Crohn's Disease : Diagnosis

To accurately diagnose Crohn's disease, a patient will likely undergo a number of laboratory tests and one or more imaging procedures that allow a doctor to visually evaluate the intestine. Laboratory tests include blood tests and stool cultures. They are used to evaluate the inflammatory process and to provide clues about the cause. There are three common imaging procedures. One is a type of X-ray, and the others use endoscopy, allowing the doctor to actually look inside the body.
Imaging studies include:

Sigmoidoscopy

Colonoscopy

Barium enema
Once transient infection has been ruled out and inflammatory bowel disease is suspected, it is important to make a correct diagnosis of either Crohn's disease or ulcerative colitis. While the two diseases have many similarities, they are distinct. Many of the newer drugs are more effective for treating for one disease than the other.

Crohn's Disease Cause

Researchers have not yet identified the cause of Crohn's disease, so it is described as an "idiopathic" disease. It is known that inflammation is part of the body's immune response, and an immune response is usually triggered by something. But to date no specific "trigger" has been found to cause the inflammatory response seen in Crohn's disease.
There is some evidence that Crohn's disease has a genetic component. While there is no simple correlation from parent(s) to offspring, the disease tends to "run" in families. As many as 20 to 25 percent of patients with Crohn's disease have a relative with CD or ulcerative colitis. There is also a higher incidence among certain ethnic groups.
In addition, some possible environmental factors have been linked to initial episodes or relapses. Crohn's disease appears to be a disease that primarily affects those living in Western, industrialized societies. Whether this is due to some condition of the environment in which people live or their diet has not been determined.

The Role Of Heredity

Physicians classify Crohn's disease as one of the "familial" or "complex" genetic diseases, as opposed to a "simple" genetic disease. In simple genetic diseases, such as sickle cell disease or cystic fibrosis, a person who inherits a copy of the defective gene from each parent is certain to get the disease.
In Crohn's disease, this is not the case. In fact, 75 to 80 percent of people with Crohn's disease have no relative with either Crohn's disease or ulcerative colitis. But because there are fewer than 500,000 Americans with Crohn's disease, the level of multiple incidence in families (20 to 25 percent of Crohn's patients) means that the risk of being diagnosed with the disease is statistically somewhat higher in individuals who have a family member with either Crohn's disease or ulcerative colitis.
Other evidence that suggests a genetic basis for Crohn's disease is the fact that populations who have intermarried closely within their communities for many generations, such as Eastern European Jews, have a higher incidence of inflammatory bowel disease than do other groups.

Weakened Immune Response

In the healthy intestine, certain types of bacteria (enteric microflora) are present and necessary. In fact, between one billion and one trillion normal intestinal bacteria exist in every gram of intestinal content. These "normal" bacteria contribute to the process of digestion and keep abnormal bacteria, which can enter the GI tract in food, water, etc., from surviving and causing illness.
If abnormal bacteria do survive and multiply, the body recognizes them as invading organisms, or "antigens." To a certain extent, these antigens are ignored in the GI tract - the immune system has a certain level of tolerance for them.
But immunologic evidence shows that in the intestines of those with inflammatory bowel disease, some of this tolerance for bacteria is lost. The TH1 cells, which are responsible for activating the immune response against invading organisms, do their job. But the TH2 cells, which are responsible for deactivating the immunologic response after invading organisms are destroyed, fail to perform theirs.
The result is an inflammatory overreaction, resulting in pain, fever, and, sometimes, tissue damage.
Some evidence also suggests that flare-ups of Crohn's disease or ulcerative colitis are a heightened response to seasonal allergies, upper-respiratory infections, or other transient illnesses.

So, What is Crohn's Disease

Crohn’s disease is an ongoing disorder that causes inflammation of the digestive tract, also referred to as the gastrointestinal (GI) tract. Crohn’s disease can affect any area of the GI tract, from the mouth to the anus, but it most commonly affects the lower part of the small intestine, called the ileum. The swelling extends deep into the lining of the affected organ. The swelling can cause pain and can make the intestines empty frequently, resulting in diarrhea.

Crohn’s disease is an inflammatory bowel disease, the general name for diseases that cause swelling in the intestines. Because the symptoms of Crohn’s disease are similar to other intestinal disorders, such as irritable bowel syndrome and ulcerative colitis, it can be difficult to diagnose. Ulcerative colitis causes inflammation and ulcers in the top layer of the lining of the large intestine. In Crohn’s disease, all layers of the intestine may be involved, and normal healthy bowel can be found between sections of diseased bowel.

Crohn’s disease affects men and women equally. About 20 percent of people with Crohn’s disease have a blood relative with some form of inflammatory bowel disease, most often a brother or sister and sometimes a parent or child. Crohn’s disease can occur in people of all age groups, but it is more often diagnosed in people between the ages of 20 and 30. People of Jewish heritage have an increased risk of developing Crohn’s disease, and African Americans are at decreased risk for developing Crohn’s disease.

Crohn’s disease may also be called ileitis or enteritis.

Wikipedia article on the disease gives us a primary information as below.

Crohn's disease is a disease of the digestive system which may affect any part of the gastrointestinal tract from mouth to anus. As a result, the symptoms of Crohn's disease can vary significantly among afflicted individuals. The main gastrointestinal symptoms are abdominal pain, diarrhea (which may be visibly bloody), vomiting, or weight loss. Crohn's disease can also cause complications outside of the gastrointestinal tract such as skin rashes, arthritis, and inflammation of the eye.

The precise cause of Crohn's disease is not known. The disease occurs when the immune system attacks the gastrointestinal tract and for this reason, Crohn's disease is considered an autoimmune disease. This autoimmune activity produces inflammation in the gastrointestinal tract, and therefore Crohn's disease is classified as an inflammatory bowel disease.

Like many other autoimmune diseases, Crohn's disease is believed to be genetically linked. The highest risk occurs in individuals with siblings who have the disease. Males and females are equally affected. Smokers are three times more likely to develop Crohn's disease. Crohn disease affects between 400,000 and 600,000 people in North America. Prevalence estimates for Northern Europe have ranged from 27–48 per 100,000. Crohn disease tends to present initially in the teens and twenties, with another peak incidence in the fifties to seventies, although the disease can occur at any age.

Unlike the other major types of inflammatory bowel disease, there is no known drug based or surgical cure for Crohn's disease. Treatment options are restricted to controlling symptoms, putting and keeping the disease in remission and preventing relapse.

The disease was independently described in 1904 by Polish surgeon Antoni Leśniowski and in 1932 by American gastroenterologist Burrill Bernard Crohn, for whom the disease was named. Crohn, along with two colleagues, described a series of patients with inflammation of the terminal ileum, the area most commonly affected by the illness. For this reason, the disease has also been called regional ileitis or regional enteritis.