Collagenous colitis is a type of inflammatory bowel disease that affects the colon. This condition involves inflammation within the large intestine, leading to various digestive issues. A primary symptom is chronic watery diarrhea.
The condition is considered a form of microscopic colitis, meaning its characteristics are only identifiable when colon tissue is examined under a microscope. This differentiates it from other inflammatory bowel diseases, where inflammation may be visible during a standard colonoscopy. Understanding this microscopic aspect is key to diagnosing and managing collagenous colitis.
Understanding Collagenous Colitis
Collagenous colitis is a distinct inflammatory condition of the colon, classified as a type of microscopic colitis. Its unique diagnostic characteristic is that inflammation is not visible during a typical colonoscopy; a definitive diagnosis requires microscopic examination of colon tissue samples.
The distinguishing feature of collagenous colitis under the microscope is an abnormally thickened layer of collagen located beneath the lining of the colon. This thickened collagen band contrasts with lymphocytic colitis, another form of microscopic colitis, which shows an increased number of white blood cells called lymphocytes in the colon lining. While both conditions share similar symptoms and treatments, specific microscopic changes differentiate them. Unlike Crohn’s disease or ulcerative colitis, collagenous colitis does not cause macroscopic changes to the colon or increase the risk of colon cancer.
How Common is Collagenous Colitis
Collagenous colitis is uncommon, though it is the most frequent subtype of microscopic colitis. Incidence rates vary across studies and regions, ranging from approximately 2 to 12.2 cases per 100,000 people per year. Prevalence rates have been reported between 39.3 and 116.7 per 100,000 persons.
The condition is more frequently diagnosed in older adults, with the average age of diagnosis often in the 60s, and a peak in incidence observed in women aged 80 or older. Women are more commonly affected than men, with female-to-male ratios ranging from 2:1 to 8:1 in various studies. While cases can occur in all age groups, including children, they are rare in younger populations. Some epidemiological studies have indicated an increase in diagnosed cases of microscopic colitis, including collagenous colitis, over recent decades.
Symptoms and Diagnosis
The primary symptom of collagenous colitis is chronic, watery diarrhea, often occurring frequently, sometimes up to five to ten times daily. This diarrhea is non-bloody, distinguishing it from other types of colitis that may involve rectal bleeding. Many individuals experience additional symptoms, including abdominal pain, cramping, bloating, nausea, fatigue, and unintended weight loss.
Diagnosing collagenous colitis requires a specific approach because the colon appears normal during a standard colonoscopy. To confirm the diagnosis, a gastroenterologist performs a colonoscopy and takes multiple tissue samples from different sections of the colon. These samples are then sent to a pathologist, who examines them under a microscope. The presence of a thickened sub-epithelial collagen layer, typically 10 micrometers or more, along with increased inflammatory cells in the colon lining, confirms a diagnosis of collagenous colitis.
Managing Collagenous Colitis
The cause of collagenous colitis is often unknown, but it may involve an abnormal immune response within the gastrointestinal tract. Potential triggers include certain bacterial infections, such as Clostridium difficile or Campylobacter jejuni, or viral infections. Certain medications are also associated with its development, including nonsteroidal anti-inflammatory drugs (NSAIDs), proton pump inhibitors (PPIs), selective serotonin reuptake inhibitors (SSRIs), and some medications for high blood pressure or cholesterol.
Management of collagenous colitis is individualized and often begins with dietary adjustments and medication. Dietary changes involve avoiding common triggers like dairy products, gluten, artificial sweeteners, caffeine, and alcohol, as these can worsen diarrhea symptoms. Medication options include anti-diarrheal agents such as loperamide or bismuth subsalicylate to manage symptoms. Corticosteroids, particularly budesonide, are used to reduce inflammation in the colon and are a first-line therapy. In more severe or unresponsive cases, other medications like mesalamine, sulfasalazine, immunomodulators, and anti-TNF therapies may be considered.