IBS and Microscopic Colitis

Both IBS and microscopic colitis share the symptom of chronic diarrhea, so it's understandable to wonder if they are related. The treatment for the two conditions is very different, so you will want to be assured that you have the right diagnosis.

What Is Microscopic Colitis?

Microscopic colitis is a condition in which a person experiences chronic watery, but not bloody, diarrhea. The disease is more likely to affect women than men and risk goes up with age; the highest incidence is seen in people who are in their 60s or 70s.

There are two types of microscopic colitis: collagenous colitis and lymphocytic colitis. They differ in terms of the way they look during a diagnostic evaluation:

• In lymphocytic colitis, there is an increased number of white blood cells present in the tissue of the lining of the colon.
• In collagenous colitis, a thick layer of collagen is seen in the tissue.

That said, they are possibly just two different stages of the same disorder. Regardless of type, the two disorders are diagnosed and treated the same way.

Microscopic Colitis Symptoms

In addition to the symptom of chronic watery diarrhea, microscopic colitis may also result in:

• Abdominal pain and/or cramps
• Nausea
• Fecal incontinence
• Weight loss

Symptoms may be intermittent and, at times, the disease can resolve on its own without any medical treatment.

Causes

No one knows for sure what causes microscopic colitis. Risk factors include:

• Autoimmune diseases (including rheumatoid arthritis, celiac disease, type 1 diabetes, etc.)
• Proton pump inhibitors (PPIs)
• Smoking
• Selective serotonin reuptake inhibitors (SSRIs)
• Thyroid problems

Diagnosis

Similar to IBS, with microscopic colitis, there will generally be no sign of the disease seen during a colonoscopy. Where the two disorders differ is that microscopic colitis will show up when a sample of colonic tissue is looked at under a microscope.

In addition to a colonoscopy with biopsy, other tests will be given to rule out other diseases. Blood work, with possible endoscopy, will be recommended to rule out celiac disease. A stool test may be recommended to identify any pathogens that might be causing diarrhea.

Treatment

The treatment options for microscopic colitis are very different than the treatment options for IBS.

The first step may be to stop smoking or discontinue any medications that are suspected to be contributing to the disease.

Medication to treat microscopic colitis may be prescribed. Multiple medications have been used with variable degrees of success, including:

• Anti-diarrheals
• Cholestyramine
• Corticosteroids like budesonide
• Bismuth
• 5-aminosalicylates
• Immunomodulators, including anti-tumor necrosis factor (TNF) therapy

At its worst, microscopic colitis may be addressed through ileostomy surgery.

IBS vs. Microscopic Colitis

Having learned about microscopic colitis, you still may be wondering if you have the correct diagnosis.

According to the review, the overlap between IBS and microscopic colitis differed based on study design. In case-control studies, microscopic colitis was seen more often in people who have IBS than those who had no symptoms.

But in studies that looked at evidence across large groups, people who have IBS are no more likely to have microscopic colitis than people who don't.

Based on this meta-analysis, the authors recommend that unless you are at higher risk for microscopic colitis or any red-flag digestive symptoms, there is no need for a person with IBS to undergo a colonoscopy to rule out microscopic colitis.

Of course, if your IBS symptoms change, you should inform your doctor with the expectation that further testing may be needed to either confirm your diagnosis or obtain an accurate one.