Four children (2 boys and 2 girls, mean age 6.2 years), affected by renal pathologies characterized by volume overload (glomerulonephritis, nephrotic syndrome and chronic end-stage renal failure) were included in the study. Clinical and laboratory parameters such as the presence of edema, body weight, and diuresis were evaluated. All patients performed an abdominal ultrasound scan integrated with the 4-step VExUS protocol, which was useful for identifying venous congestion (VExUS score). The first step is the assessment of the inferior vena cava (IVC), in case of the evidence of signs of venous congestion of IVC we proceed with the next 3 steps consisting of Doppler analysis of the hepatic veins, the portal vein and the intrarenal interlobar veins [2,3].

Based on the Doppler analysis, a score from 0 to 3 is given.

• Grade 0 (No congestion): absence of congestion in the IVC;

• Grade 1 (Mild congestion): congestion in the IVC and any combo of normal or mildly abnormal patterns;

• Grade 2 (Moderate congestion) congestion in the IVC and severely abnormal pattern in a single vein;

• Grade 3 (Severe congestion): congestion in the IVC and severely abnormal pattern in two or three veins.

Fig 1: VExUS steps in paediatric patients

In the first step, IVC evaluation, the Caval Index (CI) and the Caval diameter are assessed usually in adult patients. In pediatric patients for the dimensional variability of the IVC (approx. 0.5 cm to 1 cm) and the technical limitations (restlessness), the following parameters are assessed: observational variation in caval caliber during the respiratory cycle (always dilated in the congested state) and the ratio of its caliber with aorta (IVC/Ao ratio >1 congestion; 0.8-1 euvolemia; < 0.8 hypovolemia) [2,4,5,6,7]. The second step consists of a Doppler assessment of the hepatic vein. Hepatic vein flow is in close relation with venous return, which indicates the result of the systemic mean pressure, the function of the atrium, and the right ventricle. If the right atrium pressure increases, the A wave becomes more prominent and the S wave decreases in amplitude relative to the D wave; if venous congestion increases further, a systolic flow reversal is generated [2,3].

Fig 2: Doppler spectrum of the hepatic vein with reduced S-wave compared to D-wave; Origin: UOC Department of Pediatric Radiology ARNAS Civico-Di Cristina-Benfratelli, Palermo, Italy.

Fig 3: Severe spectral alteration in hepatic vein with systolic S-wave inversion; Origin: UOC Department of Pediatric Radiology ARNAS Civico-Di Cristina-Benfratelli, Palermo, Italy.

The third step consists of a Doppler assessment of the portal vein. Physiologically, portal vein flow is wave-like and phasic with pulsatility index, or IP, (Vmax-Vmin)/Vmax < 30%; in case of vascular congestion the increased atrial contraction causes a retrograde blood flow at the level of the hepatic vein, which is then transmitted to the portal vein; therefore the portal flow increases its pulsatility with IP between 30-49% in the moderate grade and IP>50% in the severe grade [2,3].

Fig 4: Portal vein Doppler spectrum with pulsatility equal to or > 30 %; Origin: UOC Department of Pediatric Radiology ARNAS Civico-Di Cristina-Benfratelli, Palermo, Italy.

The fourth and final step consists of the evaluation of the Doppler of the renal (interlobar) veins: usually the flow is monophasic, in the presence of venous congestion the flow becomes discontinuous biphasic with Systolic/Diastolic phases until it becomes a discontinuous monophasic flow with only diastolic phase [2,3].

Fig 5: Biphasic pulsatility of the renal vein below the baseline; Origin: UOC Department of Pediatric Radiology ARNAS Civico-Di Cristina-Benfratelli, Palermo, Italy.

In our study, the scans were standardized: the inferior vena cava (IVC) was assessed by placing the probe transducer in the subxiphoid location with the supine patient; the portal vein was assessed using an intercostal scan. The suprahepatic veins were assessed in an oblique subcostal ascending scan and an intercostal scan in the uncooperative patient. The interlobar renal veins were studied in oblique-coronal scans.