title: Risk of pancreatic cancer after cholecystectomy: a cohort study in Sweden.
abstract: BACKGROUND
  Although some experimental studies have indicated that cholecystectomy may increase the risk of pancreatic cancer, data from epidemiological studies are conflicting.
  
  
  OBJECTIVE
  We conducted a register based retrospective cohort study to explore the relationship between cholecystectomy and pancreatic cancer.
  
  
  METHODS
  The cohort included 87 263 men and 181 049 women with a documented cholecystectomy for cholelithiasis between 1965 and 1997.
  
  
  METHODS
  By record linkage to the nationwide and virtually complete registers of Cancer, Emigration, and Causes of Death, the cohort was followed up until the occurrence of any cancer, emigration, death, or the end of follow up, 31 December 1997, whichever came first. Relative risk was estimated by standardised incidence ratio (SIR) using the Swedish nationwide sex, age, and calendar year specific cancer incidence rates as reference.
  
  
  RESULTS
  During the period of observation, 1053 cases of pancreatic cancer were found, among which 231 (22%) occurred within 12 months after operation. After excluding cases and person years accrued during the first two years of follow up, we observed a non-significant 6% excess risk for pancreatic cancer (95% confidence interval (CI) -2 to 14%). The relative risk did not increase with increasing follow up duration, with a SIR equal to 0.98 (95% CI 0.79-1.20) 20 years or more after operation. Patients with a comorbidity of diabetes or chronic pancreatitis had higher relative risks (SIR=1.79, 95% CI 1.39-2.28; SIR=3.17, 95% CI 1.37-6.24, respectively). After excluding patients with recorded diabetes or chronic pancreatitis, the relative risk was close to unity (SIR=1.01, 95% CI 0.94-1.09).
  
  
  CONCLUSIONS
  Our findings do not support the hypothesis that cholecystectomy increases the subsequent risk of pancreatic cancer.
authors.affiliation: Department of Medical Epidemiology, Karolinska Institutet, Stockholm, Sweden. Weimin.Ye@mep.ki.se
authors.forename: W
authors.initials: W
authors.lastname: Ye
authors.forename: J
authors.initials: J
authors.lastname: Lagergren
authors.forename: O
authors.initials: O
authors.lastname: Nyrén
authors.forename: A
authors.initials: A
authors.lastname: Ekbom
mesh_terms: D000328:Adult; D000368:Aged; D002763:Cholecystectomy / Q000009:adverse effects*; D015331:Cohort Studies; D016001:Confidence Intervals; D048909:Diabetes Complications; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000209:etiology*; D010195:Pancreatitis / Q000150:complications; D012189:Retrospective Studies; D012307:Risk Factors; D013548:Sweden