Introduction
Endoscopic transpapillary gallbladder drainage (ETGBD) has been reported to be effective
for acute cholecystitis, for which emergency cholecystectomy and percutaneous transhepatic
gallbladder drainage (PTGBD) are considered to be high risk because of coagulopathy,
administration of antithrombotic drugs, and poor physical condition [1]
[2]
[3]
[4]
[5]. In previous reports, two types of ETGBD – endoscopic naso-gallbladder drainage
(ENGBD) and endoscopic gallbladder stenting (EGBS) – showed no difference in technical
success, clinical success, or early adverse events (AEs) [6]
[7]
[8]
[9]. Although both types are suitable for treatment of acute cholecystitis, EGBS is
considered to be superior in terms of patient quality of life [6].
In general, traditional biliary plastic stents are substituted for gallbladder stents
in EGBS. However, there is no sufficient evidence about which type of plastic stent
is suitable for EGBS, especially for long-term placement. Although standard biliary
plastic stents have a straight shaft, gallbladder stents are placed with a deeper
curve than biliary stents because of anatomical features. Thus, problems may be encountered,
such as stent migration due to strong axial force and kinking at the bent portion.
Moreover, because a longer stent is often needed for the gallbladder than for the
bile duct, a traditional biliary stent may be too short for EGBS.
To overcome these problems, we developed a new design for a plastic stent for EGBS. In
this study, we examined short- and long-term outcomes of EGBS using standard stents
and the novel stent for acute cholecystitis and evaluated the efficacy of the novel
stent.
Patients and methods
Patients
A total of 198 patients underwent ETGBD (117 males and 81 females; age, 73.6 ± 11.7
years) (mean ± standard deviation [SD]) for acute cholecystitis at St. Marianna University
School of Medicine Hospital between March 2011 and September 2017. None of the patients
were suitable candidates for emergency cholecystectomy and percutaneous transhepatic
gallbladder drainage (PTGBD) because of high risk of coagulopathy, administration
of antithrombotic drugs, poor physical condition, advanced age, or coexistence of
choledocholithiasis. In terms of anatomy, 190 patients had normal stomachs, four had
Billroth-I reconstruction, three had Billroth-II reconstruction, and one had Roux-en-Y
(R-Y) reconstruction. Although bile duct cannulation was unsuccessful in one patient
and guidewire (GW) insertion into the gallbladder was unsuccessful in 20 patients,
the GW could be placed into the gallbladder in 177 patients. In our hospital, after
placing the GW into the gallbladder, a 7-Fr tapered catheter with side holes is inserted
into the gallbladder to suction bile and irrigate it with saline. In two patients,
insertion of the tapered catheter was impossible. Among the 175 patients in whom the
tapered catheter could be inserted, 80 underwent ENGBD, 82 underwent EGBS, and 13
underwent endoscopic gallbladder aspiration.
Among the 82 patients who underwent EGBS, 12 patients in whom we use modified stent
created by cutting various types of nasobiliary tube were excluded. In total, 70 patients
in whom EGBS was performed using the newly designed stent or standard biliary stents
(39 males and 31 females; age, 75.0 ± 11.5 years) were selected as subjects and were
evaluated retrospectively. After September 2016, we performed EGBS in 23 patients
using the newly designed stent and classified these patients into the novel stent
group. On the other hand, we defined 47 patients who underwent EGBS using standard
biliary stents (double-pigtail type, 35; straight type, 12) before August 2016 prior
to introduction of the newly designed stent as the control group ([Fig. 1]).
Fig. 1 Flowchart of the study.
EGBS technique
We used a duodenoscope (JF260V or TJF260V; Olympus Medical Systems, Tokyo, Japan)
and performed bile duct cannulation by conventional contrast cannulation or wire-guided
cannulation. After bile duct cannulation, a hydrophilic GW (e. g., Radifocus, Terumo
Co., Ltd., Tokyo, Japan) was passed through the cystic duct and inserted into the
gallbladder. After changing the GW to a stiff type, we inserted a 7-Fr tapered catheter
with side holes (CX-PTCD kit [PD-EN7F (ST) 180C4], Gadelius Medical, Tokyo, Japan)
into the gallbladder over the GW, suctioned the bile, and subsequently irrigated the
gallbladder with saline ([Fig. 2]). Next, we measured the length from the papilla to the gallbladder using the GW
and placed the stent so that the tip was at the fundus of the gallbladder.
Fig. 2 A 7-Fr tapered catheter with side holes is inserted into the gallbladder and suction
the bile and irrigate with saline.
All endoscopic retrograde cholangiopancreatography (ERCP) procedures were performed
under the supervision of an expert who has performed more than 1000 such procedures.
Gabexate mesylate was administered at a dosage of 600 mg/day on the day of the procedure
to all patients to prevent post-ERCP pancreatitis.
Novel stent
We developed a novel stent for EGBS (GBest-N stent; Hanaco Medical Co., Saitama, Japan)
([Fig. 3]). The length of the novel stent has a variation of 11 cm, 13 cm, 15 cm, 17 cm, and
19 cm. The tip of the stent has a three-dimensional spiral-shaped structure, and there
are side holes inside the spiral. The spiral-shaped tip is expected to prevent migration
of the stent. Further, by opening the side holes inside of the spiral part of the
stent, it is anticipated that the side holes will not be obstructed even if the stent
adheres to the contracted gallbladder wall and drainage will be maintained. The shaft
of the stent is 7 Fr and semicircular and it also has side holes. When inserted into
the gallbladder, the stent is often placed in a curved manner because of the anatomical
structure. Because the stent is semicircular, it fits well and is not expected to
migrate because the axial force of the stent is reduced. In patients with abnormal
coagulation, endoscopic sphincterotomy (EST) cannot be performed, and cholestasis
could develop at the papilla. The side holes on the shaft are designed to drain the
bile from the common bile duct. The distal side of the stent is straight, with a flap
to prevent proximal migration. [Fig. 4] shows placement of a novel stent into the gallbladder.
Fig. 3 Newly designed gallbladder stent (GBest-N stent).
Fig. 4 Deployment of a newly designed stent into the gallbladder.
Stents used in the control group
The stents used in the control group were as follows: double-pigtail stents: 35 [Advanix
(Boston Scientific, Natick, Massachusetts, United States): 16, SET-ERBD-72 stents
(Hanaco Medical Co., Saitama, Japan): 12, CX-T stents (Gadelius Medical, Tokyo, Japan):
5, PBD-203 stent (Olympus Medical Systems, Tokyo, Japan): 1, and Zimmon biliary stent
(Cook Japan, Tokyo, Japan): 1]; straight type stents: 12 [Through Pass (Gadelius Medical,
Tokyo, Japan): 11 and CX-T stent (Gadelius Medical, Tokyo, Japan): 1].
Measurements
In the novel stent group and the control group, we retrospectively examined and compared
the following: patient background, details of endoscopic procedures, technical success
rate of EGBS, clinical success rate for acute cholecystitis, early AEs, and late AEs.
Cholecystitis severity was determined according to the Tokyo Guidelines 2013 (TG13)
for acute cholecystitis [10]. We defined technical success of EGBS as the tip of the stent remaining in the gallbladder
and clinical success as when clinical symptoms and laboratory test results showed
an improving tendency within 3 days after EGBS. Early AEs were those that occurred
within 7 days, and late AEs were those that occurred at least 8 days after EGBS. The
diagnosis and severity of AEs included pancreatitis, bleeding, perforation, and cholangitis
based on the consensus guidelines by Cotton et al. [11]. We defined as stent distal migration not only when the stent migrated to the intestine
or out of the body but also when a large part of the stent tip slipped out of the
gallbladder. Especially with a pigtail stent, migration was defined as when only the
tip of the stent was caught in the neck of gallbladder or cystic duct ([Fig. 5]).
Fig. 5 A case of stent migration in endoscopic gallbladder stenting using double-pigtail
stent. a Immediately after stent placement. b At the time of stent migration.
This study was approved by the Institutional Review Board of St. Marianna University
School of Medicine (approval number: 3891).
Statistical analysis
We used StatMate IV (ATMS Co., Ltd., Tokyo, Japan) for statistical analysis to compare
the two groups and performed the chi-square test, Fisher’s exact test, and Welch’s
t test as needed. Univariate and multivariate logistic regression analyses were performed
using SPSS (version 19; SPSS, Chicago, IL, USA). A P value < 0.05 was considered to be statistically significant.
Results
Patient backgrounds
There was no significant difference between the novel stent group and the control
groups in terms of age, sex, severity of cholecystitis, comorbidities (cholecystolithiasis,
choledocholithiasis, malignant diseases), history of procedure for papilla of Vater,
parapapillary diverticulum, or use of antithrombotic drugs (not significant; N.S.)
([Table 1]).
Table 1
Patient characteristics.
|
Novel stent group
|
Control group
|
P value
|
|
No. of patients
|
23
|
47
|
|
|
Age (mean ± SD)
|
73.0 ± 10.8
|
76.0 ± 11.8
|
0.308
|
|
Sex (male/female)
|
12/11
|
27/20
|
0.677
|
|
Severity of cholecystitis
|
|
|
2
|
5
|
0.865
|
|
|
12
|
21
|
0.555
|
|
|
9
|
21
|
0.659
|
|
Cholecystolithiasis
|
21
|
40
|
0.728
|
|
Choledocholithiasis
|
7
|
17
|
0.635
|
|
Malignant diseases
|
4
|
6
|
0.876
|
|
Malignant biliary stricture
|
1
|
3
|
0.839
|
|
Previous procedures for papilla
|
4
|
10
|
0.949
|
|
|
3
|
7
|
0.876
|
|
|
0
|
2
|
0.810
|
|
|
1
|
0
|
0.713
|
|
|
0
|
1
|
0.713
|
|
Papillary diverticulum
|
10
|
23
|
0.667
|
|
Use of antithrombotic drug
|
7
|
13
|
0.809
|
SD, standard deviation; EST, endoscopic sphincterotomy; EPBD, endoscopic papillary
balloon dilation
Details of endoscopic procedures
[Table 2] show details of the endoscopic procedures. Patients in whom EST was performed before
EGBS comprised 34.8 % (8/23) of the novel stent group and 40.4 % (19/47) of the control
group, showing no difference (N.S.). Stent diameter and length used for EGBS were
no different between the two groups (N.S.). Although there was no significant difference,
the rate of endoscopic biliary drainage was slightly lower in the novel stent group
[8.7 % (2/23) vs 23.4 % (11/47), P = 0.246]. All endoscopic pancreatic stenting was performed to prevent post-ERCP pancreatitis.
Table 2
Endoscopic procedures.
|
Novel stent group
|
Control group
|
P value
|
|
No. of patients
|
23
|
47
|
|
|
Endoscopic procedure for papilla
|
|
|
8
|
19
|
0.649
|
|
|
15
|
28
|
|
|
Endoscopic gallbladder stenting
|
|
|
23
|
0
|
|
|
|
0
|
35
|
|
|
|
0
|
12
|
|
|
|
23/0
|
46/1
|
0.713
|
|
Length of stent (≤ 15 cm/≥ 16 cm)
|
18/5
|
33/14
|
0.477
|
|
Common bile duct stone removal
|
5
|
9
|
0.949
|
|
Biliary drainage
|
2
|
11
|
0.246
|
|
ENBD
|
1
|
3
|
0.839
|
|
EBS
|
1
|
8
|
0.268
|
|
Pancreatic stenting
|
4
|
11
|
0.790
|
EST, endoscopic sphincterotomy; ENBD, endoscopic nasobiliary drainage; EBS, endoscopic
biliary stenting
Technical and clinical success rates for EGBS
In 70 patients in whom the GW and the tapered catheter could be inserted into the
gallbladder before EGBS, the technical success rate for EGBS was 100 % in both the
novel stent and control groups.
The clinical success rate for acute cholecystitis was 100 % (23/23) in the novel stent
group and 95.7 % (45/47) in the control group, indicating no significant difference
(N.S.) ([Table 3]). The stents used in two patients in whom clinical improvement could not be obtained
in the control group were both double-pigtail type 7 Fr-15 cm long Advanix (Boston
Scientific). In one patient, poor drainage due to a kink in the stent was improved
by exchanging the stent with a double-pigtail 7 Fr-16 cm long SET-ERBD-72 stent (Hanaco
Medical Co.). In the other patient, cholestasis at the papilla was due to stent placement
without EST, and cholecystitis was improved by performing additional EST and endoscopic
biliary stenting (EBS).
Table 3
Clinical outcomes and adverse events.
|
Novel stent group
|
Control group
|
P value
|
|
No. of patients
|
23
|
47
|
|
|
Clinical success (% (n))
|
100 (23)
|
95.7 (45)
|
0.810
|
|
Adverse events
|
|
|
13.0 (3)
|
17.0 (8)
|
0.936
|
|
|
1
|
2
|
|
|
|
1
|
1
|
|
|
|
1
|
3
|
|
|
|
0
|
1
|
|
|
|
0
|
1
|
|
|
|
4.3 (1)
|
40.4 (19)
|
0.004
|
|
|
0
|
15
|
0.006
|
|
|
0
|
4
|
0.372
|
|
|
1
|
0
|
0.713
|
|
|
17.4 (4)
|
57.4 (27)
|
0.004
|
|
Follow-up period (mean ± SD (range) days)
|
120 ± 143 (4 – 573)
|
162 ± 252 (4 – 950)
|
0.371
|
EST, endoscopic sphincterotomy; SD, standard deviation
Adverse events
The details of AEs are shown in [Table 3]. The rate of early AEs was 13.0 % (3/23) in the novel stent group and 17.0 % (8/47)
in the control group, indicating no significant difference (N.S.). In the novel stent
group, early AEs included mild pancreatitis in one patient, EST bleeding in one, and
obstructive jaundice in one. On the other hand, in the control group, there was mild
pancreatitis in two patients, EST bleeding in one, obstructive jaundice in three,
cystic duct perforation in one, and a stent kink in one. Among the two groups, obstructive
jaundice in four patients was caused by cholestasis at the papilla because of stent
placement without EST, and additional EBS and/or EST led to improvement. All early
AEs were improved by conservative therapy or endoscopic procedures.
Rates of late AEs during the observation period [novel stent group, 120 ± 143 days;
control group, 162 ± 252 days (mean ± SD); P = 0.371] were 4.3 % (1/23) in the novel stent group and 40.4 % (19/47) in the control
group, indicating a significantly higher rate in the control group (P = 0.004). Details of late AEs were liver abscess in one patient in the novel stent
group and stent distal migration in 15 and recurrence of cholecystitis in four in
the control group. The rate of stent distal migration in the control group was high
(31.9 % (15/47)), which was significantly higher than that in the novel stent group
(P = 0.006). In addition, stent migration was the cause of recurrence of cholecystitis
in four patients in the control group.
The total rate of combined early and late AEs was 17.4 % (4/23) in the novel stent
group and 57.4 % (27/47) in the control group, indicating a significantly higher rate
in the control group (P = 0.004).
A comparison of AEs for each type of stents is shown in [Table 4]. Although there was no difference in early AEs among novel, pigtail, and straight
stents, the novel stent had significantly lower rates of late AEs and stent distal
migration compared with the other stents. Among the three stent types, the straight
stent had the highest rates of late AEs and stent distal migration. Mean duration
from stent placement to migration in the control group was 69.5 ± 69.0 days (mean ± SD).
There was no difference in time from stent placement to migration between pigtail
and straight stents (N.S.).
Table 4
Comparison of the adverse events for each type of stents.
|
Novel stent
(n = 23)
|
Pigtail stent
(n = 35)
|
Straight stent
(n = 12)
|
P value
|
|
|
|
|
N vs P
|
N vs S
|
P vs S
|
|
Adverse events (% (n))
|
|
|
13.0 (3)
|
17.1 (6)
|
16.7 (2)
|
0.959
|
0.827
|
0.684
|
|
|
4.3 (1)
|
31.4 (11)
|
66.7 (8)
|
0.031
|
< 0.001
|
0.071
|
|
|
0 (0)
|
25.7 (9)
|
50.0 (6)
|
0.023
|
0.001
|
0.231
|
|
|
0 (0)
|
5.7 (2)
|
16.7 (2)
|
0.666
|
0.212
|
0.566
|
|
|
4.3 (1)
|
0 (0)
|
0 (0)
|
0.831
|
0.737
|
―
|
|
|
17.4 (4)
|
48.6 (17)
|
83.3 (10)
|
0.033
|
< 0.001
|
0.078
|
|
Follow-up period (mean ± SD, days)
|
120 ± 143
|
180 ± 270
|
112 ± 190
|
0.276
|
0.899
|
0.349
|
|
Time periods to migrate (mean ± SD, days)
|
―
|
84 ± 84
|
68 ± 52
|
―
|
―
|
0.656
|
N, novel stent; P, pigtail stent; S, straight stent; SD, standard deviation
Risk factors for stent distal migration
Univariate and multivariate logistic regression analyses were performed to identify
risk factors for stent distal migration. Univariate analysis identified straight type
stent as the only significant risk factor for stent distal migration [P = 0.016; odds ratio (OR), 5.44; 95 % confidence interval (CI), 1.43 – 20.72]. Moreover,
the newly designed stent significantly correlated with a lack of migration (P = 0.001; OR, 0.58; 95 % CI, 0.47 – 0.73) ([Table 5]). Multivariate analysis also identified straight type stent as significant risk
factor for stent distal migration (P = 0.011; OR, 8.81; 95 % CI, 1.66 – 46.83) ([Table 6]).
Table 5
Risk factors for stent distal migration (univariate analysis).
|
Migration (+)
|
Migration (–)
|
P value
|
OR (95 %CI)
|
|
No. of patients
|
15
|
55
|
|
|
|
Age (> 80)
|
4
|
24
|
0.373
|
0.470 (0.133 – 1.660)
|
|
Sex (female)
|
7
|
24
|
1.000
|
1.130 (0.359 – 3.555)
|
|
Novel stent
|
0
|
23
|
0.001
|
0.582 (0.465 – 0.728)
|
|
Pigtail stent
|
9
|
26
|
0.561
|
1.637 (0.524 – 5.341)
|
|
Straight stent
|
6
|
6
|
0.016
|
5.444 (1.431 – 20.716)
|
|
Length of stent (< 12 cm)
|
4
|
5
|
0.091
|
3.636 (0.838 – 15.782)
|
|
Severe cholecystitis
|
2
|
5
|
0.637
|
1.538 (0.267 – 8.850)
|
|
Acalculous cholecystitis
|
2
|
7
|
1.000
|
1.055 (0.195 – 5.699)
|
|
Malignant biliary stricture
|
0
|
4
|
0.571
|
0.927 (0.861 – 0.999)
|
|
Post-EST papilla
|
8
|
29
|
1.000
|
1.025 (0.326 – 3.217)
|
|
Biliary drainage
|
2
|
11
|
0.720
|
0.615 (0.121 – 3.137)
|
|
Pancreatic stenting
|
4
|
11
|
0.723
|
1.455 (0.388 – 5.453)
|
|
Papillary diverticulum
|
5
|
28
|
0.258
|
0.482 (0.146 – 1.595)
|
OR, odds ratio; CI, confidence interval; EST, endoscopic sphincterotomy
Table 6
Risk factors for stent distal migration (multivariate analysis).
|
P value
|
OR (95 %CI)
|
|
Age (> 80)
|
0.177
|
0.343 (0.073 – 1.621)
|
|
Sex (female)
|
0.726
|
1.297 (0.303 – 5.556)
|
|
Stent type (straight)
|
0.011
|
8.805 (1.656 – 46.826)
|
|
Length of stent (< 12 cm)
|
0.107
|
4.738 (0.715 – 31.406)
|
|
Severe cholecystitis
|
0.537
|
1.862 (0.259 – 13.367)
|
|
Acalculous cholecystitis
|
0.987
|
1.019 (0.106 – 9.806)
|
|
Post-EST papilla
|
0.770
|
1.247 (0.284 – 5.476)
|
|
Biliary drainage
|
0.419
|
0.450 (0.065 – 3.123)
|
|
Pancreatic stenting
|
0.230
|
3.213 (0.478 – 21.622)
|
|
Papillary diverticulum
|
0.313
|
0.459 (0.101 – 2.084)
|
OR, odds ratio; CI, confidence interval; EST, endoscopic sphincterotomy
Discussion
Although ETGBD with ENGBD or EGBS is an effective alternative method when emergency
cholecystectomy and PTGBD are considered high risk [1]
[2]
[3]
[4]
[5], ETGBD is technically difficult. In the last 10 years, the technical success rate
is reported to be 64 % to 96 % [5]
[6]
[7]
[8]
[9]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20]. ETGBD’s technical difficulty is associated with the inherent complexity of inserting
the GW into the gallbladder. Moreover, even when GW placement in the gallbladder is
successful, subsequent placement of the stent may be complicated. In this study, if
a 7-Fr tapered catheter could be inserted into the gallbladder before stent insertion,
the technical success rate was 100 % for both novel stent and control groups. With
this approach of insertion of a tapered catheter into the gallbladder before stent
placement, cystic duct bougie can be achieved and subsequent insertion of any stent
is expected to improve. In addition, we consider successful insertion of a tapered
catheter as predictive of subsequent success of stent placement. Theoretically, the
longer, tortuous tip of the novel stent might be an obstacle to pushing the stent
and it may be inferred that it is harder to insert than standard stents. However,
using the novel stent, it was not hard to insert into the gallbladder compared with
standard stents. The tapered tip and relatively hard shaft of the novel stent may
contribute to good insertability. We acknowledge that the stent may have been easy
to place in the cases in this study because no cases were included in which the 7
Fr tapered catheter could not be inserted into the gallbladder.
Clinical success rates with ETGBD for acute cholecystitis are reported to be 83 %
to 100 % in per-protocol analyses [5]
[6]
[7]
[8]
[9]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]. It has also been reported that the clinical success rate with ETGBD is roughly
10 % lower than the technical success rates in intention-to-treat analysis because
of the accumulation of purulent material, sludge, or gallstones, thus hindering effective
drainage [13]
[22]
[23]. In this study, clinical success rates for cases in which EGBS was technically successful
were 100 % in the novel stent group and 95.7 % in the control group, which are both
extremely favorable. Suctioning viscous bile and irrigation of the gallbladder with
saline through a tapered catheter prior to stent placement may have contributed to
this favorable outcome.
EGBS-specific early AEs include cystic duct perforation, stent kinking, and obstructive
jaundice without EST. In subjects undergoing EGBS, EST often cannot be performed because
of abnormal coagulation; however, stent placement without EST could lead to outflow
obstruction of bile at the papilla. Therefore, with the novel stent, side holes were
opened at the shaft in anticipation of bile drainage from the common bile duct. However,
there was one case of obstructive jaundice due to cholestasis in the novel stent group
and the efficacy of the side hole at the shaft was unclear.
In this study, the rate of late AEs in the control group was high (40.4 %), and the
rate of stent distal migration was quite high at 31.9 %. Moreover, in four patients
who developed acute cholecystitis in the control group, the cause was stent distal
migration. According to previous reports, stent distal migration not only causes exacerbation
or recurrence of cholecystitis but also leads to severe complications such as pancreatitis
[24] and intestinal perforation [25]
[26]. Therefore, especially in cases of long-term stent placement, stent selection should
be performed with prevention of migration in mind. In this study, univariate analysis
indicated that a straight stent was the risk factor associated with migration; thus,
straight stents should be avoided for long-term placement of EGBS. Inoue et al. [19] reported good long-term outcomes using a newly designed stent that was straight
stent on the distal side and a small half-pigtail one on the proximal side (stent
migration: 0 % [0/23], cholecystitis recurrence: 0 % [0/23], cholangitis: 4.3 % [1/23]).
Thus, we assumed that a straight stent might be associated with less migration than
a double-pigtail type, and we used straight stents for a while. However, results from
this study show that stents that are straight on both proximal and distal sides often
migrate.
In addition, the high rate of stent migration compared with previous reports may be
related to the definition of stent migration. We defined stent distal migration not
only as when a stent migrated to the intestine or out of the body but also when a
large part of the tip slipped out of the gallbladder. Therefore, especially with a
pigtail stent, we termed a stent as having migrated when only its tip was caught in
the neck of gallbladder or cystic duct ([Fig. 5]). In previous reports, there are no detailed descriptions of the definition of stent
migration, but when the tip of the stent was caught in the neck of gallbladder or
cystic duct, it may not have been judged as a migration.
Remarkably, there was no stent distal migration in the novel stent group. We assume
that the factors that contributed to prevention of stent migration include: (1) the
three-dimensional spiral shape of the stent tip; (2) the maximum stent length of 19 cm,
allowing for placement at a sufficient depth; (3) the semicircular shape of the stent
shaft reducing the stent’s axial force; and (4) the straight distal end of the stent,
meaning that it is less affected by food passing and intestinal peristalsis. We believe
that among these factors, the semicircular shape of the stent shaft was the most effective
in preventing stent migration. Standard biliary stents have a straight shaft, which
requires bending when placed in the gallbladder to accommodate the regional anatomy.
Therefore, a straight shaft must create a strong axial force [27]
[28]. We consider that the semicircular shape of the stent with low axial force contributes
to prevention of migration. Although the basic policy in this study was to place the
stent tip at the fundus of the gallbladder in both the novel stent group and the control
group, there may be more cases in which the stent can be inserted to the target site
because of the longer lengths available. Moreover, multivariate analysis in this study
revealed that the straight stent was a risk factor for migration. Although the distal
end of the novel stent is straight, there were no cases of migration in the novel
stent group. It is apparent that when only the distal end is straight, it is not a
risk factor for migration.
Several limitations of this study exist. First, the design is single-center and retrospective.
In addition, although there were no statistical differences and the novel stent group
had a slightly shorter observation period compared with the control group [120 ± 143
vs 162 ± 252 (mean, days)]. However, because the observation period of the novel stent
group was longer than the mean duration from placement to migration in the control
group [69.5 ± 69.0 (mean, days)], we believe that evaluation was sufficient. To resolve
these limitations, comparison and verification of the novel stent and traditional
stents with a randomized controlled trial are desirable in the future.
Conclusion
In conclusion, EGBS using the novel stent (GBest-N stent) led to good results for
technical and clinical success, and AEs. In terms of technical and clinical success
and early AEs, EGBS was effective for acute cholecystitis regardless of whether the
traditional or novel stent was used. However, in terms of long-term outcomes, stent
distal migration and associated recurrence of cholecystitis occur frequently with
the traditional biliary stent. The novel stent had significantly lower rates of late
AEs and stent distal migration compared with the traditional biliary stent. Thus,
if long-term stent placement is necessary, the novel stent is more effective.
