Colitis is an inflammation of the lining of the colon (large intestine) that can cause chronic diarrhea. There is a myriad of reasons why colitis may occur, including infection with bacteria, viruses, parasites, Crohn’s Disease and ulcerative colitis. Among the variations of colitis, microscopic colitis is unique. A routine colonoscopy may reveal a normal looking lining of the colon, yet under the light of a microscope, the biopsies will show inflammation. Similarly, Irritable Bowel Syndrome can cause chronic diarrhea and a colonoscopy will reveal a normal looking lining of the colon, and the biopsies of the colon will be normal. For these reasons, IBS is not considered a type of colitis.
There are two types of microscopic colitis. One is collagenous colitis in which there is an abnormal layer of protein (collagen). The other is lymphocytic colitis where instead of the collagen layer, you find white blood cells (lymphocytes) underneath the lining of the colon. They both have very similar presentations, symptoms and treatments.
The best test to diagnose microscopic colitis is a colonoscopy with biopsies of the right and left colon. There are two types of procedures by which the colon is evaluated: a colonoscopy and a sigmoidoscopy. A colonoscopy is the complete evaluation of the entire colon, while a sigmoidoscopy is a simpler procedure that only looks at the last 1/3 of the colon. The physician is more likely to find abnormalities through a colonoscopy than through a sigmoidoscopy. Thus, a colonoscopy is the preferred diagnostic procedure.
It’s not clear exactly why microscopic colitis develops, but there’s very likely more than one reason. Certain drugs such as nonsteroidal anti-inflammatory drugs (NSAIDS: ibuprofen, naprosyn), SSRI type antidepressants, and antacids such as the PPI’s (omeprazole, lansoprazole, pantoprazole, etc.) may trigger or worsen microscopic colitis. Genetic predisposition also has been implicated as the cause of microscopic colitis. There may also be an increased incidence of microscopic colitis in patients with celiac disease. The typical case of microscopic colitis is a middle aged woman with gradual onset of chronic, non-bloody, watery diarrhea that persists over months to years. It may worsen with the hormonal imbalance that happens during menopause. The chances of getting microscopic colitis increase if the patient is female, older than 50 years, smoking (past or present), on medications that have been linked to the disease and is suffering from an autoimmune disease (type 1 diabetes, autoimmune thyroiditis).
There is no evidence that microscopic colitis leads to an increase risk of colon cancer, as with ulcerative colitis. The clinical course of microscopic colitis is not as aggressive as Crohn’s Disease and ulcerative colitis. Management of microscopic colitis includes lifestyle changes aimed at reducing the diarrhea and discontinuing drugs like Nsaids and PPi’s. Dietary recommendations include reducing the amount of caffeine, lactose and fat in the diet. In many cases, treatment with antidiarrheal medications is necessary. Loperamide, Bismuth (Pepto Bismol), bulking agents like psyllium, or bile acid binding resins like cholestyramine are commonly used in the treatment of microscopic colitis. In more severe cases of diarrhea, corticosteroids can be used as treatment. Corticosteroids are medications that decrease inflammation and reduce the activity of the immune system. However, these medications can have many side effects. Budesonide, is a type of corticosteroid that is considered to be safer with fewer side effects, than others such as prednisone. Therefore, this is the treatment of choice.
So, if you or someone you know suffers from diarrhea that has lasted for weeks, please contact your gastroenterologist for further evaluation and management. Microscopic colitis is a chronic condition with symptoms that may come and go intermittently and cannot be diagnosed with blood tests or stool studies. In order to diagnose microscopic colitis, a physician must obtain a biopsy from the colon. In most cases, it can be easily treated and symptoms managed so patients can function normally.
1.Incidence, Prevalence, and Temporal Trends of Microscopic Colitis: A Systematic Review and Meta-Analysis. Tong J, Zheng Q, et al: Am J Gastroenterol; 2015;110 (February): 265-276.
2.Nguyen GC, Smalley WE, Vege SS, Carrasco-Labra A, Clinical Guidelines Committee. American Gastroenterological Association Institute guideline on the medical management of microscopic colitis. Gastroenterology. 2016 Jan;150(1):242-6.