The purpose of this study is to compare the effect of lumen-apposing metal stent (LAMS) and double pigtail plastic stents (DPPSs) on the drainage of pancreatic walled-off necrosis (WON), mainly to observe the efficacy and safety of LAMS for WON.

Patient with pancreatic walled-off necrosis (WON) would be treated randomized with lumen-apposing metal stent (LAMS) or double pigtail plastic stents (DPPSs) under the guidance of Endoscopic Ultrasonography. The investigators compare the effect of the two stents, including technical success, clinical success, adverse event, recurrence, and so on.

Inclusion Criteria:

1. Subject with ages from 18-80 years old
2. Subject with pancreatic pseudocysts confirmed by CT
3. Subject with a history of MSAP or SAP, the pseudocysts were formed more than 3 months
4. The size of pseudocyst is more than 6 cm, and the cyst adjacent to the gastric wall
5. Subject has the symptoms related with the pseudocyst
6. The consent form has been signed

Exclusion Criteria:

1. Subject is younger than 18 years or older than 80 years
2. Pancreatic pseudocyst communicate with the main pancreatic duct
3. Subject can't accept the endoscopic procedure
4. Pancreatic pseudocyst with infection or subject diagnosed with pancreatic abscess
5. The distance between gastric and the wall of the pseudocyst is more than 1 cm
6. Subject with 2 or more than 2 cysts
7. Subject has blood coagulation dysfunction
8. Pregnant or subject has mental disorders