From the Guidelines
Microscopic colitis causes chronic watery diarrhea, abdominal pain, and fatigue due to inflammation of the colon's lining that is only visible under a microscope. There are two main types: lymphocytic colitis and collagenous colitis, both characterized by increased inflammatory cells in the colon tissue. The exact cause remains unknown, but several factors likely contribute, including autoimmune responses, medications (particularly NSAIDs, PPIs, and certain antidepressants), bacterial or viral infections, genetic predisposition, and bile acid malabsorption, as noted in the 2018 guidelines for the investigation of chronic diarrhoea in adults by the British Society of Gastroenterology 1. The condition is more common in older adults, particularly women over 50, and may be associated with other autoimmune disorders like celiac disease, rheumatoid arthritis, and thyroid disorders, with a prevalence of microscopic colitis ranging from about 50 to 200/100 000, as reported in the same guidelines 1. While not life-threatening, microscopic colitis significantly impacts quality of life through persistent diarrhea, which can lead to dehydration, electrolyte imbalances, and weight loss if left untreated, as highlighted in the American Gastroenterological Association Institute guideline on the medical management of microscopic colitis 1. The inflammation disrupts normal fluid absorption in the colon, resulting in the characteristic watery diarrhea that defines this condition. Key points to consider include:
- The clinical presentation and risk factors for microscopic colitis, as reviewed in the 2018 guidelines 1
- The importance of colonoscopy with biopsies of multiple segments of the colon for diagnosis, as recommended in the American Gastroenterological Association Institute guideline 1
- The potential for coexisting causes of chronic diarrhea, such as celiac disease, and the need to consider these in patients with refractory symptoms, as noted in the same guideline 1. The goal of medical therapy is to relieve symptoms and improve quality of life while minimizing drug-related adverse effects, as stated in the American Gastroenterological Association Institute guideline 1.
From the Research
Causes and Risk Factors of Microscopic Colitis
- Microscopic colitis (MC) is an inflammatory disease of the colon and a common cause of chronic watery diarrhea, predominantly in older patients 2.
- The disease encompasses 2 different subtypes, lymphocytic colitis and collagenous colitis, with the colon typically appearing normal endoscopically in MC, and the diagnosis requiring histologic evaluation 2, 3.
- Risk factors for MC include increasing age, female sex, presence of other autoimmune diseases, and possibly the use of certain medications, such as proton pump inhibitors, nonsteroidal anti-inflammatory drugs, selective serotonin reuptake inhibitors, and statins 2.
Clinical Presentation of Microscopic Colitis
- The clinical presentation of MC is nonspecific and includes watery nonbloody diarrhea, nocturnal stools, fecal urgency, abdominal pain, arthralgias, and weight loss 2, 3.
- The disease course of MC is variable, with some patients experiencing occasional, intermittent symptoms, and others demonstrating more chronic and even progressive symptoms 2.
Treatment and Management of Microscopic Colitis
- The approach to treatment is similar for both lymphocytic colitis and collagenous colitis and should be guided by the severity of the patient's symptoms 2, 4.
- Offending medications highly associated with MC should be eliminated as clinically possible, and in patients with mild symptoms, antidiarrheals such as loperamide are the initial choice 2.
- For moderate-severe disease, budesonide is recommended for induction of clinical remission, and in those with recurrent symptoms, low-dose budesonide may be required for maintenance therapy with close monitoring for potential adverse effects 2, 4, 5.