Microscopic colitis is an inflammatory bowel disease in which chronic watery diarrhea is the leading symptom. This condition affects the colon and rectum, and has two forms: collagenous colitis and lymphocytic colitis.
Definition & Facts
This disorder is called "microscopic" because doctors must take multiple colonic biopsies and examine tissues under a microscope for diagnosis. Colonoscopic appearances are normal in most patients. Approximately two out of every 10,000 people may develop this condition each year.
Health care professionals use the term microscopic colitis to describe both lymphocytic colitis and collagenous colitis because the symptoms and treatment options for each respective form of the disease are similar. Some experts claim that lymphocytic colitis and collagenous colitis are different phases of the same disorder rather than separate problems.
This condition occurs in the large bowel, which is the last part of the digestive tract. Unlike other types of colitis, it cannot be diagnosed with a colonoscopy or flexible sigmoidoscopy. Ischemic colitis, radiation proctitis, infectious colitis, and ulcerative colitis all trigger inflammation and visible abnormalities of the lining of the colon.
Microscopic colitis is responsible for over 13 percent of all cases of unexplained abdominal bloating and diarrhea. Since the colon lining is not ulcerated, the stool does not contain pus or blood. Compared to other inflammatory bowel diseases, this condition does not increase the risk of cancer and rarely requires surgery. Eating or avoiding certain foods can help relieve digestive discomfort and reduce inflammation in the colon.
Patients can experience as many as 20 bowel movements a day. Like other inflammatory disorders, microscopic colitis causes irritation and swelling in the gut. Most individuals diagnosed with this condition require a combination of anti-diarrheal and nonsteroidal anti-inflammatory drugs, antibiotics, and dietary changes.
Symptoms & Complaints
Other common symptoms include unexplained weight loss, nausea, abdominal pain, fecal incontinence (loss of bowel movement control), and nutritional deficiencies. Diarrhea occurs when the excess collagen and inflammation in the bowel interfere with absorption of water from the colon. For this reason, individuals suffering from microscopic colitis may become dehydrated. Their symptoms can come and go frequently. This inflammatory disorder may also cause:
- Loose stool
- Severe bloating
- Bile acid malabsorption
- Altered small bowel dysfunction
- Five to 20 watery bowel movements per day
- Enteropathic arthritis
- Passing little to no urine
- Rectal bleeding
- Stomach cramps
Both forms of the disease are characterized by diarrhea, which can be continuous or episodic. Approximately seven percent of patients develop enteropathic arthritis affecting one or several joints. About 17 to 40 percent of individuals with microscopic colitis suffer from other immune-related disorders, such as celiac disease, giant-cell arteritis, Sjögren’s syndrome, myasthenia gravis, thyroiditis, and rheumatoid arthritis.
The disorder typically affects middle-aged patients, but can affect children and young adults too. Its cause is unknown. Research indicates that microscopic colitis might be of autoimmune origin. Women have a higher risk of microscopic colitis than men.
Only a limited number of familial cases have been reported. It is estimated that up to 12 percent of patients have a family history of inflammatory bowel diseases. Most patients have a high rate of matrix metallopeptidase 9 gene polymorphisms and tumor necrosis factor alpha.
Some experts suggest that microscopic colitis may be also caused by hormonal factors, which explains its occurrence in middle-aged women. Studies have found that smoking and alcohol consumption can increase the risk of developing this condition. Patients who smoke contract microscopic colitis about 10 years earlier than non-smokers. This disease is also more common in people with lung cancer.
Certain drugs can lead to the development of microscopic colitis. These include antipsychotics, antidepressants, proton-pump inhibitors, aspirin, ranitidine, and nonsteroidal anti-inflammatory drugs. These medications can kill the good bacteria in the gut (gut flora).
Other possible causes are bile acid malabsorption, infection of the gastrointestinal tract (viral gastroenteritis and bacterial gastroenteritis), Clostridium difficile colitis, altered epithelial barrier function, and abnormal collagen metabolism.
The symptoms of microscopic colitis are largely due to the inflammatory process and high levels of immunoreactive, prostaglandin E2.
Diagnosis & Tests
This inflammatory condition is diagnosed by using a microscope to examine tissue samples taken from the lining of the colon. During a colonoscopy or flexible sigmoidoscopy, the doctor may perform a biopsy, extracting tissue for laboratory analysis. Tissue samples should be obtained from the right side of the colon. Laboratory and radiographic tests may be needed to rule out differential diagnoses like inflammatory bowel syndrome, ulcerative colitis, infectious colitis, and Crohn’s disease.
The doctor will assess the patient's risk factors and medical history. The diagnostic procedures used for identifying microscopic colitis are minimally invasive. A full colonoscopy and routine stool cultures are recommended. Most patients also present increased levels of inflammatory markers in the stool, which tests like erythrocyte sedimentation rate test can help detect.
Treatment & Therapy
There is no permanent cure for microscopic colitis. Treatment aims to improve the patient's quality of life and achieve clinical remission. Celiac disease and other associated conditions should be appropriately managed. Patients are advised to quit smoking and avoid alcohol.
Eating smaller meals throughout the day and avoiding inflammatory foods may help relieve symptoms. Anti-diarrheal medications, anti-inflammatory drugs, and corticosteroids are almost always effective in treating this condition. The doctor may also prescribe immunomodulators, antibiotics, cholestyramine resin, or anti-TNF therapies to improve digestive function and block bile acids. Patients who continue to have relapses may need long-term treatment.
Prevention & Prophylaxis
Gluten, refined sugar, hydrogenated fats, additives, and food chemicals affect digestion and interfere with the gut flora, which may increase the risk of developing microscopic colitis. Certain foods, such as milk, cheese, deli meats, beans, and wheat, irritate the digestive tract and cause inflammation. Daily probiotic supplements can help restore and maintain the microbiome.