Introduction
Despite advances in pancreaticobiliary imaging, precise delineation and characterization
of intraductal superficial lesions remain challenging [1 ]
[2 ]. Accurate diagnosis of intraductal neoplasms of the bile duct, including premalignant
and early malignant lesions, can have a profound impact on management. Therefore,
peroral cholangioscopy (POC) holds promise as an advanced technique when conventional
endoscopic retrograde cholangiopancreatography (ERCP) or other imaging modalities
cannot be used to obtain a diagnosis [3 ]
[4 ]
[5 ].
The two currently available POC techniques are disposable digital single-operator
cholangioscopy (D-SOC; SpyGlass DS Direct Visualization System; Boston Scientific,
Marlborough, Massachusetts, USA) and direct POC (D-POC) using an ultraslim endoscope.
The device used for D-SOC is a catheter-based system that operates through the working
channel of the duodenoscope, providing favorable image quality and easy maneuverability
[6 ]. D-POC is another single-operator cholangioscopy (SOC) technique in which the endoscope
directly enters the biliary tree, ensuring advantages such as high-quality endoscopic
images, image-enhanced endoscopy, and high performance of procedures using a large
(2.0–2.2 mm) working channel [2 ]
[7 ].
Although D-SOC and D-POC are both established modalities for the diagnosis and treatment
of biliary diseases, their efficacies have not been compared in appropriate trials.
Therefore, we compared the usefulness of these two systems in terms of diagnosis of
intraductal superficial lesions of the bile duct (ISL-Bs).
Methods
Patients and study design
This study was a retrospective analysis of prospectively collected data of consecutive
patients who underwent both D-SOC and D-POC from November 2020 to June 2022 at a single
tertiary referral center. The inclusion criteria were age >18 years, suspected biliary
diseases requiring POC, dilated common bile duct (CBD) >8 mm, and any previous sphincteroplasty
procedure such as major endoscopic sphincterotomy and/or papillary balloon dilation.
The exclusion criteria were diffuse stricture of the distal CBD, ampullary stenosis,
bleeding tendency (platelet count <50 000 cells/mm3 or international normalized ratio >1.5), contraindications to ERCP, and patient refusal
to undergo POC. The study was approved by the Institutional Review Board of SoonChunHyang
University Bucheon Hospital (approval number SCHBC 2022–12–014–001). All authors had
access to all study data and reviewed and approved the final manuscript.
The D-SOC system
The detailed specifications of the endoscopes used for D-SOC and D-POC are shown in
[Table 1 ] and [Fig. 1 ]. The D-SOC system contains a disposable 10-Fr access and delivery catheter (SpyScope
DS; Boston Scientific), capital equipment, and disposable 1.0-mm biopsy forceps (SpyBite;
Boston Scientific) for tissue acquisition. The access and delivery catheter comprise
a fiberoptic probe, a 1.2-mm working channel, and two dedicated 0.6-mm irrigation
channels. The fiberoptic probe provides favorable digital image processing with an
integrated 120° field of view. The access catheter has a tapered tip and a four-way
tip deflection system that improves manipulation and enables easy advancement into
the proximal bile duct. Two dedicated irrigation channels contribute to unimpeded
observation and forceps biopsy procedures without interruption for cleaning. The recently
introduced version of the D-SOC device (SpyGlass DS II Direct Visualization System;
Boston Scientific) features a new complementary metal oxide semiconductor chip that
provides higher-resolution digital images (62 250 pixels) and an automatic light control
that minimizes central hot spots [8 ]
[9 ]. A newly modified biopsy forceps (SpyBite Max; Boston Scientific) with serrated
teeth and two elongated fenestration holes can obtain maximal tissue acquisition for
the accurate differential diagnosis of intraductal lesions.
Table 1 Specifications of peroral cholangioscopy systems.
D-POC
D-SOC
D-POC, direct peroral cholangioscopy; D-SOC; disposable digital single-operator cholangioscopy.
1 Olympus Medical Systems, Tokyo, Japan.2 Multibending endoscope (third-generation prototype).3 Boston Scientific, Marlborough, Massachusetts, USA.4 SpyBite Max biopsy forceps can acquire twice as much tissue as SpyBite because of
its serrated teeth and two elongated fenestration holes.
Cholangioscope
GIF-XP290N1
CHF-Y00101,2
SpyScope DS II catheter3
1100
1330
2140
5.4
4.9
3.5
1
2
1
2.2
2.2/1.0
1.2
140°
110°
120°
210°/90°/100°/100°
Two-directional angulation (proximal two-way: 90°, distal two-way: 200°/100°)
Four-way >30° (with accessory device in working channel)
Yes
Yes
Yes
7 o’ clock
5 o’ clock
6 o’ clock
Yes
Yes
No
Biopsy forceps
FB-39Q
SpyBite Max biopsy forceps4
1.8
1.0
4.5
4.1
1950
2860
2.0
1.2
Fig. 1 Cholangioscopy instruments. a Left: 10-Fr access and delivery catheter (SpyGlass DS II; Boston Scientific, Marlborough,
Massachusetts, USA); right: ultraslim endoscope (XP-290N; Olympus Medical Systems,
Tokyo, Japan). b Left: 1.0-mm biopsy forceps (SpyBite Max; Boston Scientific); right: 5-Fr biopsy
forceps (FB-39Q; Olympus Medical Systems).
The D-POC system
D-POC is another established POC technique in which a cholangioscope is directly inserted
into the bile duct [3 ]
[10 ]
[11 ]. D-POC offers an extremely high resolution image quality equivalent to that of standard
esophagogastroduodenoscopy or colonoscopy, improving the ability to clearly observe
intraductal lesions and perform targeted biopsy sampling. As D-POC utilizes videoscopy,
image-enhanced endoscopic techniques such as narrow-band imaging (Olympus Medical
Systems, Tokyo, Japan) or i-SCAN digital contrast (Pentax Medical, Tokyo, Japan) can
be applied using the conventional endoscopic setting [12 ]
[13 ]. A relatively large working channel (2.0–2.2 mm), which allows 5-Fr instruments
for interventional procedures and ease of irrigation, enhances the optimal intraductal
visualization and accurate acquisition of tissues [3 ]
[14 ]. Where specialized accessories such as an intraductal balloon catheter are required
to successfully advance a conventional ultraslim endoscope into the bile duct, the
prototype multibending ultraslim endoscope (CHF-Y0010; Olympus Medical Systems) can
be used, which has two bending sections (90° upward and downward in the proximal section;
200° upward and 100° downward in the distal section), making it possible to introduce
an ultraslim endoscope into the relatively acute angle of the biliary system without
any device assistance (free-hand technique) [15 ]
[16 ].
Procedures
Patients were placed in the prone position under conscious sedation after intravenous
administration of systemic antibiotics. All patients underwent preceding ERCP using
a standard duodenoscope (JF-260V or TJF-260V; Olympus Medical Systems). Endoscopic
sphincterotomy was performed before the POC procedure if not performed previously.
In all patients, both D-SOC and D-POC were performed sequentially by two experienced
endoscopists (J.H.M. and Y.N.L).
To improve the visualization quality of POC examinations, we minimized the use of
contrast agents during ERCP and performed the ERCP procedure with gentle maneuvers
to avoid bile duct injuries. After ERCP, D-SOC was initiated by introducing the 10-Fr
access and delivery catheter (SpyScope DS II; Boston Scientific) through the working
channel of the duodenoscope and advancing it into the bile duct over the 0.025-inch
guidewire (VisiGlide 2; Olympus Medical Systems). After the catheter successfully
reached the hilar portion of the bile duct, the guidewire was removed for optimal
visualization. Irrigation with saline solution (sterile 0.9% [w/v] sodium chloride)
and repeated suction were performed through the two dedicated 0.6-mm irrigation channels
and the 1.2-mm working channel. Then, the bile duct was examined by repeated advancement
and withdrawal of the access catheter. After detection and characterization of the
ISL-B, POC-guided forceps biopsy (POC-FB) was conducted using a 1.0-mm diameter biopsy
forceps (SpyBite Max) for tissue confirmation.
After the D-SOC procedures, D-POC was performed using one of several ultraslim endoscopes
(GIF-XP260N, GIF-XP260NS, GIF-XP290N, or CHF-Y0010 [prototype multibending ultraslim
endoscopes]; Olympus Medical Systems) according to the standardized protocol [11 ]
[15 ]
[17 ]. The cholangioscope was inserted into the bile duct using a 5-Fr intraductal balloon
catheter (MTW Endoskopie, Wesel, Germany) or the free-hand technique. For intraductal
balloon-guided insertion, the 5-Fr balloon catheter was introduced over the guidewire
and the balloon was inflated and anchored into the branch of the intrahepatic duct
[18 ]. Then, the ultraslim endoscope was advanced over the balloon catheter into the bile
duct under endoscopic and fluoroscopic control [7 ]
[17 ]
[18 ]. For free-hand insertion, the endoscope was advanced directly into the bile duct,
while the second bending portion of the multibending ultraslim endoscope was held
in an upward-angled position to maintain an acute angle [15 ]
[19 ]. Careful irrigation with saline solution and frequent suction were repeatedly performed
through the 2.0–2.2-mm working channel to enhance endoscopic visualization. Carbon
dioxide was insufflated using an automated insufflation system (Colosense CO-3000;
Mirae Medics, Seoul, South Korea) to reduce adverse events (AEs) [20 ]. The biliary tree was repeatedly examined under white-light and narrow-band imaging.
POC-FB was performed using a 5-Fr biopsy forceps (FB-39Q; Olympus Medical Systems)
for histopathologic analysis.
Regardless of the POC system used, at least three biopsy specimens were obtained per
patient. All histopathologic analyses, including evaluation of the tissue adequacy
of the obtained biopsy specimens, were performed by a single experienced pathologist
(H.K.K.). The final diagnosis was based on histopathologic proof of malignancy in
a surgical specimen or POC-FB specimen or no overt malignancy for at least 12 months
during the follow-up clinical course for benign cases.
Outcome measurements and definitions
The primary outcome was the ISL-B detection rate, and the secondary outcomes were
the technical success rates of POC and POC-FB, total procedure time, visualization
quality, AEs, and tissue adequacy. The ISL-B detection rate was defined as appropriate
detection of intraductal superficial lesions requiring tissue confirmation under direct
visualization. Technical success of POC was defined as successful insertion of the
cholangioscope through the ampulla of Vater and advancement to the bifurcation of
the biliary tree. Technical success of POC-FB was defined as successful application
of tissue sampling maneuvers to suspected ISL-Bs. The total procedure time was defined
as the time from oral advancement of the endoscope to the end of the examination.
Visualization quality was graded on the following three-point scale: “fair” (presence
of unclear but identifiable abnormalities), “good” (able to clearly and correctly
distinguish abnormalities), or “excellent” (able to visualize the details of the surface
structure and microvascular patterns with high definition). Visualization quality
was independently assessed by the investigators, and any discrepancies were resolved
by discussion and consensus. The characteristics of the lesion were analyzed by dividing
into the surface structure and surface microvascular pattern according to the previous
literature [3 ]
[14 ]
[21 ]. Lesions characterized by a surface structure with cluster of nodules or long papillary
villi exhibiting branching, or those with microvascular architecture marked by tortuous
or irregularly dilated vessels, were classified as suspected malignant. Conversely,
lesions displaying a simple depressed surface structure, scarring, or single raised
lesions without microvessels were considered suspected benign. Lesions not fitting
these descriptions were categorized as indeterminate. AEs were defined according to
the American Society for Gastrointestinal Endoscopy criteria and included cholangitis,
pancreatitis, bleeding, perforation, and air embolism. Tissue was considered adequate
if it contained biliary epithelium; a specimen that contained only fibrous or connective
tissue was considered inadequate.
Statistical analysis
Continuous variables are presented as mean and SD, and were compared using the paired
t test. Categorical variables are presented as frequency (percentage) and were compared
using McNemar’s test. The mean procedure times were compared using the paired t test. The visualization quality of D-SOC and D-POC were compared using the extended
Mantel–Haenszel chi-squared test for trend. P values of <0.05 in a two-tailed test were considered statistically significant. All
statistical analyses were performed using Rex software (version 3.5.0; RexSoft Inc.,
Seoul, South Korea).
Results
During the study period, 38 patients (mean age 70.3 [SD 9.9] years; 22 women) underwent
both D-SOC and D-POC (see Table 1s in the online-only Supplementary material). The indications for POC included confirmation
of bile duct clearance and investigation of possible ISL-Bs after stone removal in
20 patients (52.6%), evaluation of ISL-Bs that were suspected based on previous imaging
in 16 patients (42.1%), and accurate delineation of an intraductal tumor before surgery
in 2 patients (5.3%). During D-POC, an intraductal 5-Fr balloon catheter was utilized
in 23 patients (60.5%), while free-hand insertion using a multibending ultraslim endoscope
was attempted in 15 patients (39.5%).
ISL-B detection rate
D-POC had a marginally higher ISL-B detection rate (34.2% vs. 28.9%, P = 0.68). D-SOC and D-POC did not show a significant difference in the detection of
suspected malignant lesions (27.3% vs. 23.1%) ([Table 2 ]).
Table 2 Outcomes of peroral cholangioscopy.
Outcomes
Type of POC
P value
D-SOC (n = 38)
D-POC (n = 38)
POC, peroral cholangioscopy; D-SOC; disposable digital single-operator cholangioscopy;
D-POC, direct peroral cholangioscopy; ISL-B, intraductal superficial lesion of the
bile duct; NA, not applicable.
Technical success of POC, n (%)
38 (100)
35 (92.1)
0.25
ISL-B detection rate, n (%)
11 (28.9)
13 (34.2)
0.68
3/11
3/13
4/11
5/13
4/11
5/13
Visualization quality, n/N (%)
0.03
2/11 (18.2)
7/13 (53.8)
3/11 (27.3)
4/13 (30.8)
6/11 (54.5)
2/13 (15.4)
Total procedure time, mean (SD), minutes
11.00 (1.33)
19.03 (2.95)
<0.001
Adverse events
3 (7.9)
NA
1 (2.6)
NA
2 (5.3)
NA
Technical success of POC
D-SOC had a higher technical success rate than D-POC but the difference was not statistically
significant (100% vs. 92.1%, P = 0.25) ([Table 2 ]). Technical failure of D-POC occurred in three patients; the multibending ultraslim
endoscope failed to intubate into the CBD in one patient, and, in two patients, the
ultraslim endoscope dislodged into the duodenum after removal of the intraductal balloon
catheter owing to instability of the endoscope. In one of these latter patients, an
ISL-B had been confirmed by D-SOC (Fig. 1s , [Video 1 ]).
Nodular lesion with regularly dilated and tortuous vessels identified by disposable
digital single-operator cholangioscopy that could not be identified by direct peroral
cholangioscopy owing to technical failure.Video 1
Visualization quality
D-POC had a significantly higher visualization quality than D-SOC (P = 0.03) ([Table 2 ]). Of the four patients classified as having “fair” visualization quality after D-SOC,
one was reclassified as “good” after D-POC and three were reclassified as “excellent.”
Two patients who were classified as having “good” after D-SOC were reclassified as
“excellent” after D-POC ([Fig. 2 ]).
Fig. 2 Cholangioscopic views and specimen treatment. a During
disposable digital single-operator cholangioscopy, a nodular lesion with blood clots
was
identified and the quality was classified as “good” based on the ability to correctly
distinguish abnormalities. b During direct peroral
cholangioscopy, the nodular lesion with irregularly tortuous and dilated vessels was
more clearly observed. c Narrow-band imaging revealed the
surface structure and microvascular pattern with high definition, and the visualization
quality was reclassified as “excellent.” Adenocarcinoma was diagnosed on hematoxylin
and
eosin staining (d Gross specimen. e
Magnification ×10. f Magnification ×20).
Procedure time
The mean procedure time was significantly shorter with D-SOC than D-POC (11.00 [SD
1.33] vs. 19.03 [SD 2.95] minutes, P < 0.001) ([Table 2 ]).
AEs
AEs occurred in three patients (7.9%; cholangitis in two and cholecystitis in one),
and all patients were treated conservatively. No severe AEs, including air embolism,
were recorded after the procedures ([Table 2 ]).
Technical success of POC-FB
POC-FB was successful in 81.8% (9/11) of D-SOC procedures and 84.6% (11/13) of D-POC
procedures (P = 0.69) ([Table 3 ]). In two patients with failed POC-FB during D-SOC, it was difficult to accurately
position the biopsy forceps on the target lesions because of the inflexible maneuverability
of the cholangioscope with the biopsy forceps in the working channel. In two patients
with failed POC-FB during D-POC, POC-FB was impossible because the stability of the
ultraslim endoscope was lost after removal of the intraductal balloon catheter. The
tissue adequacy tended to be higher with D-POC than D-SOC, but the difference was
not significant (90.9% [10/11] vs. 77.8% [7/9], P = 0.57).
Table 3 Outcomes of peroral cholangioscopy-guided forceps biopsy.
Characteristics
Type of POC
P value
D-SOC (n = 11)
D-POC (n = 13)
POC, peroral cholangioscopy; D-SOC; disposable digital single-operator cholangioscopy;
D-POC, direct peroral cholangioscopy; POC-FB, peroral cholangioscopy-guided forceps
biopsy; CBD, common bile duct; IPN-B, intraductal papillary neoplasm of the bile duct.
Technical success of POC-FB, n (%)
9 (81.8)
11 (84.6)
0.69
Location of POC-FB, n (%)
3 (27.3)
3 (23.1)
>0.99
6 (54.5)
7 (53.8)
0.97
2 (18.2)
2 (15.4)
>0.99
Tissue adequacy, n/N (%)
7/9 (77.8)
10/11 (90.9)
0.57
Final diagnosis, n (%)
n = 15
5 (33.3)
3 (20.0)
2 (13.3)
10 (66.7)
Of the 15 patients who underwent POC-FB using D-SOC or D-POC, 5 patients were diagnosed
with intraductal neoplasms of the bile duct (cholangiocarcinoma, n = 3; intraductal
papillary neoplasm of the bile duct, n = 2). Two of the patients with cholangiocarcinoma
underwent surgery with curative intent. Patients with benign lesions were managed
by close observation, including one patient whose tissue specimen was inadequate after
the use of both POC techniques (Fig. 2s ).
Discussion
Timely identification and discrimination of biliary abnormalities is crucial [22 ]. However, current imaging modalities have limited utility in diagnosing various
biliary diseases, including minute intraductal superficial lesions confined to the
bile duct wall [3 ]
[14 ]. POC can overcome this limitation by enabling real-time detection of ISL-Bs through
direct visualization and accurate diagnosis of intraductal neoplasms of the bile duct
through targeted biopsy sampling [14 ]
[21 ].
With recent technologic advancements, POC has evolved from a cumbersome and time-consuming
two-operator system to resource-saving SOC systems such as D-SOC and D-POC [23 ]
[24 ]. Although both D-SOC and D-POC were introduced to overcome the limitations of the
conventional mother–baby cholangioscopic system, the two systems have differences
in terms of image quality, procedural technique, cholangioscope maneuverability, and
available accessories for intervention [6 ]
[25 ].
In the present study, we compared the specific strengths and weaknesses of the two
systems for the management of ISL-Bs in real clinical practice. D-SOC had a higher
technical success rate than D-POC, although the difference was not statistically significant.
Technical failure of D-POC occurred in three patients; in one patient who underwent
D-POC using the multibending ultraslim endoscope, intubation could not be achieved,
and in two patients who underwent intraductal balloon-guided D-POC, the endoscope
position could not be maintained after removal of the intraductal balloon catheter.
D-SOC not only demonstrated 100% technical success but also successfully detected
ISL-B and obtained adequate tissue specimens in one of the three patients in whom
D-POC failed (Fig. 1s , [Video 1 ]). A major advantage of D-SOC is its robustness during the procedure. During D-SOC,
the duodenoscope can act as a counterweight to provide maximal stability to the access
catheter even in difficult anatomic situations, enabling more stable examinations
than D-POC. Conversely, during D-POC, the duodenoscope should be completely removed,
and specialized accessories or endoscopes are required to prevent large loop formations
that may occur within the gastric fundus or the deep portion of the duodenum. Although
the intraductal balloon catheter-guided POC method showed high technical success,
it can be less stable than D-SOC because firm anchoring of the intraductal balloon
within a branch of the intrahepatic duct can sometimes be difficult. In addition,
the intraductal balloon catheter should be withdrawn from the working channel for
subsequent procedures, including forceps biopsy, and this can create technical difficulties
in maintaining the desired endoscope position. The multibending ultraslim endoscope
enables direct insertion of the cholangioscope without any accessories by providing
more acute angulation and improved pushability, but its technical superiority can
only be achieved by highly experienced endoscopists [15 ]. Considering that the technical success of D-POC may rely on the availability of
specialized equipment, and that D-POC requires experience and involves a steep learning
curve in order to perform it effectively, the difference in technical success between
D-SOC and D-POC might be greater for less experienced physicians.
Notably, D-POC showed a marginally higher ISL-B detection rate and a significantly
higher visualization quality than D-SOC. This is critical because optimal visualization
and precise tissue sampling for suspicious bile duct lesions is of utmost importance;
in some cases, the features of the bile duct lesions may not be visualized with sufficient
accuracy to allow for treatment decisions. Various features of D-POC appear to provide
particularly advantageous visualization capabilities, including its advanced image
clarity, wide field of view (140°), and availability of image-enhanced endoscopy techniques
such as narrow-band imaging or i-SCAN digital contrast. In the present study, these
advantages not only led to a higher detection rate but also provided better characterization
of ISL-Bs. In particular, possible neoplastic changes such as a granular, villous,
papillary or nodular surface structure and dilated, tortuous, and irregular microvascular
patterns could be more easily identified ([Fig. 3 ]) [14 ]
[21 ]
[26 ].
Fig. 3 Cholangioscopic views and specimen treatment. a During
disposable digital single-operator cholangioscopy (D-SOC), a granular lesion with
dilated
vessels was identified and the quality was classified as “good” based on the ability
to
correctly distinguish abnormalities. b During direct peroral
cholangioscopy (D-POC), the granular lesion with regularly dilated vessels without
tortuosity became more identifiable. c Narrow-band imaging
revealed the surface structure, microvascular pattern, and lesional margins with high
definition, and the visualization quality was reclassified as “excellent”. Adenocarcinoma
was diagnosed on hematoxylin and eosin staining (d Magnification
×100. e Magnification ×400).
D-SOC had a significantly shorter procedure time than D-POC. Successful D-POC requires
a series of procedures including insertion and fixation of the intraductal balloon
catheter in the intrahepatic duct, the removal of the duodenoscope, and advancement
of the ultraslim endoscope over the intraductal balloon catheter [7 ]
[18 ]. By contrast, D-SOC requires only insertion of the access catheter through the working
channel of the duodenoscope and intubation into the biliary tree for observation,
which can significantly shorten the overall procedure time compared with D-POC [7 ]
[27 ].
D-SOC and D-POC showed no significant difference in the technical success rate of
POC-FB, but the reasons for this differed. During D-SOC, POC-FB failed in two patients
because it was difficult to maintain the endoscope in an optimal position owing to
the limited angulation of the cholangioscope with the biopsy forceps in the working
channel. During D-POC, POC-FB failed in two patients because of instability of the
ultraslim endoscope after removal of the intraductal balloon catheter. Although D-POC
may have an advantage over D-SOC in terms of cholangioscope angulation during POC-FB
(i.e. the ultraslim endoscope is directly intubated into the biliary tree), D-SOC
can provide effective operator control in terms of cholangioscope stability with the
support of the duodenoscope.
In this study, 77.8% of specimens obtained with D-SOC and 90.9% obtained with D-POC
were adequate for histologic examination. Although there was a trend toward higher
tissue adequacy with D-POC, we did not detect a concrete difference in tissue adequacy.
A 5-Fr biopsy forceps (FB-39Q) may theoretically collect a larger amount of tissue;
however, a 1.0-mm biopsy forceps with specially designed serrated teeth and two elongated
fenestration holes (SpyBite Max) can efficiently maximize tissue acquisition.
In a previous study, POC caused cholangitis in 4%–22% of patients [20 ]. Our results are consistent with that study, as mild cholangitis occurred in 5.3%
(2/38) of patients. Although it was difficult to compare the differences in AEs between
the two procedures owing to the study design, all AEs resolved after conservative
treatment, and no severe AEs or mortality occurred during the study period. The relatively
low rate of AEs is expected to be associated with the repeated irrigation and suction
of fluids and the use of carbon dioxide (Colosense CO-3000) to maintain low pressure
in the bile duct [7 ]
[28 ].
Our study has several limitations. First, it was a single-center retrospective study
in which sample size calculation was not performed. Although selection bias was reduced
because D-SOC and D-POC were performed on the same patient group, this study may have
been underpowered by the rather small number of patients. Second, the nonrandomized
sequence of D-SOC and D-POC procedures may potentially induce performance bias. The
POC procedure was initiated with D-SOC, followed by D-POC, in all patients to minimize
the insertion and removal process of the duodenoscope. Although this strategy was
adopted to reduce the potential risk of AEs and patient discomfort, this can compromise
the reliability of the results; the endoscopists can be biased to the results of the
preceding POC procedure, and this could have influenced their assessment of the visualization
quality. In addition, the prior D-SOC procedures might affect the visual assessment
of subsequent D-POC procedures owing to possible bile duct injuries such as bleeding.
Third, the technical success of POC was not compared in patients with a CBD diameter
of ≤8 mm. As the ultraslim endoscopes used in our study had an external diameter of
5–6 mm, we tried to include patients with a CBD diameter of >8 mm after sufficient
endoscopic sphincterotomy and/or endoscopic papillary balloon dilation. Therefore,
the technical success of D-SOC may be higher than that of D-POC in patients with a
common bile duct diameter of ≤8 mm. Fourth, we could not directly compare the size
of the tissue specimens between the two techniques. Whether the difference in the
biopsy forceps led to an actual difference in the mean size of the tissue specimen
remains unclear. Fifth, we focused only on the diagnostic interventions of two POC
systems. Therapeutic interventions such as electrohydraulic lithotripsy, direct stent
placement, or tumor ablation were not evaluated. Such evaluations are being planned
for our next study. Finally, the results were obtained from two experienced endoscopists
with advanced skills in POC. The favorable results of our study might not be replicated
by endoscopists with a broader range of skill levels.
In conclusion, our results demonstrated that both POC systems were safe and useful
procedures for the detection, characterization, and diagnosis of minute ISL-Bs. Whereas
D-SOC exhibited a shorter procedure time and a tendency for a higher technical success
rate, D-POC provided superior visualization quality, allowing detailed observation
of the surface structure and microvascular patterns. Future technologic advancements
in cholangioscopic systems, such as improved image quality, application of image-enhanced
endoscopy technique, larger working channels, enhanced irrigation and suction functions,
and increased maneuverability, are expected to facilitate more accurate diagnosis
of various biliary diseases.
