Pilot Study: The Effects of Slice Parameters and the Interobserver Measurement Variability in Computed Tomographic Hepatic Volumetry in Dogs without Hepatic Disease

SIMPLE SUMMARY: Computed tomographic hepatic volumetry is usually time-consuming due to large numbers of slices. This study aimed to evaluate the relationship between slice interval and number of slices on hepatic volume in dogs using CT and to determine the interobserver variability of CT volumetric measurements for dogs without evidence of hepatobiliary disease which had undergone abdominal CT using either 2.5-mm or 3.75-mm slice thicknesses. Interobserver variability was low, with a mean percent difference in the hepatic volume of 3.3% among all observers. The mean percent differences in hepatic volumes generally increased when using larger slice intervals; however, the greatest percent difference was not always larger in larger slice intervals. The greatest percent differences in hepatic volume were decreased when using larger numbers of slices; the percent differences were <5% when using ≥20 slices for hepatic volumetry. Manual CT hepatic volumetry can be a good tool for a non-invasive assessment of liver volume with low interobserver variability in dogs, and a relatively reliable result would be acquired using ≥20 slices in dogs. ABSTRACT: Manual computed tomographic (CT) hepatic volumetry is a non-invasive method for assessing liver volume. However, it is time-consuming with large numbers of slices. Reducing the slice number would expedite the process, but the effect of fewer slices on the accuracy of volumetric measurements in dogs has not been investigated. The objectives of this study were to evaluate the relationship between slice interval and the number of slices on hepatic volume in dogs using CT hepatic volumetry and the interobserver variability of CT volumetric measurements. We retrospectively reviewed medical records for dogs without evidence of hepatobiliary disease with abdominal CT from 2019 to 2020. Hepatic volumes were calculated by using all slices, and interobserver variability was calculated using the same dataset in 16 dogs by three observers. Interobserver variability was low, with a mean (±SD) percent difference in the hepatic volume of 3.3 (±2.5)% among all observers. The greatest percent differences in hepatic volume were decreased when using larger numbers of slices; the percent differences were <5% when using ≥20 slices for hepatic volumetry. Manual CT hepatic volumetry can be used in dogs to non-invasively assess liver volume with low interobserver variability, and a relatively reliable result can be acquired using ≥20 slices in dogs.