Microscopic Colitis: Chronic Diarrhea Without Blood

What Is Microscopic Colitis?

Microscopic colitis is a type of inflammatory bowel disease that causes chronic watery diarrhea. The inflammation is only visible under a microscope, which is how the condition gets its name. There are two main types: collagenous colitis and lymphocytic colitis. Both types cause similar symptoms and are treated in the same way.

Microscopic colitis is characterized by inflammation in the lining of the large intestine (colon) that leads to persistent watery diarrhea. What makes this condition unique among inflammatory bowel diseases is that the colon appears completely normal during visual examination with a colonoscopy. The characteristic changes can only be detected when tissue samples (biopsies) are examined under a microscope - hence the name "microscopic" colitis.

The condition was first described in the 1970s, and our understanding of it has grown significantly since then. It is now recognized as one of the most common causes of chronic diarrhea, particularly in older adults. Studies suggest that microscopic colitis may be underdiagnosed because many patients and healthcare providers attribute symptoms to other conditions like irritable bowel syndrome (IBS).

Unlike ulcerative colitis and Crohn's disease, microscopic colitis does not cause visible ulcers or sores in the intestinal lining, and importantly, it does not increase the risk of colon cancer. However, the chronic diarrhea it causes can significantly impact quality of life, leading to social isolation, anxiety about incontinence, and difficulties with work and daily activities.

Two Types of Microscopic Colitis

Microscopic colitis is divided into two main subtypes based on what is seen under the microscope. While they share similar symptoms and treatments, the microscopic findings differ:

Collagenous colitis is characterized by a thickened band of collagen protein beneath the intestinal lining. Normally, this collagen layer is less than 7 micrometers thick, but in collagenous colitis, it increases to more than 10 micrometers and can be as thick as 60 micrometers. This type tends to be slightly more common in women.

Lymphocytic colitis shows an increased number of lymphocytes (a type of white blood cell) within the surface layer of the intestinal lining. To diagnose lymphocytic colitis, there must be more than 20 lymphocytes per 100 epithelial cells. Unlike collagenous colitis, there is no thickening of the collagen layer.

Some experts consider these two types to be part of the same disease spectrum, as patients can sometimes change from one type to another over time. A third subtype, called "incomplete microscopic colitis," describes cases that show some but not all of the characteristic features.

What Are the Symptoms of Microscopic Colitis?

The primary symptom of microscopic colitis is chronic, watery, non-bloody diarrhea that often starts suddenly and persists for weeks to months. Other common symptoms include abdominal pain or cramping that improves after bowel movements, urgency to have a bowel movement, nighttime diarrhea, fatigue, and sometimes weight loss.

Microscopic colitis typically begins suddenly, and symptoms can persist for extended periods - often weeks, months, or even years if left untreated. The severity of symptoms varies widely among patients; some experience mild inconvenience while others face debilitating symptoms that severely restrict their daily activities.

The hallmark symptom is chronic watery diarrhea without blood. Patients may experience anywhere from a few loose stools to more than ten watery bowel movements per day. Unlike inflammatory bowel diseases such as ulcerative colitis, there is typically no visible blood or mucus in the stool, which is an important distinguishing feature.

Common Symptoms

• Chronic watery diarrhea: The defining symptom, lasting more than 4 weeks, often many times per day including at night
• Urgency: A sudden, intense need to have a bowel movement, sometimes making it difficult to reach a toilet in time
• Abdominal pain and cramping: Usually improves after having a bowel movement
• Nocturnal symptoms: Diarrhea that wakes you from sleep, which is less common in IBS
• Fecal incontinence: Inability to control bowel movements, particularly concerning for patients
• Fatigue: Unexplained tiredness that may be related to dehydration or the chronic nature of the illness
• Weight loss: Can occur due to reduced food intake or malabsorption
• Bloating and gas: Some patients experience abdominal distension

Living with Microscopic Colitis

The unpredictable nature of symptoms can significantly impact quality of life. Many patients report anxiety about not being able to reach a bathroom in time, which can lead to avoiding social situations, limiting travel, and difficulty maintaining employment. The fear of incontinence, even when it rarely occurs, can be psychologically distressing.

Nighttime symptoms are particularly troublesome as they disrupt sleep, leading to daytime fatigue and reduced ability to function normally. Some patients describe feeling like their life revolves around knowing where the nearest bathroom is located.

What Causes Microscopic Colitis?

The exact cause of microscopic colitis is unknown, but it appears to result from an abnormal immune response in the colon lining. Several risk factors have been identified, including certain medications (NSAIDs, PPIs, SSRIs), smoking, autoimmune conditions, and gastrointestinal infections. Genetic factors may also play a role.

While the precise cause of microscopic colitis remains unclear, research has identified several factors that appear to contribute to its development. The condition likely results from a combination of genetic susceptibility, environmental triggers, and immune system abnormalities that lead to chronic inflammation in the colon lining.

Current understanding suggests that in susceptible individuals, various triggers can cause an inappropriate immune response in the intestinal mucosa. This leads to the characteristic inflammatory changes seen on microscopic examination - either the thickened collagen band of collagenous colitis or the increased lymphocyte infiltration of lymphocytic colitis.

Medications Associated with Microscopic Colitis

Several classes of medications have been linked to the development or worsening of microscopic colitis. It's important to note that these associations don't prove causation, and many patients develop the condition without any identifiable medication trigger:

• NSAIDs (Non-steroidal anti-inflammatory drugs): Medications like ibuprofen, naproxen, and aspirin are commonly implicated. These drugs can irritate the intestinal lining and may trigger inflammation
• Proton pump inhibitors (PPIs): Medications for acid reflux such as omeprazole, lansoprazole, and esomeprazole have been associated with increased risk
• Selective serotonin reuptake inhibitors (SSRIs): Some antidepressants may increase the risk of microscopic colitis
• Histamine H2-receptor antagonists: Medications like ranitidine have been linked to the condition
• Other medications: Statins, bisphosphonates, and certain antibiotics have also been reported as potential triggers

Other Risk Factors

Smoking is one of the strongest risk factors for microscopic colitis. Studies show that current smokers have a significantly higher risk of developing the condition compared to non-smokers, and smoking can worsen symptoms. Importantly, quitting smoking can help improve symptoms and reduce the risk of relapse.

Autoimmune conditions are frequently found alongside microscopic colitis. Patients may have celiac disease, thyroid disorders (Hashimoto's thyroiditis, Graves' disease), type 1 diabetes, rheumatoid arthritis, or other autoimmune conditions. This suggests that similar immune system abnormalities may underlie these conditions.

Gastrointestinal infections may sometimes trigger microscopic colitis, possibly by initiating an abnormal immune response that persists even after the infection clears.

Genetic factors likely play a role, as there appears to be some familial clustering of the disease. Certain genetic variants related to immune function may increase susceptibility.

How Is Microscopic Colitis Diagnosed?

Microscopic colitis can only be definitively diagnosed through colonoscopy with biopsies. During colonoscopy, the colon appears normal, but tissue samples examined under a microscope reveal characteristic inflammatory changes. Your doctor will also take a detailed medical history, perform a physical examination, and may order blood tests and stool samples to rule out other conditions.

Diagnosing microscopic colitis requires a systematic approach because the colon appears visually normal during endoscopic examination. This is why the condition is often missed or misdiagnosed as irritable bowel syndrome. The key to diagnosis is obtaining tissue biopsies during colonoscopy and having them examined by a pathologist.

Initial Evaluation

When you visit your doctor with chronic diarrhea, the evaluation typically begins with a detailed history about your symptoms: when they started, their frequency, associated factors, and how they affect your daily life. Your doctor will ask about your complete medication list, smoking history, family history of gastrointestinal diseases, and any other health conditions you may have.

A physical examination is performed, which may include gentle palpation of the abdomen to check for tenderness or masses. In most cases, the physical examination in microscopic colitis is unremarkable, but it helps rule out other conditions.

Laboratory Tests

Several laboratory tests may be ordered:

• Blood tests: Complete blood count, inflammatory markers (CRP, ESR), thyroid function tests, and celiac disease screening (tissue transglutaminase antibodies)
• Stool samples: To check for infections (bacterial, parasitic), blood, and inflammatory markers like fecal calprotectin

Colonoscopy with Biopsies

The definitive diagnostic test is colonoscopy with multiple biopsies taken from different areas of the colon. During this procedure:

• The colon is examined visually and typically appears completely normal (no ulcers, redness, or other visible abnormalities)
• Multiple tissue samples (biopsies) are taken from both the right and left side of the colon, as changes may not be uniform throughout
• The tissue samples are sent to a pathologist who examines them under a microscope

The pathologist looks for specific features depending on the type of microscopic colitis. In collagenous colitis, a thickened collagen band (greater than 10 micrometers) beneath the surface epithelium is diagnostic. In lymphocytic colitis, an increased number of lymphocytes (more than 20 per 100 epithelial cells) within the surface layer is the key finding.

Getting the Right Diagnosis

Reaching a correct diagnosis may take time. The process can involve ruling out other conditions that cause similar symptoms, including:

• Irritable bowel syndrome (IBS)
• Celiac disease
• Inflammatory bowel disease (ulcerative colitis, Crohn's disease)
• Bile acid malabsorption
• Infectious causes of diarrhea
• Small intestinal bacterial overgrowth (SIBO)

How Is Microscopic Colitis Treated?

Treatment for microscopic colitis depends on symptom severity. Mild cases may respond to dietary changes and stopping potential trigger medications. For moderate to severe symptoms, budesonide is the most effective treatment, achieving remission in 80-90% of patients. Anti-diarrheal medications like loperamide can help manage symptoms. Some patients require long-term or maintenance therapy.

The good news is that microscopic colitis responds well to treatment in most cases. The treatment approach is typically stepped, starting with simpler interventions and progressing to more intensive therapy if needed. The goal is to achieve remission (complete resolution of symptoms) while minimizing side effects.

First Steps: Lifestyle and Dietary Changes

Before or alongside medication, several lifestyle modifications can help:

Medication review: If you're taking any medications known to potentially trigger or worsen microscopic colitis (NSAIDs, PPIs, SSRIs), discuss with your doctor whether alternatives are available. Never stop prescribed medications without medical guidance.

Smoking cessation: If you smoke, quitting is one of the most important steps you can take. Smoking is associated with worse symptoms and increased risk of relapse. Healthcare providers can offer support and medications to help with quitting.

Dietary modifications: While no specific diet has been proven to treat microscopic colitis, many patients find certain foods worsen their symptoms. Common triggers include caffeine, alcohol, dairy products, artificial sweeteners, and high-fat foods. Keeping a food diary can help identify personal triggers.

Anti-Diarrheal Medications

For mild symptoms, over-the-counter anti-diarrheal medications may provide relief:

• Loperamide (Imodium): Slows intestinal movement and reduces stool frequency. Can be used as needed or regularly
• Bismuth subsalicylate (Pepto-Bismol): Has anti-inflammatory properties and may help some patients

These medications treat symptoms rather than the underlying inflammation, so they may not be sufficient for everyone.

Budesonide: The Primary Medical Treatment

Budesonide is a corticosteroid that works locally in the gut and is the most effective treatment for microscopic colitis. Unlike systemic steroids (like prednisone), budesonide is largely inactivated as it passes through the liver, resulting in fewer systemic side effects while still being effective in the intestines.

Studies show that budesonide achieves clinical remission in 80-90% of patients with microscopic colitis. The typical treatment course involves:

• Induction therapy: 9 mg daily for 6-8 weeks to achieve remission
• Tapering: Gradually reducing the dose over several weeks
• Maintenance therapy: Some patients require ongoing low-dose treatment (3-6 mg daily) to prevent relapse

Relapse after stopping budesonide is common, occurring in 60-80% of patients. For those who relapse, options include restarting budesonide or considering long-term maintenance therapy.

Treatment for Refractory Cases

For patients who don't respond adequately to budesonide or can't tolerate it, other options include:

• Bile acid binders: Cholestyramine may help, especially if bile acid malabsorption contributes to symptoms
• Immunomodulators: Azathioprine or methotrexate for those who don't respond to standard therapy
• Biologic medications: Anti-TNF drugs (like infliximab) or vedolizumab have been used in severe, refractory cases
• Surgery: Rarely needed, but creating an ileostomy or colectomy may be considered in the most severe cases that don't respond to any medication

What Can I Do to Manage Microscopic Colitis?

Self-care strategies can significantly help manage microscopic colitis symptoms. Key approaches include staying well-hydrated, identifying and avoiding food triggers, eating regular meals, quitting smoking, and using oral rehydration solutions during flares. Working with a dietitian can help develop a personalized eating plan.

While medical treatment is often necessary, there's much you can do to help manage your symptoms and maintain quality of life. These self-care strategies work best when combined with appropriate medical treatment.

Staying Hydrated

Chronic diarrhea can lead to dehydration and loss of electrolytes. It's crucial to maintain adequate fluid intake:

• Drink plenty of water throughout the day - aim for at least 8 glasses, more during flare-ups
• Use oral rehydration solutions during severe diarrhea episodes to replace lost electrolytes
• Monitor for signs of dehydration: dark urine, dry mouth, dizziness, fatigue
• Limit caffeine and alcohol as these can worsen dehydration and may trigger symptoms

Dietary Considerations

While there's no specific "microscopic colitis diet," many patients find that dietary modifications help:

• Keep a food diary: Track what you eat and your symptoms to identify personal triggers
• Eat regularly: Having consistent meal times can help regulate bowel function
• Common trigger foods to consider limiting: Caffeine, alcohol, dairy (if lactose intolerant), artificial sweeteners, high-fat foods, spicy foods
• Low-fat diet: Some studies suggest reducing fat intake may help
• Gluten-free diet: Some patients improve on a gluten-free diet, especially those with celiac disease or gluten sensitivity
• Consider lactose: Even if not formally lactose intolerant, reducing dairy may help some patients

Working with a registered dietitian who has experience with gastrointestinal conditions can be valuable. They can help ensure you maintain adequate nutrition while identifying and avoiding problematic foods.

Lifestyle Modifications

Quit smoking: This cannot be emphasized enough. Smoking increases the risk of microscopic colitis and worsens symptoms. Stopping smoking is one of the most effective interventions. Talk to your healthcare provider about smoking cessation support.

Manage stress: While stress doesn't cause microscopic colitis, it may worsen symptoms. Consider stress-reduction techniques such as regular exercise, meditation, deep breathing exercises, or yoga.

Plan ahead: When going out, know where bathrooms are located. Carry supplies like wet wipes and a change of clothes if needed. This preparation can reduce anxiety about symptoms.

When Should You See a Doctor?

See a doctor if you have persistent diarrhea lasting more than two weeks, even if symptoms come and go. Seek immediate medical attention if you have bloody stools, high fever, severe abdominal pain, signs of dehydration (extreme thirst, dizziness, dark urine), or inability to keep fluids down.

If you're experiencing chronic diarrhea, it's important to seek medical evaluation to get a proper diagnosis and appropriate treatment. Many people delay seeking care because they assume symptoms will resolve on their own or attribute them to something they ate.

Contact Your Doctor If:

• You have had diarrhea for more than two weeks
• Symptoms interfere with your daily activities, work, or sleep
• You're experiencing unintentional weight loss
• Your current treatment is no longer controlling symptoms
• You have concerns about your symptoms or medications

What Is the Long-Term Outlook?

The prognosis for microscopic colitis is generally good. It is not a life-threatening condition and does not increase colon cancer risk. Most patients achieve symptom relief with treatment. However, the condition is often chronic, with many patients experiencing relapses. With proper management, most people maintain good quality of life.

Understanding the long-term course of microscopic colitis can help set realistic expectations and reduce anxiety about the condition.

Not dangerous: Microscopic colitis is considered a benign condition. Unlike ulcerative colitis and Crohn's disease, it does not increase the risk of colon cancer. While symptoms can be very bothersome, the condition itself is not life-threatening.

Symptom control is achievable: The vast majority of patients respond well to treatment. With budesonide, 80-90% of patients achieve remission, and even those who don't respond to first-line treatment usually find an effective alternative.

Relapses are common: One of the challenges of microscopic colitis is that symptoms often return after treatment is stopped. Studies show that 60-80% of patients relapse after discontinuing budesonide. This doesn't mean treatment has failed - it means ongoing or intermittent treatment may be needed.

Spontaneous remission can occur: Some patients experience improvement without specific treatment, or may have long periods of remission between flares. The unpredictable nature of the condition means that regular follow-up with your healthcare provider is important.

Quality of life can be maintained: With appropriate treatment and lifestyle management, most patients with microscopic colitis can live normal, active lives. The key is working with your healthcare team to find the right management approach for your individual situation.