A novel formula for graft weight estimation from preoperative computed tomography volumetric measurement in living donor liver transplantation

Abstract

Background: Computed tomography (CT) is the current gold standard for preoperative assessment of graft volume in the context of living donor liver transplantation (LDLT) despite the commonly noted mismatch between CT estimated graft volume (CT-GV) and actual graft weight (AGW). Aim: to find a formula that correlates preoperative virtual CT graft volume with AGW measured on the back table. Methods: CT volumetric data as well as AGW of 125 consecutive living liver donors in the period between 2010 and 2016 were reviewed. Correlation between CT-GV and AGW was done. Formula for line of best fit was obtained by plotting CT-GV against AGW for right and left lobes using linear regression analysis. Results: One hundred and nineteen living donors had complete data allowing downstream analysis. Donors were mostly males (59.7%) with mean age of 28.4±6.7 years. Ninety-seven of them (81.5%) donated right lobe while 22 (18.5%) left lobe grafts. Mean CT-GV was 870.0±142.9 ml for right lobe grafts and 335.5±112.1 ml for left lobe grafts. Mean AGW was 851.7±162.9 g for right lobe grafts and 296.2±74.5 g for left lobe grafts. The following formulae were derived to calculate AGW (g): [0.92xCT-GV (ml)+51.48; R 2 =0.651, P<0.0001] and [0.53xCT-GV (ml)+120; R 2 =0.625, P<0.0001)] for the right and left lobe grafts respectively. Conclusion: We postulate reliable formulae to convert virtual CT-GV into AGW, to accurately correct the discrepancy between preoperative CT-GV and AGW in the setting of LDLT.

A Comparison of Actual Graft Weight and Estimated Graft Volume Calculated with New Software Used for Anatomical and Volumetric Analysis of the Liver with Computed Tomography in Living Liver Donors

“…Although calculating preoperative liver graft volume by volumetric analysis has an acceptable accuracy level in predicting actual liver volume before surgery, it is controversial that one milliliter of liver equated to one gram of liver tissue (8)(9)(10). This equation has been criticized for being based on measurements made from cirrhotic livers (1,4). Some studies have revealed that the error rate in weight estimation with CT volumetry ranges from ±5% to ±20% (11).…”

“…The weight of a liver graft which will be sufficient to meet the metabolic needs of the recipient body, has to be 40-50% of the recipient's liver weight, which corresponds to approximately 0.8-1% of the recipient's body weight (1). Therefore, it is recommended that the GRWR be not less than 0.8% for a successful liver transplant (1,2). Small for size syndrome is more likely to occur if the GRWR is below 0.8% (2).…”

“…Although the difference between the estimated graft volume (EGV) and actual graft weight (AGW) has decreased as software programs have developed, in many cases, the actual graft weight is determined to be lower than the estimated graft volume. Due to this, it has been suggested that the calculations made by Van Thiel et al were derived from cirrhotic livers and the density of non-cirrhotic livers is lower (1,(4)(5)(6). Dehydration because of preservative solutions and differences in the plane of division of the liver parenchyma are other suspected causes of volume-weight mismatch in the liver graft (6).…”

The Correlation between the CT Liver Volume and the Actual Weight of the Resected Cirrhotic Liver in Transplantation Patients

“…However, several studies suggested that this number might not be appropriate, and alternative methodsranging from a different conversion factor to a more complex formula-were proposed. 16,19,20,25 Nevertheless, these suggestions came from studying normal livers and did not account for the presence of liver cirrhosis. In the current study, we proposed a formula that can accurately predict the weight of the resected cirrhotic liver (R-squared =0.914).…”