Microscopic colitis is a common cause of chronic watery diarrhea, especially in adults aged 60 and older1 . This inflammatory condition affects the colon but often appears normal during colonoscopy, requiring microscopic examination of tissue samples for diagnosis1 . Although it can significantly impair quality of life due to symptoms like urgency and fecal incontinence, microscopic colitis does not increase the risk of colorectal cancer or reduce life expectancy2 3.
Types of Microscopic Colitis
Microscopic colitis is an inflammatory bowel disease characterized by inflammation of the colon lining that can only be seen under a microscope4 . It primarily includes two subtypes: lymphocytic colitis and collagenous colitis5 4.
Lymphocytic Colitis
Lymphocytic colitis (LC) is defined by an increased number of intraepithelial lymphocytes (white blood cells) in the colon lining, typically 20 or more per 100 epithelial cells, compared to fewer than 5 in normal tissue6 3. Some patients may also show a mildly thickened collagen layer beneath the surface lining7 . The inflammation in LC causes chronic watery diarrhea and other symptoms similar to collagenous colitis7 .
Collagenous Colitis
Collagenous colitis (CC) is characterized by a thickened subepithelial collagen band greater than 10 micrometers, whereas the normal collagen layer is about 3-4 micrometers thick7 3. Although CC may also show increased intraepithelial lymphocytes, this is usually less pronounced than in LC7 . Clinically, CC presents similarly to LC with chronic watery diarrhea and related symptoms7 .
Both subtypes share similar clinical presentations and treatment approaches despite their distinct microscopic features7 .
Symptoms of Microscopic Colitis
The hallmark symptom of microscopic colitis is chronic, watery, non-bloody diarrhea, which can range from 3 to over 10 watery stools per day during active phases3 89. Symptoms may develop gradually or appear suddenly and often follow a relapsing-remitting pattern with symptom-free intervals10 8.
Other common symptoms include:
- Abdominal pain, cramps, and bloating9
- Fecal urgency and incontinence, which can significantly impair quality of life3 82
- Weight loss and dehydration in severe or prolonged cases11
- Nocturnal diarrhea and urgency to have bowel movements9
- Occasional extraintestinal manifestations such as ocular symptoms12
Microscopic colitis symptoms can fluctuate, with periods of remission and flare-ups triggered by various factors13 .
Microscopic colitis causes inflammation of the large intestine, leading to frequent watery diarrhea and urgency. These symptoms can be disabling but are manageable with proper diagnosis and treatment11 2.
Causes and Risk Factors
Microscopic colitis is a multifactorial disease involving immune system dysfunction, genetic predisposition, and alterations in the gut microbiome14 . The exact cause remains unclear, but several contributing factors have been identified.
Abnormal Immune Response
An abnormal immune reaction targeting the colon lining is believed to drive the inflammation seen in microscopic colitis14 . This autoimmune component is supported by the frequent coexistence of microscopic colitis with other autoimmune diseases such as celiac disease, rheumatoid arthritis, and type 1 diabetes15 16. The immune dysregulation leads to infiltration of lymphocytes and collagen deposition in the colon mucosa14 .
Genetics
There is evidence for a genetic predisposition to microscopic colitis. Familial clustering of cases and genome-wide association studies have identified immune-related genetic loci linked to susceptibility17 18. A family history of other inflammatory bowel diseases may also increase risk, although this is still under investigation18 .
Gut Microbiome Imbalance
The intestinal microbiota, a complex ecosystem of microorganisms, plays a crucial role in maintaining gut health and immune balance14 . Dysbiosis—disruption of this microbial community—triggered by infections or medications may contribute to microscopic colitis development19 14. Research into microbiome changes in microscopic colitis is ongoing18 .
Risk Factors
Several risk factors increase the likelihood of developing microscopic colitis:
- Age: Most cases occur in individuals over 60 years old16 20
- Female sex: Particularly in collagenous colitis, women are more commonly affected21 6
- Autoimmune diseases: Presence of celiac disease, thyroid disorders, rheumatoid arthritis, and type 1 diabetes16
- Smoking: Tobacco use is associated with higher risk19 9
- Certain medications: Nonsteroidal anti-inflammatory drugs (NSAIDs), proton pump inhibitors (PPIs), selective serotonin reuptake inhibitors (SSRIs), statins, and others may trigger or worsen symptoms19 9
Microscopic colitis is more common in women over 60 and those with autoimmune diseases or a history of smoking. Medications such as NSAIDs and proton pump inhibitors can contribute to disease onset or flares16 199.
Diagnosis and Testing
Diagnosing microscopic colitis requires a thorough clinical evaluation and histological confirmation22 15. Because the colon often appears normal during endoscopy, tissue biopsies are essential.
The diagnostic process includes:
- Detailed symptom history focusing on diarrhea duration, frequency, and severity10
- Review of medical and family history, especially autoimmune conditions19
- Assessment of medication use and smoking status19
- Laboratory tests such as stool studies to exclude infections and blood tests to check for anemia or celiac disease10 23
- Colonoscopy with multiple biopsies from different colon segments for microscopic examination15 23
Histological features confirming microscopic colitis include increased intraepithelial lymphocytes in lymphocytic colitis and a thickened subepithelial collagen band in collagenous colitis7 15. The mucosa typically appears normal or shows subtle nonspecific changes on endoscopy20 15.
“Microscopic colitis is a common cause of diarrhea that affects a different subset of the population compared to inflammatory bowel disease. The colonoscopy can appear normal, but inflammation is present on biopsy samples.”
— Dejan Micic, MD, Loyola Medicine24
Treatment Options
Treatment of microscopic colitis aims to reduce inflammation, control diarrhea, and improve quality of life17 . Management often involves a combination of medications and lifestyle changes.
Medications
Pharmacologic therapy includes:
- Budesonide: A gut-targeted corticosteroid and first-line treatment, effective in inducing remission in most patients within 6-8 weeks25 1526. Maintenance therapy with low-dose budesonide may be needed for relapsing disease25 .
- Anti-diarrheal agents: Loperamide, diphenoxylate, and bismuth subsalicylate help reduce stool frequency and urgency17 27.
- Fiber supplements: Psyllium and other bulking agents thicken stool consistency and improve symptoms17 .
- Bile acid sequestrants: Cholestyramine and colestipol are used when bile acid malabsorption contributes to diarrhea17 23.
- Immunosuppressants and biologics: Reserved for refractory cases, including mercaptopurine, azathioprine, infliximab, and vedolizumab23 .
“Treatment often starts with oral budesonide, a steroid with 80-90% effectiveness early in the course. Unlike systemic steroids, budesonide targets the colon and has fewer systemic side effects such as bone thinning or increased blood pressure.”
— Dejan Micic, MD, Loyola Medicine24
Lifestyle Modifications
Dietary and lifestyle changes can help manage symptoms and reduce flare-ups:
- Identify and avoid individual food triggers such as caffeine, alcohol, dairy, gluten, and artificial sweeteners8 13.
- Consume smaller, more frequent meals to ease digestion8 .
- Limit fatty and fried foods to reduce diarrhea severity8 .
- Reduce high-fiber foods during flare-ups to minimize bowel irritation8 .
- Stay well-hydrated to prevent dehydration from diarrhea23 .
Professional guidance is recommended to develop personalized dietary plans and avoid nutritional deficiencies8 .
Prevention Strategies
Currently, there are no established methods to prevent microscopic colitis8 . However, symptom management through dietary modifications and avoiding known triggers may reduce flare frequency and severity8 .
Key preventive tips include:
- Keeping a food diary to identify and avoid personal dietary triggers8 .
- Limiting intake of caffeine-containing beverages and alcohol8 .
- Avoiding medications known to aggravate microscopic colitis when possible8 .
- Smoking cessation to reduce risk and improve outcomes19 .
Related Health Conditions
Microscopic colitis is strongly associated with other autoimmune and allergic diseases, suggesting shared genetic and environmental factors16 18.
Common related conditions include:
- Celiac disease: A strong link exists, with gluten ingestion causing immune-mediated injury in the small intestine16 .
- Autoimmune thyroid diseases: Both hypothyroidism and hyperthyroidism are more prevalent in microscopic colitis patients16 .
- Type 1 diabetes: Increased prevalence due to autoimmune destruction of pancreatic beta cells16 .
- Rheumatoid arthritis: Risk is approximately doubled, characterized by immune-mediated joint inflammation16 .
- Allergic conditions: Food allergies and allergic rhinitis are reported in a notable subset of patients16 .
These comorbidities highlight the importance of comprehensive evaluation and management in microscopic colitis patients12 16.
Living With Microscopic Colitis
Living with microscopic colitis can be challenging due to unpredictable symptoms and their impact on daily life3 . Patients often experience periods of remission interrupted by flare-ups triggered by diet, medications, or stress13 .
Key considerations for managing life with microscopic colitis include:
- Maintaining ongoing communication with healthcare providers to adjust treatment plans as needed16 .
- Recognizing and avoiding personal symptom triggers through diet and lifestyle changes8 .
- Understanding that most patients respond well to treatment and achieve symptom remission within weeks to months16 .
- Managing relapses effectively with medication re-initiation or adjustment16 .
- Knowing that microscopic colitis does not affect overall survival or increase colorectal cancer risk3 .
Microscopic colitis symptoms can impair quality of life, but with individualized treatment and lifestyle adjustments, most patients achieve good symptom control and maintain normal life expectancy16 3.
Frequently Asked Questions
Does microscopic colitis increase the risk of colon cancer?
No, unlike other inflammatory bowel diseases, microscopic colitis does not increase colorectal cancer risk3 .
Can microscopic colitis go away completely?
Microscopic colitis may enter remission for months or years but can relapse, especially if triggers are encountered13 .
How quickly do treatments work?
Most patients respond to budesonide within 6 to 8 weeks, with symptom improvement and remission25 .
Are probiotics recommended?
Current guidelines do not support probiotics for microscopic colitis due to insufficient evidence of benefit15 28.
When should I see a healthcare provider?
Any diarrhea lasting more than two weeks warrants evaluation to rule out microscopic colitis and other causes24 .
