Microscopic Colitis

collagenous colitis, lymphocytic colitis

Lymphocytic colitis and collagenous colitis are uncommon disorders that have been studied and described in past decades, but remain poorly understood. They are being recognised more frequently, possibly because gastroenterologists and pathologists are now more aware of these diagnoses.

The terminology remains somewhat controversial. The term "microscopic colitis", while not recognised by some authorities, generally refers to the group of disorders.

Cause of Microscopic Colitis

The cause of these conditions is unknown. Possible causes include unidentified chronic gastrointestinal infections, immune disturbance (including autoimmune disease), and medications (e.g. some non-steroidal anti-inflammatory agents, ranitidine, carbemazepine).

Lymphocytic colitis is characterised by increased lymphocytes (type of white blood cell) in the lining of the colon. Collagenous colitis is characterised by a thickening of the sub-epithelial collagen layer and increased lymphocytes in the lining of the colo

Symptoms

Patients with these disorders present with chronic diarrhoea. Abdominal pain, fatigue and weight loss are also common. A number of associated diseases may occur, including the connective tissue disorders, thyroid diseases, and coeliac disease.

Diagnosis

The diagnosis requires that other disorders first be ruled out (e.g. ulcerative colitis, Crohn's disease, gastrointestinal infections). The diagnosis can only be made by colonoscopy. The lining (mucosa) appears normal, although there may be some very subtle abnormalities. However, the diagnosis is made by the pathologist when the biopsies are examined under the microscope. Separate biopsies should be taken from several regions along the colon.

Medical Treatment

Although there is no proven treatment, a number of medications will help. These include bismuth subcitrate, mesalazine, cholestyramine and corticosteroids. Some patients will get better without any treatment.

Rarely, patients will require a diverting ileostomy (abdominal opening to remove faecal matter) because of intractable diarrhoea.