A novel over-the-scope endoscopic assisting platform for expanding therapeutic capabilities: Preclinical feasibility study (with video)

Abstract

The limitations of single-channel endoscopy in complex gastrointestinal disease prompted design of the over-the-scope endoscopic assisting platform (OTS-EAP), a low-profile cap that converts any diagnostic endoscope into a dual-channel therapeutic system. Ex-vivo bending tests and in-vivo porcine studies evaluated safety and feasibility for three tasks: 1) high-flow irrigation and suction of clot/chyme; 2) radiation-free, direct-visual stent delivery; and 3) purse-string closure of large endoscopic submucosal dissection defects. OTS-EAP preserved endoscope flexibility and torque; rapid valve-switching cleared the field within seconds, stents were deployed precisely under endoscopic view, and dual-instrument coordination simplified defect closure. The platform offers an inexpensive, radiation-sparing “third hand” for emergencies, bleeding, stenting, and suturing, warranting clinical translation.

Keywords

Endoscopy Upper GI Tract - Non-variceal bleeding - Endoscopic resection (ESD, EMRc, ...) - Dilation, injection, stenting

Introduction

Endoscopic technology has evolved from a purely diagnostic tool to a cornerstone of minimally invasive therapy. However, standard single-channel endoscopes still face inherent limitations when performing complex therapeutic interventions. The constraint of a single working channel forces the operator to frequently exchange instruments, which inevitably prolongs procedure time and increases complexity. The limited channel diameter restricts suction efficiency, a critical weakness in emergency gastrointestinal endoscopy and acute upper gastrointestinal bleeding, where blood clots can easily obstruct the channel, obscuring the visual field and hindering hemostasis [1] [2] [3]. Furthermore, certain advanced procedures, such as stent placement in complex strictures or closure of large mucosal defects after endoscopic submucosal dissection (ESD), often require synergistic use of multiple instruments—a task for which single-channel endoscopic operation is relatively more difficult [4].

Although dual-channel endoscopes offer a viable alternative, their high cost, larger diameter, and limited availability restrict their widespread use [5]. Although some over-the-scope (OTS) devices can provide additional functionality, they are often single-purpose, cumbersome to operate, and may compromise flexibility of the endoscope itself [6]. Therefore, development of a low-cost, versatile accessory device compatible with the vast inventory of standard endoscopes has become an unmet need in the field of therapeutic endoscopy.

To this end, we have developed a novel OTS endoscopic assisting platform (OTS-EAP). This device is a sheath-based system featuring an integrated transparent cap that contains an endoscope lumen and an accessory working lumen. It is designed to seamlessly upgrade any standard single-channel endoscope into a dual-channel therapeutic system, aiming to provide a "third hand" solution. This preclinical study systematically evaluated feasibility of the device and validated its potential in three high-value clinical scenarios: 1) high-flow irrigation and enhanced suction; 2) intestinal stent placement under direct visualization; and 3) assisted endoscopic purse-string suturing.

Materials and methods

Device description

The novel OTS-EAP is manufactured from a biocompatible polymer using an integrated molding process ([Fig. 1] a). [Fig. 1] f shows the overall structure of the OTS-EAP mounted on the endoscope.

Fig. 1 Structure of OTS-EAP. a Schematic of the over-the-scope endoscopic assisting platform (OTS-EAP). b Distal-tip configuration of the OTS-EAP. c Proximal-end configuration of the OTS-EAP. d distal-tip view with the OTS-EAP attached. e External view of the OTS-EAP mounted on the endoscope. f The overall structure of the OTS-EAP assembled on an endoscope. g OTS-EAP fixation at the inner lens end does not affect endoscopic bending. h The OTS-EAP fixed on the endoscope in a bent configuration. i The OTS-EAP and endoscope working channel with inserted instruments

Its three main components are as follows. The tip of the distal multi-lumen transparent cap features a beveled design to minimize mucosal injury during insertion and withdrawal. It contains a central endoscope-fixing channel (inner diameter 8.8–13.6 mm, compatible with various endoscope models) and a tangential accessory working channel ([Fig. 1] b, [Fig. 1] d, [Fig. 1] e). Extending proximally from the distal cap, the flexible sheath houses the dual-lumen structure. Depending on the model, the inner diameter of the accessory working channel ranges from 7F to 24F, with a length of 120 to 150 cm to match various endoscope models. [Fig. 1] i illustrates the endoscopic instrument channel and the OTS-EAP with instruments inserted separately. Located at the proximal end of the sheath, the proximal connector hub provides a standard port or instrument valve for the accessory channel, facilitating connection to a negative pressure suction pump, a peristaltic irrigation pump, or insertion of various therapeutic instruments ([Fig. 1] c).

Preclinical study design

The study was approved by the Institutional Animal Care and Use Committee. The experiments were bifurcated into in vitro performance evaluation and in vivo animal model assessment.

Basic performance evaluation

For in vitro flexibility testing, the OTS-EAP was mounted on standard gastroscopes and colonoscopes. By simulating maneuvers within the gastrointestinal tract, including tip deflection and shaft torsion, we assessed whether the OTS-EAP would impede inherent flexibility of the endoscope. For in vivo maneuverability testing, in anesthetized healthy domestic pigs, a gastroscope equipped with the OTS-EAP was inserted orally to evaluate its ability to pass through the pharynx, esophagus, and cardia. Comprehensive maneuvers were performed in the stomach, including advancement, withdrawal, shaft rotation, tip deflection, and retroflexed views of the fundus and angle, to assess its operability and impact on the visual field.

Core function evaluation

Function 1: Rapid irrigation and assisted suction

An in vitro model simulating upper gastrointestinal bleeding was established using chyme, fresh anticoagulated porcine blood, and thrombin to prepare various gastric contents. A high-power suction device was connected to the OTS-EAP accessory channel to test its ability to aspirate the chyme and blood clots and the results were compared with the suction effectiveness of a standard endoscopic biopsy channel. Concurrently, a peristaltic pump was connected to the accessory channel to evaluate its efficacy in rapid irrigation and clearing the operative field.

Function 2: Duodenal stent placement under direct visualization

In a live porcine model, a gastroscope equipped with the OTS-EAP (15F) was advanced to the cardia. A J-tip guidewire was first inserted through the large-caliber accessory channel of the OTS-EAP into the pylorus and duodenum. Subsequently, a bare metal stent and its delivery system were advanced through the channel over the guidewire to the target location. Finally, under continuous endoscopic monitoring, the stent was precisely positioned and released. After deployment, stent configuration, position, and expansion were observed endoscopically. Final stent position was confirmed with an x-ray machine to verify accuracy of direct-visualization placement.

Function 3: Assisted endoscopic purse-string suture

In a live porcine model, a region approximately 3 cm in diameter was marked and a conventional ESD was performed using a DualKnife. After the defect was created, a pre-loaded nylon-loop ligation device was introduced directly through the OTS-EAP accessory channel. Hemoclips inserted through the endoscope native biopsy channel, were used to anchor the nylon loop at multiple points along the defect margin. Once anchored, the nylon loop was tightened to achieve a purse-string closure. Finally, to ensure a secure closure, a second purse-string suture was applied to the outer layer. Procedure fluency and quality of the closure were recorded.

Results

Basic performance

The OTS-EAP is compatible with mainstream gastroscopes and colonoscopes available on the market. In vitro testing demonstrated that the flexible design of the OTS-EAP allowed it to conform perfectly to the endoscope shaft and bend synchronously, with no discernible restriction on endoscope maximum deflection angle or maneuverability ([Fig. 1] g, [Fig. 1] h, [Video 1]). In the live porcine model, the endoscope equipped with the OTS-EAP smoothly passed through the physiological strictures of the upper digestive tract and could be advanced and withdrawn freely. Maneuverability within the stomach was excellent, with clear retroflexed views of the fundus and cardia, and no evidence of mucosal injury or drag marks.

Download Video

Flexibility of the endoscope with the OTS-EAP.Video 1

Core functions

Function 1: Rapid irrigation and assisted suction

Rapid irrigation and auxiliary suction. In irrigation tests, compared with the built-in waterjet function of the endoscope ([Fig. 2] a), the OTS-EAP delivered a jet with significantly higher flow rate, instantly washing away simulated blood and debris and restoring a clear operative field ([Fig. 2] b). The accessory channel of the OTS-EAP also demonstrated powerful suction capacity; particulate chyme and blood clots up to several millimeters in diameter were completely removed within 5 to 10 seconds ([Fig. 2] c, [Fig. 2] d, [Fig. 2] e, [Fig. 2] f, [Video 2]), whereas the standard endoscope channel either failed to aspirate or became occluded immediately. Quantified in vitro at identical pressure (−30 kPa), the OTS-EAP auxiliary channel (15F) achieved an aspiration flow rate of 44.5 ± 1.6 mL/s, markedly exceeding the 12.4 ± 0.8 mL/s obtained through the standard endoscopic biopsy channel (mean difference = 32.1 mL/s; P < 0.0001, two-tailed paired t-test, n = 5 replicates) ([Table 1]).

Fig. 2 Rapid irrigation and assisted suction. a Standard endoscopic water jet. b High-flow irrigation delivered by the OTS-EAP. c Ex-vivo porcine stomach simulating emergent gastric food retention. d Gastric lumen after food debris clearance with the OTS-EAP. e Ex-vivo porcine stomach simulating acute upper-GI bleeding. f Gastric lumen after blood-clot removal with the OTS-EAP.

Download Video

In vivo and in vitro related tests of the OTS-EAP.Video 2

Table 1 Comparison of OTS-EAP and conventional endoscope functions.

	OTS-EAP	Conventional endoscope	P value
OTS-EAP, over-the-scope endoscopic assisting platform.
Suction flow rate (mL/s)	44.5 ± 1.6	12.4 ± 0.8	P < 0.0001
Closure time (min)	8.6 ± 0.5	10.5 ± 1.0	P = 0.0385

Function 2: Duodenal stent placement under direct visualization

The duodenal stent and its delivery system passed smoothly through the OTS-EAP accessory channel. Under direct endoscopic guidance, the duodenal bare metal stent was precisely released at the target location without any misplacement ([Fig. 3]). Gradual expansion of the stent was clearly observed endoscopically. Post-procedure x-ray confirmed that the stent position was identical to the intended position determined endoscopically, indicating that the OTS-EAP can achieve radiation-free, precise stent placement ([Fig. 3] d) (The operation process is detailed in [Video 2]).

Fig. 3 Duodenal stent placement under direct visualization. a Endoscopic, direct-view placement of a guidewire across the pylorus through the OTS-EAP in a live porcine model. b Endoscopic, direct-view deployment of a duodenal stent through the OTS-EAP. c Endoscopic appearance after stent release. d Confirmation of stent position via x-ray.

Function 3: Assisted endoscopic purse-string suture

In a live pig model, a wound of approximately 3 to 4 cm was excised in the stomach using ESD method ([Fig. 4] a). Nylon rope was inserted into the gastric cavity through OTS-EAP and titanium clips were used to reach the wound through the endoscope operating channel ([Fig. 4] b). Multiple titanium clips were used to anchor the nylon rope around the wound ([Fig. 4] c). Finally, the nylon rope was tightened to completely close the wound. After suturing, examination showed that the wound edge was well arranged and the closure was effective ([Fig. 4] d). Compared with traditional wound closure methods, use of OTS-EAP-assisted endoscopic purse-string suturing is simpler and takes less time. Similarly, in the porcine model, purse-string closure of a 3 × 4 cm ESD defect was completed in 8.6 ± 0.5 min when the OTS-EAP was used to introduce the nylon loop, compared with 10.5 ± 1.0 required for conventional clip-and-loop suturing via the native channel alone (P < 0.05, two-tailed unpaired t-test, n = 3 replicates) ([Table 1]).

Fig. 4 Assisted endoscopic purse-string suture. a 3 × 4 cm ESD defect created in the porcine stomach. b Nylon loop introduced through the OTS-EAP; clips inserted via the endoscope working channel. c Clips anchoring the loop to the mucosal margin. d Defect closed with a clip-and-loop “purse-string” suture delivered through the OTS-EAP.

Discussion

This study provides strong preliminary evidence for our novel OTS-EAP as a highly promising and innovative tool. On one hand, it can temporarily equip a diagnostic endoscope with an auxiliary waterjet function. More importantly, it successfully transforms a standard single-channel endoscope into a multifunctional, dual-channel therapeutic platform, effectively addressing several key pain points in current clinical practice.

The platform demonstrates revolutionary potential in managing acute gastrointestinal bleeding. It can be quickly and easily mounted on almost all endoscope models, offering a low-cost, high-yield advantage during emergency endoscopy services. A clear visual field is a prerequisite for successful hemostasis. Beyond external methods such as patient repositioning, conventional endoscopes, with their narrow suction channels, are often powerless against massive bleeding, large blood clots, or large food boluses. The OTS-EAP large-caliber suction channel provides the endoscopist with a "battlefield cleaner," capable of rapidly clearing visual obstructions, identifying bleeding points, and buying precious time for precise hemostasis. This function holds significant clinical value for improving the success rate of acute bleeding management.

Furthermore, this technology is very beneficial for endoscopic stent placement. Traditionally, after guidewire placement under endoscopic view, the stent and its delivery system must be advanced after withdrawing the endoscope [7]. Lacking direct endoscopic guidance, intestinal stent placement relies heavily on fluoroscopy, exposing both patients and medical staff to ionizing radiation and requiring the procedure to be performed in a specialized radiology suite [8] [9] [10]. The OTS-EAP large-caliber working channel, for the first time, allows the entire stent delivery system to be guided and deployed under direct endoscopic visualization. This means that gastrointestinal stents, including colonic and duodenal stents, can be placed endoscopically. For duodenal and colonic stent placement using a standard scope, the OTS-EAP facilitates direct visualization of the proximal stent position, reducing reliance on radiological guidance. However, radiological confirmation of the distal end may still be required in complex anatomical cases, and the device’s key advantage lies in simplifying the placement process and improving precision without mandatory radiation exposure.

In addition, the OTS-EAP simplifies the process of endoscopic purse-string suturing. By providing a second working channel, the OTS-EAP enables synergistic instrument operation. The endoscope does not need to be withdrawn throughout the procedure, the nylon loop position can be adjusted along with the endoscope, and the depth of the nylon loop pusher can be manipulated for precise control. This transforms a complex, multistep process into an intuitive "two-handed" operation. This not only shortens procedure time but also has the potential to flatten the learning curve for such advanced endoscopic techniques, making them accessible to more patients.

Compared with existing dual-channel endoscopes, the OTS-EAP, as an add-on device, offers greater cost-effectiveness and flexibility, with the potential for rapid, widespread adoption, allowing medical institutions to fully leverage their vast inventory of diagnostic and single-channel endoscopes. Compared with single-function OTS devices, the platform-based design of the OTS-EAP provides a broader and more promising platform for many existing endoscopic instruments.

Limitations

This study is a preclinical animal experiment; its safety and efficacy in humans await ethical approval and validation. Despite its beveled and smooth design, the OTS-EAP increases the overall outer diameter of the endoscope. Its passability through particularly narrow lesions (e.g., cricopharyngeal achalasia, post-corrosive esophageal strictures) will require further clinical data. In addition, operating an endoscope equipped with the OTS-EAP requires a short learning period.

Conclusions

The novel OTS-EAP, as an innovative "add-on" dual-channel system, demonstrated excellent performance and significant application potential in this preclinical study. By providing high-flow auxiliary water, powerful suction, delivery of large-caliber devices, and enabling synergistic "two-handed" operation, it effectively enhances the therapeutic capabilities of standard endoscopes, showing unique advantages in managing gastrointestinal bleeding, achieving radiation-free stent placement, and assisting in complex suturing. This device is poised to become a key platform driving the advancement of therapeutic endoscopy, and its clinical translation is eagerly awaited.

Contributorsʼ Statement

Jie Xia: Conceptualization, Data curation, Methodology, Project administration, Writing - original draft. Muhan Li: Conceptualization, Methodology, Writing - review & editing. Feifei Wang: Methodology. Xincong Xi: Methodology. Yueqin Qian: Data curation. Xinjian Wan: Conceptualization, Project administration, Writing - review & editing.

Conflict of Interest

The authors declare that they have no conflict of interest.

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Publication History

Received: 19 September 2025

Accepted after revision: 05 January 2026

Accepted Manuscript online:
12 January 2026

Article published online:
27 January 2026