Self-Expanding Duodenal Stent (TTS)

Full introduction of self-expanding duodenal stent (self-expandable duodenal metal stent D-SEMS)

The self-expanding duodenal stent is a minimally invasive endoscopic instrument for gastric outlet obstruction (GOO). The mainstream is the nickel-titanium memory alloy self-expanding stent, which relies on automatic expansion and opening of the duodenal stenosis under body temperature. Rapid relief of nausea and vomiting, and inability to eat, is one of the preferred options for palliative treatment of advanced upper gastrointestinal tract tumors, and is similar to esophageal and bile duct stents as self-expanding stents in the gastrointestinal tract, but is more specifically designed for the anatomy of the duodenum and the special structure of the bile-pancreatic opening.

I. Working principle

The stent is compressed in the slender delivery sheath at the factory, passed through the endoscope/duodenoscope, and crossed the duodenal stenosis section under the guidance of X-ray;After release, the nickel-titanium alloy uses the shape memory effect to automatically stretch into a mesh cylindrical structure at the human body temperature of 37 ℃, producing a continuous and gentle radial support force, expanding the narrow intestinal cavity, and reconstructing the stomach-duodenum pathway;The film-coated version can block the duodenal fistula and prevent the tumor from growing inward. The flared ends on both sides reduce the risk of displacement and are suitable for the curvature of the duodenum.

II. Structure, Material and Classification

1. infrastructure

· Skeleton: Nickel-titanium memory alloy weaving / laser cutting, extremely flexible, can adapt to the physiological curvature of the duodenal descending and horizontal parts, and resist the squeezing of intestinal peristalsis;The two ends are equipped with platinum-iridium development marks, enabling precise positioning during surgery; The two ends of the trumpet are designed to be folded outwards, anchoring the intestinal wall and reducing displacement.

· Specifications: The main body diameter is 18–24 mm, and the length is 40–12 mm. After release, there is a shortening rate of about 25%. When selecting, it is necessary to reserve more than 2 cm at both ends of the narrow section.

· Transmission system: small outer diameter sheath tube, can pass through the endoscope working channel, part of the stent support release 70% of the inner re-recycled to adjust the position.

2. Membrane type (clinical core classification)

· Naked metal stent

Without a cover, strong support, low price, tumors / granulations are easy to grow into the mesh, the period of unobstructed passage is short, and it is often used for late malignant obstruction with a short survival period.

·Partially covered stent

The bare metal anchoring at both ends and the covering of the middle section, which can prevent dislocation and prevent tissue ingrowth, is the first choice in clinical practice.

· Full-coverage membrane stent

Overall silicone / polyurethane coating, completely blocking the tumor from growing inward, can be removed and replaced endoscopically; It is suitable for benign stenosis, duodenal fistula, and preoperative transition, but the risk of displacement is significantly higher than that of bare stents.

· Special support

Anti-reflux valve stent: reduce reflux of gastric contents; Particle-coated stent: dual action of local radiotherapy and expansion to delay tumor progression.

III. Clinical indications

1. Malignant esophageal outlet obstruction (primary use)

Pancreatic cancer, duodenal cancer, gastric cancer, ampullary cancer, abdominal lymph node metastasis compressing the duodenum, unable to be surgically removed, alleviating stubborn nausea, vomiting, and difficulty eating; Palliative treatment of advanced tumors, rapid recovery of oral feeding, and creation of conditions for chemotherapy and targeted therapy.

2. Benign lesion

Patients with postoperative stricture of anastomosis, stricture of gastric ulcer scar, stricture of duodenum after radiotherapy, and poor balloon dilation effect; Duodenal perforation, bile-intestinal fistula, closure and drainage of intestinal fistula.

3. Other: transitional treatment for anastomotic obstruction after subtotal gastrectomy and extrinsic duodenal stenosis.

Contraindication

The duodenum has multiple extensive obstructions, complete occlusion, severe intra-abdominal adhesions, a large amount of ascites, and coagulation dysfunction, making endoscopy intolerable.

IV. Insertion operation method

The whole process is minimally invasive and painless under sedation:

1. The endoscope was used to explore the narrow segment, and the guidewire was passed through the distal end of the narrow segment;

2. Utilize a guiding wire-based pusher support system to precisely locate the target under visualization, avoiding the duodenal papilla (the opening of the bile and pancreatic ducts).

3. Slowly release the stent and confirm that the expansion is good and the position is appropriate;

4. After surgery, you can gradually try a liquid diet after several hours of observation.

If bile duct obstruction is combined simultaneously, bile duct stent + duodenal stent can be inserted at the same time or at different times, and both stents can solve jaundice + feeding obstruction simultaneously.

V. Strengths and Weaknesses and Flow Time

Stent type, duration of patency, retrievability, displacement risk, applicable scenarios

Naked metal stent 2–4 months Cannot be removed Very low Late-stage malignant obstruction, survival time

Partially covered stent 4–6 months Difficult to remove Low Common malignant duodenal obstruction

Full-coverage stent 5–8 months Can be completely removed High benign stenosis, intestinal fistula, short-term transition

Compared with surgical stomach-small intestine anastomosis: stent trauma is minimal, hospitalization time is short, and patients can eat within 1-3 days after surgery; The disadvantage is that it is easy to block in the long run, and it needs to be cleared up again.

VI. Common Complications

Early complications (within 1 week after surgery)

Transient upper abdominal pain, nausea, minor gastrointestinal bleeding, bile duct obstruction (pressure on the papilla), and stent displacement. Symptomatic antispasmodics, anti-infectives, and endoscopic adjustments can generally alleviate these conditions.

Long-term complications

1. Stent blockage: Bare stents are more likely to have tumors growing inward, while covered stents are more likely blocked by food residue and granulation tissue;

2. Stent displacement: high incidence of full-coverage stent, which can detach to the jejunum in severe cases;

3. Prolonged bleeding, intestinal perforation, repeated reflux, bile duct infection;

4. The tumor overgrows and covers both ends of the stent, causing obstruction again.