Collagenous Colitis

Collagenous colitis is a microscopic colitis, a type of inflammatory bowel disease (IBD) characterized by chronic watery diarrhea. Unlike other forms of IBD like Crohn’s disease or ulcerative colitis, which cause visible inflammation of the bowel lining, collagenous colitis gets its name from a characteristic thickened layer of collagen that develops beneath the lining of the colon, which can only be seen under a microscope during a biopsy. This thickening, along with inflammation, impairs the colon’s ability to absorb water, leading to persistent diarrhea. It is a relatively uncommon condition, primarily affecting middle-aged and older adults, particularly women.

Causes:

The exact cause of collagenous colitis is unknown, but it is believed to involve a combination of genetic predisposition, immune system dysfunction, and environmental factors. It’s thought to be an autoimmune or inflammatory response to something in the colon.

• Immune System Dysregulation:
  • The immune system may mistakenly attack the healthy cells in the colon lining, leading to inflammation and the deposition of collagen.
  • This suggests an autoimmune component, as collagenous colitis is often associated with other autoimmune diseases.
• Genetic Factors: While not as strongly linked as in Crohn’s or ulcerative colitis, there may be a genetic susceptibility in some individuals.
• Medications:
  • This is a well-established cause. Several medications have been linked to collagenous colitis, most notably:
    • NSAIDs (Nonsteroidal Anti-inflammatory Drugs): Such as ibuprofen, naproxen, aspirin.
    • Proton Pump Inhibitors (PPIs): Such as omeprazole, lansoprazole, esomeprazole (used for acid reflux).
    • SSRIs (Selective Serotonin Reuptake Inhibitors): Certain antidepressants.
    • Statins: Cholesterol-lowering drugs.
    • Ranitidine: An H2 blocker.
  • Symptoms often improve or resolve when the offending medication is stopped.
• Bile Acid Malabsorption: Some theories suggest that an excess of bile acids reaching the colon may contribute to inflammation and collagen deposition.
• Bacterial Toxins or Viral Infections: While not definitive, some researchers believe certain infections could trigger the immune response in predisposed individuals.
• Smoking: Studies suggest that smoking may increase the risk of developing collagenous colitis.
• Associated Autoimmune Diseases: People with collagenous colitis often have other autoimmune conditions, such as:
  • Celiac disease.
  • Autoimmune thyroid disease (e.g., Hashimoto’s thyroiditis).
  • Rheumatoid arthritis.
  • Type 1 diabetes.

Symptoms:

The hallmark symptom of collagenous colitis is chronic, non-bloody watery diarrhea. Other symptoms are generally related to this persistent bowel disturbance.

• Chronic Watery Diarrhea:
  • The most common and often debilitating symptom. Can be severe and frequent (5-15 or more loose, watery stools per day).
  • Typically non-bloody.
  • Often occurs day and night.
• Abdominal Pain and Cramping: Often relieved after a bowel movement.
• Abdominal Bloating and Gas.
• Urgent Need to Defecate.
• Fecal Incontinence: Due to urgency and frequent loose stools.
• Weight Loss: Can occur due to fluid loss and sometimes poor absorption.
• Dehydration.
• Fatigue.
• Nausea.

Diagnosis:

Diagnosis of collagenous colitis cannot be made based on symptoms alone, as they overlap with other conditions like irritable bowel syndrome (IBS). A colonoscopy with biopsies is essential for definitive diagnosis.

• Medical History and Physical Exam: The doctor will ask about symptoms, their duration, frequency, and severity, as well as medication use and any family history.
• Blood Tests: Generally normal, but may be done to rule out other conditions or check for electrolyte imbalances due to chronic diarrhea. Inflammatory markers (ESR, CRP) are typically normal or only slightly elevated, unlike other IBDs.
• Stool Tests: To rule out infectious causes of diarrhea (e.g., bacteria, viruses, parasites). Fecal calprotectin, an inflammatory marker in stool, is usually normal or mildly elevated, helping distinguish from Crohn’s or ulcerative colitis.
• Colonoscopy with Biopsies:
  • This is the definitive diagnostic test. The colon lining often appears normal or only subtly inflamed during a colonoscopy, which is why biopsies are crucial.
  • Multiple tissue samples are taken from different parts of the colon.
  • Under a microscope, the pathologist observes the characteristic thickened sub-epithelial collagen band and signs of chronic inflammation in the lamina propria.

Treatment:

Treatment for collagenous colitis aims to reduce inflammation, control diarrhea, and improve quality of life. It often involves identifying and removing triggers, followed by medications.

• Identify and Remove Triggering Medications:
  • If a medication (especially NSAIDs or PPIs) is suspected, stopping it is often the first and most effective step. Symptoms may resolve within weeks after discontinuation.
• Anti-Diarrheal Medications:
  • Loperamide (Imodium): Can help reduce the frequency and urgency of bowel movements.
  • Bismuth Subsalicylate (e.g., Pepto-Bismol): May help bind toxins and reduce diarrhea.
• Corticosteroids:
  • Budesonide (Entocort EC): A common first-line treatment. It’s a corticosteroid that acts locally in the gut with less systemic absorption, reducing side effects compared to traditional steroids like prednisone. Highly effective for inducing remission.
  • Prednisone: May be used for severe flares but less commonly due to systemic side effects with long-term use.
• Bile Acid Sequestrants:
  • Cholestyramine, Colestipol, Colesevelam: If bile acid malabsorption is suspected or confirmed. These medications bind bile acids in the intestine, preventing them from irritating the colon.
• Immunomodulators:
  • (e.g., azathioprine, mercaptopurine) Rarely used for severe, refractory cases that don’t respond to other treatments.
• Biologics: (e.g., infliximab, adalimumab) Very rarely considered for severe, refractory cases, typically if microscopic colitis features overlap with other IBD.
• Dietary Modifications:
  • While not a cause, some individuals find temporary relief by avoiding certain foods that can worsen diarrhea, such as caffeine, dairy (if lactose intolerant), artificial sweeteners, or high-fiber foods during flares.
  • A balanced diet is encouraged.
• Surgery:
  • Extremely rare for collagenous colitis. May be considered as a last resort in very severe, refractory cases causing debilitating symptoms unresponsive to all medical therapies.
  • Involves removing part or all of the colon.

Most individuals with collagenous colitis respond well to treatment, especially budesonide, and can achieve long-term remission. Ongoing management with a gastroenterologist is important.