The BILNOR study is a prospective multicenter observational study evaluating how common bile duct stones are best managed in patients undergoing cholecystectomy. The study focuses particularly on transcystic laparoscopic common bile duct exploration (LCBDE) and assesses stone clearance, technical success, complications, and health-economic outcomes in routine clinical practice. A secondary aim is to compare LCBDE with intraoperative ERCP regarding efficacy, complication rates, and costs. Approximately 340 patients from several Norwegian centers are planned to be included starting in March 2026.

The BILNOR study (Cholecystectomy with intraoperative management of bile duct stones in Norway) is a prospective, multicenter observational study evaluating how common bile duct stones (CBDS) are best managed when patients also need a cholecystectomy. Although ERCP followed by later cholecystectomy is still the most frequently used strategy, it often requires two separate procedures, with additional discomfort, risk, admissions, and costs. Single-stage alternatives-either intraoperative ERCP (including rendezvous techniques) or laparoscopic common bile duct exploration (LCBDE)-may reduce resource use and improve the patient pathway, but are unevenly available across Norwegian hospitals and have differing complication profiles.

The primary focus of BILNOR is transcystic LCBDE, a technique implemented at Oslo University Hospital in 2019 using a structured "step-up" approach (e.g., saline flushing, pharmacologic relaxation, guidewire passage, papillary balloon dilatation up to 8 mm, and transcystic choledochoscopy with stone extraction; intraoperative ERCP if needed/available). The study will estimate real-world stone clearance (defined as no repeat biliary intervention within 90 days), technical success (intraoperative clearance on cholangiography), and 30-day complications including a study-specific definition of post-procedure pancreatitis, as well as bile leak and other Clavien-Dindo graded events. Health economic outcomes (length of stay and costs per patient) and which procedural steps are most often required to achieve clearance are also assessed.

A secondary aim is to compare LCBDE with intraoperative ERCP regarding efficacy, complication rates, and costs, including a non-inferiority assessment for stone clearance. The planned total sample size is approximately 340 patients (155 per group plus allowae for dropouts). Learning-curve effects will be addressed with center-level sensitivity analyses excluding early cases. Inclusion is planned to start March 1, 2026, with expansion to additional centers as the technique spreads in Norway.

Inclusion criteria:

• Age over 18 years

• Preoperatively image proven choledocholithiasis or bile duct sludge (US / CT / MRI)

  • ≤ 8 mm size
  • ≤ 5 stones
  • Not proximal bile duct stones

• Planned cholecystectomy with intraoperative bile duct clearance (LCBDE or intraoperative ERCP)

Exclusion criteria:

• Previous cholecystectomy
• Medically unfit for surgery (frailty, comorbidity)
• Technically inoperable (hostile abdomen, inflammatory processes, bleeding conditions, cirrhosis)
• Pregnancy

Eligible patients will be identified during routine clinical evaluation by the treating surgical team. Either in the outpatient clinic or in the ward for emergency admitted patients.