Factors Affecting Liver Regeneration in Donors’ Grafts in Living Donor Liver Transplant (LDLT). A Center Experience.

Factors Affecting Liver Regeneration in Donors’ Grafts in Living

Donor Liver Transplant (LDLT). A Center Experience.

Morsi Mohamed,1 MD; Wael Mansy,1 MD; Yehia Attwa,2 MD; Magdy Amin,3 FRCS; Karim Boudjema,4 MD.

1) General Surgery Department, Zagazig University.

2) General Surgery, Dean of Faculty of Medicine, Zagazig University.

3) Liver Transplant Unit in Hepato-biliary Department, El-maadi Armed Forces

Hospital.

4) Liver transplantation team in El-Maadi Armed Forces hospital. Professor of

Hepato-Biliary Surgery and Liver Transplant, Rennes University, France.

Background: Liver regeneration for donors’ graft in living donor liver transplantation (LDLT), is an example of liver regeneration in normal liver. In this study we spotted the light on liver regeneration in donors after LDLT, focusing on factors affecting it. Aim: To study the impact of different factors on liver regeneration in donors of living donor liver transplantation.

Patients and methods: Between May 2009 and June 2013, 80 living donor liver transplants were performed in the liver transplant unit in EL-Maadi Armed Forces Hospital. All donors who provided liver grafts underwent volumetric spiral computed tomography (CT) scans preoperatively and postoperatively at time intervals of 1week and 1,3 and 6 months. Patients’ demographics, surgical data, and postoperative outcomes were correlated with liver regeneration data. 63patients were males and 17 patients were females, with mean age 27.97yrs ±5.3. They provided {72} right lobe (RL) grafts and 8 right posterior sector (RP) grafts.

Results: No donor operation was aborted and surgical morbidity rate was {33.75%}, mostly biliary. All RP donors achieved complete liver regeneration after 3 months; only four RL donors achieved complete liver regeneration at 6 months.

Conclusion: In this study, it was found that there were factors affecting regeneration like age, gender of the patient and graft size. But no effect was found with many factors as peri- operative liver function tests, steatosis, BMI, operative time, blood loss, blood transfusion and postoperative complications.

Key words: Liver transplantation, liver regeneration, living donors.

Introduction:

Liver transplantation is one of the most effective  ways  of  treatment  for  many patients   with   liver   failure   whatever   the cause. It gives a strong impact on the patient outcome.1 Over the past 15 years LDLT had been  used  and  developed  tremendously.2

Liver regeneration is critical in adult living donor   liver   transplantation   (LDLT),   and size considerations affect the selection of appropriate donor and recipient pairs.3 Single center  studies  have  shown  that  recipients

have rapid liver regeneration but that many donors do not regain total liver volume, even after 1 year.4

Normal liver regeneration is a complicated process  as  it  depends  on  the  activation of more than one hundred genes and involvement  of  numerous  growth  factors.5

Portal hemodynamics, vascular outflow, graft to recipient weight ratios (GRWR), humoral factors, and graft quality have all been implicated  in  affecting  liver  regeneration. Left lobe donors provide even smaller grafts,

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and  makes  the  procedure  potentially  safer for the donor but increases the risk for the recipient.6,7

This process is highly effective, after hemi- hepatectomy and liver donation; the volume and function of the liver are largely restored after two or three weeks, and completely after six months. Few studies concerned with liver regeneration in healthy living donors. But many studies discussed liver regeneration after partial hepatectomy for benign and malignant tumors.8–10

Patients and methods:

Between May 2009 and June 2013, the surgical team in Liver Transplant Unit in El- Maadi Armed Forces Compound Hospital performed 80 LDLT using right lobe grafts from 72 healthy donors and right posterior sector grafts (segment VI&VII) from 8 healthy donors. Twice weekly, a multidisciplinary screening committee composed of the members  of  the  surgical  team  radiologist and internal medicine doctors met to review the recipient donor couple and evaluate the recipient risk, indication of transplant and other options if transplant was not indicated. The most common indications were liver cirrhosis  44  patients  (55%)  and  HCC  20 cases (25%) caused by HCV infection, while other indications found in 16 patients (20%).

Our  donors’  criteria  included;  age  (18-

45yrs),   should   related   to   recipient   and blood group compatibility. All the donor demographics were recorded regarding age, sex, weight and height. BMI, blood group, degree of steatosis, type of the graft, CT total liver volume, and CT right graft volume were evaluated. Potential donors are told of the risk of donor and morbidity and mortality.

All donors underwent liver function tests preoperatively and daily at the 1st week postoperative, then at 1, 3 and 6 months postoperatively.    All    donors    underwent liver biopsy to exclude donors with macro- vesecular steatosis more than 10%.

Liver  US  Duplex  was  done  to  assess the hepatic venous and portal anatomy preoperatively then at day 1, 3, 7 postoperatively   to   exclude   portal   vein

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thrombosis or fluid collection. It also was done postoperatively at 1, 3 and 6 months, to detect the increase in the portal flow and presence or absence of portal hypertension.

Also multiphase abdominal computed tomography angiography (CTA) was performed preoperatively to delineate liver morphology, volume, and vascular anatomy. Then, it was performed at 1week, 1, 3 and 6 months post- operatively to detect increasing ratio of regeneration.

The CT volumetry protocol used to assess donor liver volume; was using manual measurements to calculate liver volumes by hand-tracing the liver outline on the axial portal venous phase images Figure (1).

On preoperative CT scans using hepatic veins  as  guidance,  we  measured  the  total liver volume; the volume of the right lobe of the liver; the remnant liver volume, which included the (caudate lobe, IV, bi-segment II

& III). For the right lobe, a line parallel to the right side of the middle hepatic vein was drawn, and the circumference of the right side of the liver was marked manually in slices 1 cm thick. When the estimated liver remnant volume is less than 35%, the candidate, was considered unsuitable as a living donor.

The graft recipient weight ratio (GRWR) had been used to assess the graft size of a potential donor, and values of less than 0.8% had been associated with increased post- transplantation mortality and morbidity.

Seventy two donors underwent right hepatectomy;  the  remained  liver  was  the left lobe with preservation of the MHV in the  donors.  While  in  the  eight  donors  of right posterior sector graft, we took segment VI, VII with preservation of left lobe plus segment V, VIII in the donors.

All the operative details were recorded regarding the length of the operation, blood loss, autologous blood and fresh frozen plasma (FFP) transfusion, actual right lobe graft   weight,   and   posterior   sector   graft weight and donor remnant volume. All donor complications, defined as any unexpected events, were collected prospectively and recorded, both minor and major complications were recorded. All donors were monitored

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for 6 months postoperatively for surgical and medical complications.

Statistical analysis: Donor remnant volume

{DRV} was calculated as the estimated total liver volume {TLV} minus the actual graft weight {AGW}. Regeneration was expressed as a percent of the original TLV using follow- up computed tomography {CT} liver volume. Total liver volume by cm3 was recorded at the time interval of follow-up.

Increased ratio was calculated by this formula     {regeneration     LV–DRV}/DRV*

100}. As regeneration LV was the new remnant liver volume at the time interval of follow-up and DRV was the remnant liver volume (the donor remnant volume at day

0). Data are expressed as mean + standard deviation. Person’s correlation was used to analyze associations between two continuous variables. Statistical analyses were done using the statistical package for the social science

{SPSS}. A p  value  <0.05  was  considered

statistically significant.

Results:

Eighty living donors with compatible blood groups were evaluated, seventy two (56 males and 16 females) underwent right hepatic resection with preservation of MHV in the donor while only eight (7 males and

1 female) underwent right posterior sector (segment VI, VII) hepatic resection. Most common blood group was O (38.75%). Regarding age donors were relatively young (27.97±5.3years) with normal body weight and height (Body mass index 25.2±3.37) Table (1).

The donor operative time was (6.16±0.88) hours with an estimated blood loss (1118±833 ml.). Blood transfusion was in 14 donors with (2.67±2.03) units and fresh frozen plasma in

15 donors with (2.7±1.38 units). ICU length stay for all donors was (2±1) days and hospital stay for all donors was (9±3) days Table (2).

The preoperative liver volume measured by CT volumetry program was (1677±225.3 cm3) for right lobe graft and (1653.6±187.1 cm3) for right posterior sector graft. Multi-detector CT scan was excellent in predicting mean right lobe  liver  volume  {predicted  957.8±177.1

ml vs. Actual 858.9±165.3 g} P <0.001 by paired t test. The actual mean right posterior sector  graft  liver  volume  was  (597±104.8 g). Actual graft volume was 89.7% of the CT predicted right lobe liver volume. The donor’s remnant liver volume was (47.1±5.2

%) of TLV in right lobe and (63.7±4.8 %) of

TLV in right posterior. The mean GRWR was

1.05% Table (3).

Liver regeneration and function recovery: Liver regeneration was measured at 1week and at 1, 3, 6 months postoperatively and calculated using helical CT scan. The eight donors of the right posterior graft nearly reached the preoperative whole liver volume after  3months.  Four  donors  of  right  lobe graft (one male, one female) also, nearly reached the preoperative whole liver volume after 6 months. Postoperative liver enzymes revealed initial high elevation in the first 3 days then declined gradually, reached the baseline after 7 days postoperative. The total bilirubin returned to normal level at post- operative day (pod) 7 except in 4 donors (2 of  them  complicated  with  cholangitis  and

2 of them complicated with intra-operative bleeding  and  blood  transfusion)  returned to normal level at pod 30. In all right lobe donors we didn’t harvest the MHV to prevent outflow obstruction of segment IV and to maintain regeneration of the caudate lobe and segment IV.

Duplex  US  was  done at  first two  days to   exclude   any   portal   vein   thrombosis and fluid collection and then at the time of CT volumetry. The liver duplex revealed increased in the portal flow and to some extent increased portal pressure leading to transient splenomegaly for 3 months then return to normal size afterwards.

Factors affecting liver regeneration:

1.    Graft   type:   Donor   residual   liver volume  was  (63.7±4.8%)  of  RT  posterior graft reached to (99.6±0.21%) at POD 90, and was (47.1±5.4%) of RL donors reached to (95.2±1.7%) at POD 180. The increased ratios of the remnant liver were high in the RL donors when compared with the RT Posterior donors {P <0.001}. However, the liver enzymes and total bilirubin levels were

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high in the RL donors in the 1st week more

than RT post. Graft Table (4,5), Figure (2).

2. Donor sex: Right hepatectomy was carried in 16 female donors and 56 male donors. Donor residual liver volume was (47.9±5.3%)    in    male    donors,    reached to (95.3±1.8 %) at POD 180, and was (43.6±4.7%) in female donors, reached to (94.6±1.1%) at POD 180. The remnant liver of female group showed rapid regeneration than male group especially in POD7, increased ratios were (68.8%) in females vs. (44.2%) in males and remnant liver in female group increased from (43.6%) to (74.3%) of TLV vs. From (47.9%) to (68.7%) of TLV in male group, (% of regeneration per day) was (4.39%) in female group vs. (2.97%) in male group in POD 7 {P <0.001}.

3. Donor age: All RL donors were analyzed. There were six donors below 20 years (group1), forty eight donors between 20 and 30 years (group2), and twenty six donors above 30 years (group3). The preoperative TLV, remnant liver volume showed no significant difference between age groups. The liver regeneration was slow in the teenagers at POD 7, the increased ratio was (33.9%) in group1, (46.9%) in group2 and (53.9%) in group3 (P<0.001).

4. Remained liver/donor weight (RL/DW) ratio: Donors divided to groups according to RL/DW ratio into group1 (between 0.6 and 0.8, N=18), group 2 (between 0.81 and 1, N=29) and group 3 (between 1.01 and 1.2, N=33). The remnant liver volume was (41.2 %) of TLV increased to (95.8 %) of TLV in group1, (47.7 %) of TLV increased to (95 %) of TLV in group2 and (54.3 %) of TLV increased to (95.1 %) of TLV in group3. The increased ratios were high in group1 (P <0.001).

5. Remnant liver size: We divided all donors to groups according to remained liver volume to (group 1, N=6) less than 40% of preoperative TLV, (group 2, N=56) between

40% and 50% and (group 3, N=18) more than 50%.The remnant liver volume was (69.1%)  of  TLV  increased  to  (94.1%)  of TLV in group1, (69.1%) of TLV increased to (95.1%) of TLV in group 2 and (69.5%) of TLV increased to (94.6%) of TLV in group

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3. The increased ratios were high in group1

(P <0.001) Figure (3).

6. Fatty change of donor liver: Donors divided into 3 groups, group1 (no steatosis) as no fatty degeneration in 52 donors, group

2 with fatty change less than 5% in 18 donors and group 3 with fatty change between 5 and

10% in 10 donors. There was no significant difference between groups on regenerated liver volume.

7. Postoperative complications and blood transfusion: Donors divided according to blood transfusion into 2 groups, no blood transfusion in group1 in 23 donors and with blood  transfusion  in  group2  in  57  donors. Also we divided the donors according to postoperative complications into group1 (morbidity) in 27 donors and group2 (no morbidity) in 53 donors. There was no significant difference between groups on regenerated liver volume.

Discussion:

Liver transplantation is a recent solution for patients with end stage liver disease. Graft of the right lobe of the liver was world wild trend for living donor liver transplantation because of enough volume and function of right lobe to meet the metabolic need of adult recipient.7  The development of refinements in surgical techniques, unique anatomy and physiology of the liver expands living donor partial liver transplantation.10 Appropriate graft weight is important in liver transplant to  provide  better  graft  regeneration  and avoid graft failure due to small-for-size syndrome.11,12

Multi-slice CTA was used for evaluating liver  vascular  anatomy;  CT  was  also  a useful technique for estimating right-lobe graft volume and right posterior sector graft volume.9,11,13

Replication of hepatocytes generally starts within 1 day after a major resection.12 The initiation and synchronization of replication in different types of hepatic cells depend on the extent of the resection, tissue damage, or both. Low-grade tissue damage or a relatively small resection (removal of less than 30% of the liver) substantially reduces

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Figure (1): CT Volumetry Protocol. A. Abdominal CT outlines liver for volumetry. B. Whole liver volume. C. Right lobe with MHV. D. Right lobe without MHV.

Figure (2): Postoperative liver regeneration and function recovery according to the type of the graft. A: % of TLVs. B: Increased ratio of the remnant liver volume. C: AST. D: T. Bilirubin.

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Figure (3): Postoperative liver regeneration. A: According to RL/DW ratio. B: According to size of the remnant liver.

Figure (4): Liver regeneration in right lobe graft, 19yrs male donor. A. Whole liver preoperative

1332cm3. B. One month, whole liver 81.2 % of TLV. C. 3 months, whole liver 91.7% of TLV. D.

6 months, whole liver 99.9% of TLV.

the replication rate, which also appears to be less synchronized than after a large resection (removal of 70% of the liver).14–16

The human body responds to partial hepatectomy not by regenerating lost segments but by inducing hyperplasia in the liver remnant.14,15,18

A study using serial MRI measurements showed that donor and recipient mass increased by 144% and 99%, respectively by 2

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months. Regeneration appears to be greatest in the first week. Kamel and colleagues used CT scans to assess liver regeneration in recipients and donors. They found an increase in donor and recipient liver size of (42%±26%) vs. (86%±11%), (67%±41%) vs. (120%±27%), and (74%±46%) vs. (75%±37%) at 1, 2, and

6 months, respectively. Of note, the overall the rate of growth was greater in recipients than donors.10,19,20

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Table (1): Donor’s characteristics:

Table (2): Donors’ operative data:

(Table 3) Donor liver graft characteristics:

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Table (5): Liver graft regeneration, according to the type of the graft:

In a study done by Kwon et al., to evaluate the extent of liver regeneration and recovery of liver function, Serial CT scan was performed preoperatively, at postoperative day (POD)

#7 and POD #30. The remained liver volume after harvest increased to 144.6% at POD #7, and 181.4% at POD #30, which was 88.5% of preoperative total liver volume 7. In another report by Marcos he found that donor liver mass increased by 101%, 110%, 115%, and

144% at 7, 14, 30, and 60 days after resection, respectively.6

Overall liver regeneration was 83.3±9.0%

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of the total liver volume (TLV) by 1 year in a study done by Pomfret, and there was no effect of age, body mass index (BMI), operative time, estimated blood loss, postoperative complications, or perioperative liver  function  tests  on  liver  regeneration the latter continued throughout the first postoperative year. Only one donor achieved complete liver regeneration during this time period in this series; however, all donors had maintained normal liver function without long-term   complications.   Longer   follow- up was recommended to determine whether

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In a more recent study, donor outcome and liver regeneration in 13 males and 14 females were evaluated. Donor RLV was 40.8±6.6% of original TLV at surgery, 79.8±12.0% by

6  months,  and  97.2±10.8%  by  12  months. At 3 months the liver of the older donors (> or =50 years) had grown significantly more slowly than in younger donors (70.4±9.2% vs. 79.3±9.6%, P = 0.0391) and authors concluded  that  residual  liver  regenerated to its preoperative size by 1 year. However, meticulous care should be taken in donors with liver steatosis and aged donor.23–26

In this study the regeneration of the remnant  liver  was  significantly  different with sex of the donors, age of the donors, type of the graft, size of the remnant liver and  the  remnant  liver/donor  weight  ratio, and  not  affected  by  steatosis  of  the  graft, BMI, operative time, estimated blood loss, postoperative complications, or perioperative liver function tests on liver regeneration.

The remnant liver regenerated was more in right lobe graft donors than in right posterior graft donors; the overall liver regeneration was 95.2% of total liver volume by 6 months in donors of right lobe graft and nearly reached the total liver volume in donors of right posterior sector graft by 3 month.

The volume of the right lobe was bigger in female donors than male donors; we harvested 56.4% of TLV in female donors and 52.1% of TLV in male donors that means the remnant liver size in female was less than in males. The remnant liver of female group showed rapid regeneration than male group especially in POD7, we found this to be curious, knowing that estrogen induced liver regeneration Figure (4).

The remnant liver of teenagers group showed significant slow regeneration until POD 7, we couldn’t explain the reason of this result. The liver regeneration of this group had no difference to other group in POD30, POD90 and POD180.

Remnant liver also regenerated more rapidly and persisted significantly until POD180 in the donors who had a remnant liver volume less than 40% of TLV. And in

ratio from 0.6 to 0.8. Our result showed more rapid regeneration of liver in those who had a small remnant liver volume especially early after resection, and the remnant liver volume of 35% of TLV would be enough to safe recovery of liver function.

Because the portal venous flow velocity has a trigger effect on liver regeneration. The increased portal flow in the donors who got a less amount of remnant liver and donors who had less remained liver/donor weight ratio might influence more rapid liver regeneration. We checked portal flow increased velocity and volume by duplex US liver at the time interval of CT volumetry.18,27,28

In our program we didn’t use donors with fatty liver more than 10% of steatosis. As a result, we could not find any differences of liver regeneration and function recovery between the donors group with different degree of steatosis.

Conclusion:

The regeneration of the remnant liver was significantly different with sex of the donors, age of the donors, type of the graft, size of the  remnant  liver  and  the  remnant  liver/ donor weight ratio, and there was no effect of steatosis of the graft, anatomical vascular and   biliary   variations,   BMI,   operative time, estimated blood loss, postoperative complications, or perioperative liver function tests on liver regeneration.

Liver regeneration after donor hepatectomy is  affected  mainly  by  how  small  remnant liver volume, and how much portal flow or portal hypertension to the remnant liver and subsequent compliance of the remnant liver.

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