venous doppler study is a reliable tool in diagnosing cases of acute obstructive uropathy. Though its use as single parameter to identify obstruction still needs further studies, it can be used in conjugation with b mode ultrasound and arterial Doppler to identify obstruction.

Functional evaluation of the urinary tract by duplex Doppler ultrasonography in patients with acute renal colic

Purpose

To determine the role of duplex Doppler ultrasonography (DDU) in patients with acute unilateral renal obstruction.

Subjects and methods

A total of 161 patients with suspected renal colic due to urolithiasis were evaluated by DDU followed by intravenous urography (IVU). The mean intra-arterial resistive index (RI) and the difference of mean resistive index between both kidneys (delta RI) were determined for each person. An RI value of ≥0.70 and a delta RI value of ≥0.06 were taken as the discriminatory threshold for obstruction. IVU results were considered the “ reference standard” against which renal DDU findings were compared.

Results

IVU showed both kidneys to be normal in 51 patients and with unilateral ureteric obstruction in 110 patients. The mean RI for obstructed kidneys was 0.67 (0.048), which was significantly higher (P-value <0.05) than a mean RI of contralateral normal kidneys 0.59 (0.04). The mean delta RI in patients with unilateral ureteric obstruction was significantly higher than that in patients with normal kidneys, at 0.076 (0.03) and 0.03 (0.05), respectively. In patients with complete obstruction, sensitivity of RI and delta RI were 77.5% and 92.5% with a specificity of 84.3% and 90.1%, respectively. In patients with partial obstruction, the sensitivity of these values was 22.8% and 62.8% with a specificity of 84.3% and 90.1%.

Conclusion

Delta RI is more sensitive and specific than RI in acute renal obstruction. However, due to relatively low sensitivity for detection of partial obstruction, DDU cannot replace IVU as the standard imaging technique.

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

OBJECTIVES

To provide reference values of intrarenal venous impedance index (VII) measured with duplex Doppler ultrasonography in a healthy adult population and to assess the usefulness this index for evaluating the functional status of kidney in patients with diabetic nephropathy (DN).

METHODS

Between May 2005 and December 2009, Doppler ultrasonography of both kidneys was performed in 164 healthy volunteers (controls) and 58 patients with DN. Renal interlobar and segmental vein Doppler waveforms and VII were obtained and compared between groups using the Student's t test. Correlation between VII and serum creatinine concentration (SCC) was calculated.

RESULTS

In controls, the mean VII was lower in interlobar than in segmental renal veins (p < 0.01), without difference between the right and left kidneys. Waveform modulation was dampened in DN patients whose mean VII (0.32 ± 0.18) was lower than in controls (0.38 ± 0.18) (p < 0.01). SCC showed moderate correlations (r = 0.65) with intrarenal VII in the patient group.

CONCLUSIONS

Renal VII is typically lower in DN than in controls and moderately correlated with SCC, which reflects renal function in DN, but does not offer a significant advantage over arterial resistance index.

A new radiological approach to cyclic mastalgia: venous doppler ultrasound

OBJECTIVE

To evaluate the role of the venous system in cyclical mastalgia.

MATERIALS AND METHODS

25 healthy women and 39 women with cyclic mastalgia underwent venous Doppler examination in both pre- and postmenstrual period. Upper-outer quadrant veins of breast were evaluated. The impedance indices of both groups were compared in both the premenstrual and postmenstrual period.

RESULTS

During the premenstrual period, venous impedance indices were significantly higher in the patients with cyclic mastalgia (p=0.004) than in the control group. After the menstrual period, there was no difference in venous impedance indices between the groups.

CONCLUSION

Excessive tissue oedema might be responsible for both a tension-mediated pain and a compression of the venous system thereby showing higher impedance than that in control group.

Voie excrétrice supérieure : physiologie, physiopathologie des obstructions et explorations fonctionnelles

The urine is transported from the renal papilla to the bladder through the upper urinary tract which allows this transport to be safe and comfortable, i.e., without any risk or pain for the kidney. This active transport depends on the smooth muscle contractile properties. The upper urinary tract is totally autonomous; this feature allows the preservation of its function after renal transplantation. However, despite its accessory role, the autonomous nervous system can modulate its activity. Upper urinary tract obstruction involves adaptative mechanisms which are different depending on the type (acute, chronic, acquired or congenital) of obstruction. Functional evaluations of the upper urinary tract are aimed at identify the urine transport conditions and the relationship between obstruction and clinical conditions such as hydronephrosis, pain or impaired renal function.

Renal venous Doppler sonography in preeclampsia

OBJECTIVE

The elevation in blood pressure associated with preeclampsia appears to be associated with a shift in the renal pressure natriuresis curve. Pressure natriuresis is modulated by renal medullary pressure. In obstructive uropathy, Doppler sonography has been used to indicate changes in renal venous impedance, possibly measuring alterations in medullary pressure and compliance in this condition. The hypothesis tested in this study was that an elevation in renal venous pulsation may occur in preeclampsia compared with normal pregnancy.

METHODS

Seven patients with clinical evidence of preeclampsia were referred for fetal well-being confirmation by sonography in the third trimester. Seven pregnant patients without renal disease or hypertension reviewed in the third trimester served as a control group. Doppler studies of the interlobar arteries and veins of both kidneys were performed, with a total of 14 kidneys imaged per group. Arterial and venous impedance indices were obtained. The impedance indices for the patients were compared by the Student t test.

RESULTS

No significant difference was noted between the arterial resistive indices. The mean venous impedance index for the hypertensive patients was 0.50 +/- 0.12, and that for the control patients was 0.37 +/- 0.06 (P = .003).

CONCLUSIONS

Preeclampsia in the third trimester appears to be associated with altered medullary venous pulsation, possibly indicating reduced medullary pressure.

Pediatric applications of abdominal vascular Doppler: Part II

Ultrasound is a remarkably powerful and versatile modality for pediatric imaging, without requiring exposure to radiation or sedatives. By providing information on blood flow, Doppler sonography can reveal details about normal physiology and disease processes not discernable from gray-scale anatomic images alone. In part I, the basics of hemodynamics and effects on the Doppler waveform were discussed, along with clinical applications in hepatic disease. In part II, the application of Doppler in renal disease and in conditions affecting the deep abdominal vessels are discussed. The role of ultrasound contrast agents in pediatric Doppler imaging is briefly reviewed.

Doppler sonography of renal obstruction: value of venous impedance index measurements

OBJECTIVE

Arterial resistive index values have poor sensitivity and specificity for alterations in renal perfusion induced by collecting system obstruction. We aimed to determine whether the intrarenal venous impedance index values could be useful in evaluating renal parenchymal compliance in cases of obstruction and in differentiating acute obstruction from chronic cases.

METHODS

Fifteen patients with acute renal colic having unilateral stone disease and another 15 patients having unilateral chronic obstruction due to various causes were evaluated sonographically. The diagnosis was confirmed either by computed tomography or intravenous urography in all cases. Fifteen subjects with normal kidneys were investigated as a control group. All patients were examined prospectively by conventional and Doppler sonography. The impedance indices and peak flow signals of the interlobar arteries and veins of both kidneys were calculated from spectral Doppler waveforms in all 3 groups.

RESULTS

The mean venous impedance index on the acutely obstructed side was lower than the index on the unobstructed side: 0.25 +/- 0.07 and 0.53 +/- 0.3 (mean +/- SD), respectively (P = .005). The mean venous impedance index on the acutely obstructed side was less than the indices both on the chronically obstructed side and in the control subjects (P > .0001). In acute cases, the mean arterial resistive index on the obstructed side was higher than the index on the unobstructed side: 0.62 +/- 0.06 and 0.57 +/- 0.06, respectively (P = .001). No statistically significant difference was detected between other parameters evaluated for the test and control groups.

CONCLUSIONS

Renal venous impedance index values may be helpful in evaluating renal hemodynamics in obstruction and in differentiating acute obstruction from chronic cases when used in conjunction with the arterial resistive index.

Renal vein Doppler ultrasound of maternal kidneys in normal second and third trimester pregnancy

The flow pattern in intrarenal veins depends on renal parenchymal histology and cardiac physiology. The intrarenal venous impedance index obtained by Doppler ultrasound is related to compliance in vein, and can be helpful in the assessment of renal parenchymal compliance. The purpose of this study was to determine whether normal pregnancy has a significant effect on intrarenal venous blood flow, and assess if the physiological pyelocaliectasis causes a measurable reduction in venous impedance indexes in pregnant women. Doppler ultrasound of intrarenal veins was performed in 35 asymptomatic pregnant women in the second and third trimester of gestation, and in 24 non-pregnant healthy women. After grading the degree of hydronephrosis, venous impedance index was obtained from the interlobar veins. The venous waveforms in pregnant women showed diminished phasic oscillations owing to elevated pre-systolic flow. The mean venous impedance indexes in pregnant women were significantly lower than the values in non-pregnant subjects, 0.30+/-0.10 versus 0.44+/-0.06 in the right (p<0.001), and 0.36+/-0.11 versus 0.41+/-0.07 in the left kidney (p=0.03). There was an inverse correlation between the grade of pelvicalyceal dilatation and the venous impedance indexes in both kidneys in pregnant women (r=-0.62, p<0.001 for the right kidney, and r=-0.38, p=0.05 for the left kidney). An abnormally reduced venous impedance index in pregnant women can at least in part be explained by reduced vascular compliance from increased interstitial pressure subsequent to partial obstruction of ureters by the gravid uterus, and caution should be exercised in interpreting it as a sign of pathological ureteral obstruction.

The reversibility of reduced cortical vein compliance in normal-pressure hydrocephalus following shunt insertion

Superficial cortical venous compression secondary to alterations in craniospinal compliance is implicated in the pathogenesis of normal pressure hydrocephalus (NPH). A reduction in the pulsation in the outflow of the cortical veins would be expected to occur following compression of these veins and this has been shown in NPH. If cortical vein compression is a causative factor in NPH, it would be expected that cortical vein compliance as measured by pulsatility would be significantly altered by a curative procedure i.e. shunt tube insertion. My purpose is to compare the blood flow pulsatility characteristics in a group of patients with NPH before and after shunt tube insertion. I initially studied 18 subjects without pathology with MRI flow quantification studies of the cerebral arteries and veins to define the range of normality. The main study involved 18 patients with idiopathic dementia and mild leukoaraiosis who served as controls and seven patients with NPH studied before and after shunt insertion. Arterial, superior sagittal and straight sinus pulsatility was not significantly different between the patients with idiopathic dementia and those NPH patients before or after shunting. Cortical vein pulsatility before shunting in the patients with NPH was 43% lower than in those with idiopathic dementia ( P=0.006). Following shunting, cortical vein pulsatility increased by 186% ( P=0.007). There is thus reduced compliance in cortical veins in NPH which is significantly increased in patients who respond to insertion of a shunt tube. These findings suggest that reversible elevation in cortical vein pressure and reversal of the normal absorption pathway for cerebrospinal fluid may be behind the pathophysiology of NPH.