Microscopic Colitis: Symptoms, Causes, and UK Treatment Guide

Microscopic colitis is a type of inflammatory bowel disease (IBD) that affects the lining of the colon (large intestine). Unlike more well-known conditions such as ulcerative colitis or Crohn’s disease, the inflammation in microscopic colitis is not visible during a standard colonoscopy. The bowel lining typically appears healthy to the naked eye; however, when tissue samples (biopsies) are taken and examined under a microscope, characteristic inflammation is found.

There are two primary subtypes: lymphocytic colitis and collagenous colitis. In lymphocytic colitis, there is an increased number of white blood cells (lymphocytes) in the lining. In collagenous colitis, a thick layer of connective tissue (collagen) develops under the lining. Both types result in similar symptoms and are managed in much the same way within the UK healthcare system, following NICE (National Institute for Health and Care Excellence) evidence-based pathways.

The hallmark of microscopic colitis is chronic, non-bloody, watery diarrhoea. Patients often describe the onset as sudden, sometimes following an infection or a change in medication. Key symptoms include:

• Watery diarrhoea: This can occur multiple times a day and may be very urgent.
• Nocturnal symptoms: Waking up during the night to pass stool is a significant indicator that the issue is inflammatory rather than functional (like IBS).
• Abdominal pain: Cramping and discomfort are common but usually less severe than in acute infections.
• Weight loss and fatigue: Dehydration and nutrient loss from frequent bowel movements can lead to tiredness and unintentional weight loss.
• Faecal incontinence: The urgency can be so intense that some patients experience accidents.

The exact cause of microscopic colitis remains unclear, but it is believed to be an overactive immune response triggered by various factors. Research suggests that certain medications are strongly linked to the development of the condition. These include non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, proton pump inhibitors (PPIs) used for acid reflux, and some antidepressants.

Other risk factors identified by UK health researchers include:

• Age and Gender: It is most commonly diagnosed in women over 50, though men and younger people can also be affected.
• Autoimmune conditions: There is a higher prevalence among those with coeliac disease, type 1 diabetes, or rheumatoid arthritis.
• Smoking: Evidence suggests smokers are at a higher risk and may develop symptoms at a younger age.
• Bile acid malabsorption: In some cases, how the body processes bile can irritate the colon lining.

If you present with chronic watery diarrhoea, your GP will likely first rule out infections or coeliac disease through blood and stool tests. However, the definitive diagnosis of microscopic colitis requires a colonoscopy or sigmoidoscopy where biopsies are taken throughout the colon.

UK Treatment Options

Treatment aims to induce remission and improve quality of life. The first step usually involves reviewing medications that might be triggering the inflammation. Lifestyle adjustments, such as reducing caffeine and alcohol, may also help. Budesonide, a targeted steroid that acts mainly in the gut, is the gold-standard treatment recommended by NICE for moderate to severe cases. If symptoms are mild, anti-diarrhoeal medications like loperamide may be used to manage stool consistency.

Bowel habits are a sensitive topic, but persistent changes should never be ignored. If you have been suffering from watery diarrhoea for more than two weeks, booking a consultation to speak to a GP online is a proactive first step. An online doctor can review your symptoms, assess your medical history, and discuss whether your current medications—such as long-term PPIs—could be contributing to your gut concerns.

An online consultation provides a calm, private environment to discuss the frequency and nature of your symptoms. While a physical biopsy is required for a formal diagnosis, a GP can advise on the necessary tests, provide sick notes if the condition is impacting your ability to work, and help you navigate the next steps in the UK health system.

Living with a chronic bowel condition can be challenging, but most people with microscopic colitis respond well to treatment and lead normal lives. Managing flare-ups often involves identifying personal triggers. For some, specific foods may worsen symptoms, while for others, stress management is key. It is important to stay hydrated, especially during periods of frequent diarrhoea, using oral rehydration salts if necessary. Regular follow-ups with your healthcare provider ensure that your treatment plan remains effective and that any side effects from medications are monitored.