Examination of inferior vena cava is useful in conditions with borderline intravascular amount of fluid – either significant deficit or excess. Proper detection of inferior vena cava may be difficult in case of its collapse. It can often be mixed up with aorta, which would result in a completely wrong assessment of the fluid amount.
The most reliable method for proper identification of inferior vena cava is the visualisation of right atrium using subcostal projection and visualising its transfer to inferior vena cava by titling of the scanning plane in the caudal direction. Inferior vena cava can be visualised across liver from the right side (from mid-clavicular to mid-axillary line, simply from the place providing sufficient acoustic window) in case of absence of suitable acoustic window in subcostal projection: