Introduction Microscopic colitis is a chronic inflammatory bowel disease characterised by normal or almost normal endoscopic appearance of the colon, chronic watery, non-bloody diarrhoea and distinct histological abnormalities, which identify three histological subtypes, the collagenous colitis, the lymphocytic colitis and the incomplete microscopic colitis. With ongoing uncertainties and new developments in the clinical management of microscopic colitis, there is a need for evidence-based guidelines to improve the medical care of patients suffering from this disorder. Methods Guidelines were developed by members from the European Microscopic Colitis Group and United European Gastroenterology in accordance with the Appraisal of Guidelines for Research and Evaluation II instrument. Following a systematic literature review, the Grading of Recommendations Assessment, Development and Evaluation methodology was used to assess the certainty of the evidence. Statements and recommendations were developed by working groups consisting of gastroenterologists, pathologists and basic scientists, and voted upon using the Delphi method. Results These guidelines provide information on epidemiology and risk factors of microscopic colitis, as well as evidence-based statements and recommendations on diagnostic criteria and treatment options, including oral budesonide, bile acid binders, immunomodulators and biologics. Recommendations on the clinical management of microscopic colitis are provided based on evidence, expert opinion and best clinical practice. Conclusion These guidelines may support clinicians worldwide to improve the clinical management of patients with microscopic colitis.

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Background: Collagenous colitis is characterised by diarrhoea, lymphocytic inflammation, and a thickened subepithelial collagen layer in the colorectal mucosa. No standard treatment of the disease is established. Aims: To investigate the clinical and histological effect of oral budesonide (Entocort, AstraZeneca) in the treatment of collagenous colitis. Patients: Twenty patients with collagenous colitis (collagen layer >10 µm) and diarrhoea (>4 stools/ day and/or stool weight >200 g/day). Methods: A randomised, double blind, placebo controlled trial of budesonide treatment. Patients were randomised to placebo or budesonide for eight weeks. Stool frequency and stool weight were registered before and after treatment. Sigmoidoscopy was performed before and after treatment, and biopsies at fixed locations were obtained for morphometric analysis. Results: Ten patients were randomised to budesonide and 10 to placebo. All 10 patients receiving budesonide had a clinical response compared with two in the placebo group (p<0.001). In the budesonide group, stool weight was reduced from 574 g/day to 200 g/day and stool frequency was reduced from 6.2/day to 1.9/day (p<0.01). The histological inflammation grade in the sigmoid mucosa and the thickness of the collagen layer were significantly reduced. A correlation between the grade of inflammation as well as collagen layer thickness and stool weight was found. No side effects were reported. Eight of 10 patients had relapse of symptoms within eight weeks after stopping treatment. Conclusions: Budesonide is a highly effective and well tolerated treatment of collagenous colitis. There is a high risk of relapse after stopping eight weeks of treatment.

Article first published online 19 May 2015.