X-ray exam of ducts during gallbladder surgery may not reduce injury risk

While some advocate use of a radiologic examination of ducts during gallbladder surgery to prevent common duct injury, the benefits are unclear. Adding to the debate, a study published Aug. 28 in JAMA found no significant association between the procedure and reduced risk of injury. 

Results varied widely based on the type of analysis used, with previous studies relying on administrative data that can lead to different conclusions, explained Kristin M. Sheffield, PhD, of the University of Texas Medical Branch, Galveston, and colleagues.

“Failure to account for potentially confounding variables not routinely captured in administrative databases has a major effect on the interpretation of the findings,” they wrote.

The exam in question—intraoperative cholangiography—is thought to prevent common duct injury during gallbladder removal, or cholecystectomy, and the short- and long-term morbidity that accompanies such complications. Biliary anatomy misidentification and resulting injury occurs in 0.3 – 0.5 percent of cases, according to the authors.

To measure the association between intraoperative cholangiography use during cholecystectomy and common duct injury, Sheffield and colleagues conducted a retrospective cohort study of Texas Medicare claims data from 2000 through 2009. Included in the study were beneficiaries 66 years or older who underwent inpatient or outpatient cholecystectomy for conditions including biliary colic or biliary dyskinesia, acute cholecystitis, or chronic cholecystitis. Claims for common duct repair within one year of cholecystectomy were considered the result of major common duct injury during gallbladder removal.

Sheffield and colleagues conducted the study as an instrumental variable analysis, with percentage of intraoperative cholangiography use at the hospital and by surgeon as the instrumental variables. This technique is used to balance unmeasured confounding variables and better align risk factors in comparator groups.

Data revealed nearly 93,000 Medicare beneficiaries 66 years or older underwent cholecystectomy at 307 hospitals in Texas during the study period, with 40.4 percent conducted with intraoperative cholangiography. Common duct injury occurred at a rate of 0.21 percent in patients undergoing gallbladder removal with intraoperative cholangiography and 0.36 percent in patients without the radiologic exam.

Logistic regression modeling that controlled for patient, surgeon and hospital characteristics demonstrated an association between common duct injuries and cholecystectomies performed without intraoperative cholangiography, but this association disappeared when confounding was controlled through instrumental variable analysis, reported the authors.

Sheffield and colleagues explained that observational data commonly lack complete information on factors influencing selection of treatment. Intraoperative cholangiography could be performed routinely or used to confirm injury or detect common duct stones.

In high-use hospitals where intraoperative cholangiography is a matter of routine (handling more than two-thirds of cholecystectomies), the rate of injury was six times higher when cholangiography was not performed. However, routine use may be prevented based on complicating factors such as unclear anatomy that are also associated with increased risk of injury, thus skewing results. Likewise, while advocates for routine intraoperative cholangiography may point to improved injury rates at facilities that implement its use, benefits may be attributable to additional surgical training, increased awareness of anatomy and increased surgeon awareness of outcome measurement as opposed to the procedure itself.

“Based on these results, routine intraoperative cholangiography should not be advocated as means for preventing common duct injury,” concluded the authors.