Current mechanisms and techniques for placement of self-expandable metal stents in acute colonic obstruction

Abstract

Acute colonic obstruction, a life-threatening condition often caused by malignant or benign strictures, necessitates rapid and effective intervention to avoid severe complications such as bowel perforation or sepsis. Self-expandable metal stents (SEMS) have emerged as a minimally invasive, effective treatment alternative, either as a bridge to surgery or for palliation in malignant cases. This editorial focuses on the current mechanisms and techniques for SEMS placement in acute colonic obstruction, discussing the various endoscopic approaches, stent design considerations, technical success rates, complications, and long-term outcomes. We explore cutting-edge techniques such as fluoroscopy-free endoscopic placement, two-person colonoscopy, and the use of advanced endoscopic equipment like slim gastroscopes and ultrathin endoscopes. Additionally, the editorial delves into complications associated with SEMS placement, such as stent migration, perforation, and occlusion, and discusses strategies to mitigate these risks. Finally, future directions in SEMS technology, including advancements in stent design and optimal timing for surgery, are presented.

Key Words: Acute colonic obstruction; Self-expandable metal stents; Endoscopic stenting; Colorectal carcinoma; Palliative treatment; Bridge-to-surgery; Technical success; Complications; Stent design; Fluoroscopy-free stenting

Core Tip: This editorial discusses the mechanisms and techniques involved in the placement of self-expandable metal stents (SEMS) in patients with acute colonic obstruction. It highlights recent advancements in endoscopic stenting methods, including fluoroscopy-free techniques and the use of slim and ultrathin endoscopes. The editorial covers the choice of stent design, technical success rates, common complications, and long-term outcomes of SEMS placement. It also explores future directions, including the optimization of stent designs and the timing for subsequent surgery. SEMS represents a significant advancement in the management of acute colonic obstruction, offering a safe and effective alternative to emergency surgery.

INTRODUCTION

Acute colonic obstruction is a potentially fatal condition often requiring immediate intervention to prevent complications like bowel perforation, ischemia, or sepsis. The causes of acute colonic obstruction can be either malignant or benign. Malignant obstructions, often due to colorectal cancer, are particularly challenging to manage due to the rapid progression of the disease and the need for timely surgical intervention. In the context of colorectal malignancy, 8%-29% of patients may present with acute colonic obstruction at the time of diagnosis. This highlights the clinical urgency of managing these cases promptly. Traditionally, emergency surgery has been the standard approach for managing acute colonic obstruction. However, the development of self-expandable metal stents (SEMS) has provided an alternative, minimally invasive treatment modality, particularly in cases of malignant obstruction.

SEMS can be utilized either as a bridge to surgery (BTS) or for palliative purposes in patients with advanced, non-resectable malignancies. The advantages of SEMS placement include reduced need for emergency surgery, avoidance of stoma formation, and the ability to optimize patients preoperatively. This editorial aims to explore the mechanisms, techniques, and clinical outcomes associated with SEMS placement in the management of acute colonic obstruction, with a focus on the current state of the art, challenges, and future directions.

MECHANISMS AND TECHNIQUES FOR SEMS PLACEMENT

The placement of SEMS for acute colonic obstruction is typically performed using endoscopic techniques. The main goal is to relieve obstruction and either facilitate surgery or provide symptom palliation. The key techniques for SEMS placement include fluoroscopy-assisted stenting, fluoroscopy-free stenting, and various endoscopic techniques to optimize stent deployment.

Endoscopic stenting without fluoroscopic guidance

Recent studies have demonstrated that endoscopic SEMS placement without the use of fluoroscopy is a safe and effective alternative, with a high technical success rate ranging from 91.7% to 98.6%[1]. The technique is also associated with clinical success rates of 86.1% to 94.9%[2]. A major benefit of this approach is the reduction in radiation exposure, which makes the procedure safer for both patients and clinicians. Moreover, the absence of fluoroscopy simplifies the stenting process, making it particularly suitable for cases of acute colonic obstruction where fluoroscopy may not always be immediately available.

Two-person colonoscopy approach

In more complex cases or challenging anatomical locations, such as the right colon, the two-person colonoscopy approach has shown to be beneficial. In this method, one operator handles the colonoscope while the other controls the deployment of the SEMS. Studies have shown that this technique achieves high technical success rates (98.6%) and clinical success rates (94.9%)[3]. The two-person approach is advantageous when dealing with difficult cases, such as those with severe distention or those located in hard-to-reach areas.

Use of slim gastroscope and combined endoscope techniques

The application of slim gastroscopes in conjunction with standard colonoscopes is another effective strategy for SEMS placement, particularly in patients with distorted anatomy due to malignant tumors. This combined technique has been associated with technical success rates of 94.4% and clinical success rates of 94.4%[4]. Similarly, the use of ultrathin endoscopes combined with guidewire replacement techniques has achieved a 100% technical success rate and a clinical success rate of 96.8%. These advanced techniques offer excellent visualization and improved maneuverability, especially in cases of complex anatomy.

Water and gel immersion techniques

To improve visualization during stent placement, water and gel immersion techniques have been introduced. These techniques help to reduce intraluminal pressure and enhance visibility, particularly in cases with poor luminal views due to the presence of blood or stool. A small-caliber tapered transparent hood combined with an electrolyte-free gel has been utilized to maintain endoscopic visibility and ensure safe and effective SEMS insertion[5]. These techniques significantly enhance the ability to place SEMS safely in cases where conventional methods might fail due to poor visualization.

Synthesis of clinical scenarios

At the end of this section, we would like to provide a brief synthesis to help clarify the clinical contexts in which each approach is most appropriate. Fluoroscopy-free techniques are particularly suitable for resource-limited settings or urgent bedside procedures, where access to fluoroscopy may be restricted. These techniques offer a radiation-free solution while maintaining high success rates. On the other hand, combined endoscopic techniques, such as using slim gastroscopes or two-person colonoscopy, are more applicable in complex cases, particularly when dealing with challenging anatomical locations or patients with significant anatomical distortion due to malignancies. These approaches enhance visualization and maneuverability, improving the success of SEMS placement in such difficult scenarios.

STENT DESIGN AND SELECTION

The mechanical properties of SEMS play a significant role in determining clinical outcomes. Various stent designs, such as low axial force and high axial force stents, differ in their suitability for specific clinical situations.

Low axial force vs high axial force stents

Low axial force stents are associated with lower perforation rates (0%) and high technical success rates (97.5%), making them ideal for managing malignant obstructions in which the risk of perforation is a significant concern[6]. Conversely, high axial force stents, while effective, carry a higher risk of perforation (2.0%-5.0%) but are still considered appropriate for palliation in advanced malignancies[7]. The choice between low and high axial force stents should be based on the patient’s specific condition and the nature of the obstruction.

Stent diameter and length

The selection of stent diameter and length is essential to ensuring successful SEMS placement. Longer stents are typically used for left-sided obstructions, while shorter stents are more suitable for right-sided obstructions. However, longer stents have been associated with an increased risk of perforation[7]. The selection of the appropriate stent size is influenced by the location and severity of the obstruction, as well as the anatomical characteristics of the patient.

OUTCOMES AND COMPLICATIONS

Technical and clinical success rates

The overall technical success rates for SEMS placement in acute colonic obstruction range from 91.7% to 100%, while clinical success rates range from 86.1% to 96.8%[1,2]. Clinical success is typically defined as the resolution of symptoms and radiological findings within 24 hours of stent placement. These high success rates make SEMS a promising alternative to emergency surgery in many cases of acute colonic obstruction.

Complications

The most common complications associated with SEMS placement include stent migration (0.5%-1.0%), insufficient expansion (0.5%), and perforation (1.4%-5.0%)[3,6]. Stent occlusion and stool impaction are also reported but are less frequent. Hemorrhage is a rare complication, with no cases reported in some studies[3]. Strategies to minimize these risks include the careful selection of stent type and size, appropriate patient positioning, and meticulous endoscopic technique.

Long-term outcomes

For palliative stenting, studies report that 63.9% of patients experience non-recurrent colorectal obstruction at 1 year, and 71.2% remain free of obstruction until death or the last follow-up[7]. In BTS cases, stenting reduces the need for emergency surgery and stoma formation, with relatively low complication rates[8].

CHALLENGING CASES AND SPECIAL CONSIDERATIONS

Right-sided obstructions

Stenting for right-sided obstructions presents unique challenges due to the larger luminal diameter and higher migration rates compared to left-sided obstructions. However, SEMS can still be effective in select patients, particularly those with comorbidities that preclude more invasive surgery[9].

Benign strictures

SEMS placement is also used in patients with benign strictures, such as those resulting from Crohn’s disease or post-operative adhesions. These patients often require stents as a BTS or for symptom relief. Technical success rates in these cases are typically around 87%, with complication rates of 14%[10].

Extracolonic obstruction

SEMS placement has been extended to extracolonic obstructions, such as those caused by extrinsic compression from nearby organs or tumors. This technique is safe and effective, with high clinical success rates[11].

FUTURE DIRECTIONS

Optimal timing for surgery

The optimal timing for surgery after SEMS placement remains controversial. Current evidence suggests that performing surgery 2 weeks after stent placement allows for adequate preoperative optimization and minimizes the risk of perforation or other complications[8]. However, further investigation is needed to establish standardized protocols regarding the ideal timing for surgery across different patient populations and clinical settings.

Multidisciplinary approaches

A multidisciplinary approach, involving gastroenterologists, surgeons, and radiologists, is essential to optimize patient selection and reduce complications. This collaborative effort ensures that patients receive the most appropriate treatment for their individual circumstances[11]. Ongoing research into the effectiveness of team-based decision-making models could enhance treatment strategies and lead to better patient outcomes.

Technological advancements

Advancements in stent design, such as the development of zero-border stents, which have shown promising results with very low perforation rates, could improve clinical outcomes significantly[12]. Further research is required to evaluate the long-term efficacy, safety, and cost-effectiveness of these new stent designs, particularly in the context of large-scale clinical trials.

CONCLUSION

SEMS have revolutionized the management of acute colonic obstruction, providing a minimally invasive alternative to emergency surgery[13]. Advances in endoscopic techniques and stent designs have improved outcomes, making SEMS a viable option for both bridge-to-surgery and palliative purposes. However, challenges remain, particularly in the management of right-sided obstructions and benign strictures. Future research should focus on optimizing stent design, patient selection, and multidisciplinary collaboration to further enhance the safety and efficacy of SEMS placement.