ORIGINAL ARTICLE

Multivariate Analysis of Factors Influencing Length of
Hospitalization and Medical Costs of Cholecystectomy for Acute
Cholecystitis in Japan: A National Database Analysis
Atsuhiko Murata,1 Kohji Okamoto, 2 Shinya Matsuda,1 Kazuaki Kuwabara, 3 Yukako Ichimiya,1Yasufumi Matsuda,1 Tatsuhiko Kubo1 and Yoshihisa Fujino1

1 Department of Preventive Medicine and Community Health, School of Medicine, University of Occupational andEnvironmental Health, Fukuoka, Japan

2 Department of Surgery, Yahata Municipal Hospital, Fukuoka, Japan

3 Department of Health Care Administration and Management, Graduate School of Medical Sciences,

Kyushu University, Fukuoka, Japan(Received for publication on November 15, 2012)(Revised for publication on January 18, 2013)(Accepted for publication on February 21, 2013)(Published online in advance on August 5, 2013)

Little information is available on the factors influencing length of stay (LOS) in hospital and medical
costs during hospitalization associated with cholecystectomy for acute cholecystitis. We determined
the independent factors affecting LOS and medical costs of patients who underwent cholecystectomy
for acute cholecystitis based on data from the Diagnosis Procedure Combination (DPC) database. In
2008, a total of 2176 patients with acute cholecystitis were referred for cholecystectomy to 624 hospitals in Japan. We collected patient characteristics and data on treatments for acute cholecystitis
using the DPC database and identified independent factors affecting LOS and medical costs duringhospitalization using multiple linear regression models. Analysis revealed that early cholecystectomy was significantly associated with a decrease in LOS, whereas longer preoperative antimicrobial
therapy was significantly associated with an increase of LOS: the standardized coefficient for earlycholecystectomy was −0.372 and that for preoperative antimicrobial therapy was 0.353 (P < 0.001).
These procedures were also significant independent factors with regard to medical costs during hospitalization: the standardized coefficient for early cholecystectomy was −0.391 and that for preoperative antimicrobial therapy was 0.335 (P < 0.001). Early cholecystectomy significantly reduces the
LOS and medical costs of cholecystectomy for acute cholecystitis, while preoperative antimicrobial
therapy increases LOS and medical costs during hospitalization. These results highlight the need for
health care implementations such as promotion of early cholecystectomy, appropriate use of antimicrobial drugs, and centralization of patients with cholecystectomy for acute cholecystitis in Japan.
(doi: 10.2302/kjm.2012-0015-OA; Keio J Med 62 (3) : 83–94, September 2013)

Keywords: acute cholecystitis, health care costs, cholecystectomy, antimicrobial therapy, databaseand biliary tract obstruction.1,2 In the United States, acutecholecystitis afflicts more than 20 million people annually and results in direct costs of more than US$6.3 billion.2,3 According to a comprehensive survey of health

Introduction
Acute cholecystitis is an acute inflammatory diseaseof the gallbladder usually caused by bacterial infection

Reprint requests to: Atsuhiko Murata, MD, PhD, Department of Preventive Medicine and Community Health, School of Medicine, Universityof Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan, E-mail: amurata@med.uoeh-u.ac.jp
Copyright © 2013 by The Keio Journal of Medicine
83

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Murata A, et al: Factors Affecting LOS and Cost of Cholecystectomy

and welfare in Japan, the number of those with acutecholecystitis increased by approximately three times between the 1970s and 1990s.4 Acute cholecystitis is oneof the most frequently encountered conditions in daily
medical practice in developed countries.
Cholecystectomy is widely performed in many countries as a surgical treatment for acute cholecystitis.5–8
In particular, laparoscopic cholecystectomy has been
increasingly adopted as the standard method of surgery
over the past 15 years, and the safety and efficacy of thissurgical approach have been confirmed by many studies.6–8 Furthermore, laparoscopic cholecystectomy isrecognized as a cost-effective treatment for patients withacute cholecystitis.8–10 Zacks et al.9 reported that laparoscopic cholecystectomy significantly reduced hospital costs as well as length of stay (LOS) and mortality
compared with open procedures. Therefore, laparoscopiccholecystectomy is a significant advance in health carequality for patients with acute cholecystitis.9,10
Little information is available on the factors influencing LOS in hospital and medical costs during hospitalization associated with cholecystectomy for acute cholecystitis. In addition, there have been no reports of analyses of
LOS and medical costs based on hospital discharge datataking into account patient characteristics, other treatments for the management of acute cholecystitis, and thetype of cholecystectomy. Determination of independent
factors that affect LOS and medical costs during hospitalization of patients who undergo cholecystectomy foracute cholecystitis could benefit the quality managementof patient medical care and could have significant implications for health care policy decision making in Japan.
In this study, we determined the factors affecting LOS
and medical costs during hospitalization of patients undergoing cholecystectomy for acute cholecystitis. This
was achieved using the national administrative databasedeveloped in a Japanese case-mix system project named
Diagnosis Procedure Combination (DPC).

DPC system is common practice in Japan. The number of
acute care hospitals has increased in the administrative
database of the DPC system. Data from approximately
450,000 inpatients have been collected as of 2007, andthese make up approximately 90% of the total acute care
inpatient hospitalizations during this time.12–14
Each patient’s financial data, claim information, anddischarge summary, including principal diagnosis, complications, and comorbidities during hospitalization,
are recorded in the administrative database of the DPC
system. These data are coded according to the International Classification of Diseases and Injuries 10th Revision (ICD-10). This administrative database also contains comprehensive medical information, including allinterventional and surgical procedures, medications, anddevices that have been indexed in the original Japanese
code. The Ministry of Health, Labour and Welfare of Japan assigns these codes (e.g., laparoscopic cholecystectomy is defined as K672-2 in the original code).11–14 The
administrative database of the DPC system contains total medical costs, including all costs for each completed
procedure. These costs are obtained using a standardized
fee-for-service payment system and are recorded in thenationally uniform fee table.15 The date and the amountof care delivered that day are also recorded in the DPC
administrative database.11–15

Materials and Methods
Administrative database associated with the DPC system
In Japan, the health care system has severe financial
issues due to expensive advances in medical technology,
a rapidly aging society, and extended patient hospitalizations.11 To address these issues, the Ministry of Health,Labour and Welfare and its affiliated research institutehave begun investigating whether the Japanese case-mix
classification system can be used to standardize medical
profiling and payment.11 In 2003, this resulted in Japanesecase-mix projects based on the DPC system being introduced to 82 academic hospitals (the National Cancer Center, the National Cardiovascular Center, and 80 university
hospitals).12–14 Reimbursement of insurance based on the

Study setting
We selected 2176 patients diagnosed with acute cholecystitis who underwent cholecystectomy during hospitalization in 624 DPC participating hospitals (56 academic
and 568 community hospitals) between April and December 2008. These hospitals are dispersed throughout Japanand play a leading role in providing acute care medicine,advancing medical research, and educating students andmedical residents.11–15 The principal diagnosis of acutecholecystitis was recorded using the ICD-10 code; in thepresent analysis, acute cholecystitis was coded as K810.
The use of DPC data was permitted by all institutions
and hospitals that provided detailed data. The research
protocol of the study was approved by the ethics committee of medical care and research of the University ofOccupational and Environmental Health, Kitakyushu,
Japan.
Study variables
Study variables included the type of cholecystectomy(laparoscopic or open procedures), the timing of cholecystectomy (early or delayed procedures), cholecystectomy-related complications, age, sex, chronic comorbid
conditions, use of ambulance transportation and the intensive care unit (ICU), hospital type and size, in-hospitalmortality, LOS, and medical costs during hospitalization.

Keio J Med 2013; 62 (3): 83–94

Early cholecystectomy was defined as cholecystectomy
performed within 4 days of admission, as described inprevious studies.16,17 Cholecystectomy-related complications were defined as any of the following ICD-10 codes:
cholecystectomy-related complications (T80-T87); bowel
obstruction (K650, K658-9, K660, and K913); and peritonitis (K560, K562, and K565-7).18 Age categories werestratified as follows: less than 50 years, 50–59 years, 60–
69 years, 70–79 years, and 80 years or more. The Charlson Comorbidity Index (CCI) was used to determine
the severity of chronic comorbid conditions. The CCI
is widely used for measuring comorbidity and has beenpreviously validated.11,13–15 The CCI score was calculated for each patient; previous studies have demonstrated
an association between the CCI and the ICD-10 code.19
The CCI score represented the score of all types of comorbidity, and we initially analyzed it as a continuous
variable. However, to simplify the results, we establishedthree categories of severity of comorbidity for categorical variables as follows: 0=mild; 1=moderate; and ≥2=severe.11,13–15 We classified the type of hospital as academic
or community. We also categorized the size of hospitals
into three groups based on the number of hospital beds
as follows: small (<200 beds), medium (200–600 beds),
and large (>600 beds).15 Regarding the analysis of medical costs, we assumed a yen-to-dollar exchange rate of
approximately 80 yen to the US dollar (October 2012).
In addition, we collected data in the DPC database withregard treatments for acute cholecystitis other than cholecystectomy, i.e., intravenous antimicrobial therapy andgallbladder drainage (endoscopic or percutaneous procedures). In this study, we classified the preoperative andpostoperative administration of intravenous antimicrobial drugs and calculated the duration of antimicrobial
therapy for each patient. Regarding the selection of thesetreatments, we referred to the Tokyo Guidelines for acutecholecystitis.7,20,21
Statistical analysis
For tests of statistical significance, we used the chisquare test for categorical data and the Mann–Whitney
U test for continuous variables. For the main analyses of
LOS and medical costs during hospitalization, multiple
linear regression models were used to identify the independent factors for patients that affected LOS and medical costs. These models addressed potential confounding variables in the case mix data by controlling for theseverities of chronic comorbid conditions and additional
factors related to LOS and medical costs during hospitalization, such as types and timing of cholecystectomy,
cholecystectomy-related complications, age, sex, use ofambulance transportation and the ICU, duration of preoperative and postoperative intravenous antimicrobial
therapy, gallbladder drainage, and hospital type and size.

85

We also performed a stratified analysis to take into account the severity of acute cholecystitis using data for
hospital type and size. Because the distributions of LOS
and medical costs during hospitalization were skewed to
the right, LOS and medical costs were log-transformedin this model. In addition, the variance inflation factor(VIF) was used as a measure for the degree of multicollinearity of each independent variable with the other independent variables in a regression model.
A value of P < 0.05 was considered significant. All statistical analyses were performed using the STATA statistical software package version 11.0 (Stata Corporation,
College Station, TX, USA).
Results
A total of 2126 patients who had undergone cholecystectomy for acute cholecystitis were identified for thisstudy: 1271 patients underwent laparoscopic cholecystectomy and 855 patients underwent open cholecystectomy
across 624 hospitals. The in-hospital mortality after admission was 0.7%, while the in-hospital mortality within
30 days after admission was 0.4%. The mean LOS of all
patients was 21.1 ± 17.3 days and the mean medical cost
was US$12,341.5 ± US$14,083. The breakdown of LOS
and medical costs during hospitalization is shown in Figure 1A and B.
The clinical characteristics and presentations of the patients are shown in Table 1. Patients who underwent laparoscopic cholecystectomy were significantly more likely
to have had early cholecystectomy (P < 0.001). There
was no significant difference with regard to the proportion of cholecystectomy-related complications and malepatients between procedures. Use of the ICU was significantly higher in patients who had open cholecystectomy
than in those who had laparoscopic procedures (19.3% vs.
7.4%, P < 0.001). Regarding other treatments for acutecholecystitis, patients who had open cholecystectomy
underwent longer postoperative antimicrobial therapy
and more gallbladder drainage before cholecystectomy
compared with those who had laparoscopic cholecystectomy (P < 0.001). The in-hospital mortality of patientswas significantly higher in patients who underwent opencholecystectomy compared with those who underwent
laparoscopic cholecystectomy (1.5% vs. 0.1%, P < 0.001).
A significant variation of mean LOS and medical costs
during hospitalization was observed between groups (P< 0.001). The mean LOS and costs during hospitalization
were significantly higher for delayed procedures than forearly procedures for both laparoscopic and open procedures (P < 0.001; Fig. 2A and B).
Multiple linear regression analyses of factors associated with hospital LOS are presented in Table 2. The
largest VIF among all the variables was 2.80 (patients
aged 80 years or more), indicating little need for concern
regarding problems caused by multicollinearity. After

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Murata A, et al: Factors Affecting LOS and Cost of Cholecystectomy

Fig. 1 The length of stay (LOS) and medical costs during hospitalization.
Breakdown of the data for hospital LOS (A) and medical costs during hospitalization (B).

adjustment for potentially confounding demographic andclinical variables, early cholecystectomy was most significantly associated with a decrease in LOS. The standardized coefficient for early cholecystectomy was −0.372(P < 0.001). In addition, laparoscopic cholecystectomy
was also associated with a decrease in LOS with a standardized coefficient of −0.184 (P < 0.001). These results
indicate that LOS was significantly shorter in patients

Keio J Med 2013; 62 (3): 83–94

87

Table 1 Clinical characteristics and presentations of patients based on Japanese national administrative database
Laparoscopic cholecystectomy (n = 1271)

Open cholecystectomy (n = 855)

P value

50.3
49.7
1.6

42.3
57.7
1.8

<0.001

10.2
11.1
21.6
29.3
27.8

10.1
12.5
18.8
28.9
29.7

0.479

56.1

57.6

0.498

64.4
18.5
17.1
17.9
7.4

49.8
25.2
25.0
16.7
19.3

<0.0015.3 (5.9)
3.9 (4.4)
21.4

5.6 (7.0)
6.3 (6.7)
33.5

0.248
<0.001<0.001

10.3
89.7

11.4
88.6

0.448

23.1
54.0
22.9

22.2
60.0
17.8

0.008

0.1
18.3 (15.0)10765.1 (11824.4)

1.5
25.2 (19.4)
14684.9 (16626.1)<0.001<0.001<0.001Cholecystectomy
Timing of cholecystectomy (%)
Early (within 4 days)
Delayed (5 days or more)
Cholecystectomy-related complications (%)
Patient characteristics
Age categories (%)
Less than 50 years
50–59 years
60–69 years
70–79 years
80 years or moreSex (%)
Male patients
Severity of comorbid conditions (%)
Mild (CCI, 0)
Moderate (1)Severe (2 or more)
Ambulance transportation (%)
Use of intensive care unit (%)
Other treatments for acute cholecystitis
Antimicrobial therapy
Preoperative administration (days, SD)
Postoperative administration (days, SD)
Gallbladder drainage before cholecystectomy (%)
Hospital characteristics
Hospital type (%)
Academic hospitals
Community hospitals
Hospital size (%)
Small (< 200 beds)
Medium (200–600 beds)
Large (> 600 beds)
Clinical outcomes
In-hospital mortality (%)
Mean length of stay (days, SD)
Mean medical costs (dollars, SD)

0.766

0.465
<0.001

CCI, Charlson comorbidity index; SD, standard deviation.

who underwent early cholecystectomy or laparoscopiccholecystectomy. Conversely, longer preoperative antimicrobial therapy was significantly associated with anincrease in LOS with a standardized coefficient of 0.353(P < 0.001). Furthermore, longer postoperative antimicrobial therapy was also associated with an increase in LOS
with a standardized coefficient of 0.312 (P < 0.001). Patients aged 70–79 years and those aged 80 years or more,
moderate and severe comorbid conditions, use of an ICU,

and gallbladder drainage were slightly associated with anincrease in LOS.
Early cholecystectomy and laparoscopic cholecystectomy were also considerably associated with a decrease
in medical costs during hospitalization (Table 3). The
standardized coefficient for early cholecystectomy was−0.391, while that for laparoscopic cholecystectomy was−0.187 (P < 0.001). Medium-sized and large hospitals
were slightly associated with a decrease in medical costs

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Murata A, et al: Factors Affecting LOS and Cost of Cholecystectomy

Fig. 2 Effect of early and delayed procedures on mean LOS and medical costs during hospitalization.
Effect of early and delayed procedures for both laparoscopic and open cholecystectomies: Mean hospital LOS (A) and mean medical
costs during hospitalization (B).

Keio J Med 2013; 62 (3): 83–94

89

Table 2 Linear regression analysis of factors associated with log-transformed length of hospitalization
Independent variables
Kinds of cholecystectomy
Laparoscopic cholecystectomy(Reference: open cholecystectomy)
Timing of cholecystectomy
Early cholecystectomy(Reference: delayed cholecystectomy)
Cholecystectomy-related complications
Occurred(Reference: did not occur)Age
50–59 years
60–69 years
70–79 years
80 years or more
(Reference: less than 50 years)
Sex
Male patients(Reference: female patients)
Severity of comorbid conditions
Moderate conditions
Severe conditions(Reference: mild conditions)
Ambulance transportation
Used(Reference: not used)
Intensive care unit
Used
(Reference: not used)
Antimicrobial therapy
Preoperative administration (per day)Postoperative administration (per day)
Gallbladder drainage
Performed(Reference: not performed)
Hospital type
Academic hospitals(Reference: community hospitals)
Hospital size
Medium-sized hospitals
Large hospitals(Reference: small hospitals)

Unstandardized coefficient

95% confidence intervalStandardized coefficient

P value– 0.256[– 0.296, – 0.216]– 0.184<0.001– 0.523[– 0.567, – 0.480]– 0.372<0.0010.057[– 0.084, 0.199]

0.010

0.428

0.004
0.038
0.075
0.099

[– 0.027, 0.109][– 0.029, 0.106][0.003, 0.146][0.019, 0.179]

0.026
0.025
0.044
0.046

0.245
0.267
0.039
0.014

– 0.001[– 0.039, 0.036]– 0.001

0.928

0.067
0.130

[0.019, 0.114][0.082, 0.179]

0.040
0.077

0.005
<0.0010.024[– 0.024, 0.074]

0.013

0.328

0.086

[0.027, 0.145]

0.041

0.004

0.037
0.038

[0.034, 0.041][0.035, 0.042]

0.353
0.312

<0.001<0.001

0.112[0.066, 0.157]

0.072<0.001– 0.065[– 0.125, – 0.004]– 0.0290.035– 0.057– 0.066[– 0.103, – 0.011][– 0.123, – 0.010]– 0.041– 0.039

0.015
0.021

F-test for the model: P < 0.001, R 2 = 0.594.

during hospitalization (standardized coefficients: −0.047
and −0.041, respectively). The largest VIFs among all thevariables were 2.78 (patients aged 80 years or more), indicating little need for concern regarding problems caused
by multicollinearity. Increased duration of preoperativeand postoperative antimicrobial therapies significantly
raised medical costs during hospitalization. The standardized coefficient for preoperative antimicrobial therapy was 0.335, while that for postoperative antimicrobial
therapy was 0.294 (P < 0.001).

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90

Table 3 Linear regression analysis of factors associated with log-transformed medical costs during hospitalization
Independent variables
Kinds of Cholecystectomy
Laparoscopic cholecystectomy(Reference: open cholecystectomy)
Timing of cholecystectomy
Early cholecystectomy(Reference: delayed cholecystectomy)
Cholecystectomy-related complications
Occurred(Reference: did not occur)Age
50–59 years
60–69 years
70–79 years
80 years or more
(Reference: less than 50 years)
Sex
Male patients(Reference: female patients)
Severity of comorbid conditions
Moderate conditions
Severe conditions(Reference: mild conditions)
Ambulance transportation
Used(Reference: not used)
Intensive care unit
Used
(Reference: not used)
Antimicrobial therapy
Preoperative administration (per day)Postoperative administration (per day)
Gallbladder drainage
Performed(Reference: not performed)
Hospital type
Academic hospitals(Reference: community hospitals)
Hospital size
Medium-sized hospitals
Large hospitals(Reference: small hospitals)

Unstandardized coefficient

95% confidence intervalStandardized coefficient

P value– 0.286[– 0.331, – 0.242]– 0.187<0.001– 0.605[– 0.654, – 0.556]– 0.391<0.0010.072[– 0.086, 0.230]

0.012

0.371

0.043
0.039
0.073
0.091

[– 0.033, 0.120][– 0.036, 0.115][– 0.006, 0.153][0.001, 0.180]

0.026
0.023
0.039
0.038

0.266
0.312
0.071
0.045

– 0.003[– 0.046, 0.039]– 0.002

0.877

0.084
0.152

[0.030, 0.137][0.097, 0.206]

0.045
0.081

0.002
<0.0010.026[– 0.028, 0.081]

0.013

0.347

0.077

[0.011, 0.144]

0.033

0.021

0.039
0.039

[0.036, 0.043][0.035, 0.044]

0.335
0.294

<0.001<0.0010.126[0.075, 0.178]

0.074<0.001– 0.063[– 0.131, 0.004]– 0.0260.067– 0.071– 0.075[– 0.123, – 0.020][– 0.139, – 0.012]– 0.047– 0.041

0.007
0.019

F-test for the model: P < 0.001, R 2 = 0.581.

Finally, stratified analyses for log-transformed LOS
and medical costs during hospitalization were performed
using a multiple linear regression model. Early cholecystectomy, laparoscopic cholecystectomy, and preoperativeand postoperative antimicrobial therapies were indepen-

dent factors that influenced LOS and costs during hospitalization (Tables 4 and 5).

Keio J Med 2013; 62 (3): 83–94

91

Table 4 Stratified analysis associated with log-transformed length of hospitalization
Independent variables

Unstandardized coefficient

95% confidence intervalStandardized coefficient

P value– 0.263– 0.453
0.055
0.039

[– 0.380, – 0.147][– 0.582, – 0.324][0.044, 0.066][0.029, 0.050]– 0.185– 0.320
0.450
0.330

<0.001<0.001<0.001<0.001– 0.210– 0.410
0.052
0.025

[– 0.299, – 0.103][– 0.517, – 0.303][0.041, 0.062][0.018, 0.033]– 0.137– 0.286
0.400
0.245

<0.001<0.001<0.001<0.001– 0.266– 0.584
0.031
0.046

[–.322, –.210][–.645, –.523][0.027, 0.035][0.040, 0.051]– 0.192– 0.410
0.331
0.349

<0.001<0.001<0.001<0.001– 0.276– 0.468
0.047
0.033

[– 0.362, – 0.191][– 0.567, – 0.369][0.037, 0.056][0.025, 0.041]– 0.207– 0.348
0.386
0.274

<0.001<0.001<0.001<0.001

Academic hospitals
Large hospitals
Laparoscopic cholecystectomy
Early cholecystectomy
Preoperative administration
Postoperative administration
Community hospitals
Small hospitals
Laparoscopic cholecystectomy
Early cholecystectomy
Preoperative administration
Postoperative administration
Medium-sized hospitals
Laparoscopic cholecystectomy
Early cholecystectomy
Preoperative administration
Postoperative administration
Large hospitals
Laparoscopic cholecystectomy
Early cholecystectomy
Preoperative administration
Postoperative administration

There were no academic hospitals with less than 600 beds.

Discussion
Numerous studies regarding analysis of LOS and medical costs for patients undergoing cholecystectomy foracute cholecystitis have been reported worldwide. However, few studies have analyzed LOS and medical costs ofpatients undergoing cholecystectomy for acute cholecystitis taking into account patient characteristics and othertreatments using a national administrative database.
Therefore, an analysis focusing on patient characteristics
and other treatments, rather than solely on the type ofcholecystectomy, was required to develop more effective
strategies for the management of acute cholecystitis. We
conducted the present study using the Japanese administrative database to determine the factors that affect LOS
and medical costs during hospitalization of patients who
had undergone cholecystectomy for acute cholecystitis .
The current study demonstrated that early cholecystectomy reduced LOS and medical costs, whereas preoperative
antimicrobial therapy for cholecystectomy significantly
increased LOS and medical costs during hospitalization.
Regarding the effect of early cholecystectomy on LOS
and medical costs of patients who underwent cholecystectomy for acute cholecystitis, our current results are consistent with those of several previous studies.22–25 Fromthe 1980s (when laparoscopic cholecystectomy was notcommon) onward, early cholecystectomy has been recognized as a relatively cost-effective procedure for patientswith acute cholecystitis.22,23 In the past 10 years, the efficacy of early cholecystectomy, especially in laparoscopic
procedures, has been emphasized.24,25 Chandler et al.24
reported that early laparoscopic cholecystectomy significantly reduces LOS and hospital costs, as well as operative blood loss. In a meta-analysis of early laparoscopiccholecystectomy, Gurusamy et al.25 reported that LOS isshorter by 4 days for early laparoscopic cholecystectomy
compared with delayed laparoscopic cholecystectomy.
Therefore, it is plausible that early cholecystectomy isbeneficial for the management of acute cholecystitis interms of reducing LOS and medical costs during hospitalization.
Conversely, we found that longer preoperative antimicrobial therapy was significantly associated with an increase in LOS and medical costs during hospitalization.
Recent studies also suggest that pharmacological expense
is associated with LOS and medical costs during hospitalization for acute cholecystitis.26,27 However, we consider that our results may reflect special circumstances
unique to Japan, and the association between preoperative antimicrobial therapy and LOS and medical costs
could be explained by several factors. First, many physicians in Japan routinely prescribe a long course of anti-Murata A, et al: Factors Affecting LOS and Cost of Cholecystectomy

92

Table 5 Stratified analysis with log-transformed medical costs during hospitalization
Independent variables
Academic hospitals
Large hospitals
Laparoscopic cholecystectomy
Early cholecystectomy
Preoperative administration
Postoperative administration
Community hospitals
Small hospitals
Laparoscopic cholecystectomy
Early cholecystectomy
Preoperative administration
Postoperative administration
Medium-sized hospitals
Laparoscopic cholecystectomy
Early cholecystectomy
Preoperative administration
Postoperative administration
Large hospitals
Laparoscopic cholecystectomy
Early cholecystectomy
Preoperative administration
Postoperative administration

Unstandardized coefficient

95% confidence intervalStandardized coefficient

P value– 0.299– 0.495
0.063
0.030

[– 0.424, – 0.175][– 0.633, – 0.356][0.051, 0.075][0.019, 0.041]– 0.198– 0.328
0.484
0.236

<0.001<0.001<0.001<0.001– 0.314– 0.535
0.054
0.035

[– 0.409, – 0.218][– 0.646, – 0.424][0.044, 0.065][0.026, 0.043]– 0.209– 0.353
0.399
0.253

<0.001<0.001<0.001<0.001– 0.299– 0.677
0.031
0.050

[– 0.362, – 0.236][– 0.745, – 0.608][0.026, 0.036][0.044, 0.056]– 0.195– 0.431
0.300
0.347

<0.001<0.001<0.001<0.001– 0.217– 0.478
0.053
0.026

[– 0.326, – 0.109][– 0.596, – 0.359][0.041, 0.064][0.018, 0.034]– 0.136– 0.305
0.374
0.231

<0.001<0.001<0.001<0.001

There were no academic hospitals with less than 600 beds.

microbial prophylaxis to prevent possible postoperative
infections.28,29 In addition, physicians may be motivatedby the concern that their patients may accuse them ofnegligence if short-course prophylaxis were to result inpostoperative infection.30 Therefore, some patients may
receive unnecessary antimicrobial therapy before undergoing cholecystectomy for acute cholecystitis. Second,some reports have suggested that preoperative LOS in
Japan is significantly longer than that in other developed
countries.30–32 Sekimoto et al.30 reported that the timingof cholecystectomy for acute cholecystitis was mainly
determined by the institutional policy or facilities’ ability in Japan, rather than by the clinical course of the patients. A shortage of surgeons has been recognized as aserious problem and may have resulted from unfavorable
working environments for surgeons or increased risks ofmalpractice suits, so early surgery may impose a heavy
burden on many hospitals in Japan that suffer a shortageof human resources.33 Therefore, we consider that a dependence on antimicrobial therapy, which is the mainstay
of conservative treatments for acute cholecystitis, rather
than early cholecystectomy, possibly explains why preoperative antimicrobial therapy was significantly associatedwith an increase in LOS and medical costs during hospitalization in the current study.

A major strength of the current study is the clinical data
used. Cholecystectomy for acute cholecystitis is usually
performed in acute care hospitals. One of the benefits ofthis national database is that it enables evaluation of alarge number of acute care hospitals in an unbiased manner. Our investigation involved a nationally representative sample of patients who underwent cholecystectomy
for acute cholecystitis in a community setting.11–13 Therefore, the DPC data accurately represent the actual procedures and treatments performed for acute cholecystitis.
Additionally, Japanese original payment codes were applied for details of medical data, including all procedures,devices, and medications used.11–15 These data were
documented daily for each patient.11–15 Therefore, thisadministrative database also enables interested parties
to evaluate outcomes with respect to individual detailed
medical treatments.
Several potential limitations of this study warrant mention. First, the Tokyo Guidelines determine the severityof acute cholecystitis based on laboratory data and imaging findings of patients.34 Regrettably, these patients’laboratory and imaging data are not recorded in the Japanese administrative database.11,13,14 The severity of acutecholecystitis may determine the use of some procedures
such as ventilation and hemodiafiltration or treatments

Keio J Med 2013; 62 (3): 83–94

such as vasopressors and so may affect LOS or medical
costs.35 In particular, severe cholecystitis may be related
to longer antimicrobial therapy or delayed cholecystectomy because the condition may result in serious sequelae,such as organ dysfunction or septic shock.36 Therefore,
further clinical studies evaluating the factors affecting
LOS and medical costs for patients with cholecystectomy
are required that use stricter criteria to define the severityof acute cholecystitis.
Despite these limitations, the current study demonstrated that early cholecystectomy reduced LOS and medical
costs, whereas preoperative antimicrobial therapy significantly increased LOS and medical costs during hospitalization. The current study has implications for healthcare policy decision making and quality of patient care.
Yamashita et al.7 reported that 72% of surgeons fromabroad favored early cholecystectomy, whereas only 33%
of Japanese doctors favored early cholecystectomy in aconsensus meeting for acute cholecystitis. Although one
explanation for this discrepancy could be the differencein circumstances relating to surgery between Japan andother developed countries, there is no doubt that early cholecystectomy is a relatively cost-effective procedure forpatients with acute cholecystitis. Therefore, further promotion of early cholecystectomy may result in decreasing
LOS and savings in medical costs during hospitalizationin Japan. In addition, a previous report suggested that antimicrobial prophylaxis may not be necessary for low-riskpatients with acute cholecystitis undergoing laparoscopiccholecystectomy.37 Therefore, if unnecessary administration of antimicrobial therapy can be lessened, a reduction in LOS and medical costs can be achieved while
maintaining the quality of patient care. Further clinicalstudies are required to determine the appropriate use of
antimicrobial drugs for patients with cholecystectomy,
especially in the preoperative stage.
However, it is impractical to promote early cholecystectomy in all hospitals when considering the current
circumstances relating to surgery in Japan. Therefore,
we consider that it is also essential to promote the centralization of patients who require cholecystectomy foracute cholecystitis and promote early cholecystectomy
in Japan. Regarding medical care in Japan, the specialist healthcare service provider system has been criticized
for being poorly organized with nonsystematic deliveryof services, because health policy has been based on freeaccess to hospitals, unlike in many European countries
or in the United States.14,38,39 Therefore, centralizationof patient care associated with a policy of concentrating medical services, and consequent reduction of local
hospital care, is unlikely to occur in Japan.14,39 However,the current findings provide good evidence to support thecentralization of patients who require cholecystectomy
for acute cholecystitis. Further clinical studies regarding
such centralization also might contribute to the patientreferral policy in Japan.

93

In conclusion, we have demonstrated that early cholecystectomy significantly reduces the LOS and medical
costs of cholecystectomy for acute cholecystitis, whereas
preoperative antimicrobial therapy increases LOS andmedical costs during hospitalization. These results highlight the need for health care implementations such as
promotion of early cholecystectomy and appropriate useof antimicrobial drugs or centralization of patients undergoing cholecystectomy for acute cholecystitis in Japan.
Further clinical studies are required in the near future to
realize these health care implementations for reducing
medical costs while maintaining the quality of patientcare.
Acknowledgments
This study was funded by Grants-in-Aid for Researchon Policy Planning and Evaluation from the Ministry of
Health, Labour and Welfare, Japan.
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