Appendectomy Linked to Higher Risk of Microscopic Colitis

The most common symptom of microscopic colitis is chronic, watery, non-bloody diarrhea. Episodes of diarrhea can last for weeks, months, or even years. However, many people with microscopic colitis may have long periods without diarrhea.

Appendectomy has been suggested to cause immunomodulating effects in the colon, and earlier studies have shown an inverse relationship between appendectomy and ulcerative colitis, and celiac disease. A cohort study estimated microscopic colitis (MC) to affect 1 in 115 women and 1 in 286 men and accounts for up to 20% of cases of chronic diarrhea among individuals >65 years of age.

A team of medical scientists led by the Karolinska Institutet (Stockholm, Sweden) examined data from the ESPRESSO cohort on 14,520 patients with microscopic colitis who were matched by sex, age, year of biopsy, and residential county to 69,491 controls without microscopic colitis. Of the patients with microscopic colitis, 9,836 had lymphocytic colitis and 4,684 had collagenous colitis. Patients underwent biopsy for microscopic colitis from 1990 to 2017.

The exposure was previous appendectomy, defined as appendectomy at least one year prior index biopsy demonstrating MC, or matching date in controls. Appendectomy was identified using surgical procedure codes and the NOMESCO system. The nomenclature defining complicated and non-complicated appendicitis is not standardized, therefore, complicated and non-complicated appendicitis was defined with surgical procedure codes in combination with ICD (7-10th revisions) codes.

The investigators reported that almost half of patients were diagnosed with microscopic colitis at ages 50 to 70 (43.2%), and 72% were women. Only 4.3% of patients with microscopic colitis had been diagnosed with another form of IBD. Prior to matching, 7.6% of patients with microscopic colitis and 5.1% of controls underwent an appendectomy ≥1 year earlier. Uncomplicated appendicitis was the most common diagnosis. A post-hoc analysis that stratified patients by age at appendectomy showed similar results across all subgroups.

Among over 14,500 patients, those who previously underwent an appendectomy had an overall higher risk of developing microscopic colitis (adjusted odds ratio [aOR] 1.50, 95% CI 1.40-1.61), and this relationship held true for its subtypes. The risk remained elevated even 10 years after an appendectomy (aOR 1.41, 95% CI 1.30-1.52), and the highest associated risk among patients with complicated appendicitis was seen 5 to 10 years after appendectomy.

The authors concluded that the pathophysiology of microscopic colitis is thought to be associated with a dysregulated immune response in the gut mucosa, in genetically predisposed individuals, and infiltration of T-helper cells 17 (Th17) in the lamina propria of colon has been observed, the and that appendicitis has been linked to upregulation of the Th17 pathway. The study was published on June 15, 2022 in the journal Clinical Gastroenterology and Hepatology.

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