Research Article, J Liver Disease Transplant Vol: 6 Issue: 2

Performance of International Standard Formulae in Predicting Liver Volume in Living Liver Donors

Zakareya T^1*, Abbasy M¹, Abdel-Razek W¹, Deif M² and Zakaria H³

¹Department of Hepatology, National Liver Institute, Menoufiya University, Shebeen El-Kom, Egypt

²Department of Radiology, National Liver Institute, Menoufiya University, Shebeen El-Kom, Egypt

³Department of Hepatopancreaticobiliary Surgery, National Liver Institute, Menoufiya University, Shebeen El-Kom, Egypt

*Corresponding Author : Talaat Zakareya, MD
Department of Hepatology, National Liver Institute, Menoufiya University, Shebeen El-Kom, Menoufiya, 32511, Egypt
Tel: +201111815877
E-mail: talaatzakareya@gmail.com

Received: June 23, 2017 Accepted: July 01, 2017 Published: July 08, 2017

Citation: Zakareya T, Abbasy M, Razek WA, Deif M, Zakaria H (2017) Performance of International Standard Formulae in Predicting Liver Volume in Living Liver Donors. J Liver Disease Transplant 6:2 doi: 10.4172/2325-9612.1000151

Abstract

Keywords: Total liver volume; CT volumetry; Standard liver volume formulae; Living donor liver transplantation

Introduction

Living donor liver transplantation (LDLT) has been established as a treatment for end-stage liver disease to overcome organ shortage and to expand the donor pool. Moreover, cultural, religious and historical beliefs still represent a major obstacle making deceased donor liver transplantation a prohibited practice in some countries. Accurate estimation of total liver volume, graft volume and remaining liver volume is essential to guarantee adequate metabolic demands for both recipient and donor and to avoid catastrophic drawbacks of both small for size graft and small remaining liver [1-5].

Multidetector computed tomography (MDCT) is the current gold standard modality for assessing the liver volume with a high rate of accuracy and a strong correlation with the actual liver volume [6,7]. However, the use of biometric data can accurately predict liver volume and is potentially considered a non-invasive, cheaper and quicker method and therefore could be more widely applicable [8].

Many formulae dependent on donor biometrics had emerged to predict total liver volume. Based on the studied population, there was some inter-racial and inter-ethnic variation in biometrics referred to variability in total body water, extracellular water, body surface area (BSA), body mass index (BMI) and prevalence of steatosis. This resulted in development of many international formulae with variable degrees of accuracy in predicting liver volume when applied on different groups of population [9-21].

In the current study, we studied the relationship between the calculated standard liver volume (SLV) using each of 13 reported international formulae and CT estimated liver volume (CT-LV) to evaluate the accuracy of these formulae in the prediction of liver volume among our population of living liver donors.

Methods

Data of 253 potential living liver donors who underwent laboratory and radiological pre-transplant evaluation in the liver transplantation center at the National Liver Institute, Shebeen El-Kom, Egypt were reviewed. Biometric data including weight, height, body mass index (BMI), and body surface area (BSA) were recorded for each one at the same day of CT volumetric study. Donors with missed biometric or CT volumetric data were excluded. We calculated BMI as weight in kilograms divided by height in meters squared and BSA using Mosteller’s formula [22]:

CT scans were recorded at 5-mm intervals using the 20-slice multidetector CT (Somatom Definition AS, Siemens, Germany). Liver outlinings were performed by a single operator who is well trained to recognize the relevant organ boundaries. Hepatic veins and intra-parenchymal portal venous system and the fissures that did not open into the abdominal cavity were included in the outlining. Whereas inferior vena cava, extra-parenchymal portal vein and the gall bladder were excluded [23]. Total liver volume was determined in milliliters using the automatic volumetry tool of Intellispace Portal (Philips Healthcare, Best, The Netherlands).

The SLV was calculated for each donor using the listed 13 international formulae in Table 1 then correlated with CT-LV.

Table 1: The studied standard international formulae.

Statistical Methods

Data were analyzed with SPSS version 22 for Mac (IBM Corp., Armonk, NY, USA). Scatter plots with best-fit lines were used to illustrate the correlation between the calculated liver volume by each of the studied formulae and CT-LV. Accuracy of these formulae was compared by estimation of correlation coefficient (r) and coefficient of determination (R²). Calculated SLV by each studied formula was also compared with CT-LV using paired-samples t-test for each donor. For each formula, the error in liver volume estimation was calculated as: SLV – CT-LV, and error ratio (%) as: (SLV – CT-LV) / CT-LV × 100. All analyses were two-sided and the statistical significance was set at P-value less than 0.05.

Results

One hundred fifty-four patients were included in the analyses, as they had complete biometric and volumetric data. Most of the patients were males (n=99, 64.3%). The mean age was 28.3 ± 6.8 years; weight 72.3 ± 10.9 kg, height 168.6 ± 8.9 cm, BMI 25.8 ± 3.2 kg/m² and BSA 1.8 ± 0.2 m². The mean CT-LV was 1566.7 ± 272.3 ml (Table 2). Although all 13 formulae had significant linear relationships with CT-LV (P<0.0001), none of them was accurate in predicting CT-LV (R²=0.230-0.264) (Figure 1). Age did not show significant correlation with CT-LV (P=0.634). The weight, height, BMI and BSA had positive significant correlations with CT-LV. BSA has the highest R² (0.264) (Table 3). The difference between SLV as estimated by all formulae and CT-LV was significant except for the Vauthey formula which had the least mean error ratio (-0.3 ± 17.6, P=0.090). Most of the formulae underestimated the total liver volume except that of Heinemann, Chouker, Yu, DeLand and Yuan. The highest and lowest significant liver volume underestimation was by the Fu-Gui (-400.2 ± 239 ml) and Poovathumkadavil (-124.5 ± 238.9 ml) formula respectively (P<0.0001). The significant total liver volume overestimation was highest by the Chouker formula (48.3 ± 242.4 ml, P<0.0001) and lowest by that of Yu (343.6 ± 258.9 ml, P=0.014) (Table 4).

Figure 1: Scatter plots of total liver volume (ml) as measured by CT (on the x-axis) against calculated liver volume using each of the studied formulae (y-axis) with the line of best fit. R², coefficient of determination.

Table 2: Characteristics of the studied donors.

Table 3: Correlation to total liver volume (ml) as assessed by CT.

Table 4: Comparison between liver volume as estimated by each of the standard formulae and as measured at CT.

Discussion

Living donor liver transplantation has become an accepted alternative to deceased donor liver transplantation in many countries. Calculation of liver volume is crucial to ensure adequate liver mass for both recipient and donor. There are many internationally reported formulae to predict total liver volume based on biometric data. These formulae were derived from different populations [9-21].

In the current study, we studied the accuracy of thirteen reported international formulae in prediction of total liver volume among 154 living liver donors.

Eight of the used formulae are based on BSA, 4 on body weight, and the remaining one on both body weight and height. The mean CT-LV was 1566.7 ± 272.3 ml. BSA, BMI and their components were significantly and positively correlated with CT-LV.

Although all the studied formulae had significant linear relationships with CT-LV (P<0.0001), their accuracy in prediction of liver volume was limited (R²=0.230-0.264).

It is noteworthy that eight of the thirteen studied formulae had comparable estimates of liver volume with the highest recorded R² (0.264). All of them are based on BSA, implying that it might be better than the other biometric parameters in prediction of liver volume.

The calculated SLV was underestimated by 8 formulae and overestimated by the remaining 5 formulae. It is to be noted that the formula of Vauthey had the best agreement to CT-LV with the least and non-significant error ratio (-0.3 %, P=0.090). However, it’s low R² (0.264) still denotes its poor accuracy in predicting liver volume.

The limited accuracy of the studied formulae could be referred to inter-ethnic and inter-racial variability in body indices and heterogeneity of the populations from whom these formulae were derived.

The perplexing finding in the current study was the low coefficient of determination of the basically studied biometric parameters including weight, height, BMI and BSA (R² was 0.23, 0.16, 0.04 and 0.26 respectively) reflecting their limited accuracy in spite of their linear relationships with the CT-LV. This embarrassing finding represented a limitation to derive a new formula with a better accuracy.

In our perspective, studying the correlation between donor biometrics and the actual liver volume in the back table would be of paramount value and could complement and worth this work. We are planning to be our project in the near future.

Finally we can conclude that, all the studied formulae seem to be highly specific to race and ethnicity and none of them can fit our population. Until further notice, CT volumetry remains the gold standard method for pre-transplantation liver volume assessment among our population.

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