Background:Recurrence after stone removal is common in patients with choledocholithiasis.Recent studies have indicated that dysbiosis in gut microbiota plays an important role in the formation of cholesterol gallstones.Aims:To explore the effect of probiotics supplementation on serum lipopolysaccharide(LPS)and the indicators of bile acid metabolism in patients with a high risk of cholesterol gallstone formation.Methods:Sixty choledocholithiasis patients undergoing ERCP lithotomy were recruited at the First Affiliated Hospital of Shihezi University from June 2021 to June 2023.Bile and stool samples were collected for bacterial culture.Then the patients were randomly allocated into two groups:patients in control group received conventional supportive therapy after calculus removal,while those in probiotics intervention group were given oral bifid triple viable enteric capsule 420 mg,twice a day for 6 months based on conventional therapy.Changes in serum levels of LPS,the cell wall component of Gram-negative bacteria,fibroblast growth factor 19(FGF19),the key molecule in bile acid metabolism,and cholesterol 7α-hydroxylase(CYP7A1),the rate-limiting enzyme of bile acid synthesis,were determined and compared between the two groups.Results:Escherichia coli and Klebsiella pneumoniae were the main pathogens in bile and stool of patients with choledocholithiasis.Six months after ERCP lithotomy,the serum levels of LPS and FGF19 were decreased,and the serum level of CYP7A1 was increased in both groups(all P<0.05),especially in probiotics intervention group(all P<0.05).Conclusions:Oral probiotics supplementation can reduce the serum LPS level and modulate the canonical pathway of enterohepatic circulation of bile acids--farnesoid X receptor(FXR)-FGF19 pathway in high-risk patients of cholesterol gallstone formation.These alterations reduce the cholesterol supersaturation in bile and inhibit the probability of cholesterol gallstone formation.