Lymphocytic Colitis (cont.)

Individuals with irritable bowel syndrome (IBS) do not have colitis, even though this condition is sometimes referred to as having "spastic colitis." These individuals may have symptoms that mimic colitis such as diarrhea, abdominal pain, and mucous in stool. Nevertheless, there is no inflammation of the colon (not even microscopic colitis) in patients with IBS. The cause of symptoms in IBS is not clearly known; it may be caused by either abnormal motility (abnormal contractions) of the intestinal muscles or abnormally sensitive nerves in the intestines (visceral hypersensitivity).

Microscopic colitis refers to inflammation of the colon that is only visible when the colon's lining is examined under a microscope. The appearance of the inner colon lining in microscopic colitis is normal by visual inspection during colonoscopy or flexible sigmoidoscopy. The diagnosis of microscopic colitis is made when a doctor, while performing colonoscopy or flexible sigmoidoscopy, takes biopsies (small samples of tissue) of the normal-appearing lining, and then examines the biopsies under a microscope.

There are two types of microscopic colitis: 1) lymphocytic colitis and 2) collagenous colitis.

1. In lymphocytic colitis, there is an accumulation of lymphocytes (a type of white blood cell) within the lining of the colon.
   
   
2. In collagenous colitis, there is an additional layer of collagen (scar tissue) just below the lining.

Some experts believe that lymphocytic colitis and collagenous colitis represent different stages of the same disease.

The inflammation and the collagen probably interfere with absorption of water from the colon, and cause the diarrhea.

Source: MedicineNet.com
http://www.medicinenet.com/lymphocytic_colitis/article.htm