Comparison of disposable digital single-operator cholangioscopy versus direct peroral cholangioscopy for the diagnosis of intraductal superficial lesions of the bile duct

Abstract

Background Disposable digital single-operator cholangioscopy (D-SOC) and direct peroral cholangioscopy (D-POC) using an ultraslim endoscope are established POC modalities for the diagnosis and treatment of various biliary diseases. We compared the usefulness of D-SOC and D-POC for the diagnosis of intraductal superficial lesions of the bile duct (ISL-Bs).

Methods 38 consecutive patients with suspected biliary diseases who underwent both D-SOC and D-POC were enrolled. The primary outcome was ISL-B detection rate, and the secondary outcomes were technical success of POC and POC-guided forceps biopsy sampling (POC-FB), procedure time, visualization quality, and tissue adequacy.

Results 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). D-POC had a marginally higher ISL-B detection rate (34.2% vs. 28.9%, P = 0.68) and significantly higher visualization quality (P = 0.03). The mean (SD) procedure time was significantly shorter with D-SOC (11.00 [1.33] vs. 19.03 [2.95] minutes, P<0.001). The technical success rate of POC-FB and tissue adequacy did not differ between the two techniques (D-SOC vs. D-POC: 81.8% vs. 84.6%, P = 0.69 and 77.8% vs. 90.9%, P = 0.57, respectively).

Conclusions Both POC systems were safe and useful for the detection, characterization, and diagnosis of minute ISL-Bs. While D-SOC displayed a shorter procedure time and a tendency for higher technical success rate, D-POC provided superior visualization quality, allowing detailed observation of the surface structure and microvascular patterns.

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. 1Olympus Medical Systems, Tokyo, Japan. 2Multibending endoscope (third-generation prototype). 3Boston Scientific, Marlborough, Massachusetts, USA. 4SpyBite 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
Working length, mm	1100	1330	2140
Distal end outer diameter, mm	5.4	4.9	3.5
Accessory channel
Number	1	2	1
Size, mm	2.2	2.2/1.0	1.2
Field of view	140°	110°	120°
Angulation, Up/down/left/right	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)
Suction capability	Yes	Yes	Yes
Direction from which accessories enter endoscopic image	7 o’ clock	5 o’ clock	6 o’ clock
Narrow-band imaging	Yes	Yes	No
Biopsy forceps	FB-39Q		SpyBite Max biopsy forceps4
Jaw outer diameter, mm	1.8		1.0
Jaw opening, mm	4.5		4.1
Working length, mm	1950		2860
Required endoscope working channel, mm	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
Suspected malignant	3/11	3/13
Suspected benign	4/11	5/13
Indeterminate	4/11	5/13
Visualization quality, n/N (%)			0.03
Excellent	2/11 (18.2)	7/13 (53.8)
Good	3/11 (27.3)	4/13 (30.8)
Fair	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
Cholecystitis	1 (2.6)		NA
Cholangitis	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 (%)
Hilum	3 (27.3)	3 (23.1)	>0.99
Distal CBD	6 (54.5)	7 (53.8)	0.97
Intrahepatic duct	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
Intraductal neoplasm of the bile duct	5 (33.3)
Cholangiocarcinoma	3 (20.0)
IPN-B	2 (13.3)
Benign	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.

Conflict of Interest

I.S. Shin, J.H. Moon, Y.N. Lee, H.K. Kim, J.C. Chung, T.H. Lee, J.K. Yang, Y.D. Cho, and S.-H. Park declare that they have no conflict of interest.

Acknowledgement

We thank A Ri Song, RN, Sun Hwa Cho, RN, Sun Hye Lee, RN, and the nursing staff for their assistance with the procedures. We express our gratitude to Ji Eun Moon, PhD, Senior Statistician of SoonChunHyang University Bucheon Hospital, for guidance with statistical analysis.

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• 10 Lee YN, Moon JH, Choi HJ. et al. Direct peroral cholangioscopy for diagnosis of bile duct lesions using an I-SCAN ultraslim endoscope: a pilot study. Endoscopy 2017; 49: 675-681 DOI: 10.1055/s-0043-106179. (PMID: 28564713)
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• 14 Shin IS, Moon JH, Lee YN. et al. Detection and endoscopic classification of intraductal neoplasms of the bile duct by peroral cholangioscopy with narrow-band imaging (with videos). Gastrointest Endosc 2023; 97: 898-910
• 15 Lee YN, Moon JH, Lee TH. Prospective randomized trial of a new multibending versus conventional ultra-slim endoscope for peroral cholangioscopy without device or endoscope assistance (with video). Gastrointest Endosc 2020; 91: 92-101 DOI: 10.1016/j.gie.2019.08.007. (PMID: 31442395)
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• 19 Lee YN, Moon JH, Lee TH. et al. Efficacy and safety of direct peroral cholangioscopy using a new multibending ultra-slim endoscope for the management of biliary diseases. J Hepatobiliary Pancreat Sci 2022; 29: 1292-1299 DOI: 10.1002/jhbp.1189. (PMID: 35658104)
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• 22 Kim HK, Moon JH, Choi HJ. et al. Early bile duct cancer detected by direct peroral cholangioscopy with narrow-band imaging after bile duct stone removal. Gut Liver 2011; 5: 377-379
• 23 Navaneethan U, Hasan MK, Lourdusamy V. et al. Single-operator cholangioscopy and targeted biopsies in the diagnosis of indeterminate biliary strictures: a systematic review. Gastrointest Endosc 2015; 82: 608-614 DOI: 10.1016/j.gie.2015.04.030. (PMID: 26071061)
• 24 Lee WM, Moon JH, Lee YN. et al. Utility of direct peroral cholangioscopy using a multibending ultraslim endoscope for difficult common bile duct stones. Gut Liver 2022; 16: 599-605 DOI: 10.5009/gnl210355. (PMID: 35000935)
• 25 Lee WM, Moon JH, Lee YN. et al. Usefulness of direct peroral cholangioscopy using a multibending ultraslim endoscope for the management of intrahepatic bile duct lesions (with videos). Gut Liver 2024; 18: 358-364
• 26 Itoi T, Sofuni A, Itokawa F. et al. Evaluation of peroral videocholangioscopy using narrow-band imaging for diagnosis of intraductal papillary neoplasm of the bile duct. Dig Endosc 2009; 21: S103-107 DOI: 10.1111/j.1443-1661.2009.00849.x. (PMID: 19691722)
• 27 Moon JH, Ko BM, Choi HJ. et al. Direct peroral cholangioscopy using an ultra-slim upper endoscope for the treatment of retained bile duct stones. Am J Gastroenterol 2009; 104: 2729-2733 DOI: 10.1038/ajg.2009.435. (PMID: 19623165)
• 28 Brewer Gutierrez OI, Bekkali NLH, Raijman I. et al. Efficacy and safety of digital single-operator cholangioscopy for difficult biliary stones. Clin Gastroenterol Hepatol 2018; 16: 918-926

Publication History

Received: 17 January 2024

Accepted after revision: 08 May 2024

Accepted Manuscript online:
08 May 2024

Article published online:
18 June 2024