Inclusion Criteria:

• Age 18 years or older.
• Diagnosis of acute pancreatitis according to the revised Atlanta criteria, defined by the presence of at least two of the following three features:

typical abdominal pain consistent with acute pancreatitis; serum amylase and/or lipase activity at least three times the upper limit of normal; imaging findings consistent with acute pancreatitis.

• Hospital admission due to acute pancreatitis to the study center.
• Admission during the early phase of acute pancreatitis, allowing planned upper gastrointestinal endoscopy within 24-48 hours from hospital admission.
• Ability to undergo diagnostic upper gastrointestinal endoscopy according to the investigator's and treating physician's assessment.
• Ability to provide written informed consent before enrollment and before any study-specific procedure.

Exclusion Criteria:

• Age below 18 years.
• Lack of written informed consent.
• Inability to provide informed consent before enrollment.
• Clinical condition precluding safe diagnostic upper gastrointestinal endoscopy, including hemodynamic instability, severe respiratory failure, or other unstable life-threatening condition.
• Need for emergency therapeutic upper gastrointestinal endoscopy before planned study endoscopy, for example due to active upper gastrointestinal bleeding.
• Known or suspected gastrointestinal perforation.
• Previous gastric or duodenal surgery significantly altering upper gastrointestinal anatomy and preventing reliable assessment of gastric or duodenal mucosa.
• Known advanced upper gastrointestinal malignancy affecting the stomach or duodenum.
• Pregnancy.
• Contraindication to upper gastrointestinal endoscopy or sedation according to the treating physician's or investigator's assessment.
• Any condition that, in the investigator's opinion, would make participation unsafe or would prevent completion of study procedures.