Figure 1

Migration of inferior vena cava imaging planes. Movement of the IVC during respiration introduces errors as the probe moves relative to the IVC from end inspiration to end expiration. (A) represents the imaging plane of a longitudinal view of the IVC. Probe movement off-midline results in measurement of a false diameter that is smaller than the true IVC diameter. As the IVC does not demonstrate uniform diameters along its course through the abdomen, error occurs in (B) transverse imaging where probe movement results in measurement of IVC diameter at different anatomic locations.