title: Microscopic colitis is not associated with cholecystectomy or appendectomy.
abstract: BACKGROUND
  Microscopic colitis is a common cause of chronic watery diarrhea of unknown origin. Some patients develop diarrhea after cholecystectomy, and some patients with microscopic colitis have evidence of bile acid malabsorption. However, the association between cholecystectomy and microscopic colitis has not been studied. A protective effect of appendectomy on the development of ulcerative colitis also has been reported, but its relationship with microscopic colitis has not been studied. The aim of this study was to assess cholecystectomy and appendectomy as potential risk factors for the development of microscopic colitis in a nested case-control study.
  
  
  METHODS
  Using the Rochester Epidemiology Project, we identified all Olmsted County (Minnesota) residents with an initial diagnosis of microscopic colitis between January 1, 1985, and December 31, 2001. Rates of antecedent cholecystectomy or appendectomy in patients with microscopic colitis were compared with age-, gender-, and calendar year-matched community controls through conditional logistic regression.
  
  
  RESULTS
  Microscopic colitis was identified in 130 cases. Cholecystectomy preceded the diagnosis of microscopic colitis in 12 cases (9%) compared with 17 (13%) in the control group (odds ratio [OR] 0.7; 95% CI 0.3-1.5). Appendectomy preceded the diagnosis of microscopic colitis in 39 subjects (30%) compared with 28 (22%) in the control group (OR 1.6; 95% CI 0.9-2.7). Similar results were obtained when the analysis was restricted to microscopic colitis subtype (lymphocytic colitis or collagenous colitis).
  
  
  CONCLUSIONS
  In this population-based nested case-control study, no significant association was seen between cholecystectomy or appendectomy and the development of microscopic colitis or its subtypes.
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Internal Medicine, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.
authors.forename: Aran W
authors.initials: AW
authors.lastname: Laing
authors.forename: Darrell S
authors.initials: DS
authors.lastname: Pardi
authors.forename: Edward V
authors.initials: EV
authors.lastname: Loftus
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Smyrk
authors.forename: Patricia P
authors.initials: PP
authors.lastname: Kammer
authors.forename: William J
authors.initials: WJ
authors.lastname: Tremaine
authors.forename: Cathy D
authors.initials: CD
authors.lastname: Schleck
authors.forename: W Scott
authors.initials: WS
authors.lastname: Harmsen
authors.forename: Alan R
authors.initials: AR
authors.lastname: Zinsmeister
authors.forename: L Joseph
authors.initials: LJ
authors.lastname: Melton
authors.forename: William J
authors.initials: WJ
authors.lastname: Sandborn
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001062:Appendectomy / Q000009:adverse effects*; D016022:Case-Control Studies; D002763:Cholecystectomy / Q000009:adverse effects*; D046728:Colitis, Microscopic / Q000209:etiology* / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D012307:Risk Factors