Shinshu Med J, 72⑴：19～29, 2024

A Novel Difficulty Classification for Perioperative Risk Assessment
in High-level Hepatobiliary Pancreatic Surgeries
Shiori Yamazaki, Akira Shimizu＊, Koji Kubota
Tsuyoshi Notake, Noriyuki Kitagawa, Hitoshi Masuo, Takahiro Yoshizawa
Hikaru Hayashi, Syohei Hirano, Hisamichi Inuzuka and Yuji Soejima
Division of Gastroenterological, Hepato-Biliary-Pancreatic, Transplantation and Pediatric Surgery,
Department of Surgery, Shinshu University School of Medicine

Purpose : Although mortality and morbidity rate of high-level hepatobiliary pancreatic (HBP) surgery has been
improved, which remains still high in some procedures. The difficulty of high-level HBP surgeries are varies de­pending on the surgical complexity, thereby perioperative outcomes can be variable. The aim this study was toestablish a novel difficulty classification of high-level HBP surgeries and to assess its validity.
Methods : High-level HBP surgeries were classified into four groups, A to D, in order of increasing difficulty,
based on the expert opinion. A total of 473 patients who underwent high-level HBP surgery from July 2014 to
July 2021 in our hospital were classified into aforementioned four groups, and surgical and postoperative out­
comes of which were compared.
Results : The numbers of patients in each difficulty group were as follows : A (n＝62), B (n＝278), C (n＝74) and D(n＝59). Operation time and blood loss showed a significant stepwise increase in the group A to D (p＜0.001 and
p＜0.001 respectively). The duration of postoperative hospital stay also increased significantly from the group A
to D (p＜0.001). The incidence of complications over Clavien-Dindo classification IIIa increased in group A to D
significantly (35.5 ％ vs 35.3 vs 37.8 vs 54.2 ％ ; p＝0.021). However, the 90-day mortality rates did not differ
within four groups (1.6 ％ vs 0.4 ％ vs 2.7 ％ vs 1.7 ％ ; p＝0.394).
Conclusions : The novel difficulty classification of high-level HBP surgeries can predict surgical risk in eachsurgical procedure. Further large-scale nationwide study should be warranted to confirm these results. Shinshu
Med J 72 : 19―29, 2024
(Received for publication August 8, 2023 ; accepted in revised form September 15, 2023)
Key words : High-level HBP surgery, classification, safety, education

gery (JSHBPS) has established a board certification

Ⅰ Introduction

system for training surgeons able to perform high-The safety and efficacy of hepatobiliary pancreaticlevel HBP surgeries safely and reliably2）-4）. The 90-(HBP) surgery have improved dramatically in recent

and 30-day mortality rates at board-certified train­

years, but the operative mortality rate remains higher

ing institutions were 1.7 ％ and 1.3 ％, respectively, in

1）than that of other gastrointestinal surgeries . The

2015, which were significantly lower than the rates

Japanese Society of Hepato-Biliary-Pancreatic Sur­in 20125）. However, the difficulty of high-level HBP＊

Corresponding author : Akira Shimizu

surgeries varies depending on the complexity of each

Division of Gastroenterological, Hepato-Biliary-Pancreatic,

procedure, and the perioperative outcomes thus vary

Transplantation and Pediatric Surgery, Department ofSurgery, Shinshu University School of Medicine,
3-1-1 Asahi, Matsumoto, Nagano 390-8621, Japan
E-mail : ashimizu@shinshu-u.ac.up

No. 1, 2024

accordingly. For example, the 90-day mortality fol­lowing extrahepatic bile-duct resection with bilio­
enteric anastomosis in patients with congenital biliary
19

Yamazaki・Shimizu・Kubota et al.

dilatation was 0 ％, compared with 10.3 ％ in patients

Patients who underwent high-level HBP surgery

with left trisectionectomy of the liver, even in certi­

in Shinshu University Hospital from July 2014 to July

5）2021 were included in the study. The operations offied institutions .

Advances in perioperative management and surgical38.5 ％ was performed by expert surgeons. Data on

techniques, together with changes in public awarenessthe patients’ basic characteristics, including age, sex,of medical safety, mean that perioperative death isbody mass index, American Society of Anesthesiolo­

becoming unacceptable, even after high-level HBP

gists physical status (ASA-PS), social history, andsurgery. However, in order to produce expert surgeonslaboratory data were collected. Data on surgical andable to carry out high-level HBP, it is necessary for

postoperative outcomes, including the type of surgi­

them to accumulate experience in the appropriate

cal procedure, duration of operation, intraoperative

surgeries safely and efficiently under appropriate in­blood loss, qualification of surgeon, surgeons’ career,

struction. Although several new difficulty classifica­

duration of postoperative hospital stay, postoperative

tions of liver resection have been reported

6）-8）, therecomplications, and 30- and 90-day mortalities wereis currently no classification that can act as an indicatoralso collected and evaluated. Postoperative compli­of difficulty and risk for all high-level HBP surgeries.

cations were defined and graded according to theThis study thus aimed to establish a novel difficulty

Clavien-Dindo (CD) classification system10）. All com­classification for high-level HBP surgeries to provide

plications were recorded and complications above CD

an indicator for expert training and to aid the appro­

grade IIIa were defined as major complications. The

priate allocation of surgeons, and to evaluate its va­

patients were classified into the above four groups

lidity for difficulty assessment.

according to the surgical procedure carried out, andⅡ
Ａ

Material and Methods

Classification of surgeries

their surgical and postoperative outcomes were com­pared. To compare with similar patient’s comorbidities’
backgrounds, stratification was performed based on

A questionnaire survey was administered to six

the ASA-PS and age. Liver transplantation donor

experts and three expert trainees for JSHBPS board

operations were excluded from the analysis because

certification in Shinshu University and its affiliatedit was difficult to reflect social responsibility and eth­hospital in December 2021. Expert surgeon was de­ical issues in the difficulty score.

fined as high-level HBP surgeon who certified by theＣ Comparison of classification and perioperative

JSHBPS. The surgeons were asked to evaluate andoutcomes

rank the difficulties of various high-level HBP sur­

The perioperative outcomes of the patients in thegeries on a scale of 1-10, where level 1 was “easiest”

four difficulty groups based on HBP surgeon opinion

and level 10 was “most difficult”. The survey speci­

were compared to confirm the performance of the

fied that all resections were to be considered as open,classification. Duration of operation, intraoperative

rather than laparoscopic procedures9）. All the surveys

blood loss, incidence of major postoperative complica­

were anonymous. Based on the questionnaire, high-tions, 30- and 90-day mortality rates, failure-to-level HBP surgeries were classified into four groups,

rescue (FTR) rate, and duration of postoperative hos­procedures with median score of 1 to 3 as level A :pital stay were set as outcomes measurements. The“easy”, median score 4 to 6 as B : “moderate”, median

FTR rate was defined as death in a patient with atscore 7 to 8 as C : “difficult”, and median score 9 to 10

least one postoperative complication11）. The difficulty

as D : “most difficult”. The recommendation of surgeon’sclassification effect was tested by comparing the areaslevel for high-level HBP surgeries were also collectedunder the receiver operating characteristic (ROC)by the questionnaire ; for general surgeon, HBP trainee,

curves (AUCs).

HBP expert surgeon.

Ｄ

Ｂ

Patients and data collection
20

Statistical analysis

Continuous variables were compared using theShinshu Med J. 72

For safety of high-level HBP surgery
Table 1

Difficulty score of high-level HBP surgeries based on surgeon opinion and classification

Procedures
Hepatic segmentectomy : S3
Hepatic segmentectomy : S2
Hepatic segmentectomy : S5
Hepatic segmentectomy : S6
Extrahepatic bile duct resection for congenital biliary dilatation
Distal pancreatectomy with lymph node dissection (for pancreatic cancer)
Hepatic sectionectomy : posterior
Hepatic sectionectomy : S4
Duodenum-preserving pancreas head resection
Beger’s operation
Hepatectomy with distal pancreatectomy
Hepatic segmentectomy : S7
S4a＋S5 hepatectomy with extrahepatic bile duct resection
Pancreatoduodenectomy
Inferior pancreas head resection
Right or extended right hepatectomy
Left or extended left hepatectomy
Hepatic sectionectomy : anterior
Hepatic segmentectomy : S8
Total pancreatectomy
Middle segment pancreatectomy
Hepatic sectionectomy or less and pancreatoduodenectomy
Central bisectionectomy of the liver
Hepatic segmentectomy : S1
Liver transplantation donor operation
Pancreas-preserving duodenectomy
Ventral pancreatectomy
Right or extended right hepatectomy with extrahepatic bile duct resection
Left trisectionectomy of the liver
Right trisectionectomy of the liver
Left or extended left hepatectomy and pancreatoduodenectomy
Right trisectionectomy with extrahepatic bile duct resection
Liver transplantation recipient operation
Left trisectionectomy with extrahepatic bile duct resection
Right or extended right hepatectomy and pancreatoduodenectomy
Central bisectionectomy of the liver and pancreatoduodenectomy
Right trisegmentectomy of the liver and pancreatoduodenectomy
Left trisegmentectomy of the liver and pancreatoduodenectomy

Median (IQR)

Classification

3.00 (2.00-4.25)
3.50 (3.00-4.25)
3.50 (3.00-5.00)
3.50 (2.75-5.00)
4.00 (3.00-4.50)
4.00 (3.75-5.00)
5.00 (3.75-6.00)
5.00 (4.00-6.00)
5.00 (4.50-5.50)
5.00 (4.00-5.50)
5.00 (3.00-6.00)
5.50 (3.75-6.00)
5.50 (4.00-6.00)
5.50 (4.75-6.00)
5.50 (4.75-6.25)
6.00 (4.75-6.25)
6.00 (4.75-7.00)
6.00 (4.75-7.00)
6.00 (4.75-6.00)
6.00 (4.50-6.25)
6.00 (4.00-6.50)
6.50 (6.00-7.75)
7.00 (6.50-8.00)
7.00 (5.50-8.00)
7.00 (6.50-7.25)
7.00 (6.50-7.50)
7.00 (7.00-7.00)
7.00 (5.25-7.25)
7.50 (6.25-8.00)
8.00 (6.50-8.00)
8.00 (8.00-9.00)
8.50 (7.75-9.00)
9.00 (8.50-9.51)
9.00 (7.75-10.00)
9.00 (8.50-9.50)
9.00 (9.00-10.0)
10.00 (10.00-10.00)
10.00 (10.00-10.00)

A
A
A
A
A
A
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
C
C
C
C
C
C
C
C
C
C
D
D
D
D
D
D

Abbreviation : HBP, Hepatobiliary pancreatic ; IQR, interquartile range ; A, easy ; B, moderate ; C, difficult ;D, most difficult.

Mann-Whitney U test and categorical variables were2

AUCs. To identify independent risk factors for post­compared using χ and Fisher’s exact tests. One-

operative major complication, multivariable analyses

way analysis of variance (ANOVA) was used for com­were performed along with logistic regression analysis

parisons among the four groups. Trends in perioper­with covariates with a cutoff P value＝0.10. Results

ative outcomes with a stepwise increase from groups

are expressed as odds ratios with 95 ％ confidence

A to D were evaluated using the Cochran-Armitage

intervals. All statistical analyses were performed

trend test for categorical variables and Jonckheere-using IBM SPSS version 27 (IBM Corp., Armonk, NY,

Terpstra trend test for continuous variables. The clas­

USA). The threshold for significance was P＜0.05.

sification was validated by ROC curve analysis andNo. 1, 2024

21

Yamazaki・Shimizu・Kubota et al.

Fig. 1 Numbers and proportions of patients in each high-level HBP surgery group. Distal pancreatectomy accounted
for most patients (61 ％) in group A, pancreaticoduodenectomy accounted for the highest percentage in group B(48 ％), hepatectomy with extrahepatic bile duct resection and trisesectionectomy were the main surgeries ingroup C, and liver transplant receipt accounted for most patients (74 ％) in group D.

Ⅲ Results
Ａ Difficulty scores for high-level HBP surgeries

high-level HBP surgery are shown in Fig. 1. In theentire cohort, 62 patients underwent group A, 278
group B, 74 group C, and 59 group D surgeries.

The median and interquartile range (IQR) of the

The background characteristics of the patients arescore for each high-level HBP surgery based on HBPshown in Table 2. Stratification was performed bysurgeon opinion is shown in Table 1. Based on these

ASA-PS ≤ 2 and age ≥ 57-year-old, to compare theopinions, the high-level HBP surgeries were classified

similar patients’ backgrounds. There was no signifi­

into four groups. Surgical procedures with portal vein,cant difference in sex (P＝0.553) or body mass index

inferior vena cava, or hepatic vein reconstruction(P＝0.717) among the four groups, whereas age (P＝were assigned as 1-rank-up group of difficulty clas­

0.015) was still difference among four groups. The

sification based on HBP surgeon opinion.

preoperative rates of comorbid diabetes mellitus, hy­

Ｂpertension, cardiovascular or pulmonary diseases

Patient characteristics
Among 496 patients who underwent high-level

HBP surgeries in Shinshu University Hospital during

were similar in all four groups.
Ｃ

Surgical and postoperative outcomes2014 to 2021, 22 patients who underwent liver trans­

The surgical and postoperative short-term out­

plantation donor operation were excluded. A total ofcomes are summarized in Table 3. Operation time

473 patients were therefore enrolled in this study. The(median : 375 min vs 526 min vs 652 min vs 794, re­numbers and proportions of patients undergoing each

spectively ; P＜0.001), blood loss (300 ml vs 405 ml vs22

Shinshu Med J. 72

For safety of high-level HBP surgery
Table 2 Characteristics of patients who underwent high-level HBP surgeries for ASA-PS ≤ 2 and age ≥ 57
Group AGroup B

Group CGroup D

(n＝51)(n＝224)(n＝65)(n＝29)

P valueSex, male

70 (68-76)
30 (58.8)

72 (66-78)
146 (65.2)

72 (66-78)
44 (67.7)

68 (63-72)
16 (55.2)

0.015b
0.553c

BMI, kg/m2a21.7 (20.4-23.8)

22.1 (19.8-24.5)

22.5 (20.4-24.7)

22.1 (19.7-22.9)

0.717bPreoperative comorbidity
Diabetes mellitus

17 (33.3)

65 (29.0)

15 (23.1)

4 (13.8)

0.458cHypertension

26 (51.0)

128 (57.1)

33 (50.8)

11 (37.9)

0.243cCardiovascular disease

6 (11.8)

12 (5.4)

2 (3.1)2 (6.9)0.189cPulmonary disease

2 (3.9)12 (5.4)

8 (12.3)

2 (6.9)0.213cSocial history
Smoking

21 (41.2)

126 (56.3)

38 (58.5)

15 (51.7)

0.119cDrinking

30 (58.8)

149 (66.5)

44 (67.7)

20 (69.0)

0.779cParametersaAge, year

Note : Values in parentheses are percentages unless indicated otherwise.
Abbreviation : BMI, body-mass index ; ASA-PS, American Society of Anesthesiologists physical status.
aMedian (IQR)b

Kruskal-Wallis test.

c

Pearson’s chi-square test.

Table 3 Surgical and postoperative outcomes in patients who underwent high-level HBP surgeries for ASA-PS ≤ 2 and age ≥ 57
Group A
(n＝51)

Group B
(n＝224)

Group C
(n＝65)

Group D
(n＝29)

P value

Blood loss, ml

375 (304-441)
300 (150-560)

526 (409-612)
405 (250-650)

652 (562-709)
700 (500-1200)

794 (644-962)
900 (550-4000)＜0.001b＜0.001b

Transfusion

6 (11.8)35 (12.6)

26 (40.0)

18 (62.1)＜0.001c

Expert surgeon

8 (15.7)

64 (28.6)

37 (56.9)

22 (75.9)＜0.001c

Surgeons’ career, yeara

19 (6-35)

23 (5-35)

29 (17-35)

29 (20-25)＜0.001c

Postoperative outcomesMorbidity

37 (72.5)

181 (80.8)

55 (84.6)

27 (93.1)

0.028c20 (39.2)

87 (38.8)

28 (43.1)

15 (51.7)

0.285cPostoperative hospital stay, day

15 (11-39)

20 (13-38)

24 (18-40)

35 (23-49)＜0.001b30-day mortality
90-day mortality

0 (0)1 (2.0)0 (0)1 (0.5)0 (0)2 (3.1)

0 (0)
0 (0)

0.732c30-day failure to rescue
90-day failure to rescue

0 (0)1 (2.8)0 (0)1 (0.6)0 (0)2 (3.6)

0 (0)
0 (0)

0.814cParameters
Surgical outcomes
Operation time, minaa

Major complication ≥ CD grade IIIaa

Note : Values in parentheses are percentages unless indicated otherwise.
Abbreviation : CD grade, Clavien-Dindo classification grade.
aMedian (IQR)b

Jonckheere-Terpstra trend test.

cCochran-Armitage trend test.

700 ml vs 900 ml, respectively ; P＜0.001), intraopera­

significant stepwise increases with increasing difficulty.

tive transfusion rate (11.8 ％ vs 12.6 ％ vs 40.0 ％ vs

The duration of postoperative hospital stay was also62.1 ％, respectively ; P＜0.001), expert surgeon rate

significantly associated with the degree of difficulty(15.7 ％ vs 28.6 ％ vs 56.9 ％ vs 78.9 ％, respectively ;(median : 15 days vs 20 days vs 24 days vs 35 days,

P＜0.001) and surgeons’ career (19 years vs 23 years

respectively ; P＜0.001). A trend test of the incidence

vs 29 years vs 29 years, respectively ; P＜0.001) showedof morbidity was significant increased with increasing

No. 1, 2024

23

Yamazaki・Shimizu・Kubota et al.
Table 4 Comparison of surgical and postoperative outcomes in patients who underwent group C and D high-level HBP
surgeries between non-expert surgeons versus expert surgeonsParameters
Surgical procedures
Right or left trisectionectomy of the liver
Right or left hepatectomy with extrahepatic bile duct resection
Central bisectionectomy of the liver
Left or extended left hepatectomy and pancreatoduodenectomy
Liver transplantation recipient operation
Right or extended right hepatectomy and pancreatoduodenectomy
Trisectionectomy of the liver with pancreatoduodenectomy
Trisectionectomy of the liver with portal vein resection
Trisectionectomy of the liver with extrahepatic bile duct resection
The others (with portal vein resection)
Surgical outcomes
Operation time, mina
Blood loss, mla
Transfusion
Postoperative outcomesMorbidity
Major complication ≥ CD grade IIIa
Postoperative hospital stay, daya
30-day mortality
90-day mortality
30-day failure to rescuer
90-day failure to rescuer

Non-expert(n＝48)

Expert(n＝85)

1 (2.1)
12 (25.0)
3 (6.3)1 (2.1)14 (29.2)
0 (0)
0 (0)
0 (0)
1 (2.1)16 (33.3)

7 (8.2)23 (27.1)
2 (2.4)4 (4.7)23 (27.1)
5 (5.9)2 (2.4)6 (7.1)8 (9.4)5 (5.9)711 (625-958)
1025 (650-3410)
29 (60.4)

689 (579-831)
850 (540-1420)
46 (54.1)

0.065
0.139
0.504

43 (89.6)
19 (39.6)

70 (82.4)
41 (48.2)

0.442
0.368

28 (18-38)
1 (2.1)1 (2.1)1 (2.3)1 (2.3)28 (20-50)
0 (0)2 (2.4)0 (0)2 (2.9)

0.320
0.361
1.000
0.381
1.000

P value
0.113

Note : Values in parentheses are percentages unless indicated otherwise.
Abbreviation : CD grade, Clavien-Dindo classification grade.
aMedian (IQR)

difficulty (72.5 ％ vs 80.8 vs 84.6 vs 93.1 ％, respectively ;was only in non-expert surgeon group.

P＝0.028). However, major complications ≥ CD gradeＤ Independent preoperative prognostic factors for

IIIa and 90-day mortality rates did not differ amongmajor complications

the four groups (39.2 ％ vs 38.8 ％ vs 43.1 ％ vs 51.7 ％,The results of univariate and multivariate analyses

respectively ; P＝0.285 and 2.0 ％ vs 0.5 ％ vs 3.1 ％of the preoperative risk factors for major postopera­

vs 0 ％, respectively ; P＝0.732) and there were no sig­

tive complications are shown in Table 5. The cut-off

nificant differences in 30- or 90-day FTR rates among

value for age was determined by ROC curve analysis,

the four groups (30-day : 0 ％, 0 ％, 0 ％, and 0 ％ ; 90-

and age ≥ 57 years was considered positive. In multi­

day : 2.8 ％ , 0.6 ％ , 3.6 ％ , and 0 ％ , respectively)

variate analysis, age ≥ 57 years (odds ratio : 2.152,(Table 3).

95 ％ confidence interval : 1.286-3.600 ; P＝0.004) and

Additionally, the group C and D high-level HBP

difficulty classification D (odds ratio : 2.836, 95 ％ con­surgeries which by non-expert surgeons were com­

fidence interval : 1.318-6.103 ; P＝0.008) were indepen­

pared with expert surgeons (Table 4). There wasdent risk factors for major postoperative complications.

trend that the operation time was longer in non-expert

Ｅ

Performance of difficulty classification

surgeon group, however, there was not any signifi­

Surgical difficulty was indicated by operation time,cant difference between two groups about morbidity

blood loss, postoperative complications, and durationand mortality. 30-day mortality and 30-day FTRof postoperative hospital stay. To develop the ROC

24

Shinshu Med J. 72

For safety of high-level HBP surgery
Table 5 Uni- and multivariate analysis of the preoperative risk factors for postoperative major complications
Univariate
Variables

Multivariate

Odds ratio

P

Age≥ 57 yearsa

1.667 (1.038-2.675)＜0.001＜57 yearsa

1.000 (reference)

Sex
Male
FemaleBody-mass index≥ 25 kg/m2＜25 kg/m2
Smoking
Yes
No
Drinking
Yes
No
Hypertension
Yes
No
Diabetes mellitus
Yes
No
Pulmonary disease
Yes
No
Heart disease
Yes
No
ASA-PS≥3
1-2
Difficulty classification
D
C
B
A
Expert surgeon
Yes
No

Odds ratioP

2.152 (1.286-3.600)

0.004

1.000 (reference)

0.892 (0.640-1.243)
1.000 (reference)

0.499

0.832 (0.516-1.341)

0.450

1.000 (reference)
1.033 (0.713-1.496)
1.000 (reference)

0.864

1.088 (0.740-1.601)
1.000 (reference)

0.667

0.924 (0.634-1.344)
1.000 (reference)

0.678

1.092 (0.711-1.678)
1.000 (reference)

0.687

0.788 (0.330-1.836)
1.000 (reference)

0.591

0.734 (0.293-1.836)
1.000 (reference)

0.508

0.683 (0.389-1.200)
1.000 (reference)

0.185

1.288 (0.999-1.660)
1.095 (0.766-1.546)
0.982 (0.559-1.765)
1.000 (reference)

0.051
0.606
0.982

1.065 (0.737-1.538)
1.000 (reference)

0.738

2.836 (1.318-6.103)
1.066 (0.526-2.160)
0.986 (0.563-1.005)
1.000 (reference)

0.008
0.860
1.796

Note : Values in parentheses are 95 ％ confidence intervals.
Abbreviation : ASA-PS, American Society of Anesthesiologists physical status.
a

The cut-off value was determined using Receiver Operating Characteristic curve analysis.

curves, we converted the continuous variables of op­≥ 20 days were set as positive values, while lower

eration time, blood loss, and duration of postopera­

values were set as negative values. The AUC for op­

tive hospital stay into dichotomous variables based

eration time was 0.739 (P＜0.001), for blood loss wason their median values. An operation time ≥ 530 min,

0.690 (P＜0.001), for morbidity was 0.575 (P＝0.024),

blood loss ≥ 450 ml, and postoperative hospital stayand for postoperative hospital stay was 0.649 (P＜No. 1, 2024

25

Yamazaki・Shimizu・Kubota et al.

Fig. 2 Receiver operating characteristic curves for performance of difficulty classification according to operation
time, blood loss, morbidity, and postoperative hospital stay.

or complexity of the different types of HBP surgery.

0.001) (Fig. 2).
Ⅳ

Discussion

Several complexity classifications of liver resection
have been reported to stratify surgical and postoper-

Although the safety of high-level HBP surgeries

ative outcomes, including operation time, blood loss,

has increased, the 90-day mortality rate differs wide-and morbidity8）7）14）. Lee et al.6）9） showed the complex-

ly depending on the surgical procedure5）. Attempts

ities of various liver resections using expert opinions

to provide benchmark values to help standardize sur-and formed a new classification, followed by studies

gical outcomes for some high-level HBP surgeries

targeting the difficulty classification of liver resec-

12）
13）

have been reported. These procedures are recog-tion. However, there is currently no difficulty classifi-

nized as HBP surgeries with high degrees of difficul-

cation system covering all high-level HBP surgeries,

ty and complexity, which require surgeons to under-

including not only liver resections, but also biliarygo theoretical, gradual, and efficient education andand pancreatic surgeries. To the best of our knowl-training systems to become proficient and thus im-edge, the present study is the first to attempt toprove the safety of these procedures, based on a sim-

establish a difficulty classification system aimed at

ple and accurate system for classifying the difficulty

improving the safety of high-level HBP surgeries

26

Shinshu Med J

Vol. 72

For safety of high-level HBP surgery

of FTR rate11） has been presented as an indicator forand the efficacy of expert training.
In this study, high-level HBP surgeries were clas­

evaluating postoperative outcomes. Endo18） highlighted

sified into four groups based on expert HBP surgeon

the differences in the performance of hepatopancre­

opinion. This methodology of difficulty classification

atoduodenectomy, as an extremely difficult surgicalbased on expert opinion was also adopted in previous

procedure, among certified levels of institution by fo­

studies, and allowed the perceived difficulties of vari­cusing on FTR. In the present study, there were noous surgical procedures to be quantified and reflectedsignificant differences in 30- and 90-day FTR rates

6）9）. In the present study, the surgi­

among groups A to D. This may suggest that patients

cal difficulty levels were well-balanced among sur­were rescued by the appropriate treatment of com­geons and the results were in line with the 90-day

plications, given that the incidence of major compli­

mortality rates in Japan according to the National

cations tended to increase gradually with increasing

Clinical Database. However, it is also necessary todifficulty, while the FTR rates were similar among

confirm if the established difficulty classification is

all four groups. However, the small sample size of theappropriate. Although the current sample size wasentire cohort and limited number of events means

too small to determine if this difficulty classificationthat it is difficult to draw a definitive conclusion fromwas appropriate based on the mortality rate, surgicalthese results. FTR may thus be an indicator for eval­difficulty can also be represented by operation time anduating outcomes in relation to difficulty group, as

in a classification

15）

blood loss . Operation time and blood loss showed

well as a useful indicator of institutional and operator

significant stepwise increases in groups A to D in thecriteria for each level of high-level HBP surgery.

present study, in line with increasing subjective diffi­

This study had several limitations. First, this was aculty. Differences in surgical outcomes, such as oper­

retrospective study with a small sample size, making

ation time and blood loss, among different difficulty

it difficult to reach definitive conclusions. Second, thislevels has been used to evaluate the accuracies of dif­

was a single-center study, which did not consider

ficulty scoring systems for patient16）17）and of the com­

institution and surgeon levels based on the JHBPS

7）

board certification system. Third, the surgical proce­

Furthermore, Kawaguchi et al. and Jang et al. eval­dure points were not adjusted according to theuated the accuracy of classification systems for re­surgeon’s experience, because of the small number offlecting surgical difficulty using ROC curve analyses

surgeons who completed the questionnaire. Finally,of operation time and blood loss. In line with these

based on our institutional characteristics, three qua­studies, ROC curve analysis showed good perfor­

ters of group D was liver transplantation recipient

mance in the current novel difficulty classification for

operation and it might contain bias. However, more-differentiating these surgical outcomes. These find­experienced surgeons may tend to evaluate the sameings suggest that this novel difficulty classification

surgical procedure as being easier than less-expe­

accurately reflected the complexity of the surgicalrienced surgeons6）9）. The perceived difficulty scoresprocedures.

derived from surgeons’ opinions should thus be adjust­plexity classification of liver resection procedures .
8）

7）

Postoperative outcomes, such as mortality, morbid­

ed according to the individual surgeon’s background

ity, and the incidence of major complications, havecharacteristics, including their experience, certification,

also been used as important indicators for evaluating

and affiliation6）9）.

the validity of classification systems. In the present

Despite these drawbacks, we believe that our find­study, the morbidity rate of any complications in­ings will be of interest to HBP surgeons, given that,creased in line with increasing difficulty (P＝0.028).

to the best of our knowledge, this represents the first

In contrast, however, the mortality rates were similarreport of a novel difficulty classification of high-levelin all four groups, possibly due to the low mortality

HBP surgeries able to predict the surgical risk asso­

rate in the study population. Furthermore, the concept

ciated with each surgical procedure. Moreover, thisNo. 1, 2024

27

Yamazaki・Shimizu・Kubota et al.

classification is also considered useful for the educa­

nationwide studies are needed to confirm these results.

tion of surgeons. Factors related to a surgeon’s career,

Acknowledgments

such as years of experience, number of cases han­dled, and certification, need to be collected to evaluate

We thank Susan Furness, PhD, from Edanz (https://this difficulty classification. In this study, the numberjp.edanz.com/ac) for editing a draft of this manuscript.

of years in the surgeons’ careers was recorded, andthere was a significant stepwise increased with in­creasing difficulty. These results suggest that theclassification provides a valid basis for selecting sur­geons based on difficulty.

The authors declare that they have no conflict ofinterest.
Informed consent was obtained from all individual
participants included in the study.

In conclusion, we established a novel difficulty clas­

This study protocol was approved by the Ethics

sification for high-level HBP surgeries based on

Committee of Shinshu University School of Medicine

surgeon opinion. This classification may provide an(registration number : 5358) and was conducted inindicator of difficulty and complexity, which will aid

accordance with the principles of the Declaration of

the appropriate allocation of surgeons and the effi­

Helsinki.

cient and safe training of experts. Further large-scale
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（2023. 8. 8 received ; 2023. 9. 15 accepted）

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