Inter-rater reliability of sonographic measurements of the inferior vena cava.

Background: Bedside ultrasound is emerging as a useful tool in the assessment of intravascular volume status by examining measurements of the inferior vena cava (IVC). Many previous studies do not fully describe their scanning protocol. Objectives: The objective of our study is to evaluate which of three commonly reported IVC scanning methods demonstrates the best inter-rater reliability. Methods: Three physicians visualized the IVC in the three planes and utilized M-mode to measure the maximal and minimal diameter during quiet respiration. Pair-wise correlation coefficients were determined using Pearson Product Moment Correlation. Results: The most reliable pair of measurements (inspiratory and expiratory) was using the anterior mid-axillary line longitudinal view with a Kappa value for both at 0.692. Conclusion: Imaging with the anterior mid-axillary longitudinal approach using the liver as an acoustic window provides the best inter-rater reliability in measurements of the IVC. Likewise, our findings demonstrate that IVC measurements differ based on anatomic location.