1
Introduction
Point of Care Ultrasound (POCUS) is emerging and being established as a core clinical bedside skill across all medical specialties and subspecialties worldwide. It helps clinicians to evaluate the anatomy including the vasculature and measure the blood velocity using doppler imaging. Venous Excess Ultrasound Score (VExUS) is an advancement and integrated development of POCUS to assess volume status or venous congestion. In 2020, Beaubien-Soligny and colleagues introduced this novel approach that used ultrasound to assess congestion patterns in the inferior vena cava, hepatic, portal and renal veins. Their work showed that specific venous doppler changes, when systematically evaluated, correlated strongly with the risk of Acute Kidney Injury (AKI) in post Coronary Artery Bypass Graft (CABG) patients . This tool, initially intended for postoperative cardiac patients, rapidly gained wider relevance in intensive care settings to visualize and quantify systemic venous congestion.
Venous excess or venous congestion is a consequence and a measure of fluid overload. Fluid overload is a marker of mortality and is being increasingly used as a surrogate marker for morbidity and mortality, especially in critically ill patients ,. Minor levels of venous congestion can also be associated with organ dysfunction, especially in patients with liver failure . We have less tools to accurately assess the volume status despite our understanding of the high impact. Physical exam and current other basic bedside tools do not offer adequate reliability and accuracy. The gold standard is right heart catheterization, but it is invasive and cannot be used as a follow up tool considering critically ill patients and risk of right heart catheterization (RHC). VExUS scoring can be graded and can be used as a tool to assess as a surrogate marker for venous excess instead of invasive measurements like RHC.
VExUS scoring can be graded and can be used as a tool to assess positive fluid balance and fluid overload. Beaubien-Soligny et al. with a multidisciplinary team approach composed of intensivists, anesthesiologists, emergency physicians and nephrologists established a VExUS grading system prototypes based on the severity of venous ultrasonographic markers. It is scored and graded by evaluation of Inferior vena cava (IVC) diameter, doppler wave forms of hepatic vein (HV), portal vein (PV) and intrarenal veins (IRV). They investigated the performance of different venous congestion grading systems based on ultrasound markers to predict AKI after cardiac surgery. They found that severe congestion, defined as the presence of severe flow abnormalities in multiple doppler patterns with a dilated IVC offered the strongest association with the development of AKI compared with other combinations of ultrasonographic features. They recommended further studies to validate this grading system in different clinical settings, confirm the optimal criteria for diagnostic performance and determine whether it could be used to personalize interventions to improve organ perfusion. The aim of this article is to provide a comprehensive review of VExUS and its overview of validation, diagnostic implementation and results of interventions in different clinical settings.
2
Technique and grading of VExUS
VExUS examination relies heavily on Doppler examination. Unlike B-mode examination, doppler examination is technically challenging for the novice. The VExUS exam should ideally be concluded in four to 5 min and is frequently repeated as clinically necessary. Therefore, a degree of practice and familiarity with the ultrasound machine’s controls is essential. VExUS can be performed with a curvilinear probe, which is an ideal choice, but it can be equally well performed with a phased array probe.
Aspiring for the best picture will take time for the novice, but it is well spent in the process of achieving mastery. Understanding the physics of doppler phenomena will be useful in optimizing the doppler signal. The first and foremost concept is the doppler angle. The doppler shift depends on the cosine of the angle between the ultrasound beam and the direction of the blood flow. For best results, it has to be targeted below 60°, and to make it possible, we have to insonate the vessel at an angle . The sample volume box should be placed in the region of interest, and the size should be adjusted so that the flow signal from the center of the vessel lumen will be obtained, but not the extraneous or extravascular signal. Similarly, the color box size needs to be adjusted. Fine-tuning of the wall filter will also help us in obtaining a good signal.
Another important control to be adjusted is the pulse repetition frequency (PRF), which is also called as scale. To pick up low flow, a low PRF or higher scale setting will be useful. Real-time B-mode, color doppler, and spectral doppler will reduce the frame rate and also reduce the quality of the image and should be avoided. Adjustment of the gain settings is easy, as increased gain will bleed the signal beyond the vessel wall, and the operator will be forced to adjust to limit the color signal within the wall .
Knowledge about these settings will be useful, but should not deter the operator in attempting the examination even before mastering. Most of the machines will be equipped with a control which will optimizes all the factors in a single go without one excessive tweaking. This auto-optimized knob is a boon which, in the near future, will be more robust and AI-enabled, and hence, with little practice, anyone can perform a good doppler examination. While selecting the equipment, it shall be prudent to use as high-end machine as possible and also one with simultaneous recording of ECG. This ECG recording option will be necessary for the examination of hepatic veins . But, if necessary, in emergency situations any machine can be readily used to assess venous congestion, even in the ambulance.
The VExUS examination starts with the foremost important vessel, the inferior vena cava (IVC). The IVC can be evaluated by subxiphoid or from the mid-axillary line, but the subxiphoid window is advisable. Always start by insonating the IVC in the short axis and then rotating to long axis . This habit has the advantages as one intuitively uses the liver as a window and also shall not mistake turgid, pulsatile IVC for aorta.
IVC measurement is performed in the long axis, 2 cm below the right atrium–IVC junction. M-mode ( Fig. 1 ) or B-mode ( Fig. 2 ) measurements are equally good, and cross-checking with the short axis will not take much time. The IVC might be surprisingly dilated in thin habitus and in athletic individuals. IVC dimension is less than or equal to 2 cm corresponds to VExUS grade 0, and hence culminating the examination without further interrogation.
M-mode measurement of IVC.
B-Mode measurement of IVC.
Standard VExUS protocol assigns a Grade 0 score based solely on an Inferior Vena Cava (IVC) diameter less than or equal to 2 cm. It is the opinion of the author that proceeding to full VExUS if the IVC is less than 2 cm as it can point out organ level congestion.
IVC examination is followed by hepatic vein which is a technically more demanding examination. ECG correlation is essential for hepatic vein. Subxiphoid window is easy to perform in most of the individuals, but coronal plane imaging from the mid axillary line is almost always possible even with the obese habitus individuals.
Standard hepatic vein doppler ( Fig. 3 ) consists of two antegrade waves the systolic S wave which corresponds to the QRS complex of the ECG, and the diastolic D wave which occurs after the T wave of ECG. For a simplified interpretation, mild congestion is suggested where the D wave velocity exceeds the S wave velocity. Severe venous congestion is manifested by S wave reversal resulting in single dominant D wave. Hepatic vein doppler interpretation needs echocardiography correlation many times, not only that ECG abnormality such as prolonged PR interval etc can also have impact on hepatic vein interpretation .
Hepatic venous doppler showing two prominent antegrade S and D waves.
Next vein of importance to be evaluated is portal vein. Portal vein like a hepatic vein is best evaluated through the coronal plane from the mid axillary line. This vein can be identified by the bright echogenic wall in contrast to the hepatic veins which do not have a discernible wall . The portal vein may sometimes be obscured anteriorly by prominent hepatic artery pulsations. With increased grades of hepatic parenchymal disease; the hepatic arterial waveform becomes more pulsatile and more readily seen than in normal patients. In such a diseased heart and liver, the hepatic arterial doppler will be seen anterior to the portal vein and its pulsatile flow may cause artifacts within the portal vein. Hence, it is advisable to place the color box as in the central portion of the portal vein or more towards its posterior aspect rather than anteriorly .
The assessment of the portal vein doppler ( Fig. 4 ) is based on portal vein pulsatility fraction (PVPF) which is calculated by evaluating portal vein waveform. It is derived as Vmax- Vmin/Vmax x 100. In the normal portal vein, pulsatility fraction is less than 30 %. With elevated congestion, the PVPF increases. A PVPF of 30–50 % suggests mild venous congestion while the value exceeding 50 % indicates severe congestion. One important pitfall for any doppler examination is that the waveform depends upon the distal vascular resistance. When the liver parenchyma becomes stiff as in cirrhosis, the resistance increases and so does the pulsatility .
Portal vein Doppler showing undulating wave pattern.
Last vessel of importance to be evaluated is the renal vein doppler. Main renal vein is not targeted. Instead, intrarenal, intralobular and segmental veins are targeted. The study is best performed when the kidney filling almost enters the screen and depth should be decreased so that the kidney occupies the full screen. At this setting, good renal pulsations are seen and intrarenal arcuate veins could be insonated. With good spectral trace, the renal arterial flow will be displayed above the baseline and venous flow below it. The color box should be further reduced and refined to optimize the renal vein doppler. The renal vein doppler is also performed in the mid-axillary line slightly inferior to the window for the portal vein . The normal renal vein ( Fig. 5 ) shows continuous pattern with minimal pulsatility. As the venous congestion increases, the renal capsule limits expansion, increasing the intrarenal resistance. This results in loss of continuous flow on the renal vein .
Continuous Renal vein doppler wave form.
In mild congestion the continuous flow is interrupted and then systolic and diastolic waves can be identified. In severe venous congestion, only single D-wave is seen, as S-wave becomes reversed, just like in hepatic vein.
The data obtained from these three major vessels and IVC are assessed in grading the VExUS ( Fig. 6 ). Each of the three vessels doppler signature can be classified as normal, mildly abnormal, and severely abnormal. If the IVC diameter is less than 2 cm, it corresponds to grade 0. If the IVC diameter exceeds 2 cm, three grades of congestion are classified based on the multiple vessel evaluation. For each doppler wave pattern, the presence of one or more mildly abnormal waveforms corresponds to grade 1. A single severe waveform aligns with grade 2, and two or more severe waveforms are present, indicating VExUS grade 3, representing severe venous congestion .
Simple graphic for easy recall of the wave forms and VExUS grading.
3
Inter-user operability differences and standardized– reliability and reusability
Validation of any ultrasonographic technique requires assessing both inter-rater reliability (IRR)—the consistency of image interpretation among observers—and inter-user reproducibility (IUR)—the consistency of results when data from the same patient are acquired by different ultrasonographers. Currently, standardized protocols and best practices for VExUS have not been established, and its real-world application varies considerably. To address these gaps, Longino et al. conducted a multicenter, multidisciplinary, prospective observational study evaluating the IRR, IUR, and the potential role of ECG integration in VExUS interpretation .
The study found that the overall VExUS examination demonstrated higher IRR and IUR than its individual components, suggesting that the redundancy of the composite VExUS score may mitigate variability in the interpretation of single parameters. The renal component exhibited the lowest IRR and IUR, likely reflecting the inherent challenges of acquiring and interpreting renal Doppler images—commonly considered the most technically demanding. Future refinements of the VExUS protocol should therefore include robust evaluation of the renal view’s performance characteristics.
Notably, the introduction of ECG tracing for the final 30 patients improved IRR, consistent with prior studies showing that ECG integration enhances the reproducibility of venous doppler ultrasonography of the hepatic and renal vasculature. The ECG likely aids interpreters in distinguishing waveform variations caused by cardiac versus respiratory cycles—a frequent source of misinterpretation in VExUS analysis. These findings support incorporating ECG tracing into standardized VExUS protocols to improve interpretive reliability and consistency .
4
Clinical implications
4.1
Risk of AKI in post CABG patients
As introduced early, in 2020, Beaubien-Soligny and colleagues first used VExUS to study the impact of fluid overload to predict AKI in post CABG patients . The presence of at least two severe alterations of hepatic vein, portal vein or intra-renal venous flow on pulse-wave Doppler ultrasound and an IVC of ≥ 2 cm of diameter at ICU admission after cardiac surgery indicates a high risk of post-operative AKI. Severe congestion (Grade 3) defined by the VExUS C grading system was the most strongly associated with AKI (HR 3.69, CI 1.65–8.24, p = 0.001).
4.2
VExUS in acute congestive heart failure (CHF)
The study by Landi et al. likely the first to provide VExUS score validation in an Emergency Department (ED) population, focused on patients admitted for suspected Heart Failure (HF), and reliably performed on any patient presenting to the ED with a clinical suspicion of venous congestion. It included patients with renal insufficiency, iatrogenic fluid overload, etc. It showed that severe venous congestion, with a VExUS score of 3 at the initial assessment of admission to ED with acute decompensated HF, predicts inpatient mortality, HF-related death, and early readmission. It also showed that severe venous congestion, lower RV systolic function, and worsened renal function are associated with poor outcome of readmission or death due to HF. Also important in the study was the VExUS score was found to be technically feasible in almost all patients, despite tachypnea and incomplete cooperation, which made interpretation feasible and adequate in an ED setting .
4.3
VExUS in acute CHF, cardiorenal syndrome (CRS) and Acute Kidney Injury (AKI)
The study done by Bharadwaj et al. which supported the validity of VExUS score in Cardiorenal syndrome (CRS) patients with severe fluid overload. It did not use renal vein doppler in the VExUS score. It showed that serial VExUS scoring is correlated with AKI staging . Out of 30 patients, 20 patients with resolving AKI also correlated with the downward/improving trend of VExUS score accounting for majority (87 %) of cases associated with a decreasing trend of fluid balance. This emphasized that the dynamic trend of VExUS grading correlated with the improving clinical condition. Chen et al. published a meta-analysis correlating AKI with elevated central venous pressure (CVP) and CVP did not show improving trend with AKI resolution. This shows CVP trend might not truly reflect the clinical picture because of its limitations, and possibly also because different patients may have different levels of tolerance of CVP, whereas Doppler flow markers may better reflect the severity of organ congestion and potential dysfunction.
The VExUS score demonstrates good diagnostic accuracy for cardiorenal AKI and moderate accuracy for hypovolemic AKI. However, it is unable to distinguish subtypes related to renal or systemic vasodilatation and should not be used in isolation to determine the etiology of AKI in the emergency department ,. In patients with decompensated heart failure (HF), splanchnic venous congestion commonly occurs, leading to progressive increases in intra-abdominal pressure that contribute to AKI secondary to volume overload ,. In a prospective observational study of 40 patients with acute HF admitted to the intensive care unit, Mullens et al. found that elevated central venous pressure—rather than reduced cardiac output—was the primary mechanism driving AKI, underscoring the pivotal role of venous congestion in renal dysfunction. More recently, Sovetova et al. conducted a prospective study involving 100 patients with VExUS grade 3, revealing a significantly higher risk of AKI (47 % incidence) and an association with diuretic resistance characterized by a diminished natriuretic response .
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