The aim of this retrospective, register-based study is to investigate whether access, or no access, to endoscopic retrograde cholangiopancreatography (ERCP) at a surgical unit is associated with the risk of complications in patients undergoing laparoscopic cholecystectomy with common bile duct stones detected on intraoperative cholangiography.

Annually, approximately 15,000 cholecystectomies are performed in Sweden. Cholecystectomy is indicated if gallstones cause recurrent biliary colic or complications. Gallstones can pass from the gallbladder into the common bile duct. Common bile duct stones (CBDS) can potentially cause biliary obstruction, cholangitis and pancreatitis.

Intraoperative cholangiography (IOC) during cholecystectomy is performed as a standard in Swedish surgical units. The arguments for routine IOC are several; routine IOC is associated with reduced risk of bile duct injury in patients with previous or ongoing cholecystitis, early detection of bile duct injury has been suggested to improve survival, and CBDS found by IOC, even small ones <4 mm, are associated with increased risk of complications and need for unplanned endoscopic retrograde cholangiopancreatography (ERCP) if no effort is made to clear the common bile duct.

American guidelines suggest performing IOC as a routine in adult patients undergoing laparoscopic cholecystectomy. Many countries do not practice routine IOC because it prolongs cholecystectomy and the evidence supporting its use is considered insufficient. European guidelines do not include routine IOC as a recommendation. On the other hand, both American and European guidelines advocate treatment of all CBDS, symptomatic or not.

CBDS represent a well-recognized clinical dilemma, especially when encountered first on IOC during cholecystectomy. In those situations, intraoperative treatment of CBDS has not been planned in advance.

There are several different approaches to remove CBDS. Worldwide, the two most common methods used are preoperative endoscopic retrograde cholangiopancreatography (ERCP) followed by cholecystectomy, or laparoscopic exploration of the common bile duct during cholecystectomy. In Sweden, the predominant treatment strategy for CBDS encountered on IOC is intraoperative ERCP.

The ERCP procedure itself is associated with a non-negligible risk of complications. The most common, and potentially severe, complication is post-ERCP pancreatitis (PEP). According to observational studies based on data from the Swedish Registry for Gallstone Surgery and ERCP (GallRiks), rendezvous-ERCP is associated with less complications, mainly PEP, compared to postoperative rendezvous-ERCP, and rendezvous-ERCP reduces the risk of PEP compared to conventional ERCP.

There are major differences between Swedish regions in the treatment of gallstone disease and outcome, probably because of different local routines. All units in Sweden performing cholecystectomies must be able to handle CBDS encountered at IOC, according to the national guidelines. The same guidelines advocate intraoperative ERCP with the rendezvous technique. ERCP volumes differ greatly between different surgical units in Sweden and the proportion of units performing ERCP has decreased over time. Smaller volumes of ERCP per surgeon are associated with more complications, including PEP.

In Sweden, part of the gallbladder surgery has moved from emergency care hospitals to elective, and sometimes private units, over the last few decades. Some of these units lack the equipment or expertise necessary for ERCP. Thus, despite what current national guidelines recommend, patients undergoing cholecystectomy, with a finding of CBDS on IOC, do not have the option to be treated with intra- or postoperative ERCP in such a surgical unit. Their CBDS must be treated in another way intraoperatively or with postponed ERCP after transfer to another unit.

How these structural differences in ERCP access at cholecystectomy affect the type of treatment of CBDS, time to treatment of CBDS, and thus complications, is not investigated. Because alternative treatment strategies to ERCP are used in units without access to ERCP, but also in units with access to ERCP, this question cannot simply be answered by the difference in complications from intra- and postoperative ERCP. Furthermore, these other strategies do not necessarily have a higher risk of complications compared to ERCP.

In a previous study, based on data from GallRiks, laparoscopic cholecystectomy with intraoperative rendezvous ERCP was associated with more complications compared to laparoscopic cholecystectomy with transcystic stent and postoperative ERCP.

The intention is to study how access to ERCP in different units affect complication rates in patients undergoing cholecystectomy when CBDS are detected on IOC. If the study shows no difference in risk of complications, there is a future possibility to transfer more gallbladder surgery out of emergency care hospitals and to enable more capacity for emergency surgery. On the other hand, if the study shows an increased risk of complications if the procedure is performed in a surgical unit without access to ERCP, there is an argument to transfer patients the other way around or establish capacity for ERCP at a greater number of hospitals.

Research question In patients undergoing laparoscopic cholecystectomy with CBDS on IOC, is there a difference in complication rates depending on access or not to ERCP at the surgical unit?

Aim and hypothesis The aim of this retrospective, register-based study is to investigate whether access, or no access, to ERCP at a surgical unit is associated with the risk of complications in patients undergoing laparoscopic cholecystectomy with CBDS detected on IOC.

The hypothesis is that laparoscopic cholecystectomy with CBDS on IOC in units with access to ERCP will be associated with less complications compared to units without access to ERCP.

PICO P Patients, ≥18 years old, undergoing laparoscopic cholecystectomy with CBDS detected on IOC in Sweden 2015-2025 and registered in GallRiks.

I There is no specific intervention performed in each group. Instead, patients undergoing cholecystectomy at a unit without access to ERCP are considered as exposed individuals.

C Patients undergoing cholecystectomy at a unit with access to ERCP are considered unexposed, serving as controls.

O Primary outcome is complications within 30 days. Complications from both the cholecystectomy and the ERCP, if performed, will be considered since the entire course of care is important from a safety perspective.

Data will be analyzed separately for acute and elective gallbladder procedures, as units without access to ERCP perform elective surgery to a very large extent.

Sweden has a distinctive approach to manage CBDS, and a nationwide register for gallbladder surgery and ERCP, GallRiks. When validated, GallRiks has shown high completeness and high correctness of entered data. Taken together, this provides a unique possibility to contribute to research in gallbladder surgery.

Primary outcome Complications

Secondary outcomes Length of hospital stay, time from surgery to first treatment of common bile duct stones, unplanned ERCP after surgery due to CBDS, mortality

Inclusion Criteria:

• ≥18 years old
• Laparoscopic cholecystectomy with common bile duct stones (CBDS) detected on intraoperative cholangiography (IOC)
• Procedure registered in the Swedish Registry for Gallstone Surgery and ERCP (GallRiks) 2015-2025

Exclusion Criteria:

• Open surgery
• Conversion to open surgery
• Transgastric ERCP

Patients, ≥18 years old, undergoing laparoscopic cholecystectomy with common bile duct stones detected on intraoperative cholangiography in Sweden 2015-2025 and registered in GallRiks.