A Novel Formula for Estimating Liver Volume in Elderly Subjects: A Cadaveric study

Abstract

Introduction In general, the size of a human liver is believed to increase with age, reaching a maximum weight between 41 and 60 years of age. Afterwards, its size gradually decreases. Knowledge of how liver diameter measurements and calculated volume indices correlate with actual liver volume in elderly patients might improve volume assessments before liver transplantation and hepatic resection; and aid in the diagnosis of parenchymal diseases affecting liver size. Objectives The goals of this study were to establish reference values for liver volume in elderly subjects, and to derive a simple formula for estimating liver volume in these individuals. Methods Morphometric analyses were conducted on livers from 34 embalmed cadavers used in a medical school gross anatomy course. The actual liver volume was determined by dividing liver weight by the mean liver density. The three major diameters of the liver, craniocaudal (CC), anteroposterior (AP), and transverse (TRANS), were obtained using both manual measurements on actual specimens, as well as ImageJ metrics on photographs of these same livers. Each diameter was measured at its maximum dimension (Fig.1). The product of these diameters yielded the hepatic volume index (HVI). Based on measured diameters and HVI, estimated liver volumes were calculated and correlated with actual liver volume, and demographic factors such as age and gender. Using regression analyses, formulas correlating measured diameters as independent variables or HVI to the actual liver volume were established. Results Mean liver volume (± SD) was 982 ± 295 cm3 with a range of 613 to 1,904 cm3. The mean age was 84.1 ± 10.8 years, with no significant difference in age between female and male subjects (86.9 ± 11.6 years vs 80.5 ± 8.8 years, respectively, P = .08). Measured diameters showed strong correlation with actual liver volume for CC, AP and TRANS diameters (rs = .605, .744, and .478, respectively). Correlation with actual liver volume was stronger for calculated HVI compared to simple diameters analyzed as independent variables. Liver diameters measured with ImageJ produced an HVI showing the strongest correlation with actual liver volume (rs = .86; P < .001). A simple linear regression formula for estimating liver volume in elderly subjects, based on HVI, was obtained: LV (cm3) = (HVI*0.17) + 294.5 (R2 = .67; P < .001). No significant differences were found in assessing both intra-/inter-observer reproducibility of liver diameter measurements (P > 0.05). The accuracy of the new formula was compared with previously reported formulas (Fig.2) Conclusion These results suggested that both measured diameters and calculated HVI demonstrated excellent reproducibility and correlated strongly with liver size. This new formula, derived from these correlations, improved the accuracy of liver volume estimations in an elderly population. Implications To our knowledge, this is the first study to publish reference values of liver volume in subjects with a mean age > 70 years. Previously reported reference values and formulas resulted from data obtained from younger subjects (means of 48-57 years) and reported formulas which overestimated liver size in older subjects. This new formula might be better at predicting liver volume in elderly subjects.