Overview

Microscopic colitis (MC) is a chronic inflammatory bowel disease that affects the lower gastrointestinal tract (colon). Microscopic colitis (MC) is an umbrella term for two main subtypes: lymphocytic colitis (LC) and collagenous colitis (CC).¹

It is microscopic because the inflammation is not visible on routine endoscopy but is only by microscopic examination of colonic biopsies.

Microscopic colitis (MC)¹ is a cause of chronic watery diarrhoea, especially in older adults.  Several factors raise the risk of MC, such as age, being female (particularly for collagenous colitis), smoking, certain autoimmune diseases, and organ transplants. The list of medications linked to chronic diarrhoea is also growing, with some potentially contributing to MC. These medications include pain relievers, antidepressants, blood pressure, cholesterol, bone health, heartburn, blood clotting, and some hormone therapy medications.³

Symptoms and signs

• Chronic, watery, non-bloody diarrhoea (the most common symptom) 
• Abdominal pain or cramping 
• faecal incontinence(Inability to hold feces or stool)
• Weight loss (in some cases) 

Why is it more common in older adults?

Microscopic colitis is more common in older adults, especially those over 60. While the exact cause remains under investigation, several factors likely contribute to this increased risk³

• Weakened Immune System: As we age, our immune function naturally weakens. It may make older adults more susceptible to the underlying inflammation characteristic of microscopic colitis.
• Medication Use: Many medications commonly used by older adults, such as non steroidal anti-inflammatory drugs (NSAIDs), proton pump inhibitors (PPIs), and selective serotonin reuptake inhibitors (SSRIs), have been linked to microscopic colitis.
• Autoimmune Conditions: The prevalence of autoimmune disorders, which can make individuals more prone to microscopic colitis, also rises with age. Examples include celiac disease, thyroid disease, and rheumatoid arthritis.
• Other Potential Factors: Additional possibilities are changes in the gut microbiome (the healthy bacteria in our intestines) and undiagnosed food intolerances, which can become more prevalent with age.

Risk factors 

• Increasing age: The risk of microscopic colitis rises as you get older.
• Female gender: Women are more susceptible, particularly to collagenous colitis.
• Autoimmune conditions: Certain autoimmune diseases, like celiac disease, thyroid disease, and rheumatoid arthritis, are associated with MC.
• Malignancy (Cancer): Cancer can be a risk factor.
• Solid organ transplantation: Having received a solid organ transplant increases the risk.
• Medications: Use of certain drugs may be a risk factor, including:
  • Proton pump inhibitors (PPIs)
  • Non steroidal anti-inflammatory drugs (NSAIDs),
  • Statins
  • Selective serotonin reuptake inhibitors (SSRIs)
• Smoking: increases the frequency of watery stools and increase the risk of disease

Diagnosis

The diagnosis of microscopic colitis is by clinical symptoms, endoscopic evaluation, and histological examination of colonic biopsies. The diagnostic process typically involves:

• Medical history and physical examination
• Microscopic examination of colonic biopsies to identify the characteristic histological features of lymphocytic or collagenous colitis 
• Colonoscopy: This is a visual examination of your colon using a thin, flexible tube with a camera. It involves looking for any abnormalities in the lining of your colon. While the lining often appears normal in microscopic colitis,^4,5 it helps rule out other potential causes of your diarrhoea.
• Biopsies: Tiny tissue samples are examined from different areas of your colon during the colonoscopy. These samples are then examined under a microscope by a pathologist. It is the most crucial step for diagnosing microscopic colitis.
  • Lymphocytic Colitis: The pathologist will look for an increased number of white blood cells within the lining of the colon⁶
  • Collagenous Colitis: Here, the pathologist will look for a thickening of a protein layer beneath the colon's lining (>7 μm, compared with normal ≤5 μm)⁶

Treatment and management

The primary treatment goals for microscopic colitis are to alleviate symptoms and induce remission. Treatment options may include:

• Antidiarrhoeal medications: Medications like loperamide, bismuth subsalicylate, and methylcellulose can help manage diarrhoea⁸
• Budesonide: (a locally acting corticosteroid) This steroid medication is the most studied treatment and shows benefits for both types of MC (lymphocytic and collagenous) in targeting inflammation in the colon, a factor in MC-related diarrhoea⁸
• Immunomodulators (e.g., azathioprine, 6-mercaptopurine): In some cases, these medications might help by dampening the overactive immune response contributing to MC inflammation⁷
• Discontinuation of medications that may be contributing to the condition (e.g., NSAIDs, PPIs) 
• Bile acid chelators (Cholestyramine): If you have coexisting bile acid malabsorption, which can worsen diarrhoea, these medications help bind and remove excess bile acids from your intestines⁸

Complications

• Dehydration: Chronic diarrhoea, a hallmark symptom of MC, can lead to dehydration. It occurs when you lose more fluids than you take in. Symptoms of dehydration include fatigue, dizziness, dry mouth, and infrequent urination. In severe cases, it can become life-threatening.
• Electrolyte Imbalances: Electrolytes are minerals essential for muscle movement and nerve signaling. With diarrhoea, you lose electrolytes sodium, potassium, and magnesium. It can lead to muscle cramps, weakness, heart rhythm problems, and fatigue.
• Malnutrition: Chronic diarrhoea can make it difficult for your body to absorb nutrients from food. It can lead to malnutrition, a condition where you don't get enough essential vitamins and minerals. Symptoms of malnutrition include weight loss, fatigue, muscle wasting, and a weakened immune system.
• Increased risk of colon cancer: There is some limited research suggesting a possible link between long-standing, untreated microscopic colitis and an increased risk of colon cancer.³ However, more research is needed to confirm this association. Early diagnosis and proper management of microscopic colitis can help minimize this potential risk.

FAQS 

Is microscopic colitis a precursor to more severe conditions?

While microscopic colitis is not a precursor to more severe conditions like Crohn's disease or ulcerative colitis, it can increase the risk of colon cancer if left untreated.³

What causes microscopic colitis?

The exact cause of microscopic colitis is unknown. Many factors are associated with its development, as:

• Medications such as Non-steroidal anti-inflammatory drugs (NSAIDs), proton pump inhibitors (PPIs), and certain antidepressants
• Autoimmune disorders: Such as celiac disease, thyroid disorders, and rheumatoid arthritis
• Smoking
• Bacterial infections.

Can microscopic colitis be cured? 

While microscopic colitis is a chronic condition, it can be effectively managed with appropriate treatment, leading to remission of symptoms. However, relapse is common and needs regular management.⁹

What is the prognosis for microscopic colitis?

Microscopic colitis is generally a chronic condition with periods of remission and relapse. With appropriate treatment, most patients experience improvement in their symptoms. However, some patients may experience persistent or recurrent symptoms, requiring long-term management.

Summary

Microscopic colitis, a chronic inflammatory condition of the colon, is increasingly prevalent in older adults, particularly women.¹⁰ It is often characterized by watery diarrhoea, faecal incontinence, and abdominal pain, significantly impacting patients' quality of life. The prognosis of this condition is generally good, with appropriate treatment, which may include budesonide, leading to symptom relief.¹⁰ Diagnosis requires colonoscopy and histopathological examination, and treatment typically involves using budesonide, a locally acting glucocorticoid.¹⁰ Despite the lack of unified treatment recommendations, a systematic approach to therapy can lead to symptom control.¹¹