Pseudo Cyst Stent

Complete introduction of pancreatic pseudocyst drainage stent

The pancreatic pseudo-cyst drainage stent is the core instrument for internal drainage under the guidance of EUS (endoscopic ultrasound), which is used to establish a persistent drainage channel between the stomach/duodenum and the pseudo-cyst after acute pancreatitis, pancreatic peripancreatic fluid accumulation, pseudo-cyst, and encapsulated necrosis (WON). As an alternative to open abdominal surgery and drainage, minimally invasive and fast recovery, it is mainly divided into two categories: double pigtail plastic stent and double mushroom head lumen-apposing metal stent (LAMS, lumen-apposing self-expanding metal stent). The traditional straight type bile duct covered metal stent is no longer recommended for routine use.

I. Working principle

Under the real-time positioning of endosonography, avoid the blood vessels, puncture into the cavity of the pseudo-cyst, insert the guidewire, expand the sinus between the wall of the digestive tract and the wall of the cyst; The stent is placed across the stomach wall / duodenal wall and the cyst wall, one end is fixed in the gastrointestinal cavity, and the other end is anchored in the cyst, so that the cyst fluid can be continuously drained inward to the gastrointestinal tract, and the cyst gradually collapses and closes; The large-diameter metal stent can also allow the endoscope to enter the cyst cavity to remove necrotic tissue and clean the infected lesion.

II. Mainstream stent types, structures, and materials

1. Double pigtail plastic support (DPPS, clinical basic model)

· Material: polyethylene (PE), disposable, the retention time in the body is generally ≤28 days

· Structure: curled at both ends like a pig tail, with a straight cylinder in the middle;Standard size 7Fr, 10Fr, length 3–6cm;The self-anchoring effect of the bent structure at both ends greatly reduces the risk of displacement.

· Characteristics: low price, easy to remove, simple operation;The disadvantage is that the tube diameter is small, and when the cyst fluid is viscous and contains necrotic debris, it is very easy to block, and the recurrence rate of infection is high.

2. LAMS double mushroom head conformal self-expanding metal stent (currently preferred, especially in combination with necrosis)

· Frame: self-expanding nitinol memory alloy, fully covered membrane (polyurethane/silicone), gentle radial support force

· Structure: Overall short, both ends expanded to mushroom/flange shape, with a short straight cylinder in the middle;The two ends of the flange are respectively fixed in the stomach cavity / duodenal cavity and the cyst cavity, firmly adhering to the wall of the digestive tract and the wall of the cyst, completely preventing the displacement of the stent and the leakage of cyst fluid into the abdominal cavity; The inner diameter is commonly 10mm, 16mm, and 20mm, and the pipe diameter is much larger than the plastic support.

· Development mark: Irradiation-insensitive platinum-iridium mark on both ends, precise positioning and release under X-ray

Core advantages: large inner diameter, can enter the cyst cavity through the stent channel to clean necrotic tissue and flush, suitable for combined infection, necrotic debris-rich encapsulated necrosis

3. Traditional straight-line type covered bile duct SEMS

Early on, bile duct full-covering stents were borrowed, with no two-end fixed structure, high displacement rate, poor adhesion of cyst wall, and easy occurrence of intraperitoneal leakage, and the current guidelines clearly do not recommend routine use for pseudo-cyst drainage.

III. Clinical indications

1.Pancreatic pseudocyst (PPC): cyst wall mature, diameter ≥ 6 cm, compression of stomach and duodenum, abdominal pain, abdominal distension, eating disorder, conservative treatment not absorbed

2. Walled-off necrosis (WON): after acute pancreatitis, necrotic tissue is walled off by the capsule, combined with infection and abscess formation, requires large-diameter stent drainage + endoscopic debridement

3. Patients with peripancreatic fluid infection and cystic lesions related to pancreatic fistula who cannot tolerate surgical treatment

Contraindication

The wall of the cyst is immature, the cyst is too far away from the digestive tract wall, coagulation dysfunction, extensive adhesion in the abdominal cavity, multiple diffuse cysts.

IV. Insertion procedure (guided by EUS)

1. Ultrasound endoscopy exploration, mark the best puncture point, avoid blood vessels;

2. 19G needle puncture the cyst, insert the guidewire, and draw the cyst fluid for examination;

3. Electrocauterization of the wall of the digestive tract and the wall of the cyst, balloon dilation of the fistula;

4. Guide the delivery system of the stent along the guidewire, release it precisely under the guidance of the X-ray;

◦ Plastic stent: insert 1–2 double pigtail stents;

◦ LAMS: After release, the mushroom heads at both ends anchor the gastrointestinal cavity and the sac cavity respectively;

5. Confirm that the drainage is unobstructed, and use prophylactic antibiotics after surgery.

V. Comparison of the two types of stents

Comparison item Double pigtail plastic bracket LAMS double mushroom head metal bracket

Pipe diameter Fine (7/10Fr) Large (10–20 mm)

Shifting risk Very low Very low (flange anchoring)

The probability of blockage is high, and the viscous cyst fluid is easy to block; the probability of blockage is low, and the large diameter is not easy to block.

Necrotic debridement Cannot enter the cyst cavity by endoscopy. Debridement of necrotic tissue can be performed through the stent channel.

Retention time Short-term, several weeks Can be retained for several months, removed after cyst closure

Applicable scenarios: Simple clear cyst fluid pseudo-cyst Pseudo-cyst + encapsulated necrosis, infectious cyst

Low-cost High-cost

VI. Common Complications

1. Early (within 1 week after surgery): puncture bleeding, transient abdominal pain, fever, mild infection; LAMS has a lower bleeding risk, and the covering membrane can compress the puncture point to stop bleeding.

2. Prognosis: blockage of plastic stent, recurrence of cyst; Metal stent displacement is extremely rare, with a few cases of cyst wall hyperplasia and stent occlusion; Extremely rare cases of gastrointestinal ulcers and perforations