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Multiscale study of the hepatic volume evolution after
major hepatectomie in a porcine model
Mohamed Bekheit
To cite this version:
Mohamed Bekheit. Multiscale study of the hepatic volume evolution after major hepatectomie in a porcine model. Surgery. Université Paris Saclay (COmUE), 2018. English. �NNT : 2018SACLS033�. �tel-01753156�
Etude multi-échelle de l`évolution du volume du foie
après hépatectomie majeure chez un modèle porcine
Multiscale study of the hepatic volume evolution after
major hepatectomy in a porcine model
Thèse de doctorat de l'Université Paris-Saclay préparée à l'Université Paris-Sud
et
l`INSERM U1193, CHB, Paul Brousse
École doctorale n°569 : innovation thérapeutique: du fondamental à l'appliqué (ITFA) et sigle Spécialité de doctorat: SC
Thèse présentée et soutenue à Villejuif, le 26-1-2018, par
Mohamed Bekheit
Composition du Jury :Iréne VIGNON-CLEMENTEL
Dir Rech, Établissement : INRIA & UPMC, Paris Président
StéphanieTRUANT
Pr, Établissement : Université de Lille Rapporteur
EwenHARRISON
Dr, Établissement: Université d`Edinburgh Rapporteur
EmilieGREGOIRE
Dr, Établissement APHM Université de Marseille Examinateur
Eric VIBERT
Pr, Établissement Université Paris Saclay Examinateur
NNT
:
Université Paris-Saclay
Espace Technologique / Immeuble Discovery
Route de l’Orme aux Merisiers RD 128 / 91190 Saint-Aubin, France
Titre :
Etude multi-échelle de l`évolution du volume du foie après
hépatectomie majeure chez un modèle porcine
Mots clés : Hepatectomie majeure, porc, modulation de flux, modelisation, architecture, regeneration.
Résumé : L’ablation partielle du foie est une chirurgie qui intervient dans le traitement des lésions du foie ainsi que lors d’une
transplantation partielle de foie (donneur vivant). Grâce à la capacité de régénération du foie, quelques mois après la chirurgie il retrouve sa masse initiale. Les complications de cette chirurgie sont l’insufisance hépatique et après une transplantation le syndrome du trop petit foie. Ces deux complications sont liées à une fonction hépatique post-opératoire faible. Les relations entre l’hémodynamique du foie, son volume et ses fonctions restent à élucider pour mieux comprendre les causes de ces
complications. Lors de la chirurgie,
l’hémodynamique du foie est alterée suite à l’augmentation de la résistance au flux sanguin de l’organe. Les conséquences de cette chirurgie sur l’hémodynamique sont difficiles à analyser du fait de la double perfusion sanguine du foie. En effet, le foie reçoit du sang oxygéné via l’artère hépatique et du sang riche en nutriment via la veine porte. De plus, la régénération du foie semble dépendante des changements de débit et de pression dans la veine porte. Dans ce contexte, le objectif de cette thèse est de mieux comprendre, grâce à des modèles
mathématiques, l’influence de l’hépatectomie sur l’hémodynamique. L`objectif est l’analyse de la perfusion et de la fonction du foie. Un modèle de transport dans le sang d’un composé ainsi que la modélisation du traitement de ce composé par le foie sont développés.
.
Des mesures expétimentales sont nécessaires pour la construction et la validation de ces modèles. Des ablations du foie de différentes tailles sont effectuées sur des porcs et pendant ces chirurgies plusieurs pressions et débits sont mesurés. De plus, un colorant fluorescent est injecté avant ou après l’ablation partielle, et la fluorescence de ce composé est mesurée. Dans une première partie, la procédure chirurgicale, les conditions expérimentales ainsi que les mesures obtenues sont détaillées. Ensuite, les changements hémodynamiques, conséquence de l’ablation partielle du foie. Le modèle permet de prendre en compte les changements de volume sanguins qui peuvent se produire (saignements) lors de la chirurgie. Par
conséquent, ce modèle propose une explication de la variabilité des mesures acquises lors de ces chirurgies.
Puis, le transport dans le sang d’un composé ainsi que son traitement par le foie sont modélisés. La dynamique d’un composé depuis l’injection intraveineuse jusqu’au moment où il atteint les vaisseaux du foie est analysé avec des modèles.
Le contrôle des changements de débit et de pression de la veine porte après une hepatectomie pourrait protèger le foie restant (ou le greffon) et améliorer sa régénération post-opératoire. Les deux sujets abordés dans cette thèse ont pour but d’améliorer l’efficacité d’un dispositif médical (anneau ajustable MID-AVRTM) permettant ce contrôle.
Université Paris-Saclay
Espace Technologique / Immeuble Discovery
Route de l’Orme aux Merisiers RD 128 / 91190 Saint-Aubin, France
Title : Multiscale Study of Hepatic Volume Evolution after Major Hepatectomy in a Porcine Model
Keywords : Liver, resection, regeneration, mathematical model, hemodynamics, flow modulation Abstract : The liver is a unique organ with a
multitude of characteristics. One of these, is the remarkable ability to regenerate. In the context of secondary liver cancers and given the extensive bilobar disease that we often see in the clinical practice, most of the patients are deemed inoperable. One of the major reasons is that this category of patients, if subjected to curative resection, will leave them with insufficient liver for survival. The mechanisms by which the resultant syndrome; small for size; is not fully understood.
The beforehand work addressed certain translational aspects regarding the pathophysiology of the syndrome, the prediction of its occurrence prior to surgery. The setting and design involved the major and ultra-major resection in a porcine model. Along with continuous hemodynamic monitoring and ICG dynamic assessment, the present work lead to a few steps forward in the knowledge and understanding of the interaction between the hepatic, systemic circulation, and the hepatic regeneration. The experimentations involved CT scanning prior to the operation to gain a comprehensive knowledge on the anatomy and volume, which was repeated in a temporal fashion following a strict protocol to monitor the volume changes as well. This was accompanied by 2D and 3D histological analysis and quantification of various regeneration parameters.
The observations made during the surgical procedures and information gathered through other parameters were integrated into multiscale simulations to understand the interactions between the change of the hemodynamics and the change of the hepatic volume that result from resection or regeneration. Subsequently, a modulation device was used to test the effect of hemodynamic adjustments on the regenration and survival. This was done primarly in a 75% resection model then on a smaller scale in a 94% resection model. In the former model, the effect was more seen on the level of the function, some histological parameters but not the volume nor the survival. On the other hand, the experiments with the ring (modulation device) lead to a surviving animal as opposed to no survival of animals without the ring. At the moment, this shows a promising path for researchers to take forward to help reducing the significant mortality that could potentially follow such major resection. Not only that but this sould allow more patient s to have access to the curative treatment they would other not have it.
Synthèse de la Thèse :
L’ablation partielle du foie est une chirurgie qui intervient dans le traitement des lésions du
foie ainsi que lors d’une transplantation partielle de foie (donneur vivant). Grâce à la
capacité de régénération du foie, quelques mois après la chirurgie il retrouve sa masse
initiale. Les complications de cette chirurgie sont l’insufisance hépatique et après une
transplantation le syndrome du trop petit foie. Ces deux complications sont liées à une
fonction hépatique post-opératoire faible. Les relations entre l’hémodynamique du foie, son
volume et ses fonctions restent à élucider pour mieux comprendre les causes de ces
complications. Lors de la chirurgie, l’hémodynamique du foie est alterée suite à
l’augmentation de la résistance au flux sanguin de l’organe. Les conséquences de cette
chirurgie sur l’hémodynamique sont difficiles à analyser du fait de la double perfusion
sanguine du foie. En effet, le foie reçoit du sang oxygéné via l’artère hépatique et du sang
riche en nutriment via la veine porte. De plus, la régénération du foie semble dépendante
des changements de débit et de pression dans la veine porte.
Dans ce contexte, le objectif de cette thèse est de mieux comprendre, grâce à des modèles
mathématiques, l’influence de l’hépatectomie sur l’hémodynamique. L`objectif est l’analyse
de la perfusion et de la fonction du foie. Un modèle de transport dans le sang d’un composé
ainsi que la modélisation du traitement de ce composé par le foie sont développés.
Des mesures expétimentales sont nécessaires pour la construction et la validation de ces
modèles. Des ablations du foie de différentes tailles sont effectuées sur des porcs et pendant
est injecté avant ou après l’ablation partielle, et la fluorescence de ce composé est mesurée.
Dans une première partie, la procédure chirurgicale, les conditions expérimentales ainsi que
les mesures obtenues sont détaillées. Ensuite, les changements hémodynamiques,
conséquence de l’ablation partielle du foie. Le modèle permet de prendre en compte les
changements de volume sanguins qui peuvent se produire (saignements) lors de la chirurgie.
Par conséquent, ce modèle propose une explication de la variabilité des mesures acquises
lors de ces chirurgies.
Puis, le transport dans le sang d’un composé ainsi que son traitement par le foie sont
modélisés. La dynamique d’un composé depuis l’injection intraveineuse jusqu’au moment
où il atteint les vaisseaux du foie (artère hépatique et veine porte) est analysé avec des
modèles 1D et 0D. Les résultats des simulations numériques sont comparés aux mesures de
fluorescence de vert d’indocyanine. Afin d’analyser la dynamique du traitement du vert
d’indocyanine par le foie, un modèle pharmacocinétique est développé. De plus, grâce aux
mesures, les paramètres du modèle sont estimés dans le but de proposer une nouvelle
méthode pour estimer la fonction du foie (pendant la chirurgie).
Le contrôle des changements de débit et de pression de la veine porte après une
hepatectomie pourrait protèger le foie restant (ou le greffon) et améliorer sa régénération
post-opératoire. Les deux sujets abordés dans cette thèse ont pour but d’améliorer
l’efficacité d’un dispositif médical (anneau ajustable MID-AVRTM) permettant ce contrôle.
En effet, pour contrôler l’hémodynamique de la veine porte avec l’anneau, il faut tout
d’abord connaitre l’impact de l’hépatectomie sur l’hémodynamique. De plus, l’efficacité de
l’opération, en utilisant la mesure defluorescence du vert d’indocyanine. Cette thèse
i
I. Table of contents
I. Table of contents ... i
II. List of Tables: ... iv
III. List of Figures: ... vii
IV. List of Equations... xv
V. Preface ... xv
VI. Translational statement:... xviii
VII.List of publications ... xxii
I. Introduction ... 1
i. Anatomy of the liver ... 4
ii. Assessment of the hepatic functions ... 6
a. Biochemical assessment ... 6
b. Breath tests ... 8
c. Radiological based assessment of the liver function ... 8
d. Indocyanine green plasma disappearance rate (ICG-PDR) ... 9
e. Evaluation of the hepatic architecture ... 10
f. Imaging modalities: ... 12
g. Evaluation of the hepatic hemodynamic ... 13
h. Global live assessment of the hepatic perfusion, architecture, and excretory function ... 13
iii. Surgical disorders of the liver ... 14
iv. Role of chemotherapy in colorectal liver metastasis:... 16
ii
vi. Expanding the criteria for liver resection in colorectal liver metastasis: ... 20
a. Portal vein embolization and ligation... 20
b. Tumor progression after portal vein embolization in patients with colorectal liver metastasis ... 21
c. Two stage resection ... 22
d. ALPPS as a variant of the two-stage hepatectomy and variation ... 23
e. Single stage resection ... 23
vii. Liver regeneration ... 24
a. Phase I: The priming: ... 25
b. Phase II: The proliferation... 25
c. Phase III: The termination ... 25
d. Role of architecture in the regeneration process: ... 26
viii. The relation between hemodynamics and regeneration after resection ... 26
a. Necessity for increase in portal venous pressure/flow per unit volume ... 26
b. The role of portal vein arterialization and the theory of sinusoidal shear stress versus portal venous contents: ... 27
c. Small for size/flow syndrome ... 28
d. Limits of the safe increase in the portal venous pressure/flow ... 29
e. The portal flow modulation: ... 30
ix. Mathematical modeling and their role in liver research ... 31
II. Methods ... 33
i. Rationale of the layout ... 33
iii. Ethical approval... 34
iii
v. Study settings ... 34
vi. Description of the INRA ... 35
vii. Study design ... 37
viii. Housing and preoperative accomodation ... 39
ix. Anaesthetic protocol ... 40
x. Radiological protocols ... 42
a. CT scan and Volume analysis ... 42
b. Magnetic resonance based studies... 45
c. Fluorescence imaging:... 52
xi. Biopsy sampling ... 54
xii. Histology of the porcine liver... 58
a. Histopathological Analysis Protocol ... 58
xiii. Sacrifice ... 59
xiv. Statistical methods... 60
III. Results & Discussions: ... 61
i. Anatomy of the porcine liver and technical implications ... 61
a. Introduction to Hepatic Anatomy ... 62
b. Anatomical features... 62
c. CT scan depicted description ... 65
d. Implications ... 78
ii. Physiology... 89
iv
b. Evolution of the hematological parameters after different resection percentages: ... 97
c. Evolution of the blood gases parameters: ... 111
d. Hemodynamics ... 132
e. Kinetics of the hepatic volume evolution and the architectural changes following 75% resection ... 152
f. Normal ICG handling detected by live imaging ... 163
g. Changes following resection ... 165
h. Mortality and survival ... 168
iii. Clinical Application ... 171
i. Radiology ... 171
j. Software Applications ... 195
k. Flow Modulation Device ... 195
IV. Limitations and perspectives: ... 226
V. References ... 228
VI. Appendix ... 252
iv. MRI Elastography protocol ... 252
a. Context ... 252
b. Method ... 252
c. Results ... 252
d. Questions ... 261
VII. Abstrait ... 264
II. List of Tables:
Table 1: ‘Indirect’ serological markers for the prediction of liver fibrosis ... 12v
Table 2: The different common anti-cancerous classes in clinical use. Adapted from (115) ... 16
Table 3: Common chemotherapeutic regimens for colonic cancer. ... 18
Table 4: Examples of the known hepato-specific adverse effects of the commonly used chemotherapeutic agents. ... 19
Table 5: Total number of specimens collected from group 2-4 experiments ... 57
Table 6: The summary of the segmented lobar volumes in the studied animals ... 78
Table 7: Kidney and major electrolytes profile (samples collected from jugular vein) ... 90
Table 8: Arterial blood gases, PH and lactate levels ... 91
Table 9: Venous blood gases, PH and lactate levels ... 92
Table 10: Portal vein blood gases, PH and lactate levels ... 93
Table 11: Hepatic profile from samples collected from the internal jugular vein. ... 94
Table 12: major hematogram parameters in samples collected from the internal jugular vein. ... 95
Table 13: Hemoglobin and hematocrit levels measured in each sample type of gas analysis ... 96
Table 14: Calcium levels as measured by gas analyser in the arterial, venous and portal venous samples and the hepatic oxygen consumption and the net lactate production. ... 97
vi
Table 16: Descriptive Statisticsfor the evolution of hematological parameters following 90% liver resection ... 102
Table 17: Summary table of the available data on prothrombin time and activity. ... 105
Table 18: Descriptive statistics of the calcium levels in the blood gas samples... 111
Table 19: Summary of lactate level in both resection groups ... 115
Table 20: Oxygen tension (mmHg) in blood gases and its evolution in groups submitted to two different resection volume .. 119
Table 21: Oxygen saturation in blood gases and its evolution in groups submitted to two different resection volume ... 122
Table 22: Hepatic oxygen consumption levels in relation to the timing of liver resection. ... 124
Table 23: Evolution of the hemoglobin and haematocrit level in blood gases ... 126
Table 24: Summary of the normal pressure and flow parameters prior to clamping or resection. ... 132
Table 25: Evolution due to mechanical ventilation and heartbeat average and standard deviation. ... 133
Table 26: Hemodynamics measurements before and after resection. ... 140
Table 27: The different mass assumptions description of the total liver, left lobe, right lobe and median lobe. ... 143
Table 28: Summary of the evolution of the hepatic functions and flow parameters in the 75% resection group ... 157
Table 29: Examples from different animals with different DWI values at different time points in relation to surgery ... 174
vii
Table 31: The liver volume at each experimental time point for each resection %. ... 187
Table 32: Pre-hepatectomy data from both groups ... 211
Table 33: Different parameters measured after liver resection and on day-7 post-operative ... 213
Table 34: List of parameters quantified in 3D for bile canalicular network. ... 215
Table 35: The microarchitectural damage score for both groups. ... 220
Table 36: The main liver functions of the animals in both groups ... 223
III. List of Figures:
Figure 1: Illustration of typical hepatic segmental anatomy. ... 5Figure 2: Simplified scheme showing the components necessary for integral hepatic functions assessment ... 7
Figure 3: Schematic representation of the microarchitecture in healthy (top) and Cirrhotic (bottom) livers.. ... 11
Figure 4: Simplified scheme demonstrating the clinically relevant hepatic function assessment tests. ... 14
Figure 5: Tityus (c.1532), Michelangelo Buonarroti, Royal Collection, Windsor Castle, U.K. ... 24
Figure 6: Illustration of the various experimental models of liver regeneration. ... 32
Figure 7: One of the operating theatres at the INRA ... 36
viii
Figure 9: Flow chart demonstrating the workflow within the different iFLOW groups ... 38
Figure 10: Photograph demonstrating one animal during the CT scan images acquisition. ... 43
Figure 11: Screen shot showing the timing protocol for image acquisition during CT scan. ... 43
Figure 12: Hepatic arterial and portal venous segmentations using SyngoVia, Siemens. ... 44
Figure 13: 3D reconstructed images for planned a) 75% and b) 90% resection. ... 44
Figure 14: PC-MRI flow measurements. ROI on celiac aorta (lumen). ... 50
Figure 15: Fluorescence element of reference to normalize the measured intensities. ... 53
Figure 16: The four regions of interest are present, the liver tissue, the hepatic artery, the portal vein and the common bile duct ... 54
Figure 17: Intra-operative photograph depicting the post-resectional incisional biopsy. ... 56
Figure 18: photograph of an incisional biopsy immersed into 4% formaldehyde. ... 56
Figure 19: core needle biopsy with the deep end marked with Fuscin green. ... 57
Figure 20: A reconstructed image of the hepatic vascular anatomy.. ... 61
Figure 21: Branches of the celiac trunk and the hepatic artery... 70
ix
Figure 23: Volume rendering technique extracting the part of the arterial tree in relation to the portal vein. ... 72
Figure 24: Volume rendering technique extracting the part of the arterial tree in relation to the portal vein. ... 72
Figure 25: Intraoperative photo showing the minute arterial branch to the caudate lobe crossing over the portal trunk to the caudate lobe. ... 73
Figure 26: 3D ROI reconstruction for segmented portal and hepatic veins. ... 74
Figure 27: 3D ROI reconstruction for segmented portal and hepatic veins. ... 75
Figure 28: An intraoperative photo demonstrating portal venous branch crossing to the left lateral sector at the base of the fissure separating the left lateral from the right lateral sectors. ... 75
Figure 29: Cranial view of a 3D reconstruction of the segmented hepatic sectors showing the common trunk of draining the veins from the right lateral and one of two right medial sectors. ... 76
Figure 30: Caudal view of a 3D reconstruction of the five hepatic sectors showing their volume. ... 77
Figure 31: Neck incision with cannulated jugular vein (J) and carotid artery (ca), probes installed for flow measurements around (p) portal vein, (H) hepatic artery ... 82
Figure 32: technical aspects during liver resection ... 85
Figure 33: Tightening of the clamping tourniquet around the 75% mass ... 86
Figure 34: the passage of right angled clamp behind the first (a) and the second (b) portal pedicles ... 87
x
Figure 36: Box-plot with dots representing the alkaline phosphatase levels in both groups ... 106
Figure 37: Box-plot with dots showing ALT levels over time in both groups ... 107
Figure 38: Box-plot with dots showing ALT levels over time in both groups with the outlier excluded ... 107
Figure 39: Box-plot with dots showing Amonia levels over time in both groups. ... 108
Figure 40: Box-plot with dots showing AST levels over time in both groups. ... 108
Figure 41: Box-plot with dots showing Direct Bilirubin levels over time in both groups. ... 109
Figure 42: Box-plot with dots showing Total Bilirubin levels over time in both groups. ... 109
Figure 43: Box-plot with dots showing GGT levels over time in both groups. ... 110
Figure 44: Box-plot with dots showing the evolution of the prothrombin activity. ... 110
Figure 45: Box-plot with dots representing the evolution of calcium in the arterial system ... 113
Figure 46: Box-plot with dots representing the evolution of calcium level in the portal sample ... 113
Figure 47: Box-plot with dots representing the evolution of calcium level in the supra-hepatic venous sample ... 114
Figure 48: Box-plot with dots representing the evolution of lactate level in the arterial blood gas sample... 116
Figure 49: Box-plot with dots representing the evolution of lactate level in the portal venous blood gas sample ... 117
xi
Figure 51: Box-plot with dots representing the evolution of the transhepatic lactate level in groups ... 118
Figure 52: Error bar demonstrating the evolution of the ammonia level seen in the haematology samples. ... 118
Figure 53: Box-plot with dots illustrating the evolution of the oxygen tension in the arterial blood ... 120
Figure 54: Box-plot with dots illustrating the evolution of the oxygen tension in the portal venous blood ... 120
Figure 55: Box-plot with dots illustrating the evolution of the oxygen tension in the hepatic venous blood ... 121
Figure 56: Box-plot with dots illustrating the evolution of arterial oxygen saturation. ... 123
Figure 57: Box-plot with dots illustrating the evolution of portal venous oxygen saturation. ... 123
Figure 58: Box-plot with dots illustrating the evolution of hepatic venous oxygen saturation. ... 124
Figure 59: Box-plot with dots representing the evolution of hepatic oxygen consumption. ... 125
Figure 60: Pressures in mmHg over a few respiratory cycles before clamping or liver resection. ... 135
Figure 61: Flows in Liter/minute over a few respiratory cycles at the beginning of surgery, before clamping. ... 135
Figure 62: Pressure panel (a) showing the increase in the hepatic artery and portal venous pressures upon clamping, while the central venous and carotid artery pressures have not changed.. ... 137
Figure 63: Portal vein (a) and hepatic artery (b) flow per liver weight before and after 75% liver resection. ... 137
Figure 64: Box-plot demonstrating the amount of change in the different pressure values following the resection in each type of resection. ... 138
xii
Figure 65: Box-plot demonstrating the global reduction in the flow values following resection in the different groups. ... 139
Figure 66: Simplification of the dimensions of the mathematical fluid modelling. ... 141
Figure 67: Schematic representation of the 0D closed-loop cardiovascular and liver blood circulations. RCR block and liver lobe parameters are shown. ... 144
Figure 68: Pre-resection measurements vs simulation values in log/log scale, for each variable (unique color) ... 146
Figure 69: Measurements (full) and simulations (dash) at different states of the surgery: pre-resection, post-resection. ... 147
Figure 70: Screenshot of the observed hepatic arterial waveform before and after hepatic pedicle clamping ... 152
Figure 71: CT scan estimated liver volume in the peri-operative period ... 153
Figure 72: Portal vein (left) and hepatic artery (right) flow per liver volume ... 154
Figure 73: Histopathological analysis under light microscopy of the porcine liver ... 155
Figure 74: Boxplot representing the temporal change in the Ki67 and Bar diagram plotting the CD31 expression. ... 156
Figure 75: Normal fluorescence signal intensity curve in the four target ROIs ... 164
Figure 76: Fluorescence signal intensity curve after 75% resection in the four target ROIs ... 165
Figure 77: The fluorescence signal pattern after the 90% resection. ... 166
xiii
Figure 79: The fluorescence signal curve on the seventh postoperative day after 75% resection. ... 168
Figure 80: Biexponentional model fitting example using 9 b-values for parameter estimation, day-3 after resection. ... 173
Figure 81: Ki67 proliferative index in specimens taken at different time points. ... 175
Figure 82: 3D reconstruction of confocal microscopy images ... 176
Figure 83: Boxplot of the blood flow measurements in the celiac aorta (Qoc), portal vein (Qpv) and the hepatic artery (Qha) in the MRI (MR) and the transit time (TT). ... 177
Figure 84: Least square regression for PC-MRI and TT flow measurements. PC-MRI flow measurements. ... 179
Figure 85: Bland-Altman plot indicating the systematic difference between the flow reading in MRI and Transit time in the aorta... 180
Figure 86: Bland-Altman plot indicating the non-signifcant difference in estimation of the flow in the hepatic artery using either the MRI or the transit time method. ... 181
Figure 87: Bland-Altman plot revealing the systematic underestimation of the MRI flow readings compared to the Transit time flow readings. ... 182
Figure 88 Box-plot with dots representing the hepatic volume evolution in both groups. ... 188
Figure 89: Boxplot with dots representing the rate of hepatic mass recovery following resection in both resection %. ... 189
Figure 90: Axial CT scan image depicting the planned resected volume (blue), and the planned residual volume (pink) for 75% resection. ... 190
xiv Figure 91: Axial CT scan image depicting the recovered hepatic volume at day 3 following 75% resection (pink) and the
spleen in blue. ... 190
Figure 92: Axial CT scan image depicting the residual hepatic volume after a 90% resection (pink). The estimated volume is 114 cm3. ... 191
Figure 93: 3D reconstruction image at day 3 following a 90% resection with portal ring placement. ... 191
Figure 94: Coronal CT scan image at day 3 following a 90% resection with portal ring placement.. ... 192
Figure 95: Axial CT image at day 3 following a 90% resection with portal ring placement. ... 192
Figure 96: The MID-AVR™ in its different shapes according to the degree of balloon inflation. ... 201
Figure 97: Scatter diagram showing animal mortality in both groups stratified according to the change in portal flow per unit liver mass. ... 205
Figure 98: Porto-caval pressure gradient was significantly higher in the control group compared to the MID-AVRTM ... 206
Figure 99: Total bilirubin level was higher in the control group than in the MID-AVRTM group. ... 207
Figure 100: Biopsies taken from the control (left panel) and ring (right panel) groups . ... 208
Figure 101: Analysis of hepatocyte proliferation in regenerating pig livers ... 209
Figure 102: Analysis of hepatocyte proliferation index in regenerating pig liver. ... 210
xv Figure 104: CT scan volumetry of the hepatic remnant and evolution in 90% resection ... 222
Figure 105: The junction between the valve and the tube is showing small leak ... 225
IV. List of Equations
Equation 1: Intravoxel incoherent motion ... 45
Equation 2: The phase difference ... 47
Equation 3: The hepatic O2 consumption ... 51
Equation 4 : The hepatic net lactate production ... 51
Equation 5: 1D Model equation ... 151
Equation 6: The estimate of bias between both measures using Bland-Altman method ... 180
Equation 7: The estimate of bias in the transit time measurement ... 181
V. Preface
This work is the culmination of the scientific wealth of the Unité Inserm 1193 (Hôpital Paul Brousse, Villejuif – Directeur Pr.
D. Samuel) under the supervision of Prof. Eric VIBERT. This project is one of many projects that target the improvement of
xvi A unique feature of this project is its multidisciplinary nature. It encompassed the collaboration of Surgeon, the Paul Brousse
Team represented by Eric Vibert, CHU Tours represented by Petru Bucur, and me, mathematicians, the INRIA of Paris teams
represented by the group REO of J-F. Gerbeau, I. Vignon-Clémentel, and C. Audebert and the team MAMBA represented by
D. Drasdo, and N. Boissier with their contribution and expertise in developing mathematical models to predict the interaction
at a multiscale level, which has the potential of being integrated into software applications, hapato-scientists from IFADO in
Dortmund, Germany represented by J. Hengstler, B. Begher-Tibbe, S. Hammad, and A. Othman whose contribution was
unique in developing staining protocols and three dimensional imaging of the hepatic microarchitecture, the team from
Fluoptics France, represented by S. Guillermet, P. Rizo, A. Daures whose contribution targeted the development of novel
algorithms to precisely estimate the live fluorescence signal and its interpretation, and the team from MID France, led by
Ludovic Cazenave with their novel device for portal flow modulation. The project was granted financial support from TecSan
de l’Agence Nationale de Recherche en 2013 (ANR-13-TECS-0006, iFLOW project). With this large scientific power, this
collaboration was fruitful in achieving many of the proposed objectives.
Lastly, I am overwhelmed with the sincere mentorship I received during the entire working time from Professor Eric Vibert.
The story of me joining the project and the University to obtain this degree is something that I would remember for life.
Notably, the guidance and help I received from my honest and kind colleague; Petru Bucur, who transferred to me his
considerable experience in the porcine hepatic surgery. I do not think I will be able to forget those few years I spent learning
from him. I will not overlook the support I got from the INRA team and their collaboration to make the work flows smoothly
and without much of a hassle.
There are too many people – to whom I am grateful – to mentioning by name. However, I must acknowledge the support I got
from the mathematicians; Irene is on the top of the list. She was one of the reasons this work is walking to see the light. I am
also grateful to Dr. Seddik Hammad and Noemie Boissier who guided me through the microarchitecture work.
xvii Aberdeen 2017
xviii
VI. Translational statement:
The liver has a remarkable capability to regenerate. However, patients undergoing liver surgery often suffer from liver diseases
accompanied by a significant reduction in liver function and regenerative capacity. Postoperative liver failure is the main cause
of short-term mortality (around 5% at 3 months after surgery) after hepatectomy (5000 / year in France) due to insufficient
functional liver mass. Today, limits of liver surgery and partial liver transplantation are based on empiric minimal acceptable
liver volume that is preoperatively defined on volumetric reconstruction using CT-scan. These limits are defined according to a
priori ratios between liver volume and liver function that depend on the quality of liver parenchyma and the therapeutic
situation. However, the evaluation based on these threshold values fails if it leads to important modification of the hepatic
hemodynamics. Porcine model is one of the extensively used models for study of liver regeneration and factors implicated in
the regeneration. The study of porcine liver regeneration – among other areas – is based on the similarities to the human
anatomy and physiology. Therefore, the results of these studies are closely applicable to humans.
The primary objective of this project is to investigate the mechanistic interplay between the hemodynamic changes of the
hepatic inflow and the post-resection failure and regeneration. The understanding phase is designed using various tools, which
are commonly used in the clinical practice in order to obtain a valid translational value from this work. In addition to
understanding the pathophysiology; we targeted the deployment of novel prediction tools that will enable the hepatic surgeons
to anticipate with precision the clinical consequences of the required liver resection highlighting instead the feasible and safe
resection. Moreover, the project aims at examining the role of a newly invented intervention device to enhance the hepatic
microarchitecture integrity – a vital mediator for the proper liver function – subsequently improving the quality of the
regenerating parenchyma after major liver resection.
The study protocol was designed in a staged fashion to enable goals achievements. In this regards, animals were allocated to
xix · Group 1: composed of randomly allocated animals to undergo 75% liver resection with or without the application of the
adjustable vascular ring around the portal vein. This group consisted of 17 animals, of them 8 animals underwent liver resection
and ring placement and 9 animals underwent only liver resection. This allocation targeted the study of the safety and the efficacy
of the vascular ring in ameliorating the hepatic function and regeneration following this type of hepatectomy.
· Group 2: consecutive series of 16 animals that underwent 75% resection with 7th day sacrifice protocol. This allocation targeted
optimization of the invasive hemodynamics monitoring of the porcine model while conducting liver resection, which would
allow building up accurate predictive mathematical models at multi-scale level and investigating the role of ICG (indocyanine
green) in in-vivo evaluation of liver function during major liver resection.
· Group 3: composed of consecutively allocated animals to undergo 90% resection with and without the application of the adjustable vascular ring around the portal vein. This group consisted of 6 animals, of them 3 animals underwent 90% liver
resection with the application of the vascular ring around the portal vein and 3 animals underwent only liver resection. This
allocation targeted the study of the efficacy of the vascular ring in ameliorating liver function and regeneration following this
potentially lethal liver resection.
· Group 4: consecutive series of 6 animals that underwent 75% liver resection with 3rd day sacrifice protocol. This allocated
targeted the investigation of early volume and histopathological changes.
Originality and goals
The specific goals of this project are
1) Study the volume evolution in association with the hemodynamic and biochemical changes induced by surgery.
2) To evaluate the potential of an implantable surgical device able to modulate the portal hemodynamics to improve their
xx 3) To develop a mathematical model relating blood liver perfusion, architecture and function to assess the fluorescence signal
obtained in (1) with regard to potential liver failure and to predict the likely effect of treatment by an adjustable ring as in (2).
The model will address three levels, the whole organ level by a compartment model (macro scale), the tissue scale in which
larger vessels are represented while flow between them are mimicked by a porous media approach (meso scale) and the lobule
level in which the detailed architecture of the individual liver lobule, the smallest repetitive functional unit of liver, is
represented (micro scale). The parameters of the meso scale will be calibrated with those on the micro scale, the parameters of
the macro scale with those on the meso scale.
The main findings:
1. The technique we developed to resect the porcine liver is simple and efficient for both 75% and 90 % resection.
2. An accurate CT based anatomy as well liver volume estimation of the porcine liver is now available.
3. A critical description of the surgical anatomy of pigs to enable safe surgery and monitoring of the hemodynamic
parameters is now available.
4. A protocol to perform diffusion weighted imaging- MRI (DWI-MRI) on regenerating porcine liver is now optimized.
5. A comparison between the MRI estimated hepatic blood flow and the transit time based estimates revealed that the MRI
tends to underestimate the flow values compared to the transit time. However, the MRI values are also valid.
6. The 75% resection is unlikely to cause liver failure.
7. 90% resection is generally lethal.
8. The portal ring has promising potentials in modifying the lethal outcome of the 90% resection.
9. The porcine liver regains the majority of its resected mass during the first 3 days
10. Explanatory hemodynamic mathematical models have been constructed
Pending work and perspectives:
xxi 2. Optimization of the fluorescence model to enable predictive interpretation prior to resection.
xxii
VII. List of publications
Journal Articles:Published
1. Bekheit M, Bucur P, Vibert E, Andres C. The reference values for hepatic oxygen consumption and net lactate
production, blood gasses, hemogram, major electrolytes, and kidney and liver profiles in anesthetized large white swine
model. Transl Surg 2016;1:95-100
2. Bekheit M, Bucur P, Wartenberg M, Vibert E, Computerized tomography based anatomical description of the porcine
liver, Journal of Surgical Research (2016), doi: 10.1016/j.jss.2016.11.004.
3. Bucur P, Bekheit M, Audebert C, V-Clemente I, Vibert E. Simplified technique for 75 & 90 resection of porcine liver
with hemodynamic monitoring. Accepted Journal of Surgical research.
4. Bekheit M, Bucur P, Audebert C, Othman A, Hammad S, Cazenave L, Dirk Drasdo, Jan G. Hengstler, Irene
Vignon-Clementel and Eric Vibert. New Technique for Portal Flow Modulation in Porcine Major Liver Resection. Clin Surg.
2016; 1: 1219
5. Bucur P, Bekheit M, Chloe´ Audebert, Amnah Othman, Seddik Hammad, Mylene Sebagh, Marc-Antoine Allard,
Benoıˆt Decante, Adrian Friebel, Dirk Drasdo, Elodie Miquelestorena-Standley, Jan G. Hengstler, Irene Vignon-Clementel, Eric Vibert. Modulating Portal Hemodynamics With Vascular Ring Allows Efficient Regeneration After
xxiii 6. Chloe Audebert, Bekheit M, Petru Bucur, Irene Vignon-Clemente, Eric Vibert. Partial hepatectomy hemodynamics
changes: experimental data explained by closed-loop lumped modeling. Journal of biomechanics.
http://dx.doi.org/10.1016/j.jbiomech.2016.11.037
7. Chloe Audebert, Petru Bucur, Bekheit M, Eric Vibert, Irene Vignon-Clementel, et al.. Kinetic scheme for arterial and
venous blood flow, and application to partial hepatectomy modeling.. Computer Methods in Applied Mechanics and
Engineering, Elsevier, 2016, <10.1016/j.cma.2016.07.009>. <hal-01347500>.
8. Bekheit M, Bucur P, Vibert E. The ideal porcine model for major liver resection, is there any yet?. J Surg Res. 2017
Mar 7. pii: S0022-4804(17)30132-4. doi: 10.1016/j.jss.2017.03.00
Submitted:
9. Bekheit M, Petru Bucur, Audebert C, Miquelestorena-Standley E, V-Clemente I, Vibert E. Hepatic volume evolution
after major resection in a porcine model: an insight on the correlation between the volume increase and the pathological
changes.
10. Bekheit M, Petru Bucur, Audebert C, Adriaensen H, Bled E, Wartenberg M, , V-Clemente I, Vibert E Validation of the
hepatic and aortic blood flow values measured using phase contrast MR imaging using transit time perivascular probes
in a porcine model.
11. Chloe Audebert, Petru Bucur, Bekheit M, Eric Vibert, Irene Vignon-Clementel. Impact of 75% partial hepatectomy
xxiv 12. Noemie Boissier, Chloe Audebert, Bekheit M, Petru Bucur, Eric Vibert, Irene Vignon-Clementel.
Mathematical modeling for quantifying the impact of micro-architectural changes on hepatic and systemic
hemodynamics: insights after partial hepatectomy.
Book Chapter:
13. Bekheit M; Vibert E: Fluorescent guided liver surgery: Paul Brousse experiences and perspective. in Concepts and
Applications of Fluorescence Imaging for Surgeons (Dip and Ishizawa), Springer 2015, X pages 415
Conference proceedings:
14. C Audebert, P. Bucur, Bekheit M., E. Vibert, J-F. Gerbeau, I. E. Vignon-Clementel. Mathematical modeling of liver
hemodynamics during partial liver ablation. EUROMECH Colloquium 595: Biomechanics and computer assisted surgery
meets medical reality 29-31 August 2017, Centrale Lille, Villeneuve d’Ascq, France
15. Hans Adriansen, Bekheit M, Chloe Audebert, Petru Bucur, Eric Vibert. Elastographie par Résonance Magnétique sur
porcelet: méthode alternative et rapide pour vérifier la résistance hépatique, utilisée conjointement avec le calcul de
débit sanguin. Gen2bio 26/3/2015 La Baule, France.
16. Chloe Audebert, Petru Bucur, Bekheit M, Irene Vignon-Clement, Eric Vibert, Jean Federic. Cardiovascular closed-loop
1
I. Introduction
Major liver resection (partial hepatectomy) is being performed to treat liver lesions or for adult-to-adult living donor liver
transplantation. Due to liver regeneration, during the postoperative period lasting a few months, the patient regains a normal
liver mass. The major complications of these surgeries are postoperative liver failure (after partial hepatectomy) and
small-for-size syndrome (after partial transplantation). Both complications are related to a poor liver function. The links between liver
hemodynamics, liver volume, and liver function remain unclear and are necessary to understand these complications better.
The surgery increases the resistance to blood flow in the organ. Therefore it modifies liver hemodynamics. These changes are
difficult to understand, partly because the liver receives arterial (through the hepatic artery) and venous blood (through the
portal vein). Large modifications of the portal vein hemodynamics have been associated with poor liver regeneration.
Moreover, the liver receives 25% of the cardiac outflow. Therefore liver surgery may impact the whole blood circulation.
In this context, the first goal of this thesis is to investigate with mathematical models the impact of liver surgery on liver
hemodynamics. The second goal is to study the liver perfusion and function with mathematical models of the transport of a
compound and its processing by the liver. Data is required to build and verify these mathematical models. Therefore, liver
resections were performed on pigs, during which various pressures and flows were recorded. Moreover, indocyanine green, a
dye exclusively eliminated by the liver into the bile, is intravenously injected before or after liver resection and its fluorescence
is measured.
The first part of this thesis describes the experimental conditions and reports the measurements recorded. Then, the second part
focuses on the liver hemodynamics during partial hepatectomy. On the one hand, the hemodynamics during several surgeries is
quantitatively reproduced and explained by a closed-loop model based on ordinary differential equations. The closed-loop
model has enabled to take into account blood volume changes occurring during liver surgeries. On the other hand, the variation
2 0D and 1D equations. This may contribute to a better understanding of the change of liver architecture induced by
hepatectomy.
Next, the transport in the blood of a compound, as well as the indocyanine green processing by the liver, is studied. The 0D
and 1D equations model the dynamics of a compound from its intravenous injection to when it reaches the hepatic artery and
the portal vein. The results are compared to the indocyanine green fluorescence measurements. A new framework is
established to analyze indocyanine green fluorescence dynamics quantitatively. It consists in the development of a specific
pharmacokinetics model and its parameter identification. The aim is to provide a novel estimation of the liver function(s)
peri-operatively using indocyanine green fluorescence measurements.
The modulation of portal vein hemodynamics may protect the liver and improve the regeneration, as the portal hemodynamics
impacts the regeneration. The two topics of this thesis aim at improving the efficacy of a medical device controlling portal vein
hemodynamics (vascular ring MID-AVRTM). Knowing the hemodynamics evolution during liver surgery enable to know how
to modulate these hemodynamics with the ring. Moreover, the ring efficacy could be controlled by the indocyanine green
fluorescence measurements to quantify and thus evaluate the liver function intra-operatively. This thesis can be seen as the first
step to reach the final goals.
Understanding the organ development is crucial to comprehend the underlying mechanisms of liver regeneration following a
hepatic mass loss. The liver originates from the endoderm of the ventral bud of the foregut tube which originates from the
embryonic ventral streak. Embryonic stem cells migrate into this streak to form the definitive endoderm that further constitutes
the foregut after rotation. The embryonic stem cells (Sox17+ cells) develop from this line giving the hepatobiliary pancreatic
progenitor cell line that further gives pancreatic progenitor cells and hepatoblasts (1).
Their specification into hepatoblasts requires, among others, the endothelium (2). Endothelial cells were found significant in
the development of the liver bud and their ablation, as in VEGF receptor deficient mice, intervenes with the development of
3 Following their specification, these bipotential hepatoblasts proliferate and differentiate into hepatocytes and cholangiocytes
and express hepatocyte (αFP, albumin) and cholangiocyte (CK19) markers. Maturation is known by the expression of albumin by the hepatocytes, while the commitment of the hepatoblasts to the hepatocytes cell line is represented by the expression of αFP (3).
A subpopulation of stem cells exhibits different markers compared to the hepatoblasts (negative for albumin and αFP and adult liver cell marker [cytochrome P450s] but positive for CD34, CD133) with different characteristics where they are capable of
150 population doubling and generation of hepatoblasts (4).
The embryonic ductal plate goes into remodeling to become the canal of Hering in pediatric and adult liver (5). The
intrahepatic biliary ducts develop from the periportal hepatoblasts (6). The elongation of the hilar hepatic duct forms the large
intrahepatic biliary ducts and the peribiliary glands. The caudal part of the hepatic diverticulum connected to the foregut tube
forms the extrahepatic biliary tract and the ventral pancreas (7).
Multiple stem cell niches persist in the adult life in specific locations. Biliary stem cells are located in the peribiliary glands
around the large intrahepatic and extrahepatic biliary tree, hepatic stem cells located near or in the canal of Hering, and the
pancreatic stem cells confined to the biliary tree (6). During hepatic regeneration following injury, the oval cells residing in the
biliary radicles plays a major role in restitution of hepatic cell mass by giving rise to hepatocytes (8). In humans, the
cholangiocytes develop from the hepatoblasts located near the portal vein, while those located at a distance from the portal
vein give rise to the hepatocytes (9). Upon maturation, hepatocytes form a heterogeneous cell population which is
characterized by their different zonal metabolic characteristics (10).
The hepatic stellate cells are derived from the embryonic septum mesothelium (11). Since they express germinal markers
similar to those arising from the three germ layers, it is possible that these cells are derived from multiple sources or have a
pluripotent potential. They are located in the space of Disse representing a major constituent of the hepatic non-parenchymal
4 myofibroblasts. Their activation and quiescence are dependent on the Wnt pathway, and the knockout of B-catenin resulted in
the development of activated stellate cells (a-SMA-expressing) with dilated sinusoids (12). They are also involved in the
differentiation of hepatocytes as well as recruiting non-hepatocyte hematopoietic cells into fetal hepatic cells (13).
The kupffer cells that reside in the sinusoids and constitute around 15 % of the hepatic cells (14) are thought to have a driving
influence on the bipotential progenitor cells to undergo hepatocyte development (15).
In Zebrafish model, cells of biliary origin participated in hepatocyte formation following extensive hepatocytes loss (16). The
transdifferentiation of hepatocyte to biliary epithelium was seen in a rat model where hepatocytes contributed to the restoration
of biliary epithelium after a massive loss (17).
i. Anatomy of the liver
The normal adult human liver weighs between 968- 1860 grams (18). It receives – uniquely – a dual blood supply with 75%
from the portal vein and 25% from the hepatic artery (19,20). Based on the further divisions of the portal vein, the liver is
divided into two hemilivers (first order branching), further divided into four sections (second order branches) and 9 segments
(third order branches) (21). The segmental division of the liver has been illustrated in Figure 1.
A further ramification of the portal vein and the hepatic artery take place to a microscale level interlacing the hepatic cords –
composed of hepatocytes intervened by bile canaliculi and spaces of Disse – to form the micro-unit of the liver (22). Two –
commonly used – but different descriptions of the smallest unit exit. The hepatic lobule is organized in a hexagonal fashion
with six portal vein ramifications representing its outline and a central vein located at the center of this hexagon. This follows
the macroscale anatomical description as an extension of the portal based subdivisions of the organ (23). Each lobule is
subsequently divided into 6 sinusoidal segments or plates (24).
On the other hand, the acinus division seems to be more functional than anatomical (10). In this divisional concept, the unit is
5 functional units is supported – from the functional perspective – by studies addressing the different gene and metabolic
functions expressions in the different zones (at various distances) from the portal branch (25).
The previous description was largely based on two-dimensional structural stains. Further, in depth analysis of the ultrastructure
of the liver units suggests a more complex formation. In three dimensional analysis of the porcine hepatic unit structure,
fibrous connective tissue was found to surround the lobule in two different patterns (simple and compound) (26).
A modular structure of the hepatic micro-organization has been proposed relatively recently by Teutsch et al. initially in rats
(24) then in humans to describe the variability in the dimensions and size of the liver units (27). The modular unit is composed
of a secondary lobule that contains around 14 lobules of different dimensions surrounded by a portal vascular tree connected
and draining into a sublobular vein (27). The main interest of this information is that it shows the limited likelihood of
obtaining information representative to the truth from only a two-dimensional scan. Therefore, complex systems of scanning
and analysis have to be developed for better understanding of the normal histology and pathologic anatomy.
Figure 1: Illustration of typical hepatic segmental anatomy where segments are indicated with Latin numbers. Portal vein in green and the vena-cava in blue receiving the main hepatic veins in blue as well.
6
ii. Assessment of the hepatic functions
a. Biochemical assessment
The liver is a unique organ from several perspectives. Apart from the complex anatomy that was only revealed in the 1950s,
the complexity of its functions makes it difficult to test. The hepatic functions depend on an equilibrium among the blood
supply, architecture, and intrinsic functions as simplified in Figure 2. The liver has various functions that are broadly classified
into synthetic, storage, detoxification, and excretory functions. The relevant matter to this manuscript is the lack of a single
summative laboratory test that could be useful in depicting the hepatic dysfunction (28).
Therefore various methods are concurrently used in the assessment of the hepatic functions. The traditional system proposed
by Dr. Child and Dr. Turcotte from University of Michigan (29) was modified by Dr. Pugh (30) and has remained in use until
today.
In essence, the Child-Turcotte-Pugh (CTP) scoring grades the different major hepatic functions (efficiency of portal flow via
the presence of ascites, detoxification via the presence of encephalopathy, the excretory function via the serum bilirubin level,
and the synthetic function with prothrombin and albumin levels) in one system. This system scores high as a prognostic index
for mortality following interventions for portal hypertension, albeit, superseded by a newer model of end stage liver disease
(MELD score) (31). Nonetheless, the MELD score did not show superior performance over the CTP in the setting of liver
transplantation (32). This demonstrates the complexity of the assessment process and confirms that there currently is no one
system that could be used solely for as a prognostic marker for the different procedures or disease conditions. Of note, the
traditionally known hepatic functions tests (AST and ALT) could be of diagnostic value in some conditions (33) but not of
7 Figure 2: Simplified scheme showing the components necessary for integral hepatic functions assessment and some examples of their common methods of assessment. Each of these methods could express more than one function.
8 A more advanced set of tests was deployed over the years aiming at a more precise assessment of the liver function in a
quantifiable manner suitable for the modern complexity of disease and treatment (36). These tests use at least one hepatic
specific substrate that is cleared from the circulation by hepatic uptake and excretion, metabolism, or both (37). These
substrates could be exogenous (e.g., indocyanine green), natural (e.g., caffeine), or endogenous (e.g., bile). This implies that
the measure of a hepatic function using these substrates will depend on the hepatic clearance capacity determined by the
hepatic flow, the efficiency of extraction, and the hepatocytes metabolism capacity.(36).
This will naturally classify the hepatic clearance rates of substances into high and low. Thus, those with high extraction – the
indocyanine green – could be sensitive to the changes in the hepatic perfusion (38,39) as opposed to those with a low clearance
which could be more susceptible to the metabolism (40).
b. Breath tests
The fundamental principle of breath test based assessment of liver functions is that an ingested substrate is metabolized in the
liver and exhaled via the respiratory system (41). 13C-phenylalanine (PheBT) and 13C-galactose (GBT) breath tests
noninvasively assess the hepatic function by measuring the activities of two enzymes that are localized to the hepatocellular
cytosol (41).
A 13C-methacetin elimination cytochrome P45 breath test was used in a LiMAx test to assess the maximum hepatic function
(primary non-function) in a transplantation setting with a sensitivity and positive predictive value of 1 (42). The test ability to
predict the outcome of liver resection was also investigated and have shown promising with possible risk stratification ability
as well (43). The LiMAx test showed superior predictive value – of morbidity and mortality – to the Indocyanine green plasma
disappearance rate (ICG-PDR) in a setting of sepsis related hepatic dysfunction (44).
9 The role of imaging in the evaluation of hepatic function is growing. A combination of SUV mean from a PET/CT and the
AST/Platelet index (APRI) showed a high accuracy in predicting the hepatic insufficiency in patients who underwent liver
resection (45). The MRI scans showed potentials for not only the global assessment but also for segmental functional
assessment based on the signal intensity in hepatobiliary phase (46). Different techniques were utilized in the MRI based
imaging to obtain a better sensitivity as in the Volume-assisted MR relaxometry technique, which showed better performance
than MR relaxometry (47). It seems that the dynamic contrast studies could have potentials in the non-invasive quantitative
assessment of hepatic functions (48).
d. Indocyanine green plasma disappearance rate (ICG-PDR)
The role of indocyanine green in the evaluation of liver function was developed in the past century (49). The invasive serial
measurement of the plasma disappearance rate remains the gold standard for measurement despite the development of newer
tools for both invasive and non-invasive measurement (49).
Clinically, the ICG-PDR has an established role in the assessment of hepatic functions in various settings (49). It has a value in
the evaluation of the intrinsic hepatic uptake function in cirrhosis as the primary determinate of the reduction of the plasma
clearance rate (50). Besides, it has also an established role in the preoperative assessment and indication of surgery algorithms
in cirrhotic patients (51), as well as in non-cirrhotic patients (52).
The indocyanine green is an organic anion dye that is exclusively eliminated by the liver. In human livers, the sinusoidal
transport is mainly mediated by the organic anion transporting polypeptide (OATP), whereas canalicular efflux is mediated by
the multidrug resistance associated protein (MRP2) and the multidrug resistance P-glycoprotein (MDR3) (53).
The ICG-PDR provide a promising global assessment of the hepatic perfusion, uptake, and excretion. However, the
contribution of the hepatic uptake and excretion mechanisms leading to disappearance rate is poorly understood in the in-vivo
10 of the indocyanine green elimination rate in assessment of the hepatic functions – not only the perfusion and excretion
parameters – is related to competitive inhibition by the hyperbilirubinemia state resulting in the assessment of some of the
energy based hepatocytes activity (55).
Mathematical models were deployed to discriminate the contribution of the different compartments – sinusoidal flow,
hepatocellular uptake, and biliary excretion and their reflection on the overall hepatic functions (56). Despite the plausible
understanding that these models provide, their primary role remains theoretical and perhaps in applied technology for software
applications. Beyond that, the fluorescence characteristics of the ICG were found to be clinically useful in the assessment of
the hepatic function (57). It was also used for the detection of tumors (39,58) and biliary surgery (59).
Currently, there is a need for an optimized in vivo assessment of the multi-parameter hepatic function, which could potentially
be provided by an optimized use of the fluorescence characteristics of the indocyanine green (38).
e. Evaluation of the hepatic architecture
The most obvious example of the importance of the integrity of hepatic architecture to the function is seen in liver cirrhosis
(60). The bridging fibrosis will reduce the functional sinusoidal surface area and creates a variety of intra- and extra hepatic
shunts as presented in Figure 3. There are several structural and functional changes observed in colorectal liver metastasis
without chemotherapy, which ultimately lead to a degree of vulnerability of the parenchyma (61). It was noted that the
development of sinusoidal obstruction syndrome – irrespective of the cause – significantly leads to hepatic function
impairment and at least partial mechanism is attributed to the structural alteration (62,63) and makes it susceptible to
post-hepatectomy failure (64). This leads to change in the operative strategies and increased the minimum safe remnant liver
11 Figure 3: Schematic representation of the microarchitecture in healthy (top) and Cirrhotic (bottom) livers. The functional
sinusoidal area is significantly reduced with the rearrangement of the lobule. H.A: hepatic arteriole, P.V: portal venule, H.V:
Hepatic venule, F.S: functional sinusoid, C.S: capillarized sinusoid, I.H.S: intrahepatic shunt, and E.H.S: extrahepatic shunt.
Liver biopsy remains the gold standard evaluation tool of the hepatic architecture (66). Controversies, however, exist on the
definition of the adequacy of samples and the representation of the scoring systems in use as these scores are mostly qualitative
(67). Moreover, it is not complication free (68). Collagen proportionate ratio is an example of quantitative assessment
modifications implemented in the evaluation of liver fibrosis. There is potentially significant inhomogeneity in the hepatic
architecture in the two-dimensional analysis (66) for which a three-dimensional analysis was utilized (69) and showed
reproducibility but also demonstrated the important regional variability of the microarchitecture (26).
Novel invasive tools have also been tried in an attempt for in-vivo live analysis of the hepatic architecture. The confocal needle
endomicroscopy showed a reasonable discriminative ability to distinguish cirrhosis from normal architecture in animals with
no significant role in a clinical setting till now (70). Less invasive biopsy (the transjugular) was used as an alternative to the
percutaneous biopsy aiming to reduce the potential complications – particularly in ascites – with a comparable diagnostic
12 in microarchitecture as alternatives to the invasive tools (72). Several serological markers were used in an attempt to estimate
the degree of fibrosis (73). Some examples are listed in Table 1.
Table 1: ‘Indirect’ serological markers for the prediction of liver fibrosis
Name Parameters Sensitivity/Specificity
PGA index (74) Prothrombin index, gGT, apolipoprotein A1 91/81 PGAA index (75) Prothrombin index, gGT,
apolipoprotein A1, a2-macroglobulin
79/89
Fibrotest (76)
a2-Macroglobulin, haptoglobin, g-globulin, apoliprotein A1, bilirubin
75/85
Forns fibrosis index (77)
Age, platelet count, gGT, cholesterol 94/51
APR index (78) AST/Platelet ratio 89/75 GPR index (79) GGT/Platelet ratio 79/58 f. Imaging modalities:
Fibroscan – which is an ultrasound based elastography – is perhaps one of the most widely studied imaging modality to assess
the hepatic fibrosis (80). The combined use of fibroscan and fibrotest is shown to estimate similar value to the liver biopsy in
post-13 hepatectomy liver failure (82). Assessment of the microarchitecture using in-vivo fluorescence imaging showed promise in
evaluating the reperfusion injury of the transplanted grafts but yet to be quantified (39). Ex-vivo fluorescence based photon
microscopy 3D images are also useful for the quantification of the architectural parameters (83).
Diffusion weighted MRI was used to assess the hepatic microarchitecture and liver fibrosis (84). Ultrasound spectrometry was
also used to characterize the tissue ultrastructure (85). Novel methods, utilizing the contrast enhanced ultrasound, were
developed to visualize the hepatic vascular architecture in-vivo with accuracy (86). However, none of these tools was yet taken
into the clinical setting of surgical resection. The relatively new field of the assessment of the microarchitecture is the
mathematical and computational models (87).
g. Evaluation of the hepatic hemodynamic
The clinical significance of the assessment of liver hemodynamics has been a subject of extensive research and ubiquitous
correlation (88). Various methods – invasive and non-invasive – have been proposed to assess the hepatic hemodynamics.
Interestingly, a substance like the D-sorbitol was found to have a higher hepatic clearance compared to indocyanine green with
an elimination rate that is closer to the sinusoidal plasma flow (89). These findings were reproducible in volunteers with
temporary, drug induced reduction in the hepatic circulation with high accuracy (90). As mentioned above, most of the
substrates used for assessment of perfusion are useful for the assessment of the hepatic perfusion with different degrees.
h. Global live assessment of the hepatic perfusion, architecture, and excretory function
The majority of the above-described assessment methods cover one or more of the essential parameters in assessing the hepatic
function. However, none of them is suitable for an across parameter evaluation in an instant live situation.
Due to the high complexity of the liver functions, it is currently not feasible for a single test to precisely assess the entire set of
functions. Substance clearance rates remain representative for the dynamic global assessment of hepatic function without
14 persists in the available methods (91). The main reason for which no predictive model has a universally good performance is
that all there models do not have the capacity to assess the complex function. However, there is a general agreement that the
assessment tool could be either dynamic or static as simplified in Figure 4 (55). Moreover, assessment of the segmental
function of the liver was found to be helpful to avoid overestimation of the remnant potentials to recover (92). It was
demonstrated that the dynamic function tests are more reliable in the prediction of the postoperative course compared to the
static tests (93). Functional assessment of the Asialoglyprotien receptor was found to have an excellent prediction of the
postoperative course using 99mTc-GSA SPECT/CT, with a sensitivity and specificity of 100 and 92%, respectively (94).
However, a combination of tests is the common and the standard of practice for the time being (95).
Figure 4: Simplified scheme demonstrating the clinically relevant hepatic function assessment tests. Adapted from De Gasperi
2016 (55).
iii. Surgical disorders of the liver
The surgical disorders of the liver can be classified into disorders treatable by resection of some form, replacement via
