Microscopic Colitis: Symptoms, Causes, and UK Management Guide

Microscopic colitis is a type of Inflammatory Bowel Disease (IBD) that affects the large intestine (colon). While more commonly known conditions like Crohn’s disease or ulcerative colitis cause visible inflammation or ulcers, microscopic colitis is different. To the naked eye during a colonoscopy, the bowel lining often appears completely healthy and normal. The inflammation is only detectable when a small tissue sample (biopsy) is taken and examined under a microscope.

In the UK, it is increasingly recognised as a common cause of persistent, watery diarrhoea, particularly in adults over the age of 50. There are two primary subtypes: collagenous colitis, where a thick layer of protein (collagen) develops in the colon lining, and lymphocytic colitis, where there is an increased number of white blood cells (lymphocytes) within the lining. Both types result in the same primary symptom: chronic watery stools.

The hallmark of microscopic colitis is chronic, frequent, and watery diarrhoea that does not contain blood. This symptom can be debilitating, often occurring several times a day and even waking patients up during the night. Because the diarrhoea is non-bloody, it is sometimes mistaken for Irritable Bowel Syndrome (IBS), but the underlying cause is inflammatory rather than functional.

• Watery diarrhoea: Sudden and urgent bowel movements.
• Abdominal pain: Often described as cramping or discomfort.
• Urgency: A sudden, pressing need to use the toilet.
• Incontinence: Difficulty reaching the toilet in time due to the watery consistency of the stool.
• Weight loss and fatigue: Resulting from malabsorption or the body’s inflammatory response.

Symptoms can be 'relapsing-remitting,' meaning they may disappear for a period before returning (flaring up). If you are experiencing these symptoms for more than a few weeks, it is important to seek medical advice.

The exact cause of microscopic colitis remains under investigation, but research suggests it is likely a combination of genetics, immune system malfunctions, and environmental triggers. According to NICE (National Institute for Health and Care Excellence), certain medications are strongly linked to the onset of the condition.

Medication Triggers

• NSAIDs: Non-steroidal anti-inflammatory drugs like ibuprofen or aspirin.
• PPIs: Proton pump inhibitors used for acid reflux, such as omeprazole or lansoprazole.
• SSRIs: Certain antidepressants used to treat anxiety and depression.
• Statins: Medications used to lower cholesterol levels.

Other risk factors include smoking, which has been shown to increase the risk of developing the condition and can make symptoms worse. There is also a strong association with autoimmune conditions, such as coeliac disease, type 1 diabetes, and rheumatoid arthritis.

Diagnosing microscopic colitis requires a formal investigation because standard stool tests and blood tests usually come back normal. In the UK, the standard pathway involves a referral to a gastroenterologist for a colonoscopy or sigmoidoscopy.

During this procedure, a thin, flexible tube with a camera is used to look inside the colon. Because the colon looks normal, the clinician must take multiple biopsies from different parts of the bowel. These samples are then sent to a pathology lab where a specialist looks for the characteristic signs of lymphocytic or collagenous colitis. Without these biopsies, the condition is frequently missed.

Treatment for microscopic colitis aims to stop the diarrhoea and induce remission. In many cases, the first step is reviewing your current medications. If a specific drug like a PPI or NSAID is suspected of causing the flare-up, a GP may suggest stopping it or switching to an alternative. Do not stop prescribed medication without medical supervision.

Medical Treatments

• Budesonide: A targeted steroid that acts directly on the gut with fewer side effects than systemic steroids. This is often the first-line treatment for moderate to severe cases.
• Anti-diarrhoeal medication: Medicines like loperamide (Imodium) may be used for mild symptoms to slow down the bowel.
• Bile acid sequestrants: If bile acid malabsorption is also present, medications like colestyramine may help.

Lifestyle and Diet

While diet does not cause microscopic colitis, avoiding triggers like caffeine, alcohol, and high-fat foods can help manage symptoms during a flare. Quitting smoking is also highly recommended to improve long-term outcomes.

If you are struggling with persistent watery diarrhoea that is affecting your quality of life, you should speak to a GP online or in person. Many patients delay seeking help, assuming their symptoms are 'just something they ate' or standard IBS. However, if your symptoms last for more than two weeks, a clinical review is necessary.

An online doctor can perform an initial assessment by reviewing your medical history, current medications, and symptom patterns. They can provide advice on managing symptoms, order initial stool tests to rule out infections (like C. diff), and provide a referral letter for a private or NHS gastroenterologist if microscopic colitis is suspected. Accessing an online GP in the UK is a convenient way to start the diagnostic process without waiting weeks for an initial appointment.