title: Gallstone disease is associated with rectal cancer: a meta-analysis.
abstract: BACKGROUND
  Increased levels of secondary bile acids after cholecystectomy and cholelithiasis are believed to increase the risk of colorectal cancer, and several studies have suggested that the risk of colorectal cancer may be the greatest proximally. Numerous conflicting studies have been published and it remains unclear whether the risk is apparent in the rectum. This meta-analysis aims to determine the risk of developing rectal cancer following gallstone disease or cholecystectomy.
  
  
  METHODS
  The prospective protocol included a literature search of PubMed, MEDLINE, EMBASE, and Current Contents (1950-2011). Selection criteria were developed to sort for studies exploring the relationship between cholelithiasis, cholecystectomy, and rectal cancer in an adult population. A random-effects model was used to generate pooled odds ratios (OR) and 95% confidence intervals (CI). Publication bias and heterogeneity were assessed.
  
  
  RESULTS
  Of the 2358 studies identified, 42 were suitable for final analysis. There were 1,547,506 subjects in total, 14,226 diagnosed with rectal cancer, and 496,552 with gallstones or cholecystectomy. There was a statistically significant risk of rectal cancer following cholelithiasis (OR = 1.33; 95% CI = 1.02-1.73), though no risk was apparent following cholecystectomy (OR = 1.14; 95% CI = 0.92-1.41).
  
  
  CONCLUSIONS
  Cholelithiasis increases the risk of rectal cancer. No association exists between cholecystectomy and rectal cancer.
authors.affiliation: Discipline of Surgery, The Whiteley-Martin Research Centre, The University of Sydney, Nepean Hospital, Penrith, New South Wales, Australia.
authors.forename: Corinna
authors.initials: C
authors.lastname: Chiong
authors.forename: Michael R
authors.initials: MR
authors.lastname: Cox
authors.forename: Guy D
authors.initials: GD
authors.lastname: Eslick
mesh_terms: D002763:Cholecystectomy / Q000009:adverse effects*; D002769:Cholelithiasis / Q000150:complications*; D016001:Confidence Intervals; D006801:Humans; D016017:Odds Ratio; D012004:Rectal Neoplasms / Q000209:etiology*; D012307:Risk Factors