Assessing surgical risks in a population: patient histories before and after cholecystectomy

Claims data from the Manitoba Health Services Commission on all health care contacts during the 2 years preceding and the 2 years following gallbladder surgery were used to describe the histories of patients prior to cholecystectomy, and to assess surgical outcomes. The study is unique in focusing on essentially all patients in the population undergoing surgery (whether at large academic centres or small rural hospitals) and in tracking post discharge events (deaths and complications). Many patients presenting for surgery with acute/urgent conditions were previously asymptomatic or at least their gallbladder disease was undiagnosed (27%). Although overall mortality rates were low (0.7%), 26% of the deaths occurred following discharge from the hospital where surgery was performed. In addition, 3.4% of the patients were readmitted to hospital with complications of the gallbladder surgery, 13.5% continued to visit the physician with abdominal symptoms after surgery and 17% presented with psychological problems. Multiple logistic regression is used to estimate the risk of poor surgical outcomes according to a patient's presurgical characteristics. The analysis suggests that most published data are biased towards underestimating the risks associated with cholecystectomy (as well as the risks associated with other common surgical procedures).