Intraoperative cholangiography failed to reduce the risk of common-duct injury during cholecystectomy, an instrumental variable analysis of 92,000 cases showed.
Use of intraoperative imaging was associated with an injury rate of 0.21 percent compared with 0.36 percent for cholecystectomy procedures performed without cholangiography.
An unadjusted analysis demonstrated a statistically significant difference in favor of cholangiography, as did multivariable logistic regression analysis.
However, by use of instrumental variable analysis to account for unmeasured confounders, the difference between groups was no longer significant, Taylor S. Riall, MD, PhD, of the University of Texas Medical Branch at Galveston, and co-authors reported online in the Journal of the American Medical Association.
"The relationship between intraoperative cholangiography and common-duct injury was sensitive to the method of statistical analysis," the authors concluded. "Failure to account for potentially confounding variables not routinely captured in administrative databases has a major effect on the interpretation of the findings.
"Intraoperative cholangiography was not associated with significant reduction in common-duct injury using instrumental variable analysis. Instrumental variable analysis balances unmeasured confounding variables to better align risk factors in comparator groups."
The authors of an accompanying editorial noted that the challenge of using instrumental variable analysis is the identification of valid instruments. In the study by Riall and colleagues, the association between intraoperative cholangiography and common-duct injury rates has more than one potential explanation, such as a hospital mandate for intraoperative cholangiography as part of an overall strategy to improve safety and quality, the editorialists noted.
"Nonetheless, substantial variability in surgeon and hospital intraoperative cholangiography use rates has remained relatively unchanged since the 1990s, demonstrating that surgeons remain unconvinced regarding the ability of the procedure to prevent common-duct injury," wrote Karl Y. Bilimoria, MD, Jeanette Chung, PhD, and Nathaniel J. Soper, MD, all of Northwestern University in Chicago.