To Örebro University

BACKGROUND AND AIMS: Microscopic colitis (MC) is an inflammatory bowel disease and a common cause of chronic diarrhea. Appendectomy has been suggested to have immunomodulating effects in the colon, influencing the risk of gastrointestinal disease. The relationship between appendectomy and MC has only been sparsely studied.

METHODS: This was a case-control study based on the nationwide ESPRESSO cohort, consisting of histopathological examinations in Sweden, linked to national registers. Patients with MC were matched to population controls by age, sex, calendar year of biopsy and county of residence. Data on antecedent appendectomy and comorbidities were retrieved from the Patient Register. Unconditional logistic regression models were conducted presenting odds ratios (ORs) and 95% confidence intervals (Cl) adjusted for country of birth and matching factors. Further sub-analyses were made based on MC subtypes (lymphocytic colitis [LC] and collagenous colitis [CC]), follow-up time post appendectomy and severity of appendicitis.

RESULTS: The study included 14,520 cases of MC and 69,491 controls, among these 7.6% (n=1,103) and 5.1% (n=3,510), respectively, had a previous appendectomy ≥1 year prior to MC/matching date. Patients with a previous appendectomy had an increased risk of MC in total (OR 1.50, 95% CI 1.40-1.61); and per subtype CC (OR 1.67, 95% CI 1.48-1.88), LC (OR 1.42, 95% CI 1.30-1.55). The risk remained elevated throughout follow-up, and the highest risk was observed in non-complicated appendicitis.

CONCLUSIONS: This nationwide case-control study found a modestly increased risk of developing MC following appendectomy.