The Biology of Ulcerative Colitis
schematic of human intestines
The image above shows a schematic of the human intestines. Ulcerative colitis may be of these types: Distal colitis involves sigmoid colon; proctitis limited to the rectum; proctosigmoiditis involves the rectosigmoid colon, the portion of the colon adjacent to the rectum; Left-sided colitis Involvement of the descending colon, which runs along the patient's left side, Extensive colitis inflammation extends along the ascending and transverse colon; pancolitis involves the entire colon.

Ulcerative colitis is a form of inflammatory bowel disease (IBD). As the name suggests, it is a colitis; literally a disease of the colon. This disease is characterized by ulcers (open sores) in the colon. This disease should not be confused with either irritable bowel syndrome (IBD) or Crohn's disease both other forms of bowel disorders.

Ulcerative colitis is a rare disorder with an incidence of about 1 in 10 000 in the Northern Hemisphere. Though the cause of Ulcerative Colitis is unknown, it is often thought to be an autoimmune disease in which the immune system malfunctions and attacks the colon as if it were foreign to the body. Yet, in extreme cases of ulcerative colitis where where the large intestine is removed surgically both the primary and the secondary maifestations of the disease disappear — indicating that the cause of the disease lies within the colon itself.

Causes

The precise cause of ulcerative colitis is unknown, though the disorder is presumed to have a genetic component as it tends to occur in families and identical twins both tend to present with the disease if one has it. Dietary factors do not seem to be involved with the disease though modification of the diet can alleviate some symptoms if the patient is susceptible to certain foodstuffs.

Diagnosis

As with many bowel disorders diagnosis of ulcerative colitis can be problematic. Especially as the clinical presentation of the disease will depend on the extend of the condition. However, patients usually present with diarrhea mixed with blood and mucus, of gradual onset. They also may have signs of weight loss, and blood on rectal examination. Accompanying the disease there is also a degree of abdominal pain which can vary from mild discomfort to severe cramping.

Diagnosis for Ulcerative Colitis includes the following tests:

Endoscopy

A colonoscopy is by far the most reliable form of diagnosis as the procedure allows for direct visualization of the colon. Visual signs include: loss of the vascular appearance of the colon; redness of the mucosa of the colon; ulceration of the colon and the presence of pseudopolyps in the colon. To definitively differentiate ulcerative colitis from Crohn's disease biopsies are generally taken during the endoscopic examination and these are examined histopathologically. The pathology in ulcerative colitis typically involves distortion of crypt architecture, inflammation of crypts (cryptitis), frank crypt abcesses, and hemorrhage or inflammatory cells in the lamina propria.

Blood Tests

Blood tests are generally performed to check for anaemia, thrombocytosis (the presence of high platelet counts in the blood).

In addition, the following tests may also be performed:

  • Electroylte nad renal function tests are performed as chronic diarrhoea may be associated with pre-renal failure.
  • Liver function tests are also performed to check for bile duct involvement.
  • Erythrocyte sedimentation rate can be measured, with an elevated sedimentation rate indicating that an inflammatory process is present.
  • C-reactive protein can be measured, with an elevated level being another indication of inflammation.
  • X-rayss utilizing cvontrast media such as barium sulphate may be used to check the extent of the disease.

Severity of the Disease

Ulcerative Colitis often involves much, if not all of the colon and the extent of colonic involvement can be an indication of the progression of the disease (as in the image, above).

In addition there may be several symptoms and complications outside the colon itself. These include, but are not limited to: ulcers of the mouth, inflammation of the iris, inflamation of the sclera (white coating) of the eye; arthritis of the large joints, especially the knees; arthritis of the spine (ankylosing spondylitis); inflammation of the subcutaneous tissues (especially in the lower extremities); ulcerating lesions of the skin, haemolytic anaemia due to autoimmune disorders; clubbing of the ends of the fingers and inflammation of the bile duct.

Treatment

The type of treatment depends on the severity of the disease. As with Crohn's Disease the goal is to initially induce remission followed by the administration of maintenance medications to prevent a relapse of the disease.

Though it is not certain that Ulcerative Colitis is an autoimmune disorder, the first stage of attaining remission is still generally the employment of anti-inflammatory drugs to stabilize the condition. The main class of drugs used tend to be aminosalicylate anti-inflammatory drugs and 5-ASA compounds have been shown to be useful and can sometimes both induce remission and stabilize the disease. In addition corticosteroid anti-inflammatory drugs may also be used to alleviate moderate so severe flare-ups of the disease. However, the side-effects of these drugs can be severe and they tend to be used sparingly.

If the sppread of the disease in the colon is extensive then excision of the colon may be indicated. This techinique is invariably successful in curing the disease.

Once initial remission is achieved the next stage of treatment is to maintain remission. For many continued treatment with aminosalicylates is sufficient but for a number of patients more aggressive immunnosuppressive drugs must be used. Mercaptopuring immunossuppressants (Azathioprine and 6-mercaptopurine (6-MP)) are the most used immunosuppressants for this purpose. Other drugs that can be used tumor necrosis factor (TNF) inhibotors. These drgs inhibit the progression of inflammation.

Prognosis

Although ulcerative colitis is rarely fatal it does dramatically reduce the quality of life of the sufferer and this is the major medical consequence of the disease. Also, without radical surgery there is no cure for the disease and the best that can be hoped for is a stabilization of the condition.