Discrepancy between estimated and actual weight of partial liver graft from living donors

Liver volumetric and anatomic assessment in living donor liver transplantation: The role of modern imaging and artificial intelligence

The shortage of deceased donor organs has prompted the development of alternative liver grafts for transplantation. Living-donor liver transplantation (LDLT) has emerged as a viable option, expanding the donor pool and enabling timely transplantation with favorable graft function and improved long-term outcomes. An accurate evaluation of the donor liver's volumetry (LV) and anatomical study is crucial to ensure adequate future liver remnant, graft volume and precise liver resection. Thus, ensuring donor safety and an appropriate graft-to-recipient weight ratio. Manual LV (MLV) using computed tomography has traditionally been considered the gold standard for assessing liver volume. However, the method has been limited by cost, subjectivity, and variability. Automated LV techniques employing advanced segmentation algorithms offer improved reproducibility, reduced variability, and enhanced efficiency compared to manual measurements. However, the accuracy of automated LV requires further investigation. The study provides a comprehensive review of traditional and emerging LV methods, including semi-automated image processing, automated LV techniques, and machine learning-based approaches. Additionally, the study discusses the respective strengths and weaknesses of each of the aforementioned techniques. The use of artificial intelligence (AI) technologies, including machine learning and deep learning, is expected to become a routine part of surgical planning in the near future. The implementation of AI is expected to enable faster and more accurate image study interpretations, improve workflow efficiency, and enhance the safety, speed, and cost-effectiveness of the procedures. Accurate preoperative assessment of the liver plays a crucial role in ensuring safe donor selection and improved outcomes in LDLT. MLV has inherent limitations that have led to the adoption of semi-automated and automated software solutions. Moreover, AI has tremendous potential for LV and segmentation; however, its widespread use is hindered by cost and availability. Therefore, the integration of multiple specialties is necessary to embrace technology and explore its possibilities, ranging from patient counseling to intraoperative decision-making through automation and AI.

CT volume analysis in living donor liver transplantation: accuracy of three different approaches

OBJECTIVES

The aim of this retrospective study is to compare and evaluate accuracy of three different approaches of liver volume quantification in living donor transplantations.

METHODS

This is a single-center, retrospective study of 60 donors. The total and right lobe liver volumes were analyzed in the portal-venous phase by two independent radiologists who estimated the volumes using manual, semi-automated and automated segmentation methods. The measured right lobe liver volume was compared to the real weight of the graft after back-table examinations.

RESULTS

The mean estimated overall liver volume was 1164.4 ± 137.0 mL for manual, 1277.4 ± 190.4 mL for semi-automated and 1240.1 ± 108.5 mL for automated segmentation. The mean estimated right lobe volume was 762.0 ± 122.4 mL for manual, 792.9 ± 139.9 mL for semi-automated and 765.4 ± 132.7 mL for automated segmentation. The mean graft weight was 711.2 ± 142.9 g. The manual method better correlated with the graft weight (r = 0.730) in comparison with the semi-automated (r = 0.685) and the automated (r = 0.699) methods (p < 0.001). The mean error ratio in volume estimation by each application was 12.7 ± 16.6% for manual, 17.1 ± 17.3% for semi-automated, 14.7 ± 16.8% for automated methods. There was a statistically significant difference between the mean error ratio of the manual and the semi-automated segmentations (p = 0.017), and no statistically significant difference between the manual and the automated applications (p = 0.199).

CONCLUSION

Volume analysis application better correlates with graft weight, but there is no obvious difference between correlation coefficients of all three methods. All three modalities had an error ratio, of which the semi-automated method showed the highest value.

CRITICAL RELEVANCE STATEMENT

Volume analysis application was more accurate, but there is no drastic difference between correlation coefficients of all three methods.

Accuracy and Efficiency of Right-Lobe Graft Weight Estimation Using Deep-Learning-Assisted CT Volumetry for Living-Donor Liver Transplantation

CT volumetry (CTV) has been widely used for pre-operative graft weight (GW) estimation in living-donor liver transplantation (LDLT), and the use of a deep-learning algorithm (DLA) may further improve its efficiency. However, its accuracy has not been well determined. To evaluate the efficiency and accuracy of DLA-assisted CTV in GW estimation, we performed a retrospective study including 581 consecutive LDLT donors who donated a right-lobe graft. Right-lobe graft volume (GV) was measured on CT using the software implemented with the DLA for automated liver segmentation. In the development group (n = 207), a volume-to-weight conversion formula was constructed by linear regression analysis between the CTV-measured GV and the intraoperative GW. In the validation group (n = 374), the agreement between the estimated and measured GWs was assessed using the Bland–Altman 95% limit-of-agreement (LOA). The mean process time for GV measurement was 1.8 ± 0.6 min (range, 1.3–8.0 min). In the validation group, the GW was estimated using the volume-to-weight conversion formula (estimated GW [g] = 206.3 + 0.653 × CTV-measured GV [mL]), and the Bland–Altman 95% LOA between the estimated and measured GWs was −1.7% ± 17.1%. The DLA-assisted CT volumetry allows for time-efficient and accurate estimation of GW in LDLT.

Correlation between liver volume and liver weight in a cohort with chronic liver disease: a semiautomated CT-volumetry study

BACKGROUND

To estimate the optimal density coefficient for conversion of liver volume into liver weight in patients with chronic liver disease based on semiautomated CT-liver volumetry data and the histologic Ishak score of explanted liver.

METHODS

A total of 114 patients (39 female; age, 46±20 years) with chronic liver diseases who underwent liver transplantation between January 2010 and September 2020 were identified over a patient chart search at our institution and subsequently analyzed in retrospect. All patients had contrast-enhanced CT-examinations (mean, 24 days) to liver transplantation. Liver volume was calculated by a semiautomated software and results compared with the liver weight registered by the pathologist. Each explanted liver was histologically scored into six classes according to the Ishak classification where the categories were subgrouped based on recommendation of the pathologists into the following categories 0-3, 4-5 and 6.

RESULTS

Mean liver volume was 1,870±1,195, 1,162±679 and 1,278±510 mL for the categories 0-3, 4-5 and 6, respectively. Mean liver weight was 1,624±999, 1,082±669 and 1,346±559 g for the categories 0-3, 4-5 and 6, respectively. A coefficient of 0.92±0.22, 0.98±0.28 and 1.06±0.20 g/mL was found at best for conversion of liver volume into liver weight in these subgroups. Differences between Ishak-subgroups proved significant (0.002). In 4 patients with cystic liver disease, density coefficients varied significantly and were found generally lower compared to the other liver disorders.

CONCLUSIONS

Our results yielded significant differences between the density coefficients calculated along with the Ishak score and also for the subgroup with cystic liver disease.

Comparison Between Pre-operative Radiologic Findings and the Actual Operative Findings of the Graft in Adult Living Donor Liver Transplantation

BACKGROUND

Computed tomography (CT) volumetry and magnetic resonance cholangiopancreatography (MRCP) are mandatory steps for the evaluation of potential donors in living donor liver transplantation. The aim of this study is to compare the preoperative CT volumetry and biliary orifices of the donor graft to the actual operative findings.

METHODS

Between December 2013 and December 2017, 45 donors (27 men and 18 women) with a mean age of 27.3 years (range, 19-41 years) were evaluated preoperatively by CT volumetry and MRCP at the National Hepatology and Tropical Medicine Research Institute in Cairo, Egypt. Of the donors, 43 out of 45 underwent intraoperative cholangiography before and after bile duct division. The right hepatectomies for all donors, as well as the actual weight and apparent biliary orifices in the graft, were documented.

RESULTS

The mean estimated graft volume (EGV) preoperatively by CT volumetry was 894.9 ± 184.2 mL (range, 480-1687 mL), whereas the actual graft weight (AGW) intraoperatively after washout was 862.6 ± 124.4 g (range, 676-1110 g). The correlation coefficient between the EGV and AGW was significantly linear (Y = 0.96X, r² = 0.72, slope: 0.96, P < .001). The accuracy of the MRCP in preoperative biliary mapping was 76.7% whereas the accuracy of the MRCP in predicting the number of graft biliary orifices was 74.4% compared with the intraoperative cholangiography (IOC), which was 95.3% (P < .001).

CONCLUSION

The weight of the right lobe of the liver graft in living donor liver transplants (LDLTs) can be accurately predicted preoperatively by multiplying the EGV by 0.96. Also, the IOC is an essential technique for LDLT.

What are the most important predictive factors for clinically relevant posthepatectomy liver failure after right hepatectomy for hepatocellular carcinoma?

Purpose

The risk of posthepatectomy liver failure (PHLF) after right hepatectomy remains substantial. Additional parameters such as computed tomography volumetry, liver stiffness measurement by FibroScan, indocyanine green retention rate at 15 minutes, and platelet count used to properly assess future liver remnant volume quality and quantity are of the utmost importance. Thus, we compared the usefulness of these modalities for predicting PHLF among patients with hepatocellular carcinoma after right hepatectomy.

Methods

We retrospectively reviewed patients who underwent right hepatectomy for hepatocellular carcinoma between 2007 and 2013. PHLF was determined according to International Study Group of Liver Surgery consensus definition and severity grading. Grades B and C were defined as clinically relevant posthepatectomy liver failure (CRPHLF). The results were internally validated using a cohort of 97 patients.

Results

Among the 90 included patients, 15 (16.7%) had CRPHLF. Multivariate analysis confirmed that platelet count < 140 (10⁹/L) (hazard ratio [HR], 24.231; 95% confidence interval [CI], 3.623–161.693; P = 0.001) and remnant liver volume-to-body weight (RVL/BW) ratio < 0.55 (HR, 25.600; 95% CI, 4.185–156.590; P < 0.001) were independent predictors of CRPHLF. Among the 12 patients with a platelet count < 140 (10⁹/L) and RLV/BW ratio < 0.55, 9 (75%) had CRPHLF. Likewise, 5 of 38 (13.2%) with only one risk factor developed CRPHL versus 1 of 40 (2.5%) with no risk factors. These findings were confirmed by the validation cohort.

Conclusion

RLV/BW ratio and platelet count are more important than the conventional RLV/TFLV, indocyanine green retention rate at 15 minutes, and liver stiffness measurement in the preoperative risk assessment for CRPHLF.

Three-Dimensional Volumetric Assessment of Graft Volume in Living Donor Liver Transplantation: Does It Minimise Errors of Estimation?

BACKGROUND

Accurate volumetric assessment of graft and remnant liver is essential in living donor liver transplantation (LDLT) for optimal clinical outcome in both donors and recipients. Recently, three-dimensional (3D) volumetry is proposed over conventional computed tomography (CT) volumetry to minimise errors. The aim of this study is to assess the correlation of estimated graft volume (EGV) by both the methods with actual graft weight (AGW).

METHODS

One hundred fifty-four consecutive donors were enrolled prospectively. Conventional CT volumetry (semiautomatic) and 3D volumetry were performed using Myrian software. Total liver volume (TLV), EGV, and remnant liver volume (RLV) were assessed using both methods and correlated with intraoperatively measured AGW as the reference standard. Error of estimation was calculated accordingly.

RESULTS

One hundred eighteen donors underwent right hepatectomy excluding middle hepatic vein (MHV), twenty-nine donors had left hepatectomy including MHV and six donors underwent left lateral sectionectomy. The median EGV on CT and 3D volumetry was 628.5 ml (140-1300) and 634.5 ml (156-1349), respectively. The median AGW was 647 gm (200-1004). Both CT and 3D volumetry showed strong correlation with AGW (correlation coefficients: 0.834 and 0.856, respectively). Linear correlation is as follows: (a) AGW = 99.75 + 0.818 × EGV (CT) and (b) AGW = 96.03 + 0.835 × EGV (3D). The mean percentage error for CT and 3D volumetry was 14.2 ± 12.5% and 12.2 ± 11.8%, respectively. The overall accuracy of estimation of EGV improved using 3D software (P=0.015). For the subgroup of types of graft, the difference did not reach statistical significance (P=0.062, 0.214 and 0.463 for right, left and left lateral grafts, respectively).

CONCLUSION

Both conventional CT and 3D volumetric methods strongly correlate with AGW in donors of LDLT, whereas overall accuracy of estimation of graft weight improved marginally by 3D volumetry.

Resection plane-dependent error in computed tomography volumetry of the right hepatic lobe in living liver donors

Background/Aims

Computed tomography (CT) hepatic volumetry is currently accepted as the most reliable method for preoperative estimation of graft weight in living donor liver transplantation (LDLT). However, several factors can cause inaccuracies in CT volumetry compared to real graft weight. The purpose of this study was to determine the frequency and degree of resection plane-dependent error in CT volumetry of the right hepatic lobe in LDLT.

Methods

Forty-six living liver donors underwent CT before donor surgery and on postoperative day 7. Prospective CT volumetry (V_P) was measured via the assumptive hepatectomy plane. Retrospective liver volume (V_R) was measured using the actual plane by comparing preoperative and postoperative CT. Compared with intraoperatively measured weight (W), errors in percentage (%) V_P and V_R were evaluated. Plane-dependent error in V_P was defined as the absolute difference between V_P and V_R. % plane-dependent error was defined as follows: |V_P–V_R|/W∙100.

Results

Mean V_P, V_R, and W were 761.9 mL, 755.0 mL, and 696.9 g. Mean and % errors in V_P were 73.3 mL and 10.7%. Mean error and % error in V_R were 64.4 mL and 9.3%. Mean plane-dependent error in V_P was 32.4 mL. Mean % plane-dependent error was 4.7%. Plane-dependent error in V_P exceeded 10% of W in approximately 10% of the subjects in our study.

Conclusions

There was approximately 5% plane-dependent error in liver V_P on CT volumetry. Plane-dependent error in V_P exceeded 10% of W in approximately 10% of LDLT donors in our study. This error should be considered, especially when CT volumetry is performed by a less experienced operator who is not well acquainted with the donor hepatectomy plane.

Prediction of the Total Liver Weight using anthropological clinical parameters: does complexity result in better accuracy?

BACKGROUND

The performance of linear models predicting Total Liver Weight (TLW) remains moderate. The use of more complex models such as Artificial Neural Network (ANN) and Generalized Additive Model (GAM) or including the variable "steatosis" may improve TLW prediction. This study aimed to assess the value of ANN and GAM and the influence of steatosis for predicting TLW.

METHODS

Basic clinical and morphological variables of 1560 cadaveric donors for liver transplantation were randomly split into a training (2/3) and validation set (1/3). Linear models, ANN and GAM were built by using the training cohort and evaluated with the validation cohort.

RESULTS

The TLW is subject to major variations among donors with similar morphological parameters. The performance of ANN and GAM were moderate and similar to that of linear models (concordance coefficient from 0.36 to 0.44). In 28-30% of cases, TLW cannot be predicted with a margin of error ≤20%. The addition of the variable "steatosis" to each model did not improve their performance.

CONCLUSION

TLW prediction based on anthropological parameters carry a significant risk of error despite the use of more complex models. Others determinants of TLW need to be identified and imaging-based volumetric measurements should be preferred when feasible.

PREOPERATIVE COMPUTED TOMOGRAPHY VOLUMETRY AND GRAFT WEIGHT ESTIMATION IN ADULT LIVING DONOR LIVER TRANSPLANTATION

BACKGROUND

Computed tomography volumetry (CTV) is a useful tool for predicting graft weights (GW) for living donor liver transplantation (LDLT). Few studies have examined the correlation between CTV and GW in normal liver parenchyma.

AIM

To analyze the correlation between CTV and GW in an adult LDLT population and provide a systematic review of the existing mathematical models to calculate partial liver graft weight.

METHODS

Between January 2009 and January 2013, 28 consecutive donors undergoing right hepatectomy for LDLT were retrospectively reviewed. All grafts were perfused with HTK solution. Estimated graft volume was estimated by CTV and these values were compared to the actual graft weight, which was measured after liver harvesting and perfusion.

RESULTS

Median actual GW was 782.5 g, averaged 791.43±136 g and ranged from 520-1185 g. Median estimated graft volume was 927.5 ml, averaged 944.86±200.74 ml and ranged from 600-1477 ml. Linear regression of estimated graft volume and actual GW was significantly linear (GW=0.82 estimated graft volume, r2=0.98, slope=0.47, standard deviation of 0.024 and p<0.0001). Spearman Linear correlation was 0.65 with 95% CI of 0.45 - 0.99 (p<0.0001).

CONCLUSION

The one-to-one rule did not applied in patients with normal liver parenchyma. A better estimation of graft weight could be reached by multiplying estimated graft volume by 0.82.

Liver regeneration after living donor transplantation: adult-to-adult living donor liver transplantation cohort study

Adult-to-adult living donors and recipients were studied to characterize patterns of liver growth and identify associated factors in a multicenter study. Three hundred and fifty donors and 353 recipients in the Adult-to-Adult Living Donor Liver Transplantation Cohort Study (A2ALL) receiving transplants between March 2003 and February 2010 were included. Potential predictors of 3-month liver volume included total and standard liver volumes (TLV and SLV), Model for End-Stage Liver Disease (MELD) score (in recipients), the remnant and graft size, remnant-to-donor and graft-to-recipient weight ratios (RDWR and GRWR), remnant/TLV, and graft/SLV. Among donors, 3-month absolute growth was 676 ± 251 g (mean ± SD), and percentage reconstitution was 80% ± 13%. Among recipients, GRWR was 1.3% ± 0.4% (8 < 0.8%). Graft weight was 60% ± 13% of SLV. Three-month absolute growth was 549 ± 267 g, and percentage reconstitution was 93% ± 18%. Predictors of greater 3-month liver volume included larger patient size (donors and recipients), larger graft volume (recipients), and larger TLV (donors). Donors with the smallest remnant/TLV ratios had larger than expected growth but also had higher postoperative bilirubin and international normalized ratio at 7 and 30 days. In a combined donor-recipient analysis, donors had smaller 3-month liver volumes than recipients adjusted for patient size, remnant or graft volume, and TLV or SLV (P = 0.004). Recipient graft failure in the first 90 days was predicted by poor graft function at day 7 (HR = 4.50, P = 0.001) but not by GRWR or graft fraction (P > 0.90 for each). Both donors and recipients had rapid yet incomplete restoration of tissue mass in the first 3 months, and this confirmed previous reports. Recipients achieved a greater percentage of expected total volume. Patient size and recipient graft volume significantly influenced 3-month volumes. Importantly, donor liver volume is a critical predictor of the rate of regeneration, and donor remnant fraction affects postresection function. Liver Transpl 21:79-88, 2015. © 2014 AASLD.

Reappraisal of the inferior right hepatic vein preserving liver resection

BACKGROUND

To resect tumors infiltrating to the right hepatic vein at its root, right hemihepatectomy or that following portal vein embolization (PVE) is applied. If the IRHV is sizable, the IRHV preserving liver resection can be another option.

METHODS

Between 1994 and 2007, the IRHV preserving liver resection was performed in 21 patients (IRHV group). The short-term outcomes after surgery of them p.

RESULTS

There were no mortality and no significant difference between the IRHV and RH groups concerning the blood loss, the morbidity rates and the duration of hospital stay. The median operation time was shorter in the IRHV group than in the RH group (393 vs. 480 min, p = 0.0409). The median weight of resected specimen of the IRHV group was 293 g (range: 20-982), which was significantly lighter than that of the RH group (median: 680 g [250-4,300], p < 0.001). The median percentage of resected volume to standard liver volume was significantly smaller in the IRHV group than in the RH group (25.8 vs. 52.2%, p < 0.001).

CONCLUSION

The IRHV preserving liver resection remains a safe and useful procedure.

Accuracy of estimation of graft size for living-related liver transplantation: first results of a semi-automated interactive software for CT-volumetry

OBJECTIVES

To evaluate accuracy of estimated graft size for living-related liver transplantation using a semi-automated interactive software for CT-volumetry.

MATERIALS AND METHODS

Sixteen donors for living-related liver transplantation (11 male; mean age: 38.2±9.6 years) underwent contrast-enhanced CT prior to graft removal. CT-volumetry was performed using a semi-automated interactive software (P), and compared with a manual commercial software (TR). For P, liver volumes were provided either with or without vessels. For TR, liver volumes were provided always with vessels. Intraoperative weight served as reference standard. Major study goals included analyses of volumes using absolute numbers, linear regression analyses and inter-observer agreements. Minor study goals included the description of the software workflow: degree of manual correction, speed for completion, and overall intuitiveness using five-point Likert scales: 1--markedly lower/faster/higher for P compared with TR, 2--slightly lower/faster/higher for P compared with TR, 3--identical for P and TR, 4--slightly lower/faster/higher for TR compared with P, and 5--markedly lower/faster/higher for TR compared with P.

RESULTS

Liver segments II/III, II-IV and V-VIII served in 6, 3, and 7 donors as transplanted liver segments. Volumes were 642.9±368.8 ml for TR with vessels, 623.8±349.1 ml for P with vessels, and 605.2±345.8 ml for P without vessels (P<0.01). Regression equations between intraoperative weights and volumes were y = 0.94x+30.1 (R2 = 0.92; P<0.001) for TR with vessels, y = 1.00x+12.0 (R2 = 0.92; P<0.001) for P with vessels, and y = 1.01x+28.0 (R2 = 0.92; P<0.001) for P without vessels. Inter-observer agreement showed a bias of 1.8 ml for TR with vessels, 5.4 ml for P with vessels, and 4.6 ml for P without vessels. For the degree of manual correction, speed for completion and overall intuitiveness, scale values were 2.6±0.8, 2.4±0.5 and 2.

CONCLUSIONS

CT-volumetry performed with P can predict accurately graft size for living-related liver transplantation while improving workflow compared with TR.

Variability of standard liver volume estimation versus software-assisted total liver volume measurement

The estimation of the standard liver volume (SLV) is an important component of the evaluation of potential living liver donors and the surgical planning for resection for tumors. At least 16 different formulas for estimating SLV have been published in the worldwide literature. More recently, several proprietary software-assisted image postprocessing (SAIP) programs have been developed to provide accurate volume measurements based on the actual anatomy of a specific patient. Using SAIP, we measured SLV in 375 healthy potential liver donors and compared the results to SLV values that were estimated with the previously published formulas and each donor's demographic and anthropomorphic data. The percentage errors of the 16 SLV formulas versus SAIP varied by more than 59% (from -21.6% to +37.7%). One formula was not statistically different from SAIP with respect to the percentage error (-1.2%), and another formula was not statistically different with respect to the absolute liver volume (18 mL). More than 75% of the estimated SLV values produced by these 2 formulas had percentage errors within ±15%, and the formulas provided good predictions within acceptable agreement (±15%) on scatter plots. Because of the wide variability, care must be taken when a formula is being chosen for estimating SLV, but the 2 aforementioned formulas provided the most accurate results with our patient demographics.