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ORIGINAL
Regeneration of caudate lobe after living donor livertransplantation : Comparison with a surrogate model ofleft lobe graft
Yu Saito MD, PhD, FACS1), Satoru Imura MD, PhD, FACS1), Yuji Morine MD, PhD, FACS1),
Tetsuya Ikemoto MD, PhD, FACS1), Shinichiro Yamada MD, PhD, FACS1), and Mitsuo Shimada MD, PhD, FACS1)
Department of Surgery, Tokushima University, Tokushima, Japan

1

Abstract : Background : The aim of this study is to clarify the regeneration of the CL (caudate lobe) without any
reconstructions of short hepatic veins (SHVr) after LDLT (living donor liver transplantation) and compare theregeneration of the CL after right hepatectomy (Rt. Hx), as the surrogate model of extended left lobe graft (ExLLG) with complete SHVr. Methods : Eleven Ex LLGs with CL were included in this study. SHVr was not performed in all cases. The volumetry was performed before, one month and six months after LDLT. Seven patients
who underwent Rt. Hx were also included in this study as the surrogate model. Results : In Ex LLGs with CL, theregeneration rate of the large CL (> 30 ml) was worse than that of small CL (< 30 ml). In the surrogate model, theregeneration rate of the CL was not worse than other segments. However, the regeneration rate of the large CL
was also worse than that of small CL even in the presence of complete SHVr. Conclusions : The regeneration ofthe large CL was worse than that of the small CL regardless of the presence or absence of SHVr, indicating thatSHVr in Ex LLG with CL might not be necessary. J. Med. Invest. 68 : 330-333, August, 2021
Keywords : caudate lobe, short hepatic vein, living donor liver transplantation

INTRODUCTIONFirst of all, the size of an extended left lobe graft (Ex LLG)
more than doubles one month after transplantation (1), and functions as a graft for a recipient for life. However, Ex LLG has more
frequent risk of small-for-size-graft (SFSG) than right lobe graft.
SFSG sometimes causes graft failure after living donor livertransplantation (LDLT). However, RLG imposes a greater surgical risk on living donors. As a method of increasing the graftvolume in the case of SFSG in LDLT, the Shinshu group alreadyreported caudate lobe (CL) transplantation with an extended left
lobe graft (Ex LLG) was an innovative and promising method forincreasing the graft volume in LDLT (2). We have also alreadyreported a new technique for left lobe graft harvesting proved apromising approach to gain additional volume (2). However, littleis known about the fate of the CL after transplantation. As apreliminary report regarding the changes in the CL after transplantation, we already reported that regeneration rate of CL wasworse than that of left lobe (LL) at one month after LDLT without any reconstructions of short hetiv veins (SHVr), which are
drainage veins of CL that flow directly into inferior vena cava,
however, the CL volume increased in almost all patients (1). On
the other hand, it was also reported that CL could regenerate
proportionally with the LL by complete SHVr (4). It means thatthe necessity of SHVr in Ex LLG with CL is still controversial.
As our new idea in the present study, we focused on patients
after right liver resection (Rt. Hx) for liver tumors. Since CLs of
those patients were remnant with SHVs as drainage veins, thepatient with Rt. Hx could be used as the surrogate model of Ex
LLG with complete SHVr.
Abbreviations :small-for-size grafts ; SFSG, living donor liver transplantation ; LDLT,
caudate lobe ; CL, extended left lobe graft ; Ex LLG, left lobe ; LL,
reconstructions of short hetiv vein ; SHVr, multi-detector computed
tomography ; MDCT, standard liver volume ; SLV, graft volume ; GV,liver volume ; LV

Accordingly, we herein clarify the regeneration of CL in caseof Ex LLG without SHVr after LDLT and compare the regeneration of CL after Rt. Hx, as the surrogate model of Ex LLG withcomplete SHVr.

METHODS

Ethical permission
This study was approved by The Tokushima University Hospital Ethics Committee and the corresponding regulatory agencies(Tokushima Clinical Trial Management, Approved No 3215)
and all the experiments were carried out in accordance withthe approved guidelines. Meanwhile, all the patients involvedin the study signed the informed consent form and agreed toparticipate.

Patients
LDLT ; From February, 2005, to March, 2015, eleven Ex LLG
with CL were included in this study. All LDLT operations wereperformed at Tokushima University Hospital. In all cases, SHVr
did not be performed. Detailed operative techniques in LDLT
were described in previous report (2).
Rt. Hx ; From December, 2005, to April, 2015, seven patientswith initial Rt. Hx were included in this study (five patients withliver metastasis of colorectal cancer with no chemotherapy andtwo patients with liver abscess or hemangioma). These patientswere used for the surrogate model of Ex LLG with completeSHVr.
Received for publication April 5, 2021 ; accepted July 30, 2021.
Address correspondence and reprint requests to Yu Saito, MD, PhD,
Department of Surgery, Tokushima University, 3-18-15 Kuramoto-cho,
Tokushima, 770-8503, Japan and Fax : +81-88-631-9698.

The Journal of Medical Investigation Vol. 68 2021

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The Journal of Medical Investigation Vol. 68 August 2021
CT volumetry

The regeneration rate of CL in LDLT without SHVr

3D-reconstruction of the hepatic vasculature was made using
data from a contrast enhanced multi-detector computed tomography (MDCT) and SYNAPSE VINCENT software (Fuji Film
Medical Co. Ltd., Tokyo, Japan). The volumetry of each segment
was performed by “portal segmentation function” of SYNAPSE
VINCENT. The volumetry in LDLT was performed before LDLTfrom the donors and 1 month and 6 months after LDLT (Figure1). In the surrogate model, the volumetry was performed as wellbefore operation and 1 month and 6 months after operations.

The regeneration rate of CL was 18 ± 42% at one month post
LDLT and 0 ± 42% at six months post LDLT (Figure 2). 3 cases
showed 5% or more of volume decrease after LDLT, and theirpreoperative volume were all over 30 ml in volume (data were notshown). Regeneration rate of the small CL (volume ≤ 30 ml) was
39 ± 42% at one month post LDLT and 35 ± 42% at six months

Standard liver volume (SLV), graft volume (GV), and GV / SLV
estimation
SLV was calculated according to the formula described by
Urata et al. (5). All GV in this study was calculated by volumetry
using portal segmentation function.

Table 1. The regeneration of CL and LL
Caudate lobe

Left lobe

Pre1m6m

Pre

1m6m

GV (ml)28302845610231175

GV / SLV (%)

2.52.62.54089105

GV, graft volume ; SLV, standard liver volume ; m, month(s).

Regeneration rate
The regeneration rate was calculated as described below ;(Postoperative liver volume (LV) – Preoperative liver volume) /Preoperative liver volume × 100 (%)

Statistical Analysis
All results were presented as mean ± SD. Comparisons between the two groups were performed using a Chi-square test
using statistical software (JMP 8.0.1., SAS Campus Drive, Cary,
27513 NC, USA). A p-value of less than 0.05 was considered statistically significant.

RESULTSIncreasing the graft volume with CL
The LL graft volume was 456 ± 117 ml at pre LDLT,
1,023 ± 213 ml at one month post LDLT and 1,175 ± 275 ml at
six months post LDLT, corresponding to a 40%, 89% and 105%
increase respectively in GV / SLV (Table 1).
The addition of the CL increased the graft volume by 30 ± 11ml at one month post LDLT and 28 ± 13 ml at six months post
LDLT, corresponding to a 2.6% and 2.5% increase respectivelyin GV / SLV (Table 1).

Figure 1. Volumetry of CL

Figure 2. Regeneration rate of CL in LDLT without SHVr

The regeneration rate of CL was 18 ± 42% at one month post LDLT
and 0 ± 42% at six months post LDLT.

The volumetry of CL was performed by “portal segmentation function” of SYNAPSE VINCENT before
LDLT from the donors and 1 month and 6 months after LDLT.

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Y. Saito, et al. Regeneration of caudate lobe in left lobe graft

post LDLT. On the other hand, regeneration rate of the large
CL (volume > 30 ml) was -27 ± 18% at one month post LDLT and-54 ± 36% at six months post LDLT (Figure 3). It was suggested
that the large CL had worse regeneration than the small CL in
Ex LLG without SHVr.

Figure 5. Comparison of the regeneration between small and large
CL in the surrogate model with SHVr
Regeneration rate of the small CL (volume ≤ 30 ml) was 56 ± 69 % at
one month post operation and 164 ± 63% at six months post operation.
On the other hand, regeneration rate of the large CL (volume > 30ml)
was 17 ± 3% at one month post operation and 12 ± 8% at six months
post operation.
Figure 3. Comparison of the regeneration between small and large
CL in LDLT without SHVr
Regeneration rate of the small CL (volume ≤ 30 ml) was 39 ± 42% at
one month post LDLT and 35 ± 42% at six months post LDLT. On theother hand, regeneration rate of the large CL (volume > 30 ml) was-27 ± 18% at one month post LDLT and -54 ± 36% at six months post
LDLT.

The regeneration rate of CL in in the surrogate model with complete
SHVr
The regeneration rate of CL was 49 ± 62% at one month post
operation and 113 ± 93% at six months post operation (Figure 4).
Regeneration rate of the small CL (volume ≤ 30 ml) was 56 ± 69% at one month post operation and 164 ± 63% at six months postoperation. On the other hand, regeneration rate of the large CL(volume > 30 ml) was 17 ± 3% at one month post operation and12 ± 8% at six months post operation (Figure 5). It was suggested
that the large CL had also worse regeneration than the small CL
in the surrogate model with complete SHVr.

Figure 4. Regeneration rate of CL in the surrogate model with SHVr

The regeneration rate of CL was 49 ± 62% at one month post operationand 113 ± 93% at six months post operation.

DISCUSSION
The necessity of SHVr in Ex LLG with CL is still controversial. In the present study, we clarified that the regeneration of
CL in case of Ex LLG without SHVr after LDLT and compare
the regeneration of CL after Rt. Hx, as the surrogate model of
Ex LLG with complete SHVr. It was the first report using thesurrogate model of Ex LLG with complete SHVr.
Various CL venous reconstruction techniques were describedas one of the feasible solutions to overcome SFSG (6-11). Although the CL volume is small, it is important when the graftvolume is critical. We have already showed that the regeneration
rate of the transplanted CL and other left lobe graft segments.
The regeneration rate of the CL one month after transplantation
was smaller (62 ± 24%) than that of other left lobe graft segments(152 ± 35%) (3). It was already reported that with reconstructionof the inflow (6) or outflow (7), the regeneration rate of the CL
was noted to be equal to or more than that of the other left lobe
graft segments. The additional functional volume afforded by
CL venous reconstruction might provide an additional safetymargin.
On the other hand, Mikami K et al. (12) reported that theGV / SLV ratio of the whole grafts after LDLT showed no difference regardless of the presence or absence of SHVr. In thepresent study, in the surrogate model of Ex LLG with complete
SHVr, regeneration rate of the CL was not worse than other segments. However, regeneration rate of large CL (volume > 30 ml)
had worse than that of the small CL (volume < 30 ml) as well as
LDLT without SHVr cases. It was suggested that the size of CL
seemed to be important for regeneration as a new finding.
As limitations of this study, the present study was a retrospective cohort from a single institution. Although it was necessary
to add more patients in the present study, the chance of operation of open Rt. Hx with normal liver function have recentlydecreased. A prospective randomized trial with more patientnumber will be necessary in the future.
In conclusion, Ex LLG with CL was a useful method for increasing the graft volume. The regeneration of the large CL wasworse than that of the small CL regardless of the presence orabsence of SHVr. It was suggested that SHVr in Ex LLG withThe Journal of Medical Investigation Vol. 68 August 2021
CL might be not necessary and the graft size might be important
for CL regeneration.

COI DISCLOSURE
All authors had no sponsorship or funding arrangements relating to this study.

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