Microscopic Colitis

Microscopic Colitis is a collective term used to describe a group of conditions characterised by a normal endoscopic appearance of the colon, but colitis on biopsy. Subgroups of this condition include the more common Lymphocytic Colitis and Collagenous Colitis and the less common drug-induced Colonopathies and Microscopic Colitis associated with infection.

The term Inflammatory Bowel Disease is usually reserved for patients with either Ulcerative Colitis or Crohn’s Disease. Microscopic Colitis is not just less severe Inflammatory Bowel Disease, but it has distinctive histological features and a different clinical presentation. Patients describe waxing and waning watery diarrhoea often for several years prior to diagnosis. Rectal bleeding and abdominal pain are not usually features of this disease and complications associated with Inflammatory Bowel Disease (such as stricture, perforation, carcinoma or extraintestinal manifestations) are not observed. It is, therefore, preferable not to refer to such patients as having Inflammatory Bowel Disease.

What treatments are available?

The fact that patients with Microscopic Colitis have a variety of treatments and that success is not great reflects the lack of controlled trials of treatments for the condition. Most treatments have been extrapolated from those used in patients with Inflammatory Bowel Disease or Irritable Bowel Syndrome. Since Microscopic Colitis appears to be a benign condition and since no therapy is curative, every effort should be made to ensure that the treatment is not long term, or at least be in recurrent courses.

There are four lines of attack:

• Treatment of other causes of the symptoms

• Dietary modifications

• Symptomatic therapy

• Treating mucosal inflammation

Identifying and treating factors other than the colitis itself that might be contributing to the symptomatology is one approach to the treatment of Microscopic Colitis. Since Coeliac Disease occurs in up to 25% of patients with Microscopic Colitis, small bowel biopsy should be seriously considered in patients with troublesome symptoms, particularly if colonic biopsies have shown Collagenous Colitis.

A weak association with the thyroid disease has been noted, so thyroid function tests should be performed. An increasing number of drugs have been associated with this condition, but the most common drugs implicated are non-steroidal anti-inflammatory agents. If the use of one of these drugs is temporarily associated with the development of the diarrhoea, they should be discontinued.