Makindo Medical Notes

Related Subjects: |Ulcerative Colitis |Microscopic colitis |Irritable bowel syndrome |Lower Gastrointestinal (Rectal) Bleeding

Microscopic colitis is a form of inflammatory bowel disease (IBD) characterized by chronic, watery diarrhoea. Unlike other forms of IBD, microscopic colitis is not associated with an increased risk of colon cancer. This condition primarily affects older adults and often presents with symptoms of persistent diarrhoea that can significantly impact quality of life.

About

• Microscopic colitis is a form of inflammatory bowel disease (IBD) that causes colonic inflammation, but the inflammation is only detectable under a microscope (biopsy).
• It is divided into two main subtypes: Collagenous Colitis (CC) and Lymphocytic Colitis (LC), both of which present similarly but have different histopathological findings.
• Unlike Crohn’s disease or ulcerative colitis, microscopic colitis does not typically cause visible ulcers or erosions in the colon.

Types

• Collagenous Colitis (CC): Characterized by a thickened layer of collagen (a type of connective tissue) just beneath the epithelial lining of the colon. This thickened collagen layer can interfere with normal absorption of fluids, leading to chronic diarrhoea.
• Lymphocytic Colitis (LC): Characterized by an increased number of lymphocytes (a type of white blood cell) within the epithelium of the colon. The infiltration of lymphocytes leads to inflammation, contributing to symptoms of diarrhoea and cramping.

Associations

• Use of certain medications, such as Proton Pump Inhibitors (PPIs), Non-Steroidal Anti-Inflammatory Drugs (NSAIDs), Selective Serotonin Reuptake Inhibitors (SSRIs), and Oral Contraceptive Pills (OCP).
• Smoking: Linked to an increased risk of developing microscopic colitis, particularly collagenous colitis.
• Autoimmune conditions such as coeliac disease, rheumatoid arthritis, and type 1 diabetes.
• Bile acid malabsorption may exacerbate diarrhoea symptoms.
• Patients with microscopic colitis are at a slightly higher risk of developing other forms of IBD.

Clinical Presentation

• Non-bloody, chronic watery diarrhoea: The hallmark symptom, often occurring in episodes throughout the day and night.
• Abdominal pain or cramping: Mild to moderate discomfort often associated with bloating.
• Other symptoms: Nausea, fatigue, and weight loss in some cases.
• Urgency and incontinence: Patients may experience an urgent need to defecate, sometimes leading to fecal incontinence.

Investigations

• Colonoscopy: The mucosa usually appears macroscopically normal. However, biopsy of the colon is required to make a definitive diagnosis.
• Barium enema: Typically appears normal and is not commonly used for diagnosis.
• Microscopy of Collagenous Colitis: Shows a thickened subepithelial collagen layer with an inflamed lamina propria.
• Microscopy of Lymphocytic Colitis: Shows an inflamed lamina propria with increased intraepithelial lymphocytes.

Management

• Medication review: Avoid medications that may trigger symptoms (e.g., NSAIDs, PPIs).
• Dietary modifications: Reducing caffeine, lactose, and fatty foods may help manage diarrhoea. In some cases, a gluten-free diet may be beneficial, especially in patients with coeliac disease.
• Antidiarrhoeals: Loperamide (Imodium) can help reduce diarrhoea. Cholestyramine may also be effective, particularly in cases associated with bile acid malabsorption.
• Anti-inflammatory treatment: Budesonide, a corticosteroid, is commonly used for short-term control of symptoms. In more severe or refractory cases, immunosuppressive agents like azathioprine or methotrexate may be considered.
• Probiotics: Although research is still ongoing, probiotics may help restore gut flora and improve symptoms in some patients.
• Biologic therapy: For patients with refractory microscopic colitis, biologic agents like TNF inhibitors (e.g., infliximab) have shown some benefit.
• Hydration and nutrition: Maintaining hydration and electrolyte balance is important in patients with chronic diarrhoea.

Prognosis

• Microscopic colitis is typically a chronic condition but often responds well to treatment.
• Most patients can achieve remission with appropriate medical management and lifestyle adjustments.
• The condition does not carry an increased risk of colorectal cancer, unlike other forms of IBD, which is an important distinguishing factor.