Point-of-care ultrasound in diagnosis and management of congestive nephropathy

Table 1 Key sonographic findings and limitations of each application in the evaluation of congestive nephropathy

Sonographic application	Possible findings in the context of congestive nephropathy	Limitations
Lung ultrasound	Elevated extravascular lung water (B-lines) and pleural effusion	B-lines are non-specific and can be seen in non-cardiogenic pulmonary edema, lung fibrosis, contusion, and alveolar hemorrhage
Focused cardiac ultrasound (basic)	LV systolic dysfunction (qualitative and M-mode); RV systolic dysfunction (qualitative and M-mode); Pericardial effusion; Gross chamber enlargement (e.g., RV dilation leading to interventricular septal flattening); Gross valvular dysfunction (e.g., tricuspid regurgitation on color Doppler); Elevated right atrial pressure (plethoric IVC)	Lack of spectral Doppler provides limited information. Qualitative assessment relies on operator experience. IVC cannot reliably estimate RAP in mechanically ventilated patients. IVC can be small in intra-abdominal hypertension despite elevated RAP. IVC can be dilated without elevated RAP in trained athletes
Focused cardiac ultrasound (advanced)	Reduced stroke volume assessed by LV outflow tract velocity time integral. Elevated LV filling pressures assessed by mitral inflow Doppler and mitral annular tissue Doppler. Elevated pulmonary artery pressures/right ventricular systolic pressure assessed by continuous wave Doppler through the RV outflow tract and tricuspid valve. Elevated right atrial pressure assessed by tricuspid inflow and tissue Doppler	Requires higher operator skill level and training than basic cardiac ultrasound. Suboptimal views/Doppler angle limit the accuracy of measurements obtained. Some of the parameters lack validation in critical illness
Hepatic vein Doppler	Reduced amplitude or reversal of the systolic wave (Normally, systolic wave is larger than the diastolic wave)	Prone to erroneous interpretation without EKG. Cannot differentiate pressure and volume overload (applies to all components of VExUS and E-VExUS). Influenced by factors other than RAP (e.g., atrial fibrillation, RV systolic excursion). Diminished pulsatility in cirrhosis; may not accurately reflect the degree of congestion
Portal vein Doppler	Increased pulsatility (normal waveform is near-continuous)	Pulsatile portal vein can be seen in cirrhosis and healthy, young individuals without an elevated RAP. Can appear falsely normal despite elevated RAP in patients with portal hypertension
Intra-renal venous Doppler	Increased pulsatility, systolic wave reversal (normal waveform is near-continuous)	Most technically challenging of the three components of VExUS. Sampling a larger vessel such as the main renal vein instead of interlobar vein leads to mistaken interpretation
E-VExUS	IJ vein: Reduced amplitude or reversal of the systolic wave (normally, systolic wave is larger than the diastolic wave); Splenic vein: Increased pulsatility (normal waveform is near-continuous); SVC: Reduced amplitude or reversal of the systolic wave (normally, systolic wave is larger than the diastolic wave); Femoral: Increased pulsatility and elevated velocity of the retrograde component (normal waveform is near-continuous)	Not validated as a combination score though individual components are studied. EKG is required when there is no simultaneous arterial trace to delineate cardiac cycles. IJ vein: Susceptible to probe pressure due to its relatively superficial location. Splenic vein: Similar limitations as portal vein. SVC: Technically challenging to access via transthoracic windows. Femoral: Relatively less sensitive to detect elevated RAP. Severe intra-abdominal hypertension may influence the waveform

LV: Left ventricle; RV: Right ventricle; M-mode: Motion mode; IVC: Inferior vena cava; EKG: Electrocardiogram; VExUS: Venous excess ultrasound; RAP: Right atrial pressure; RV: Right ventricle; E-VExUS: Extended venous excess ultrasound; IJ: Internal jugular; SVC: Superior vena cava.