This study intends to establish the clinical staging of chronic pancreatitis based on histopathology through pancreatic duct biopsy technology.

Chronic pancreatitis (CP) is an inflammatory disease that can causes progressive fibrosis of pancreatic tissue and eventually leads to damage of pancreatic exocrine and endocrine. According to statistics, the prevalence of CP in China is 13/10 million, which is still increasing. Pancreatic duct stones are the most important pathological changes of CP. More than 50% of patients with CP are accompanied by pancreatic duct stones, which can lead to pancreatic duct obstruction, hypertension and tissue ischemia. Removal of pancreatic duct stones under Endoscopic retrograde cholangiopancreatography (ERCP) are the first choice.

Pathological features of CP include pancreatic parenchymal atrophy and interstitial fibrosis resulting from chronic inflammatory damage. Although there are numerous criteria for clinical staging and severity grading of CP, they all have their own limitations, and none of them have been validated by randomized controlled trials. There is also no clear definition of the clinical stage and severity of CP in the guidelines for the diagnosis and treatment of CP. According to the "Clinical Guideline: Chronic Pancreatitis" issued by the American College of Gastroenterology in 2020, histopathology is the "gold standard" for the diagnosis of CP.

In the past ten years, the technology of mother-daughter scope has developed rapidly. The duodenoscope is used as the mother scope, and the cholangiopancreatoscope is used as the daughter scope. The optical fiber or digital imaging system carried by the daughter scope can directly observe the internal situation of the pancreatic and bile ducts. The channel allows the endoscopist to precisely biopsy the wall of the main pancreatic duct with a biopsy forceps. This technology improves the predicament of pancreatic tissue biopsy in the past, allowing ERCP treatment in patients with CP and pancreatic tissue biopsy to be carried out simultaneously.

Inclusion Criteria:

• Patients with chronic pancreatitis or idiopathic recurrent acute pancreatitis;
• In line with the indications for ERCP treatment.

Exclusion Criteria:

• suspected to have malignant tumors;
• history of pancreatic surgery or gastrojejunostomy (Billroth II);
• bile duct stricture secondary to cholangitis or chronic pancreatitis;
• acute pancreatitis exacerbation or acute exacerbation of chronic pancreatitis;
• coagulation dysfunction (INR≥1.5 or platelet count≤50×10^9/L);
• pregnant or breastfeeding women;
• patients who refused to participate in the study.

Inpatients meeting the eligibility criteria.