This Sunday, we bring to you The United European Gastroenterology (UEG) and the European Microscopic Colitis Group (EMCG) recommendations on the clinical management of microscopic colitis (MC). Oral budesonide is the drug of choice to induce and maintain remission in patients with MC. In patients who fail to respond to budesonide, thiopurines, anti-tumor necrosis factor drugs or vedolizumab can be used.

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Microscopic colitis (MC) has emerged as a common cause of chronic non-bloody diarrhoea. Pathogenesis of MC is complex and depends on numerous factors such as luminal factors, immune dysregulation and genetic predisposition.

MC follows a variable clinical course, with chronic or recurrent mild to severe symptoms persisting for months to years. The two most frequent forms of MC are collagenous colitis (CC) and lymphocytic colitis (LC); however, there also exists an incomplete form termed incomplete MC [MCi].

The United European Gastroenterology (UEG) and the European Microscopic Colitis Group (EMCG) recently released the recommendations on the clinical management of MC. The guidelines cover information on risk factors, diagnostic criteria and treatment options for microscopic colitis. Herewith, we provide a summary of the key recommendations from the guideline.

Risk factors for MC

1. Former, but particularly current smokers have an increased risk for both CC and LC.
2. Gender plays a key role in MC development - women are at an increased risk of developing CC or LC than men. The proportion of females among MC populations has been estimated to be in the range of 52% to 86%.
3. Chronic or frequent use of proton pump inhibitors (PPIs), non-steroidal anti-inflammatory drugs (NSAIDs) or selective serotonin reuptake inhibitors (SSRIs) is associated with an increased risk of MC. However, this does not suggest a causal relationship.
4. Drugs with a suspected chronological relationship between drug introduction and onset of diarrhoea should be withdrawn.
5. MC does not increase the risk of colorectal cancer or adenoma. A special surveillance colonoscopy program is not recommended.

Clinical manifestation- What are the most common symptoms in MC?

Chronic watery, non-bloody diarrhoea is the most common symptom in MC. Watery, non-bloody diarrhoea is reported by around 84–100% of patients. Faecal urgency, nocturnal stools and faecal incontinence are other symptoms which may accompany diarrhoea.

The symptoms and endoscopic results of MC may mimic those observed with functional bowel disorders such as diarrhoea-dominant irritable bowel syndrome and chronic, functional diarrhoea. Hence, MC diagnosis should be ruled out in patients fulfilling the criteria for functional bowel disease. This point holds special significance in the presence of MC risk factors and/or in absence of IBS (irritable bowel syndrome)-therapy response.

Metrics to measure disease activity and clinical remission in MC

In the absence of a formally validated metric of disease activity, disease activity and clinical remission in MC should be assessed by the Hjortswang criteria (clinical remission: mean of <3 stools per day and a mean <1 watery stool per day during a 1-week registration).

Histological diagnosis- Endoscopic appearance of MC

Even though endoscopic findings are found with increased frequency in patients with MC; they are non-specific.

1. Criteria for the histological diagnosis of CC- The histopathologic criteria of CC are a thickened subepithelial collagenous band ≥10 µm combined with an increased inflammatory infiltrate in the lamina propria. The criteria apply to haematoxylin and eosin (HE)-stained slides.
2. Criteria for the histological diagnosis of LC- The histopathologic criteria (HE-stained slides) of LC are an increased number of IELs ≥20 per 100 surface epithelial cells combined with an increased inflammatory infiltrate in the lamina propria and a not significantly thickened collagenous band (<10 µm).
3. Criteria for the histological diagnosis of MCi- MCi comprises incomplete CC (CCi; defined by a thickened subepithelial collagenous band >5 µm but <10 µm) and incomplete LC (LCi; defined by >10 IELs but <20 IELs and a normal collagenous band). Both types show a mild inflammatory infiltrate in the lamina propria. The criteria apply to HE-stained slides.

Other recommendations for diagnosis

• In patients with suspected MC, ileocolonoscopy with biopsies should be taken from at least the right and left side of the colon
• In patients with MC, histological monitoring is not recommended
• Faecal calprotectin is not useful to exclude or monitor MC
• Patients with MC should be screened for coeliac disease
• Testing for bile acid diarrhoea is not part of routine diagnostic work-up in patients with MC; however, in patients experiencing nonresponse to budesonide treatment, bile acid diarrhea should be tested

Treatment recommendations for MC

1. Oral budesonide is recommended to induce remission in patients with CC and LC.
   1. Oral budesonide is recommended to maintain remission in patients with CC
   2. Oral budesonide is suggested to maintain remission in patients with LC
2. The use of budesonide in MC is not associated with an increased risk of serious adverse events. The risk of osteoporotic bone fractures seems not to be increased in budesonide-treated MC patients, however, the prolonged use of budesonide might be associated with a decrease of bone mineral density. In case of long-term budesonide treatment, supplementation with calcium/vitamin D and monitoring of bone mineral density may be considered.
3. Mesalazine is not recommended in patients with MC for induction of remission.
4. There is lack of evidence to recommend loperamide and bismuth subsalicylate in patients with MC. However, due to its documented effect in patients with chronic diarrhoea, loperamide may be used in mild disease.
5. Bile acid binders are suggested in patients with MC and bile acid diarrhoea.
6. Due to the lack of enough evidence, antibiotics are not recommended for the treatment of MC.
7. The use of prednisolone or other corticosteroids than budesonide is not recommended for the treatment of MC. The use of probiotics is also not recommended.
8. In patients who fail to respond to budesonide (to induce and maintain clinical remission), thiopurines, anti-tumour necrosis factor (anti-TNF) drugs, or vedolizumab are recommended.
9. Surgery can be considered as the last resort (in selected patients) if all therapies fail.

This article was originally published on September 29, 2020.