Intestinal Microbiota Composition in Patients With Chronic Pancreatitis and Pancreatic Exocrine Insufficiency

Inclusion Criteria: * Age 18 to 80 years old; any gender; * Chronic pancreatitis etiology: idiopathic, biliary dependent, drug-induced, alcoholic, dysmetabolic, CP as a consequence of recurrent and severe acute pancreatitis (postnecrotic); * History of confirming diagnostic criteria of CP (in accordance with 1) Clinical guidelines of the Russian Gastroenterological Association on the diagnosis and treatment of exocrine pancreatic insufficiency 2018; 2) Clinical guidelines of the unified European guidelines for gastroenterology, on the diagnosis and therapy of chronic pancreatitis 2017; 3) Clinical guidelines of the American College of Gastroenterology 2020); * CP diagnosis according to multispiral computed tomography of the abdominal cavity and/or endoscopic ultrasonography of pancreas: size changes; dilatation of the main pancreatic duct more than 2 mm; increased echogenicity of the walls, uneven contours and heterogeneity of the BP parenchyma, concrements or calcification of the parenchyma; * Clinical manifestations of exocrine insufficiency of pancreas: stool disorders (mushy/liquid stool, number of defecation acts \>3 p/day, undigested food remains), steatorrhea, abdominal distention, nausea/vomiting, weight loss progression with adequate caloric intake and no other objective reasons of weight loss; * Fecal elastase-1 values less than 200 µg/g (for CP groups with EPI) or more than 200 µg/g (for CP group without concomitant EPI); * Informed patient consent to participate in the study. Exclusion Criteria: * Acute pancreatitis; * Hepatitis, cirrhosis of any etiology; * Any acid-dependent diseases requiring immediate or long-term proton pump inhibitor therapy (PPI): gastroesophageal reflux disease, acute gastroduodenal erosions of any etiology; Zollinger-Ellison syndrome, etc; * Stenosis of pylorys or duodenum; * Condition after gastric resection or gastrectomy; * Obstructive and autoimmune CP; * Mesenteric ischemia syndrome; * Any other cause of chronic diarrhea (irritable bowel syndrome with diarrhea predominance, gluten enteropathy, lactase deficiency, inflammatory bowel disease, etc.); * Concomitant administration of drugs directly affecting exocrine pancreatic secretion (octreotide); * Any concomitant diseases in the stage of decompensation (cardiovascular, renal failure, diabetes mellitus, etc.); * Chronic infectious diseases requiring constant (long-term) supportive therapy, including HIV infection, etc; * Hypersensitivity to pancreatin; * Use of pro-, pre-, synbiotics, week prior to inclusion in this study; * Use of antibiotics within 4 weeks prior to inclusion in this study; * Pregnancy and lactation; * Use of prohibited concomitant therapy during the study: pro-, pre-, synbiotics, including dietary fiber preparations and lactulose, as well as antibiotics, intestinal antiseptics, loperamide, intestinal sorbents.