Microscopic colitis is an inflammatory condition of the large intestine, or colon. Its name reflects that the inflammation is only visible when colon tissue is viewed under a microscope, as the intestinal lining appears normal to the naked eye. The condition leads to persistent, watery diarrhea and may flare up and then subside, with symptoms that come and go.
Symptoms and Types of Microscopic Colitis
The defining symptom of microscopic colitis is chronic, watery, and non-bloody diarrhea. Individuals with the condition may experience five to ten bowel movements a day, which can disrupt daily life and even cause symptoms at night. This frequent diarrhea is often accompanied by abdominal cramping or pain, bloating, and a sudden urgency to use the restroom. In some instances, people may have difficulty controlling their bowels, leading to fecal incontinence.
There are two main types, distinguished only by their microscopic appearance. The first is lymphocytic colitis, which is identified by an increased number of white blood cells, called lymphocytes, within the lining of the colon. The second type is collagenous colitis. This form is characterized by the presence of a thickened layer of collagen just beneath the surface lining of the colon. While the underlying cellular differences are distinct, the patient’s experience with symptoms is nearly identical for both types.
Potential Causes and Risk Factors
While the precise cause of microscopic colitis remains unknown, several factors are associated with its development. Certain medications are strongly linked to the condition. Non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and aspirin, are common triggers. Other medications implicated include proton pump inhibitors (PPIs) used for heartburn, some antidepressants known as selective serotonin reuptake inhibitors (SSRIs), and statins.
The condition also appears to have a connection with autoimmune disorders. People with conditions like celiac disease, thyroid disorders, rheumatoid arthritis, and Sjögren’s syndrome have a higher incidence of microscopic colitis. This suggests that a misdirected immune response in the digestive tract could play a part in the inflammation.
Several demographic and lifestyle factors increase the risk of developing microscopic colitis. The condition is most commonly diagnosed in individuals over the age of 50, and it is more prevalent in women than in men. Cigarette smoking has also been identified as a significant risk factor.
The Diagnostic Process
Diagnosing microscopic colitis is challenging because the colon’s interior lining appears normal during a standard colonoscopy, so inflammation cannot be confirmed by observation alone. A patient’s reported symptoms, especially chronic watery diarrhea, will lead a physician to suspect the condition.
A definitive diagnosis requires collecting tissue samples from the colon, a procedure known as a biopsy. During the colonoscopy, a gastroenterologist will use a special instrument to take several small pieces of tissue from different areas of the colon wall.
Once the tissue samples are collected, they are sent to a laboratory where a pathologist examines them under a microscope. The diagnosis is confirmed by looking for the specific cellular changes that define either lymphocytic or collagenous colitis.
Management and Treatment Approaches
Treatment for microscopic colitis often begins with identifying and eliminating potential triggers. If a medication is suspected of causing the flare-up, a doctor may advise stopping it. Dietary adjustments can also provide relief. Common recommendations include avoiding caffeine, alcohol, and foods that are high in fat. For some, limiting dairy or gluten may also help reduce symptoms. Maintaining proper hydration is also important due to the fluid loss from chronic diarrhea.
When lifestyle changes are not enough to control symptoms, medications are often prescribed. An initial approach may involve anti-diarrheal agents like loperamide or bismuth subsalicylate to manage the frequency of bowel movements.
For more persistent symptoms, the most common and effective medical treatment is a corticosteroid called budesonide. This medication is designed to target the gut directly, which reduces inflammation in the colon with fewer side effects throughout the body compared to other steroids. In cases where these treatments are not effective, a doctor might consider prescribing medications that suppress the immune system, such as azathioprine. The goal of treatment is to bring the condition into remission.