Impact of thoracic shape on the surgical outcomes of laparoscopic‐assisted living donor hepatectomy

Abstract Background Although laparoscopic‐assisted donor hepatectomy (LADH) has become the definitive procedure for harvesting living donor livers, its surgical outcomes in association with donor body shape have not been elucidated. Methods The impact of donor factors, including thoracic shape, on LADH outcomes was retrospectively investigated. Thoracic anthropometric data were examined in all LADHs with a left/right graft between 2013 and 2022. Results The study included 210 LADHs, consisting of 106 left‐ and 104 right‐lobe donors with similar blood loss and similar operation time. Males have greater thoracic depth and greater thoracic width compared with females, respectively. Thoracic depth was associated with graft weight (p < 0.001), blood loss (p < 0.001), and operation time (p < 0.001). On multivariate analyses, blood loss >500 mL and operation time >8 h were associated with graft weight in the left‐lobe donors, and blood loss >500 mL was associated with thoracic depth in the right‐lobe donors. Conclusion The greater thoracic depth is associated with massive blood loss in right‐lobe donors. Anthropometric parameters might be helpful for estimating LADH outcomes.


| INTRODUC TI ON
Liver transplantation is a treatment for end-stage liver disease and liver failure, and due to the scarcity of deceased donor liver grafts, living donor liver transplantation (LDLT) has become widely accepted as a valid option. 1,2LDLT donors are healthy without any liver disease, but donor hepatectomy is still demanding, requiring both special attention to the graft liver quality and the donor's remnant liver.8][9][10] Laparoscopic-assisted donor hepatectomy (LADH) is currently used in 50.8%-57.5% of MIDH with the right and left graft, as reported in an international multicenter study 6 and a world survey. 11e donor safety is paramount during the living procurement, 5,12 factors associated with LADH outcomes should be thoroughly investigated.Although the advantages of MIDH, such as better cosmesis, reduced pain, and shorter hospital stay, can reduce the physical and psychological burden on donors, 13 limiting the length of skin incision during LADH can make the procedure more demanding and compromise donor outcomes, especially in the deep operative field in thick abdomen.However, impacts of thoracic anthropometric parameters on LADH outcomes have not been evaluated yet.
The aim of this study was to evaluate factors associated with LADH outcomes, with special reference to anthropometric parameters [14][15][16] of the donors' thoracic shape.

| Study design
From a prospectively maintained institutional database on liver transplantation, 312 LDLTs performed between August 2013 and April 2022 were identified.Among them, 210 patients who underwent MIDH for a right or left graft were included in the study, while 91 patients who received left lateral, right posterior, or monosegment grafts and 11 patients who underwent open donor hepatectomy were excluded from the study.All donor hepatectomies were performed using a laparoscopic-assisted hybrid approach.Donor variables, such as age, body mass index (BMI), and anthropometric parameters on the thorax, as well as donor surgical data, were retrieved from the patients' medical records.We evaluated the association between anthropometric parameters and LADH surgical outcomes, including blood loss, surgery time, and major complications.Major complications were defined as conversion cases to conventional open surgery and complications with a Clavien-Dindo Grade ≥3. 17 Postoperative bile leakage was classified in accordance with the International Study Group for Liver Surgery's definition. 18ver-to-spleen CT attenuation values ratio (L/S ratio) were adopted to assess the degree of steatosis.The L/S ratio was calculated based on the previous report. 19Surgeon experience (trainees versus experts) and institutional learning curve (the former versus latter period) was also analyzed as confounders.This study conformed to the principles outlined in the ethical guidelines of the World Medical Association Declaration of Helsinki 2013 and the Declaration of Istanbul 2018.The study was approved by the Kyoto University ethics committee (R1473-3), and the requirement for written informed consent was waived due to the retrospective nature of this study.

| Laparoscopic-assisted donor hepatectomy
At Kyoto University Hospital, LADH has been the primary choice of technique for donor hepatectomy since 2013.The liver graft was chosen to have an estimated graft-to-recipient weight ratio (GRWR) ≥0.6% and to preserve a remnant liver volume ≥30%. 20Technical details were described previously. 21Briefly, two 5-mm trocars are inserted into the right upper abdomen and the umbilicus.An assistant inserted their hand through an 8-cm upper midline incision to retract the liver.The right liver was mobilized using the hand-assisted laparoscopic approach, and several short hepatic veins were ligated and divided as needed.The midline incision was extended to 12-14 cm to allow hilar dissection and parenchymal transection using the hybrid approach.Liver parenchyma was transected under direct vision using a Cavitron ultrasonic surgical aspirator.The hanging maneuver was routinely used during the parenchymal transection.The Pringle maneuver, an inflow occlusion technique, was not used.Intraoperative cholangiography was routinely performed to identify the best location for bile duct division and to prevent biliary stenosis.Abdominal drainage was not placed on principle.

| Anthropometric data on thoracic shape
Thoracic morphology was evaluated using pooled contrast-enhanced computed tomography data (Figure 1).Thoracic depth was defined as the distance between the skin and the anterior surface of the vertebra at the level of the suprahepatic inferior vena cava.
Thoracic width was defined as the width of the bilateral ribs at their widest point in space.

| Statistical analysis
All statistical analyses were performed using GraphPad Prism (Version 9.3.1,GraphPad Software).Categorical data were compared using Fisher's exact test.Continuous data were presented as the median and interquartile range and were compared using the Mann-Whitney U test.Simple linear regression analysis was performed using a scatterplot between each factor, and the correlation coefficient (r) was calculated using Pearson's correlation test.The odds ratio (OR) of factors impacting the surgical outcome was analyzed using logistic regression analysis and described using the 95% confidence interval (CI).Variables were selected for multivariate analysis by BIC (Bayesian Information Criterion) in a stepwise algorithm.All p-values were twosided, and p < 0.05 was considered to be statistically significant.

| Thoracic anthropometric data of male versus female
Thoracic depth and width of male and female donors were summarized in Table 1, together with other demographics.Males had significantly higher BMI, greater thoracic depth, and greater thoracic width, compared with females, respectively.

| Donor characteristics and surgical outcomes
Donor background characteristics and surgical outcomes were summarized in Table 2, comprising 106 left (50.4%) and 104 right (49.6%) grafts.The left lobe donors retained the Spiegel lobe (the left part of segment 1) in the donor's remnant liver, except for one case in which the left lobe graft was combined with the Spiegel lobe.The proportion of females was significantly higher and thoracic depth and thoracic width were both greater in left-lobe donor, respectively.Graft weight was significantly less in the left-lobe donors compared with right-lobe donors (Table 2), and associated with thoracic depth in both of left-(r = 0.39, p < 0.001) and right-lobe donors (i = 0.47, p < 0.001), respectively (Figure 2A).Blood loss and operation time were similar between left-and right-lobe donors, respectively (

TA B L E 3
Univariate and multivariate analysis of predictive factors for blood loss >500 mL in left-lobe donors (A) and right-lobe donors (B).

| Predictive factors associated with unfavorable surgical outcomes
Univariate and multivariate analyses for factors associated with unfavorable surgical outcomes, such as blood loss >500 mL, operation time >8 h, and major complications were summarized in Tables 3-5.
There were 36 cases of blood loss >500 mL and 31 cases of operation time >8 h.
In the left-lobe donors, greater graft weight and greater thoracic depth were associated with blood loss >500 mL by univariate analysis, and greater graft weight was an independent predictor of blood loss >500 mL by a multivariate analysis (Table 3).Male, greater BMI, greater graft weight, greater thoracic width, and the former period were associated with operation time >8 h by univariate analysis, and greater graft weight and the former period were independent predictors of operation time >8 h by a multivariate analysis (Table 4).
No factors were associated with major complications by a univariate analysis (Table 5).
In the right-lobe donors, greater BMI and greater thoracic depth were associated with blood loss >500 mL by univariate analysis, and greater thoracic depth was an independent predictor of blood loss >500 mL by multivariate analysis (Table 3).The former period was associated with operation time >8 h by univariate and multivariate analysis (Table 4).No factors were associated with major complications by univariate analysis (Table 5).

TA B L E 4
Univariate and multivariate analysis of predictive factors for operation time >8 h in left-lobe donors (A) and rightlobe donors (B).
LDLT. 22 Previous studies revealed that overall, up to 20%-33.3% of living donors experienced postoperative morbidity, 6,23 specifically blood loss (>300 mL) in 23.5% of donors, long surgery time (>400 min) in 51.7%, and bile leakage in 1.3%-6.5% of donors. 24,25milarly, our LADH patients experienced a median blood loss of 245 mL, median operation time of 409 min, and biliary leakage in 2.9% of donors.Vascular anomalies were reported to correlate with donor complications, 24,26 and the Expert Consensus Guidelines recommended that MIDH for donors with difficult anatomy should only be considered at centers that have well-established procedures. 13large graft weighing >700 g may also predict increased MIDH difficulty. 13,27Similarly, larger grafts were associated with left-lobe donor outcomes in the current study.Moreover, greater thoracic depth was an independent predictor of blood loss >500 mL in the right-lobe donors, although a previous study did not reveal the impact of body habitus on blood loss because of its small sample size. 16e association between thoracic depth and blood loss in rightlobe donors is probably attributable to the limited access to the deep surgical field via the small incision 13 in patients with a deep thorax.Limited exposure disturbs precise parenchymal dissection and meticulous hemostasis, which are directly associated with vascular injury and bleeding.Because the ventral approach is used in LADH, [28][29][30] the hanging technique is required to improve access to the deep field during LADH, 31 although our results indicate that using only the hanging technique does not have sufficient safety when performing LADH with a deep thoracic field.One of the solutions would be extending skin incision to ensure safety in case of difficulties. 13rubashi et al. reported previously that another anthropometric parameter, the maximal distance between the surface of the right lobe and the portal vein bifurcation (RPv distance), was significantly associated with operation time in left-lobe LADH. 32 thorax disrupts access to the dorsal surgical field in the same manner; however, the wide heterogeneity in the complexity and extent of resection have prevented showing the impact of thoracic shape on surgical outcomes.9][30] In this manner, PLDH naturally has different predictive factors for its technical difficulty, including anthropometric parameters, and it potentially contributes to better outcomes in donors with a deep thorax.Further research is required to determine the impacts of thoracic shape on PLDH outcomes.
There are some limitations in the present study.This is a single-institution study for a single ethnicity, which potentially limits the reproducibility of the findings.The retrospective nature of the study requires further prospective studies to confirm the findings.

| CON CLUS ION
A greater thoracic depth contributes to greater blood loss in the right-lobe donors but did not increase the operation time and morbidity.This anthropometric parameter is helpful for estimating LADH outcomes and should be considered in preoperative planning to ensure the highest safety of living donor hepatectomy.

F I G U R E 2
blood loss and operation time were associated with thoracic depth, respectively (Figure 2B,C; blood loss, r = 0.19, p = 0.007; operation time, r = 0.18, p = 0.01).Conversion to conventional open surgery, which occurred in four patients due to significant blood loss or an inadequate field of view, was similar between left-and right-lobe donors.Postoperative biliary leakage and major complications, classified as Clavien-Dindo Grade IIIa in five and Clavien-Dindo Grade IIIb in three, were also similar between left-and right-lobe donors.Reoperations were indicated due to upper gastrointestinal perforation, liver subcapsular hematoma, and a major bile leak.Plotting of graft weight (A), blood loss (B), and operation time (C) in association with thoracic depth.
NTR I B UTI O N S KT: project development, data analysis & collection, manuscript writing.SO: project development, data analysis & collection, manuscript writing/editing.AHA: project development, data analysis, manuscript editing.TY: project development, data analysis, manuscript editing.YM: project development, data analysis, manuscript TA B L E 5 Univariate analyses of predictive factors for major complications in left-lobe donors (A) and right-lobe donors (B).

Table 2 )
, while Abbreviations: BMI, body mass index; L/S ratio, liver-to-spleen computed tomography attenuation values ratio.TA B L E 2 Background characteristics and surgical outcomes.Note: Continuous values are expressed as median [interquartile range].Abbreviations: BMI, body mass index; L/S ratio, liver-to-spleen computed tomography attenuation values ratio.