All types of surgeries are being developed and are becoming less invasive. Consequently, laparoscopic surgery is currently used in almost all surgical fields. As laparoscopic surgical techniques and instruments have improved, many experienced surgeons are attempting to reduce the number of incisions required.

Laparoscopic cholecystectomy (LC) is a less complex surgical procedure and is the first laparoscopic procedure to be performed. Since LC was first performed by Mühe [1] in 1985, it has been the standard treatment for benign gallbladder disease. Single-incision LC (SILC) was first performed by Navarra et al. [2] in 1997 and is universally practiced by many hepatobiliary surgeons.

As the demand for minimally invasive surgery increases and its application expands, it is necessary to consider the optimal indications for safe and effective application. Several studies have suggested caution regarding SILC in patients with acute cholecystitis (AC), obesity, and advanced age [3–5]. However, there is no consensus on the application of SILC in AC. Although several experienced surgeons have reported the feasibility of SILC in AC [6,7], the safety of SILC in AC remains controversial because these studies only included a very small number of patients. Therefore, we aimed to identify the safety and feasibility of SILC in patients with AC by comparing the surgical outcomes, including pain, of SILC and conventional multiport LC (CMLC).

Study population

This single-center, retrospective study included a total of 1,876 patients with AC who underwent LC between April 2010 and December 2020. Patients treated for other acute illnesses or other combined surgeries were excluded. Diagnosis and severity of AC were based on the Tokyo Guidelines 2018 (TG18) [8]. Cholecystectomy methods were classified as CMLC or SILC. Propensity scores were used to match patients who underwent SILC or CMLC in the entire cohort and subgroups according to AC severity grading (Fig 1).

Figure 1. Study flow diagram.

Selection of cholecystectomy methods

Hepatobiliary and pancreatic (HBP) surgeons determined the type of cholecystectomy to be performed. The surgeon’s decision was influenced by patient factors, such as age, sex, body mass index (BMI), previous abdominal surgery, and severity of AC, and surgeon factors, such as experience and proficiency level of SILC.

Variables of demographics, surgical and pain outcomes

Data on each patient’s characteristics were collected: age, sex, BMI, previous abdominal surgery, American Society of Anesthesiologists physical status (ASA PS) classification, percutaneous transhepatic gallbladder drainage (PTGBD), endoscopic sphincterotomy (EST), severity grading of AC, Charlson age comorbidity index, operation time, estimated blood loss (EBL), bile duct and other adjacent organ injuries during surgery, open conversion, subtotal cholecystectomy, intraoperative transfusion, length of hospital stay, postoperative complications including bile leakage, pulmonary complication, and surgical site infection, incisional hernia, 90-day readmission, 90-day reoperation, and 90-day mortality. The operative time was calculated as the time from skin incision to closure. The EBL was obtained from the operation note. Bile duct injury was defined as an injury to the biliary tract, excluding the cystic duct and the gallbladder. We defined adjacent organ injury as unintended damage (requiring repair) to organs other than the bile duct such as the colon, duodenum, small bowel, and hepatic artery. Subtotal cholecystectomy was defined as making an incision in the gallbladder, aspirating the contents, and removing most of the gallbladder wall, as much as possible, with the aim of sealing the stump instead of removing the entire gallbladder [9]. The length of hospital stay was defined as the number of days of hospitalization after cholecystectomy. Postoperative complications were graded according to the Clavien-Dindo classification [10]. The definition and classification of surgical site infection (SSI) was based on the Centers for Disease Control and Prevention guidelines [11]. The definition of bile leakage was based on the International Study Group of Liver Surgery proposal [12]. An incisional hernia was defined as a hernia at the site of an umbilical incision confirmed by postoperative physical examination or imaging studies.

Intravenous patient-controlled analgesia (IV PCA) was administered according to the patient’s choice. Information on IV PCA was obtained from anesthesia records. At the patient’s request, additional analgesics were administered intramuscularly (IM) or intravenously (IV) if the numerical rating scale (NRS) pain score was 4 or higher. The number of additional analgesic injections was calculated from medical records. Postoperative NRS pain scores at 1, 6, 24, and 48 hours postoperatively were obtained from medical records.

Surgical technique of single-incision and conventional multiport laparoscopic cholecystectomies

SILC was performed using a four-channel glove port (NELIS), flexible laparoscope (Olympus), and snake liver retractor (Artisan) to expose Calot’s triangle. We refer to this method as the modified Konyang standard method. The detailed surgical technique was described in our previous study [13].

An infraumbilical or transumbilical incision and two 5-mm incisions or one 10-mm and one 5-mm incision were made in CMLC. A cholecystectomy was performed as usual.

Propensity score matching and statistical analysis

Propensity score-matched pairs were created by matching patients who underwent SILC with those who underwent CMLC on the logit of the propensity score using 1:1 nearest-neighbor matching without replacement within the specified caliper widths. Matching was performed for the entire cohort and for two subgroups: patients with grade I AC and those with grade II/III AC. The propensity score was estimated using a logistic regression model with covariates that were expected to affect surgical outcomes: age, sex, ASA PS classification, BMI, previous abdominal surgery, preoperative PTGBD, preoperative EST, and AC severity according to TG18. Balance in each baseline covariate was assessed using standardized mean difference (SMD). An optimal balance was achieved when the SMD was 0 to 1 or below [14].

Propensity score matching was performed using R statistical software version 3.6.3 (R Foundation for Statistical Computing) and all other analyses were performed using IBM SPSS version 27.0 (IBM Corp.).

Entire cohort

Patient demographics and surgical outcomes according to the cholecystectomy method before and after propensity score matching for the entire cohort are listed in Table 1. Of the 1,876 included patients, 427 underwent SILC and 1,449 underwent CMLC. In the cohort before matching, patients who underwent CMLC were older than those who underwent SILC (54.8 years vs. 65.0 years, p < 0.001). More female patients underwent SILC than CMLC (49.9% vs. 41.1%, p = 0.002). Patients who underwent CMLC had a higher ASA PS classification (≥III; 12.4% vs. 31.7%, p < 0.001), a higher Charlson age comorbidity index (≥6; 1.2% vs. 7.3%, p < 0.001), a higher severity grade of AC (grade II, 14.1% vs. 25.8%; grade III, 2.1% vs. 4.1%; p < 0.001) and a higher frequency of preoperative PTGBD (31.6% vs. 61.1%, p < 0.001) than those who underwent SILC. The length of hospital stay was shorter in patients who underwent SILC than in those who underwent CMLC (2.9 days vs. 3.9 days, p < 0.001). The postoperative complication rate was higher in patients who underwent CMLC than in those who underwent SILC (6.1% vs. 9.9%, p = 0.021).

Table 1 . Baseline characteristics of unmatched and matched cohorts of patients with acute cholecystitis (AC).

Characteristic	Unmatched cohort					Matched cohort
	SILC	CMLC	p value	SMD		SILC	CMLC	p value	SMD
No. of patients	427	1,449				404	404
Age (yr)	54.8 ± 15.6	65.0 ± 15.6	<0.001	0.658		56.1 ± 14.8	56.3 ± 16.3	0.846	0.014
Female sex	213 (49.9)	596 (41.1)	0.002	0.175		192 (47.5)	179 (44.3)	0.397	0.064
Body mass index (kg/m2)	24.6 ± 3.3	24.8 ± 3.7	0.310	0.057		24.7 ± 3.3	24.9 ± 3.7	0.375	0.065
ASA PS classification, ≥III	53 (12.4)	459 (31.7)	<0.001	0.584		53 (13.1)	59 (14.6)	0.611	0.045
Previous abdominal surgery	72 (16.9)	265 (18.3)	0.546	0.038		72 (17.8)	75 (18.6)	0.855	0.020
Endoscopic sphincterotomy	76 (17.8)	277 (19.1)	0.588	0.035		74 (18.3)	74 (18.3)	>0.999	0
PTGBD	135 (31.6)	885 (61.1)	<0.001	0.634		135 (33.4)	118 (29.2)	0.225	0.091
Severity of AC by TG18			<0.001	0.358				0.667	0.006
Grade I	358 (83.8)	1,016 (70.1)				336 (83.2)	334 (82.7)
Grade II	60 (14.1)	374 (25.8)				59 (14.6)	64 (15.8)
Grade III	9 (2.1)	59 (4.1)				9 (2.2)	6 (1.5)
Charlson age comorbidity index, ≥6	5 (1.2)	106 (7.3)	<0.001	0.571		5 (1.2)	6 (1.5)	>0.999	0.023
Open conversion	1 (0.2)	16 (1.1)	0.169			1 (0.2)	1(0.2)	>0.999
Subtotal cholecystectomy	0 (0)	10 (0.7)	0.179			0 (0)	2 (0.5)	0.479
Bile duct injury	2 (0.5)	7 (0.5)	>0.999			2 (0.5)	2 (0.5)	>0.999
Adjacent organ injury	1 (0.2)	14 (1.0)	0.237			1 (0.2)	3 (0.7)	0.616
Intraoperative transfusion	0 (0)	6 (0.4)	0.399			0 (0)	1 (0.2)	>0.999
Operation time (min)	58.7 ± 21.6	60.4 ± 28.3	0.179			58.7 ± 22.0	57.1 ± 25.6	0.317
Estimated blood loss (mL)	22.7 ± 55.4	24.6 ± 64.8	0.553			23.4 ± 56.8	21.1 ± 71.4	0.619
Length of hospital stay (day)	2.9 ± 2.4	3.9 ± 5.7	<0.001			2.9 ± 2.4	3.5 ± 4.7	0.029
Postoperative complication (CD classification)	26 (6.1)	143 (9.9)	0.021			24 (5.9)	23 (5.7)	>0.999
≥II	22 (5.2)	141 (9.7)	0.004			20 (5.0)	22 (5.4)	0.874
≥III	10 (2.3)	63 (4.3)	0.082			8 (2.0)	11 (2.7)	0.642
Bile leakage	1 (0.2)	12 (0.8)	0.333			1 (0.2)	2 (0.5)	>0.999
Pulmonary complication	6 (1.4)	40 (2.8)	0.158			6 (1.5)	7 (1.7)	>0.999
Surgical site infection	15 (3.5)	60 (4.1)	0.659			14 (3.5)	9 (2.2)	0.397
Superficial	5 (1.2)	5 (0.3)				5 (1.2)	1 (0.2)
Deep	1 (0.2)	2 (0.1)				1 (0.2)	0 (0)
Organ/space	9 (2.1)	53 (3.7)				8 (2.0)	8 (2.0)
Incisional hernia	3 (0.7)	5 (0.3)	0.566			3 (0.7)	0 (0)	0.247
90-day mortality	0 (0)	7 (0.5)	0.323			0 (0)	0 (0)	-
90-day readmission	2 (0.5)	13 (0.9)	0.572			2 (0.5)	0 (0)	0.479
90-day reoperation	1 (0.2)	11 (0.8)	0.395			2 (0.5)	0 (0)

Values are presented as number only, mean ± standard deviation, or number (%)..

SILC, single-incision laparoscopic cholecystectomy; CMLC, conventional multiport laparoscopic cholecystectomy; SMD, standardized mean difference; ASA PS, American Society of Anesthesiologists physical status; PTGBD, percutaneous transhepatic gallbladder drainage; TG18, Tokyo Guidelines 2018; CD, Clavien-Dindo..

After propensity score matching, no significant differences were observed in the patient demographics between the two groups. The length of hospital stay (2.9 days vs. 3.5 days, p = 0.029) was shorter in the SILC group than in the CMLC group; however, there were no significant differences in open conversion, bile duct injury, operation time, EBL, or postoperative complications, including bile leakage, pulmonary complications, and SSI between two groups.

Patients with grade I acute cholecystitis

The patient demographics and surgical outcomes according to the surgical method before and after propensity score matching for grade I AC are listed in Table 2. Of the 1,374 included patients, 358 underwent SILC and 1,016 underwent CMLC. Before matching, patients who underwent CMLC were older than those who underwent SILC (53.3 years vs. 63.0 years, p < 0.001). More female patients underwent SILC than CMLC (51.1% vs. 41.6%, p = 0.002). Patients who underwent CMLC had a higher ASA PS classification (≥III; 8.4% vs. 27.1%, p < 0.001), a higher Charlson age comorbidity index (≥6; 0.6% vs. 5.8%, p < 0.001), and a higher frequency of preoperative PTGBD (22.9% vs. 51.9%, p < 0.001) than those who underwent SILC. The length of hospital stay was shorter in patients who underwent SILC than in those who underwent CMLC (2.7 days vs. 3.3 days, p = 0.002). Postoperative complications above grade II C and D classification were higher in patients who underwent CMLC than in those who underwent SILC (3.4% vs. 6.6%, p = 0.033).

Table 2 . Baseline characteristics of unmatched and matched cohorts of patients with grade I acute cholecystitis.

Characteristic	Unmatched cohort					Matched cohort
	SILC	CMLC	p value	SMD		SILC	CMLC	p value	SMD
No. of patients	358	1,016				336	336
Age (yr)	53.3 ± 15.1	63.0 ± 16.0	<0.001	0.644		54.5 ± 14.6	54.0 ± 15.6	0.662	0.034
Female sex	183 (51.1)	423 (41.6)	0.002	0.190		164 (48.8)	158 (47.0)	0.699	0.036
Body mass index (kg/m2)	24.6 ± 3.3	25.0 ± 3.7	0.102	0.105		24.8 ± 3.2	24.8 ± 3.5	0.960	0.004
ASA PS classification, ≥III	30 (8.4)	275 (27.1)	<0.001	0.674		30 (8.9)	29 (8.6)	>0.999	0.011
Previous abdominal surgery	64 (17.9)	206 (20.3)	0.366	0.063		62 (18.5)	63 (18.8)	>0.999	0.008
Endoscopic sphincterotomy	65 (18.2)	221 (21.8)	0.172	0.093		63 (18.8)	65 (19.3)	0.922	0.015
PTGBD	82 (22.9)	527 (51.9)	<0.001	0.689		82 (24.4)	86 (25.6)	0.789	0.028
Charlson age comorbidity index, ≥6	2 (0.6)	59 (5.8)	<0.001	0.704		2 (0.6)	1 (0.3)	>0.999	0.040
Open conversion	0 (0)	6 (0.6)	0.322			0 (0)	1 (0.3)	>0.999
Subtotal cholecystectomy	0 (0)	3 (0.3)	0.711			0 (0)	1 (0.3)	>0.999
Bile duct injury	2 (0.6)	4 (0.4)	>0.999			2 (0.6)	1 (0.3)	>0.999
Adjacent organ injury	1 (0.3)	8 (0.8)	0.520			1 (0.3)	1 (0.3)	>0.999
Intraoperative transfusion	0 (0)	2 (0.2)	0.973			0 (0)	0 (0)	-
Operation time (min)	57.4 ± 20.7	56.3 ± 26.0	0.438			57.6 ± 21.1	52.4 ± 21.0	0.001
Estimated blood loss (mL)	22.3 ± 59.8	19.9 ± 48.6	0.506			22.9 ± 61.7	13.1 ± 17.2	0.006
Length of hospital stay (day)	2.7 ± 2.1	3.3 ± 5.0	0.002			2.7 ± 2.1	2.7 ± 1.5	0.900
Postoperative complication (CD classification)	16 (4.5)	68 (6.7)	0.167			16 (4.8)	11 (3.3)	0.432
≥II	12 (3.4)	67 (6.6)	0.033			12 (3.6)	11 (3.3)	>0.999
≥III	6 (1.7)	25 (2.5)	0.514			6 (1.8)	4 (1.2)	0.750
Bile leakage	0 (0)	3 (0.3)	0.711			0 (0)	0 (0)	-
Pulmonary complication	2 (0.6)	15 (1.5)	0.283			2 (0.6)	1 (0.3)	>0.999
Surgical site infection	11 (3.1)	25 (2.5)	0.666			11 (3.3)	4 (1.2)	0.117
Superficial	5 (1.4)	2 (0.2)				5 (1.5)	0 (0)
Deep	1 (0.3)	0 (0)				1 (0.3)	0 (0)
Organ/space	5 (1.4)	23 (2.3)				5 (1.5)	4 (1.2)
Incisional hernia	2 (0.6)	3 (0.3)	0.840			2 (0.6)	1 (0.3)	>0.999
90-day mortality	0 (0)	2 (0.2)	0.973			0 (0)	0 (0)	-
90-day readmission	2 (0.6)	6 (0.6)	>0.999			2 (0.6)	3 (0.9)	>0.999
90-day reoperation	1 (0.3)	6 (0.6)	0.780			1 (0.3)	0 (0)	>0.999

Values are presented as number only, mean ± standard deviation, or number (%)..

SILC, single-incision laparoscopic cholecystectomy; CMLC, conventional multiport laparoscopic cholecystectomy; SMD, standardized mean difference; ASA PS, American Society of Anesthesiologists physical status; PTGBD, percutaneous transhepatic gallbladder drainage; CD, Clavien-Dindo..

After propensity score matching, there were no significant differences in the patient demographics between the two groups. Patients in the CMLC group had a shorter operation time (57.6 minutes vs. 52.4 minutes, p = 0.001) and less EBL (22.9 mL vs. 13.1 mL, p = 0.006) than those in the SILC group. Other surgical outcomes, such as open conversion, bile duct injury, and postoperative complications, were not significantly different between the two groups.

Patients with grade II and III acute cholecystitis

The patient demographics and surgical outcomes according to the surgical method before and after propensity score matching for grade II and III AC are listed in Table 3. Of the 502 included patients, 69 underwent SILC, and 433 underwent CMLC. In the cohort before matching, patients who underwent CMLC were older than those who underwent SILC (62.9 years vs. 69.9 years, p < 0.001). The other demographic characteristics were not significantly different between the two groups. Patients in the SILC group had a shorter hospital stay (3.8 days vs. 5.2 days, p = 0.010) and less EBL (24.8 mL vs. 35.4 mL, p = 0.037) than those in the CMLC group.

Table 3 . Baseline characteristics of unmatched and matched cohorts of patients with grade II and III acute cholecystitis (AC).

Variable	Unmatched cohort					Matched cohort
	SILC	CMLC	p value	SMD		SILC	CMLC	p value	SMD
No. of patients	69	433				58	58
Age (yr)	62.9 ± 15.6	69.9 ± 13.4	<0.001	0.451		64.6 ± 14.4	64.6 ± 13.9	>0.999	0
Female sex	30 (43.5)	173 (40.0)	0.673	0.071		26 (44.8)	24 (41.4)	0.851	0.069
Body mass index (kg/m2)	24.5 ± 3.6	24.4 ± 3.4	0.801	0.031		24.7 ± 3.7	25.1 ± 3.3	0.504	0.117
ASA PS classification, ≥III	23 (33.3)	184 (42.5)	0.192	0.194		21 (36.2)	21 (36.2)	>0.999	0
Previous abdominal surgery	8 (11.6)	59 (13.6)	0.787	0.064		7 (12.1)	4 (6.9)	0.526	0.159
Endoscopic sphincterotomy	11 (15.9)	56 (12.9)	0.623	0.082		9 (15.5)	10 (17.2)	>0.999	0
PTGBD	53 (76.8)	358 (82.7)	0.314	0.139		47 (81.0)	47 (81.0)	>0.999	0
Severity of AC by TG18			>0.999	0.017				>0.999	0
Grade II	60 (87.0)	374 (86.4)				49 (84.5)	49 (84.5)
Grade III	9 (13.0)	59 (13.6)				9 (15.5)	9 (15.5)
Charlson age comorbidity index, ≥6	3 (4.3)	47 (10.9)	0.144	0.319		2 (3.4)	2 (3.4)	>0.999	0
Open conversion	1 (1.4)	10 (2.3)	0.992			1 (1.7)	0 (0)	>0.999
Subtotal cholecystectomy	0 (0)	7 (1.6)	0.609			0 (0)	2 (3.4)	0.476
Bile duct injury	0 (0)	3 (0.7)	>0.999			0 (0)	0 (0)	-
Adjacent organ injury	0 (0)	6 (1.4)	0.699			0 (0)	1 (1.7)	>0.999
Intraoperative transfusion	0 (0)	4 (0.9)	0.942			0 (0)	0 (0)	-
Operation time (min)	65.2 ± 24.9	69.9 ± 31.2	0.168			66.6 ± 24.8	68.5 ± 28.6	0.704
Estimated blood loss (mL)	24.8 ± 20.9	35.4 ± 91.4	0.037			26.0 ± 21.6	29.4 ± 42.7	0.589
Length of hospital stay (day)	3.8 ± 3.5	5.2 ± 7.0	0.010			3.7 ± 3.1	5.3 ± 7.6	0.146
Postoperative complication (CD classification)	10 (14.5)	75 (17.3)	0.683			9 (15.5)	11 (19.0)	0.806
≥II	10 (14.5)	74 (17.1)	0.716			9 (15.5)	11 (19.0)	0.806
≥III	4 (5.8)	38 (8.8)	0.551			4 (6.9)	7 (12.1)	0.526
Bile leakage	1 (1.4)	9 (2.1)	>0.999			1 (1.7)	3 (5.2)	0.611
Pulmonary complication	4 (5.8)	25 (5.8)	>0.999			4 (6.9)	1 (1.7)	0.361
Surgical site infection	4 (5.8)	35 (8.1)	0.677			4 (6.9)	8 (13.8)	0.360
Superficial	0 (0)	3 (0.7)				0 (0)	0 (0)
Deep	0 (0)	2 (0.5)				0 (0)	0 (0)
Organ/space	4 (5.8)	30 (6.9)				4 (6.9)	8 (13.8)
Incisional hernia	1 (1.4)	2 (0.5)	0.883			1 (1.7)	0 (0)	>0.999
90-day mortality	0 (0)	5 (1.2)	0.807			0 (0)	1 (1.7)	>0.999
90-day readmission	0 (0)	7 (1.6)	0.609			0 (0)	0 (0)	-
90-day reoperation	0 (0)	5 (1.2)	0.807			0 (0)	1 (1.7)	>0.999

Values are presented as number only, mean ± standard deviation, or number (%)..

SILC, single-incision laparoscopic cholecystectomy; CMLC, conventional multiport laparoscopic cholecystectomy; SMD, standardized mean difference; ASA PS, American Society of Anesthesiologists physical status; PTGBD, percutaneous transhepatic gallbladder drainage; TG18, Tokyo Guidelines 2018; CD, Clavien-Dindo..

After propensity score matching, there were no significant differences in the patient demographics between the two groups. All surgical outcomes were also not significantly different between the two groups, including hospital stay (3.7 days vs. 5.3 days, p = 0.146) and EBL (26.0 mL vs. 29.4 mL, p = 0.589).

Postoperative pain outcomes

In the propensity score-matched cohort of grade I AC between the SILC and CMLC groups (336 patients in each group), no significant difference was observed in the number of patients who underwent IV PCA (88.7% vs. 90.5%, p = 0.449). The number of additional analgesic injections (1.28 vs. 1.25, p = 0.748) administered and postoperative NRS pain scores (1 hour, 4.72 vs. 4.83, p = 0.182; 6 hours, 2.85 vs. 2.87, p = 0.757; 24 hours, 2.71 vs. 2.82, p = 0.207; and 48 hours, 2.15 vs. 2.16; p = 0.877) were not significantly different between the two groups (Table 4, Fig. 2).

Table 4 . Pain outcomes of matched cohorts of patients with grade I or II/III acute cholecystitis.

Variable	Grade I acute cholecystitis				Grade II/III acute cholecystitis
	SILC (n = 336)	CMLC (n = 336)	p value		SILC (n = 58)	CMLC (n = 58)	p value
IV PCA	298 (88.7)	304 (90.5)	0.449		52 (89.7)	50 (86.2)	0.569
No. of IV/IM analgesic injections	1.28 ± 1.20	1.25 ± 1.26	0.748		0.91 ± 1.06	1.03 ± 1.27	0.580
Postoperative pain score
1 hr	4.72 ± 1.07	4.83 ± 1.07	0.182		4.57 ± 0.94	4.66 ± 1.19	0.666
6 hr	2.85 ± 0.96	2.87 ± 1.03	0.757		2.78 ± 0.97	2.43 ± 0.92	0.052
24 hr	2.71 ± 1.11	2.82 ± 1.09	0.207		2.48 ± 1.00	2.62 ± 1.36	0.535
48 hr	2.15 ± 0.96	2.16 ± 1.03	0.877		1.97 ± 1.04	1.95 ± 1.06	0.932

Values are presented as number (%) or mean ± standard deviation..

SILC, single-incision laparoscopic cholecystectomy; CMLC, conventional multiport laparoscopic cholecystectomy; IV, intravenous; PCA, patient-controlled analgesia; IM, intramuscular..

Figure 2. Pain outcomes of matched cohorts of patients with grade I acute cholecystitis. (A) The number of additional intravenous or intramuscular analgesic injections. (B) Postoperative numerical rating scale (NRS) according to the time after surgery. SILC, single-incision laparoscopic cholecystectomy; CMLC, conventional multiport laparoscopic cholecystectomy.

In the propensity score-matched cohort of grade II and III AC between SILC and CMLC (58 patients in each group), there was no significant difference in the number of patients with grade IV PCA (89.7% vs. 86.2%, p = 0.569). The number of additional analgesic injections (0.91 vs. 1.03, p = 0.580) administered and postoperative NRS pain scores (1 hour, 4.57 vs. 4.66, p = 0.666; 6 hours, 2.78 vs. 2.43, p = 0.052; 24 hours, 2.48 vs. 2.62, p = 0.535; and 48 hours, 1.97 vs. 1.95, p = 0.877) were not significantly different between the two groups (Table 4, Fig. 3).

Figure 3. Pain outcomes of matched cohorts of patients with grade II and III acute cholecystitis. (A) The number of additional intravenous or intramuscular analgesic injections. (B) Postoperative numerical rating scale (NRS) according to the time after surgery. SILC, single-incision laparoscopic cholecystectomy; CMLC, conventional multiport laparoscopic cholecystectomy.

SILC has recently become widely accepted for the treatment of benign gallbladder diseases. However, there is still no standardized surgical technique or consensus regarding the indications for SILC. The use of SILC in patients undergoing AC remains controversial. Recently, the authors analyzed 1,402 SILC procedures and reported that SILC is not recommended for patients with grade II/III AC according to the TG18 [15]. This study only included patients who underwent SILC. A comparison of perioperative outcomes according to AC severity is insufficient to confirm the safety of SILC for AC. To overcome the limitations of the previous studies, we compared the surgical outcomes of SILC and CMLC in patients with AC. This study is significant in that it included the largest number of SILC procedures in patients with AC reported to date and is the first study to compare them according to the severity of AC.

LC is more difficult in patients with AC than in those with other benign gallbladder diseases because the tissue around the gallbladder is swollen and tends to bleed easily upon manipulation. In the severity classification of AC according to TG18, the higher the severity, the greater the technical difficulty of surgery, as it may complicate AC, and the greater the risk of poor surgical outcomes, as it may include patients with septic conditions. Therefore, in the present study, we divided patients according to the severity of AC and conducted a detailed analysis.

In the overall study population, after propensity score matching, there were no statistically significant differences in most surgical outcomes between the SILC and CMLC groups; however, the length of hospital stay was shorter in the SILC group than in the CMLC group. A previous study reported shorter hospital stays in the SILC group than in the CMLC group [7]. Based on these surgical outcomes, SILC can be considered a safe and effective surgical method for AC similar to CMLC. However, when subgroup analysis was performed based on AC severity, different results were found. In grade I AC, the SILC group showed a longer operation time and greater EBL than the CMLC group, with no statistically significant difference in the length of hospital stay between the two groups. In addition, for grade II/III AC, the SILC group had a shorter operation time and length of hospital stay than the CMLC group; however, the differences were not statistically significant. In grade II/III AC, there was no significant difference in operation time and EBL between the two methods due to the high surgical difficulty regardless of SILC or CMLC; however, in grade I AC, the surgery was relatively easy, which may explain the statistically significant difference in surgical time and blood loss in both SILC and CMLC groups. The results of this study demonstrated that SILC is not associated with superior surgical outcomes in patients with AC.

SILC is generally considered more difficult than CMLC in terms of instrument arrangement and learning curve; however, its application is gradually expanding owing to its advantages in terms of fewer incisions, less postoperative pain, and better cosmetics. In the present study, there were no statistically significant differences in the postoperative pain outcomes between the SILC and CMLC groups in any of the subgroups. AC is often accompanied by preoperative pain due to inflammation, the effects of which persist even after surgery. In patients with AC, pain from cholecystitis itself and pain from the surgical incision contribute to postoperative pain. This suggests that pain reduction achieved by SILC may not be as great in patients with AC as in those with other benign gallbladder diseases. In practice, the results of this study showed that SILC did not significantly reduce postoperative pain compared with CMLC in patients with AC.

In the present study, SILC was associated with a longer operation time and more EBL than CMLC in grade I AC, and no significant differences were observed in pain outcomes regardless of the severity of AC. However, SILC showed results similar to those of CMLC for most other surgical outcomes in terms of conversion, postoperative complications, length of hospital stay, and 90-day readmission rates. Furthermore, our results showed similar surgical outcomes, including length of hospital stay, operation time, postoperative complications, conversion, and incisional hernia, when compared with those of a large cohort study of SILC that excluded patients with AC [16]. These results demonstrate that SILC performed using our institutional technique is safe and feasible for selected patients with AC. SILC should not be considered a contraindication in patients with AC. However, given that most of the surgeries in this study were performed by experienced HBP surgeons who have performed more than 1,000 SILCs, the application of SILC in selected patients with AC by experienced HBP surgeons may increase the safety of the surgery. It is difficult to suggest a specific cutoff value for the experience of SILC in AC, as this has not been studied. It is recommended that SILC be performed first in mild AC after gaining experience with cases without acute inflammation.

This study had certain limitations. First, this was a retrospective, single-center study, and bias may have existed in the results. However, we attempted to reduce bias by using propensity score matching. Second, pain is difficult to measure owing to its multifaceted and subjective nature. In this study, a complete assessment of postoperative pain could not be performed by NRS pain scores and the number of additional analgesic injections administered. Finally, the SILCs procedures included in this study were performed by three HBP surgeons, with most surgeries performed by one experienced surgeon. Therefore, SILCs performed by inexperienced surgeons on patients with AC may have skewed the results.

In conclusion, this study demonstrated that SILC had similar surgical and pain outcomes to CMLC in patients with AC; however, subgroup analysis showed that SILC was associated with poor surgical outcomes than CMLC in grade I AC. Therefore, SILC should be carefully performed in patients with AC by experienced hepatobiliary surgeons.

Ethical statements

This study was approved by the Institutional Review Board of Konyang University Hospital, and the requirement for informed consent was waived because of the retrospective study design (No. 2022-01-022).

Authors’ contributions

Conceptualization, Formal analysis, Methodology, Visualization: All authors

Data curation, Investigation: All authors

Writing–original draft: SJL

Writing–review & editing: SJL, ISC, JIM

All authors read and approved the final manuscript.

Conflict of interest

All authors have no conflicts of interest to declare.

Funding/support

None.

Data availability

The data presented in this study are available on request from the corresponding author.