The goal of this longitudinal observational cohort study is to examine the changes in the composition and diversity of gut microbiome and systemic metabolome in patients with symptomatic gallbladder stones with or without concomitant common bile duct (CBD) stones who will be undergoing cholecystectomy with or without prior endoscopic sphincterotomy (ERCP-ES) and CBD stones extraction. The main questions it aims to answer are whether there are:

• differences in gut microbiome diversity and composition before and after cholecystectomy
• differences in systemic metabolome before and after cholecystectomy
• gut microbiome and systemic metabolome changes after cholecystectomy

Participants will be asked to provide stool, urine, plasma and saliva samples prior to and 1-6 months after cholecystectomy. For patients with concomitant CBD stones who undergo ERCP-ES before cholecystectomy, bile specimens will be collected from the bile duct during ERCP-ES as well as the gallbladder and/or during cholecystectomy.

This is a longitudinal observational cohort study that will examine the changes in the composition and diversity of gut microbiome and systemic metabolome in patients with symptomatic gallbladder stones with or without concomitant CBD stones who will be undergoing cholecystectomy with or without prior ERCP-ES and CBD stones extraction.

Patients with symptomatic gallstones with or without CBD stones being planned for cholecystectomy will be recruited from both inpatient and outpatient settings. Upon enrolment, baseline clinical characteristics will be recorded, and biospecimens (stool, urine, plasma and saliva) will be collected prior to cholecystectomy for subsequent gut microbiome and systemic metabolome analysis. For patients with concomitant CBD stones who undergo ERCP-ES before cholecystectomy, bile specimens will be collected from the bile duct during ERCP-ES as well as the gallbladder during cholecystectomy, for subsequent bile microbiome analysis. After cholecystectomy, during the scheduled clinic review at 1 to 6 months post-surgery, patients will be reviewed for symptoms of post cholecystectomy syndrome (PCS) or post cholecystectomy diarrhoea (PCD), and biospecimens (stool, urine, plasma and saliva) will again be collected for subsequent gut microbiome and systemic metabolome analysis. The microbiome profile of the study cohort will be compared at baseline with matched controls from other defined cohorts. Post cholecystectomy, the study cohort will also be compared with matched cohort with cholecystectomy duration of more than 12 months.

Inclusion Criteria:

• Aged 21 years to 80 years
• Diagnosis of symptomatic gallstone disease without or with concomitant bile duct stones based on prior diagnostic radiological imaging such as transabdominal ultrasound (US), computed tomography (CT), magnetic resonance imaging (MRI) or endoscopic ultrasound (EUS).
• Will be scheduled for cholecystectomy with or without concomitant ERCP-ES for treatment.
• Patient is willing to provide informed consent before enrolment in the study.

Exclusion Criteria:

• Subjects undergoing ERCP-ES with no intention for future cholecystectomy
• Use of antibiotics or probiotics within 1 month (exception: use of antibiotics within 48 hours of cholecystectomy or ERCP, as metagenomics will be able to sequence both dead and live bacteria, and marked compositional change is not expected within this time frame)
• Presence of malignancy diagnosed within the last 1 year
• Previous gastrectomy, appendicectomy, small bowel or large bowel surgery
• Inflammatory bowel disease
• Active gastrointestinal tract infections

This single centre study at Changi General Hospital will enrol up to 65 patients aged 21 to 80 years with symptomatic gallstone disease and/ or bile duct stones who will be undergoing cholecystectomy with or without concomitant ERCP-ES as part of standard clinical treatment. There will not be stratification by demographics.