Portal vein pulsatility: An important sonographic tool assessment of systemic congestion for critical ill patients

Table 1 Summary of main limitations of sonographic splanchnic vein flow assessment

Inferior vena cava	Cylinder effect (misaligned diameter measurement in long axis)
	Abdominal aorta misinterpreted as inferior vena cava
	Presence of thrombus or obstruction
	Normally distended in young individuals and athletes due to increased venus reserve
	Distended in mechanically ventilated patients (PEEP, mean airway pressure)
	Diameter influenced by respiratory effort in spontaneous breathing patients
	Collapsed in abdominal hypertension
	Distended in tricuspid regurgitation, pulmonary hypertension, severe diastolic dysfunction, cardiac tamponade, tension pneumothorax, pulmonary embolism
Hepatic vein	Difficult interpretation in presence of arrhythmias and pacing (ECG tracing imperative)
	In case of tricuspid regurgitation, does not alone reflect venous congestion
	Decreased venous phasicity in parenchymal liver disease (cirrhosis, occlusive disease)
Portal vein	Enhanced pulsatility in thin healthy individuals
	Unreliable in parenchymal liver disease (cirrhosis, severe steatosis, occlusive disease, arteriovenous fistulas)
	Unreliable in severe portal hypertension (stagnant/retrograde flow, low velocities)
Renal vein	Technically the most challenging
	Influence of body habitus and mechanical ventilation
	Results differ between cortical versus hilar vessel interrogation
	Unknown reliability in renal parenchymal diseases and kidney transplantation