Self-Expanding Biliary Stent

Full introduction of self-expanding biliary stent (self-expanding biliary metal stent, SEMS)

The self-expanding bile duct stent is an endoscopic/interventional minimally invasive method to relieve bile duct obstruction. The core instrument for draining bile is the self-expanding stent made of nickel-titanium memory alloy. It relies on the superelasticity of the material to automatically expand the narrow bile duct in the body, quickly eliminate jaundice and control bile duct infection. It is divided into two categories: bare stent and covered stent. It is the first choice for palliative treatment of malignant bile duct obstruction.

I. Working principle

When the stent leaves the factory, it is compressed in a slender delivery sheath and delivered to the bile duct stenosis through the ERCP (endoscopic retrograde cholangiopancreatography) or percutaneous liver puncture route, guided by X-ray fluoroscopy. After retracting the outer sheath, the nitinol alloy automatically restores the pre-set mesh cylindrical structure at the human body temperature, producing a continuous and gentle radial support force to expand the narrow bile duct and reconstruct the bile drainage channel; The film-coated version can seal the bile duct fistula and block the growth of tumor tissue, and the two ends of some stents are designed with flared edges to reduce the risk of displacement.

II. Classification of structure and material

1. Main skeleton

The core is made of nickel-titanium memory alloy wire woven / laser cut, with good biocompatibility, resistance to bile corrosion, excellent elasticity, and can adapt to the physiological curvature of the bile duct; The two ends are marked with platinum-iridium non-radiation markers, and are precisely located under X-ray during surgery; The mesh is divided into closed-hole and open-hole structures. The closed-hole structure has stronger support, and the open-hole structure has better adaptability.

2. Membrane type (clinical core classification)

1) Naked metal stent (USEMS)

Without film, the metal mesh is exposed, the radial support is strong, and the price is low; The disadvantage is that tumors and granulation tissue are easy to grow into the mesh, and it is difficult to remove the stent after it is blocked, and it is mainly used for palliation of late-stage tumors and patients with a short expected survival period.

2) Partially covered stent

The two ends are fixed with naked metal, and the middle is covered with polyurethane / silicone film, which can prevent dislocation and prevent the growth of tissue, and is widely used in clinical practice.

3) Full-coverage metal stent (FCSEMS)

The whole body is covered with a wrapping film, which completely blocks the tumor from growing inward, and can be completely removed and replaced endoscopically; It is suitable for benign bile duct stenosis, bile duct perforation / fistula closure, preoperative transitional drainage, but the risk of displacement is higher than that of bare stents.

3. Special function bracket

Radioactive particle biliary stent: The stent is equipped with iodine 125 particles, which expand the bile duct and simultaneously kill the tumor with local radiotherapy, slow down the progression of the tumor, prolong the time of stent patency, and is suitable for late-stage bile duct cancer and pancreatic cancer bile duct obstruction.

III. Clinical indications

1. Malignant bile duct obstruction (primary use)

Pancreatic cancer, bile duct cancer, ampulla cancer, liver cancer metastasis compressing bile duct, palliative reduction of jaundice cannot be removed by surgery; Short-term biliary drainage before preoperative neoadjuvant therapy, followed by surgery after improvement of liver function.

2. Benign bile duct lesions

Postoperative stenosis of bile duct anastomosis, bile duct injury, inflammatory stenosis, bile duct perforation / bile leakage, refractory bile duct bleeding, temporary support drainage, promote bile duct repair.

3. Other: transitional drainage when external pressure bile duct narrowing and bile duct stones cannot be removed.

IV. Surgical implantation method

Minimally invasive procedure, no abdominal incision required:

1. ERCP approach (preferred): Enter the duodenum orally, navigate through the papilla to enter the bile duct, guide the wire through the narrow section, push the stent delivery system along the wire, and release it precisely under visual guidance.

2. Percutaneous transhepatic approach: suitable for high portal obstruction that cannot be operated by ERCP, percutaneous puncture of liver bile duct, and insertion of stent;

3. The position of the stent can be confirmed by postoperative angiography, and bile drainage can be completed to complete the operation.

V. Comparison of advantages and disadvantages

Type Duration of unobstructed passage Removability Risk of displacement Suitable scenarios

Naked metal stent 6–10 months Cannot be removed Very low Late malignant obstruction, short survival

Partially covered stent 8–12 months Difficult to remove Low Malignant stenosis at porta hepatis

Full-coverage stent 10-14 months Can be completely removed High benign stenosis, bile leak, preoperative transition

Plastic bile duct stent 3–6 months Removable Medium Expected survival time

VI. Common Complications

Early complications (within 1 week after surgery)

Acute pancreatitis, bile duct infection (cholangitis), minor bleeding, stent displacement, bile leakage, symptomatic anti-infection, antispasmodic and analgesic, most of which can be alleviated.

Long-term complications

Tumor / granulation tissue growth (high incidence of bare stent), stent occlusion, accumulation of sand and mud in bile, cholecystitis, repeated bile duct obstruction; The covered stent can greatly reduce the probability of tissue ingrowth, and the stent can be cleared or replaced endoscopically after blockage.

VII. Clinical Core Advantages

1. Minimally invasive local anesthesia operations can be tolerated by patients with advanced tumors who are elderly and have poor physical conditions;

2. It works quickly, and jaundice will quickly disappear within 1-3 days after surgery, liver function will improve, and the quality of life will be significantly enhanced;

3. Metal stents have a much longer period of patency than plastic stents, reducing the need for repeated endoscopic interventions;

4. The covered stent can simultaneously block the bile fistula and control the bile duct bleeding, which is multi-functional;

5. The particle stent has the function of drainage and local anti-tumor, which can prolong the survival time of advanced patients.