Endoscopic clip systems for hemostasis and defect closure in gastrointestinal endoscopy

Abstract

Endoscopic clips are widely used for tissue approximation and hemostasis in gastrointestinal endoscopy. Since their introduction, significant technological advancements have expanded their functionality and versatility. Modern through-the-scope clips are now available in a range of designs with differences in open width, stem length, rotatability, opening/closing capabilities, and tensile strength - allowing tailored application depending on lesion size, location, and indication. Over-the-scope clips represent a more recent innovation, enabling robust, full-thickness closure of larger defects, ulcers, leaks, and fistulas. Mounted externally on the distal tip of the endoscope, Over-the-scope clips accommodate a fundamentally different and larger clip design compared to through-the-scope systems, allowing for deeper tissue capture and stronger compression. This review summarizes recent advances in endoscopic clipping, discusses device selection based on lesion characteristics and anatomical location, and provides practical technical tips. Emphasis is placed on the “anatomy” of clips, decision-making in clip choice, and optimal positioning techniques to maximize procedural success and safety in gastrointestinal defect closure and hemostasis.

Key Words: Clips; Endoscopy; Hemostasis; Closure; Through-the-scope; Over-the-scope clip; Bleeding; Perforation

Core Tip: Endoscopic clipping has evolved considerably, with modern through-the-scope clips and over-the-scope clips offering versatile, effective options for hemostasis and gastrointestinal defect closure. This article summarizes essential device features, comparative performance, and practical, evidence-based techniques for optimal clip selection and deployment. A clear understanding of clip anatomy, technical principles, and escalation thresholds is crucial for achieving durable closure, improving safety, and enhancing clinical outcomes.

INTRODUCTION

Advances in therapeutic gastrointestinal (GI) endoscopy have expanded the role of endoscopic clips across a wide range of clinical indications. Originally developed for endoscopic treatment of GI bleeding, these tools are now integral to numerous endoscopic interventions, including tissue approximation, stent fixation, and even to provide traction during advanced resection techniques[1,2]. This article explores the evolution of endoscopic clipping systems, their expanding clinical applications, and technical considerations to optimize their use in modern endoscopic practice.

THE EVOLUTION OF ENDOSCOPIC CLIPS

Historical perspective

Endoscopic clipping emerged in the mid-1970s, when Hayashi and Kudoh introduced the first device - termed the “staunch clip” - for endoscopic control of GI bleeding[1,3,4]. Early experience was discouraging because clip application was technically complex and retention rates were low[5]. In the early 1990s, Binmoeller et al[5] in Germany refined the delivery concept by developing a reloadable endoclip system that enabled more precise placement and rapid deployment, making clinical application more practical and effective.

By the 1990s, the role of endoscopic clips had expanded well beyond hemostasis[5,6]. Clips were being explored as a potential tool for the closure of perforations, fistulas, and anastomotic leaks; prevention of post-polypectomy bleeding; fluoroscopic guidance; marking of surgical resection sites; and securing feeding tubes, among other uses. Over the years, clips have become a standard component of every endoscopist’s toolkit, particularly for the management of GI bleeding and mucosal defects[7,8].

While through-the-scope (TTS) clips remain the mainstay for mucosal and small submucosal defects, treatment of larger or deeper wall defects may benefit from stronger and larger closure systems[2,9]. This need led to the development of over-the-scope clips (OTSCs) - such as the Ovesco system (Ovesco Endoscopy, Tubingen, Germany) - which are mounted externally on the endoscope tip and deployed using suction and/or graspers to achieve full-thickness closure. OTSCs are particularly effective for large perforations, post-surgical leaks, and refractory fistulas, offering closure strength comparable to surgical sutures[10-12].

Today, the therapeutic endoscopist has access to a comprehensive range of closure tools - from TTS clips for rapid mucosal apposition, to OTSCs for high-strength, full-thickness repair, to suturing devices for complex, large, or irregular lesions. Device selection is guided by defect size, location, etiology, and operator expertise, underscoring the need for individualized, case-by-case decision-making in endoscopic defect closure.

TYPES OF ENDOSCOPIC CLIPS

Endoscopic clips are mechanical devices that approximate tissue for hemostasis and defect closure in the GI tract[2,3,13]. These clips vary in material (e.g., nitinol, titanium, stainless steel) but most modern models are magnetic resonance imaging-conditional when used according to manufacturer specifications[14]. Clips function by drawing opposing tissue edges together with articulating arms, achieving compression or occlusion for bleeding control and/or tissue apposition and defect closure[7]. Devices vary in shape, open width, stem length, closing force, and rotatability, and whether or not they can re-open after initial closure[10,15].

Endoscopic clips are generally classified by their mode of deployment: (1) TTS clips: Delivered through the working channel of the endoscope; and (2) OTSC: Mounted externally on the distal tip of the endoscope for application over larger or deeper defects.

TTS CLIPS

TTS clips are deployed through the working channel of a standard endoscope. Its mechanism of action is mechanical compression resulting in apposition of tissue with the clip arms[13,16]. Most systems are pre-loaded for rapid deployment[3]. Newer clips feature wider arms allowing closure of larger defects such as perforations of leaks and hemostasis in challenging positions[10,15]. Most clips have a stem of approximately 8 mm to 9 mm but in narrower areas such as the esophagus, shorter-stem variants can facilitate safer, more precise placement. The choice of clips generally depends on the size, location, orientation, and access[16-18].

Anatomy of a TTS clip

A TTS clip consists of two metallic arms/prongs with a distal teeth/hook and a stem/tail (Figure 1). The prongs come together to grasp the tissue. The distal teeth may have varying design to maximize tissue capture or compression. The stem/tail is the part that connects the arms and when the clip is about to be deployed, it allows the clip to open into a V-shape. The clip is delivered through a catheter system with a handle spool/slider and neck/rotation grip that allows the endoscopist to position, rotate, and deploy the clip precisely. The working length of most delivery catheters ranges from 225 cm to 250 cm, compatible with standard endoscopes, colonoscopes, and enteroscopes[3].

Figure 1 Anatomy of a through-the-scope clip. A: Endoscopy clip; B: Delivery catheter system.

Features of TTS clips

Several design features differentiate TTS clips and determine their suitability for specific clinical scenarios. These include opening width (also called arm span), stem/tail length, rotatability, overshoot, the ability to open and close before deployment, and tensile strength (Table 1). Understanding these characteristics is essential when selecting the most appropriate clip for a given therapeutic application[15,18]. Supplementary Table 1 summarizes currently available clips and their differentiating features[19-33].

Table 1 Features of through-the-scope clips.

Feature	Importance
Open width	Determines the width of tissue grasp; distance between the distal teeth when the clip is opened to the maximum
Stem/tail length	Affects reach, especially in deeper lesions; also important to consider on narrow areas
Rotatability	Allows precise positioning
Overshoot	Rotation exceeding 30 degrees after stopping
Open-close mechanism	Allows repositioning of clips prior to deployment
Tensile strength	Grasp of the clip to the apposed mucosa

Indications

Endoscopic clips are widely employed across a broad range of GI indications, both therapeutic and prophylactic. Therapeutically, they are most commonly used for hemostasis in cases of non-variceal GI bleeding, including peptic ulcers, Dieulafoy lesions, Mallory-Weiss tears, colonic diverticular bleeding, and post-polypectomy bleeding[2,8,11,34-36]. During treatment of bleeding ulcers, endoscopic clips offer mechanical tissue apposition and non-thermal closure, which may be advantageous in areas with very thin or friable tissue. It is worth noting however, that some larger ulcers with large areas of exposed submucosa may be difficult to close with TTS clips unless the vessel itself is large enough to be clipped directly. Ultimately, the choice between TTS clipping, OTSC clipping and thermal therapy should be individualized based on lesion characteristics, bleeding severity, anatomical location, and operator expertise. In some cases, combination therapy - using injection, clips, and/or cautery - may offer superior hemostasis[2,6]. In addition to bleeding control, endoscopic clips serve a vital role in the closure of GI defects, such as iatrogenic perforations, mucosal defects, anastomotic leaks, and fistulas (Figure 2)[7,10,37].

Figure 2 Indications of endoscopic clips. A: Mechanical tissue apposition for hemostasis in bleeding solitary rectal ulcer; B: Closure of gastrointestinal defect after endoscopic full thickness resection using a combination of through-the-scope clips and X-tack system (Boston Scientific, Marlborough, MA, United States); C: Closure of post-polypectomy defect; D: Traction during esophageal endoscopic submucosal dissection; E: Lesion localization after biopsies with additional tattoo; F: Securing stents or enteral feeding tubes. GI: Gastrointestinal; ESD: Endoscopic submucosal dissection.

Clips may also be used for lesion localization, for example to identify the location of a refractory bleeding ulcer requiring subsequent angiographic embolization, or to help surgeons plan for resection of a difficult-to-find lesion by using the clip as a radiopaque marker[38]. In addition, it can serve as an adjunct to tattoo as marking when tattoo diffusion or transmural injection is a concern[39,40].

In select cases, TTS clips can be adapted as traction devices during complex resections such as endoscopic submucosal dissection (ESD) and difficult cannulations in endoscopic retrograde cholangiopancreatography[41,42]. Traction-assisted ESD techniques are evolving quickly, and recent techniques include attaching an elastic band or orthodontic string to a deployed clip, applying directional tension to facilitate effective tissue resection[43].

Selective, prophylactic defect closure after polyp resection by endoscopic clips is increasingly supported by evidence. This is most often considered after high-risk resections, such as large endoscopic mucosal resection (EMR) and ESD, difficult locations such as the right colon or duodenum, antithrombotic exposure, to mitigate the risk of delayed bleeding and, in selected settings, perforation risk[8,44,45]. For pedunculated polyps with thick stalks, pre-resection mechanical ligation (e.g., clip or loop with or without epinephrine) is advised to prevent post-polypectomy hemorrhage[2]. Several thresholds and criteria have been proposed to guide the use of prophylactic clip placement following EMR. Among these, the most robust evidence supports complete clip closure of right-sided colonic EMRs ≥ 20 mm in size, where randomized controlled trials and meta-analyses have demonstrated a significant reduction in delayed post-polypectomy bleeding[46-49]. Recently, a randomized trial also demonstrated a reduction in delayed bleeding after colorectal ESD[50].

TTS clips also serve a critical role in third-space endoscopic procedures, including peroral endoscopic myotomy and gastric peroral endoscopic myotomy, where they are commonly used to close mucosal entry sites following submucosal tunneling. In these settings, TTS clips provide a reliable, efficient means of closure, helping to minimize the risk of leak-related complications[51,52]. TTS clips have a growing number of ancillary applications across therapeutic endoscopy, reflecting ongoing innovation in technique and device use. These include securing enteral feeding tubes, temporarily anchoring self-expandable metal stents to reduce the risk of migration[2,17].

Deployment of a TTS clip

TTS clips are straightforward to use, but durable hemostasis or closure requires a deliberate, stepwise technique[7,16,18,36].

Select which clip to use: Choose based on defect size, location/angle, tissue quality (e.g., friable, fibrotic), device features (reopenable, rotatable, short- vs long-stem, closing force), device availability, and operator expertise.

Prepare the field and scope: Irrigate and adequately visualize the lesion. Park the target at the working-channel quadrant (most of the time at 7 o’clock when using a gastroscope, and at 5 o’clock when using a colonoscope). A transparent distal attachment cap may improve stability and control.

Load and advance the clip: Introduce the clip through the channel. When the tip appears, open the jaws just beyond the scope tip and keep the target close to the endoscope for precise rotation and depth control.

Orient correctly: Aim for perpendicular apposition to maximize tissue capture and compressive force. If anatomy forces a tangential approach, adjust rotation, scope position, or use a “zipper” strategy (sequential edge-to-center approximation) to reduce tension across the gap.

Grasp with suction, then test closure: At the target, apply gentle suction to draw tissue into the jaws and gradually close while confirming the intended tissue is captured. If suboptimal, reopen and reposition before committing to deploy.

Deploy and verify placement: Fully close and deploy by completely pulling the slider/handle spool. Confirm apposition or hemostasis if a bleeding lesion. Gently probe with a water jet. Place additional clips as needed.

Know when to escalate: If hemostasis or closure is not achieved after 2-3 well-placed clips, or the target is > 1-2 cm, fibrotic, or with brisk arterial bleeding, escalate to thermal or combination therapy, OTSC, or endoscopic suturing.

SPECIALIZED TTS CLIPS

Newer TTS clips - wider span, anchoring-pronged, dual-action, and high-closing-force designs - were developed to address the size, access, and tissue-grasping limitations of conventional clips (Figure 3)[10,53-56]. Although device costs are higher, early clinical series report greater technical feasibility and more durable defect closure, including after EMR/ESD and in challenging locations. Robust comparative and long-term outcome data are still needed.

Figure 3 Specialized through-the-scope clips. A: MANTIS (Boston Scientific, Marlborough, MA, United States): Anchor-pronged arms with sharp distal teeth; B: Lockado (Micro-Tech Co. Ltd., Nanjing, China): Two opposing rows of atraumatic teeth for enhanced grip; C: Dual action tissue (Micro-Tech Endoscopy, United States Inc., Ann Arbor, MI, United States): Two independently operable arms flanking a central post with dual color-coded handles. DAT: Dual action tissue.

MANTIS clip

The MANTIS clip (Boston Scientific, Marlborough, MA, United States) is a novel anchor-pronged, TTS clip engineered to close large GI defects (e.g., post-EMR/ESD) by enabling tissue apposition independent of jaw opening width. It is deployed with a three-step “hold-and-drag” technique: Anchoring the “Truegrip” prong to one tissue margin, mobilizing by applying controlled traction to draw tissue toward the opposing defect edge while maintaining perpendicular alignment, then closing and releasing for definitive apposition[53,57]. The mantis-like claw design is intended to enhance grip and stability throughout traction, and early clinical series report high technical success and durable closure, including after colonic ESD[53,58].

Lockado clip

The Lockado clip (Micro-Tech Co. Ltd., Nanjing, China) is a TTS clip distinguished by its arm design: Two opposing rows of atraumatic teeth, including small secondary teeth distinct from the tips, which markedly increase friction and resist tissue slippage[54]. These multiple grasping points concentrate compressive force at maximal contact areas, improving purchase on fibrotic or mobile tissue. It has a short stem minimizing visual obstruction, and it is compatible with side-viewing endoscopes. With a 22-mm maximum opening width, the clip can regrip and reposition after partial closure, facilitating precise edge approximation for larger defects such as post-ESD defects in the colon (Supplementary Table 1)[59].

Dual action tissue clip

The dual action tissue clip (Micro-Tech Endoscopy, United States Inc., Ann Arbor, MI) is a novel TTS device for closing large mucosal defects whose distinct feature is two independently operable arms flanking a fixed central post[55]. Each arm can be opened and closed separately to sequentially capture opposing edges and apply traction for approximation - similar to the “hold-and-drag” technique described for the MANTIS clip[57]. Color-coded handles (blue and gold) distinguish the respective clip arms during deployment[55,60]. The clip provides a 15-mm maximum opening width with an approximate 60-degree jaw angle, is repositionable before deployment, and can be used alone or to secure edges while additional TTS clips complete the closure. Limitations include the lack of rotational capability and a larger clip profile that necessitates a therapeutic endoscope with a ≥ 3.2 mm working channel (Supplementary Table 1).

PERFORMANCE CHARACTERISTICS AND LIMITATIONS OF TTS CLIPS

Despite broad utility, TTS clips may underperform in fibrotic tissue, tangential approaches, and larger defects, where shallow bite and suboptimal alignment limit durable closure or hemostasis. Bench testing helps translate device traits to case selection. In a comparative study of five TTS clips, Resolution 360 rotated the fastest and, together with SureClip and DuraClip, maintained rotation across straight segments, the duodenal sweep, full retroflexion, and the duodenoscope elevator engaged, favoring these devices when precise orientation is critical[15]. Overshoot was lowest with SureClip and Resolution 360 in straight configuration, though all clips exceeded about 75% overshoot under stressed positions, underscoring the need for incremental knob turns, frequent re-centering, and when available, renewable mechanisms. In tensile/closing-force testing, QuickClip Pro generated the highest peak tensile force, while Instinct and Resolution 360 provided strong closure and compression in gel models-features advantageous for fibrotic edges or pulsatile vessels where deeper purchase is required[15]. Practically, these data support a feature-first selection strategy: Prioritize rapid, controlled rotation for awkward anatomy; favor higher closing-force designs for scarred or high-tension targets; and use reopenable, rotatable systems when stepwise repositioning is anticipated. Table 2 summarizes key limitations of TTS clips[2,10,11,14,34,35,61-64].

Table 2 Limitations of through-the-scope clips.

Limitation	Description
Mechanical factors
Shallow bite with mucosal capture only	Scarred or edematous bases (e.g., fibrotic ulcers, post-ESD beds) reduce tissue grip, so closure or hemostasis may be unreliable - particularly for larger defects (> 10-15 mm) or tangential targets. In these settings, OTSC or suturing may be preferable than TTS[10,61]
Device or handling constraints	Some TTS clips are one-shot at deployment (limited recapture) and with imprecise rotational control. Likewise, multiple clips increase time, cost, and lumen clutter, hindering additional therapy[2,11]
Misfires resulting to technical and safety risks	Misfires resulting to opposite-wall capture or serosal injury can occur with off-axis closure. In addition, accessories may be entrapped (e.g., loop/snare) or mucosa torn if traction is applied after partial closure
Clip migration and dwell time variability	Clips usually detach within weeks (animal and clinical data often cite 1-4 weeks), but prolonged retention can occur (reports up to 3-5 years), which may also create MRI-compatibility considerations depending on the clip[14,62-64]
Lesion factors
Difficult access or angle	Locations such as the cardia, lesser curve, and posterior duodenal wall limit perpendicular apposition and precise jaw placement; long/looped positions also cause suboptimal rotation[2]
Brisk bleeding and clot burden	Active arterial bleeding can obscure the field and prevent adequate tissue capture; thermocoagulation or combination therapy is preferred when clip compression alone is insufficient[2,11,34]
Large vessels and wide defects	Clip compressive force may be inadequate for thick-caliber bleeding vessels or defects > 1-2 cm, where OTSC or even suturing has higher durable success[10,61]
Performance in specific etiologies	For colonic diverticular bleeding, meta-analyses show higher early rebleeding with clipping vs EBL, underscoring TTS limitations in these types of lesions[35]

TTS: Through-the-scope; ESD: Endoscopic submucosal dissection; OTSC: Over-the-scope clip; MRI: Magnetic resonance imaging; EBL: Endoscopic band ligation.

OTSCS

OTSCs are cap-mounted, nitinol devices that offer distinct therapeutic advantages over standard TTS clips, including broader tissue capture, higher compressive force, and the ability to achieve near full-thickness closure - making them particularly valuable in the management of large defects, fistulas, and refractory bleeding. A preloaded clip on a transparent distal cap is attached to the scope tip and is released with a handle-trigger mechanism, allowing a broad tissue bite and sustained compression for near full-thickness apposition[10].

Two systems are widely used (Figure 4): (1) Ovesco clip (Ovesco Endoscopy, Tubingen, Germany): Hand-wheel/traction-thread actuation routed through the working channel; tissue capture with suction and dedicated graspers (e.g., Twin Grasper Anchor); conceptually similar to variceal band ligation; and (2) Padlock clip (STERIS, Ireland): Externally mounted on the scope with a trigger/cable actuation that preserves the working channel for accessories.

Figure 4 Anatomy of over-the-scope clips. A: Ovesco clip (Ovesco Endoscopy, Tubingen, Germany) is a bear-claw-shaped nitinol clip available in multiple cap sizes with three tooth profiles - type t (short spikes for compression/anchoring), type a (blunt, compressive), and type gc (elongated spiked teeth for robust gastric wall purchase)[32]; B: Padlock clip (STERIS Endoscopy, Ireland) is a hexagonal nitinol ring with six inward-facing prongs and tissue controllers that limit penetration depth and provide circumferential purchase. Citation for Figure 4A: OVESCO Endoscopy. OTSC^® System. [cited 30 October 2025]. Available from: https://ovesco.com/otsc-system/. It was obtained from the public manufacturer’s product page (Supplementary material).

By design, OTSCs capture more tissue and generate higher compressive force than TTS clips, enabling more durable hemostasis and defect closure - especially with fibrotic edges, larger gaps, or tangential sites[32,33,56,65]. Although initially adopted as rescue therapy for refractory non-variceal upper GI bleeding, iatrogenic perforations, and leaks, randomized trials and meta-analyses now support first-line OTSC use in selected high-risk bleeding scenarios, showing lower early rebleeding and higher clinical success vs standard endoscopic therapy[66-70]. OTSCs are also reported to be effective for perforations, post-resection defects, and fistula/leak management, where full-thickness compression is advantageous[37,71,72].

Anatomy and features of an OTSC clip

OTSCs are magnetic resonance imaging-conditional when used according to the manufacturer’s instructions. The Ovesco clip is preloaded on a transparent cap (Figure 4)[56,65]. It offers four clip sizes matched to cap dimensions and three tooth profiles tailored to indication - type a (atraumatic, blunt teeth) for compressive hemostasis; type t (traumatic, short spikes) for combined compression and anchoring in slippery or fibrotic tissue; and type gc (gastric closure, with elongated spikes) for robust gastric wall closure[32].

By contrast, the Padlock system is a hexagonal, about 11 mm nitinol ring with six inward-facing prongs and “tissue controllers” that lift, approximate, and secure tissue while limiting penetration depth. Inter-prong gaps allow egress of blood, aiding healing[65]. Padlock achieves a circumferential hold through its inward prongs and radial compression technology[33,56,65].

Indications

OTSCs are used when durable, broad tissue capture is needed e.g., fibrotic edges, large defects, or tangential locations and for hemostasis, full-thickness apposition, and device anchoring (Padlock/Ovesco)[56,65]. Evidence from randomized trials and meta-analyses supports first-line use in selected high-risk NVUGIB, with lower early rebleeding and higher clinical success vs standard endoscopic therapy[18,56,66,67,69]. Beyond hemostasis, OTSCs are effective for acute iatrogenic perforations, post-surgical or anastomotic leaks, and fistulas (e.g., gastrocutaneous, colorectal), where near full-thickness apposition improves sealing and durability[71-73]. Additional uses include post-EMR/ESD defect closure - especially in thin-walled locations such as the duodenum - and stent fixation to prevent migration when clinically indicated[37,65] (Figure 5).

Figure 5 Deployed over-the-scope clip. A: An Ovesco clip was used for hemostasis of a bleeding duodenal ulcer with pulsatile vessel; B: A Padlock clip was deployed to close a tracheoesophageal fistula after application of argon plasma coagulation on the edges[73]. Citation for Figure 5B: Rai P, Bhargava R. Successful closure of post-tracheostomy large chronic tracheoesophageal fistula with new over-the-scope clip. Dig Endosc 2017; 29: 634. Copyright© The Authors 2025. Published by Wiley. The author obtained permission from the publisher and was approved (Supplementary material).

Deployment of an OTSC

Both Ovesco and Padlock systems are cap-mounted but differ in actuation. Table 3 outlines a stepwise guide to OTSC deployment.

Table 3 Steps in deployment of an over-the-scope clip.

Steps	Ovesco clip (Ovesco Endoscopy)	Padlock (STERIS)
Set up the device	Attach hand wheel to biopsy port; inspect cap/clip and release thread	Attach external trigger/cable; inspect cap/clip; and confirm trigger function
Mount the cap on the endoscope and route actuation	Preload clip on transparent cap; route release thread through the working channel to hand wheel	Preload clip on cap; route actuation cable externally, leaving the working channel free
Prepare target site	Irrigate and adequately visualize the lesion	Same as Ovesco
Orient correctly	Center the lesion near the working-channel. Advance with cap over target; adjust torque or insufflation for a perpendicular approach	Same as Ovesco
Capture tissue	Use suction and/or Anchor or Twin Grasper; draw edges into cap	Use suction and grasping device via free channel to pull edges into cap more easily
Fire the clip	Rotate hand wheel to tension thread and deploy (similar to esophageal variceal band ligation mechanism)	Squeeze external trigger to deploy; no channel thread
Verify closure	Confirm apposition and hemostasis; irrigate or gently probe with a water jet	Same as Ovesco
Know when to escalate	If closure or hemostasis incomplete, add thermal/adjunct clips or place a second OTSC; consider suturing	Same as Ovesco

OTSC: Over-the-scope clip.

Limitations of OTSC clips

While OTSC clips can cater larger defects and defects not addressed by TTS clips, both Ovesco and Padlock OTSC systems share practical limitations that affect workflow and case selection. Because each device is cap-mounted, the endoscope generally must be withdrawn, assembled, then reinserted before deployment[74]. This adds time and setup complexity compared with TTS clips. Additionally, the cap-mounted design of OTSCs increases the overall diameter of the endoscope tip, which can pose challenges when navigating through narrow or tortuous anatomy - such as mild esophageal strictures or complex oropharyngeal pathways. Unlike TTS clips, which can close and re-open as needed prior to firing, OTSC clips fully deploy at the moment of firing and cannot be reopened or repositioned.

Clinical effectiveness of OTSC closure may be varied by defect type and tissue health. Success is highest in acute perforations and bleeding but not optimal in fibrotic or inflamed lesions such as chronic leaks and fistulas. Pooled reports show overall clinical success around about 78%, with high rates for hemostasis (about 86%), perforation (85%), defect closure following endoscopic resection (92%), and stent fixation (80%). It has lower rates for anastomotic leaks (about 72%) and fistulas (about 55%), underscoring reduced efficacy in indurated tracts[9,12,75].

OTSC therapy is also more costly than standard TTS therapy. However, recent economic analyses suggest that OTSC can be cost-effective as a first-line treatment for high-risk NVUGIB by reducing rebleeding and retreatment. Nonetheless, device price and training requirements remain barriers to routine adoption[76].

Finally, device misfire or incomplete deployment - from suboptimal thread or cable routing, inadequate suction capture, or improper trigger actuation - can occur. These can be mitigated with a brief pre-deployment rehearsal, checklist-based set-up, and simulation practice to standardize hand mechanics.

PRACTICAL RECOMMENDATIONS FOR ENDOSCOPIC CLIP SELECTION AND PLACEMENT

Optimize visualization and approach

Center the target at the working-channel quadrant and, when available, use a transparent distal cap to stabilize the scope and allow controlled opening of the clip just beyond the tip without causing mucosal trauma[7,36]. Clear the field with irrigation and suction, adding dilute epinephrine injection for oozing when appropriate, to restore a clean view for precise alignment of the clip. If alignment remains suboptimal after one to two attempts, stop and reposition rather than persisting at an unfavorable angle[17]. Handle an open clip cautiously as dragging or sweeping can injure the mucosa or dislodge a previously placed clip[7].

Match the device to the anatomy and tissue

In narrow or pediatric lumens (e.g., proximal esophagus near the upper esophageal sphincter, diverticula), select short-stem, reopenable TTS clips (e.g., DuraClip, Lockado, Retentia) for maneuverability and visualization[17]. In thin-walled sites (duodenum, cecum) or fibrotic bases, favor high-closing-force or long-span clips and take small, incremental bites to avoid tearing (e.g., Instinct clip). For large or gaping defects, traction/anchoring designs (e.g., MANTIS with pronged claws; or dual-action tip with independently operable arms) to approximate edges before definitive closure[53,54,57]. When working in retroflexion, the duodenal sweep, or with side-viewing scopes, choose thin-shaft, precisely rotatable clips (e.g., Resolution 360, SureClip) that tolerate strained configurations, or consider a scope with a large working channel[15,16,18]. A practical maneuver is to advance the clip to the channel tip, withdraw a few millimeters, then re-approach to regain axial control[16].

Adopt deliberate, evidence-based placement strategies

The following techniques can be performed to standardize tissue apposition, optimize alignment, and minimize tension to promote durable closure.

Pre-clip alignment: Simulate closure visually (and with gentle suction) before committing, ensuring a perpendicular, submucosal bite[44,77].

Zipper closure: Place multiple clips edge-to-edge from one margin toward the center to progressively reduce gap tension; particularly useful after EMR/ESD in thin mucosa[17,78].

Anchor-and-pull: Anchor one edge with an arm of a clip, then pull the opposite margin into alignment to achieve apposition; add subsequent clips as required[57,58].

Technical points in TTS deployment

Work distal to proximal so previously placed clips do not obscure the view[17]. Avoid grasping too close to the defect edge (risk of tearing) and target a perpendicular mucosa-plus-submucosa bite. As the clip closes, apply gentle suction to draw the intended layer into the jaws. If the grasp is shallow or off-axis, reopen and reposition on reopenable models[36]. Do not drag an open clip across intact mucosa[7].

Technical points in OTSC deployment

For tangential access, fibrotic rims, or defects that exceed the TTS span, an OTSC provides a deeper, more durable bite. Prepare for scope withdrawal and cap mounting. Twin graspers or an anchor device improve capture of stiff or retracted edges. Simulation on transparent models helps standardize suction capture and firing cadence, and robust suction or firm grasp is essential to include full-thickness layers prior to release. OTSC is particularly useful in the posterior duodenal bulb and other locations amenable to a head-on approach[18,74].

Apply scenario-based choices and maintain a clear escalation threshold

If apposition or hemostasis is not achieved after 2-3 well-placed TTS clips, or if the target is > 1-2 cm, markedly fibrotic or tangential, or shows arterial or brisk bleeding, escalate to thermal or combination therapy, OTSC, or other closure techniques like endoscopic suturing (Table 4)[7,8,17,69,79].

Table 4 Examples of clinical scenarios and approach to clipping.

Clinical scenario	Recommended approach to clipping
Oozing ulcer-base bleeding	Optimize visualization with irrigation and/or dilute epinephrine. Apply a reopenable TTS clip to the culprit vessel. Combine with thermal or inject-and-clip therapy if the base is fibrotic. Escalate after 2-3 well-placed clips without control[8]
Hemostasis in narrow-lumen anatomy or pediatrics	Use short-stem clips (e.g., Steris, MicroTech). Maintain modest insufflation, and take small incremental grasps to avoid opposite-wall capture. Confirm blanching before clip release[17,18]
Small perforation closure	Clear the target area. Perform an edge-to-center zipper closure with high-force, reopenable TTS clips in small, perpendicular bites. Escalate early to OTSC if closure remains incomplete[78]
Closure after EMR/ESD	Perform an edge-to-center zipper closure using reopenable, rotatable, high-force clips. For wide defects, pre-approximate with MANTIS or DAT and complete with long-span clips. The ROLM technique using clip with eyelet and nylon line may aid closure of large defects[79]. Consider prophylactic closure in the duodenum or cecum. Escalate to OTSC or suturing if closure is suboptimal[7,78]
Training or general use	Prioritize reopenable, rotatable clips that tolerate multiple repositioning. Use a standardized checklist: Target centered, perpendicular approach, suction-assisted grasp, blanching confirmed before release, and adhere to stop rules[17]

TTS: Through-the-scope; EMR: Endoscopic mucosal resection; ESD: Endoscopic submucosal dissection; DAT: Dual action tissue clip; ROLM: Reopenable clip-over-the-line method; OTSC: Over-the-scope clip.

TRAINING AND COMPETENCY

As with most clinical skills, competency in endoscopic clipping is optimally developed through a structured training pathway that includes simulation-based practice[80]. This may involve ex vivo, porcine, or validated animal-free bleeding models to rehearse visualization, tissue apposition, and clip deployment techniques for hemostasis and defect closure before performing these procedures in patients[81-83]. This can be followed by stepwise, proctored clinical cases, with emphasis on mastering TTS clip selection and placement (alignment, perpendicular bite, reopening and repositioning, and escalation thresholds). Subsequent use of OTSCs can be incorporated as part of a graduated learning curve, aligned with the principle, endorsed by major gastroenterology societies, that proficiency in advanced endoscopic interventions should be grounded in a strong foundation of core endoscopic skills[84]. Ongoing skills maintenance is supported by hands-on workshops and curricula from major societies (e.g., American Society for Gastrointestinal Endoscopy, European Society of Gastrointestinal Endoscopy, etc.) that provide supervised training in clipping and GI bleeding management. Where feasible, programs may consider incorporating validated tools to assess competency and tracking key procedural outcomes, such as successful hemostasis or defect closure. Given the variability in clinical exposure, particularly to active bleeding cases, structured simulation and targeted feedback can be valuable adjuncts to help prepare trainees for independent practice.

CONCLUSION

Endoscopic clips have transformed the management of GI bleeding and closure of GI defects. Modern TTS clips offer convenience and versatility for most mucosal closures, while OTSCs provide robust options for larger or deeper defects. Successful endoscopic closure depends not only on device selection but also on understanding anatomy, technique, and anticipating challenges. As devices evolve and expertise broadens, endoscopic closure is increasingly shifting the therapeutic landscape - offering a less invasive, highly effective alternative to surgery in a growing number of GI conditions.