Crohns Disease

Crohn's disease, a type of inflammatory bowel disease (IBD), is a condition in which the lining of your digestive tract becomes inflamed, causing severe diarrhea and abdominal pain. The inflammation often spreads deep into the layers of affected tissue. Like ulcerative colitis, another common IBD, Crohn's disease can be both painful and debilitating and sometimes may lead to life-threatening complication.
While there's no known medical cure for Crohn's disease, therapies can greatly reduce the signs and symptoms of Crohn's disease and even bring about a long-term remission. With these therapies, many people afflicted with Crohn's disease are able to function normally in their everyday lives.

Symptoms

Crohn's disease
Signs and symptoms of Crohn's disease can range from mild to severe and may develop gradually or come on suddenly, without warning. They include:
Diarrhea. The inflammation that occurs in Crohn's disease causes cells in the affected areas of your intestine to secrete large amounts of water and salt. Because the colon can't completely absorb this excess fluid, you develop diarrhea. Intensified intestinal cramping also can contribute to loose stools. In mild cases, stools may simply be looser or more frequent than usual. But people with severe disease may have dozens of bowel movements a day, affecting both sleep and ordinary activities.
Abdominal pain and cramping. Inflammation and ulceration may cause the walls of portions of your bowel to swell and eventually thicken with scar tissue. This affects the normal movement of intestinal tract contents through your digestive tract and may lead to pain and cramping. Mild Crohn's disease usually causes slight to moderate intestinal discomfort, but in more serious cases, the pain may be severe and occur with nausea and vomiting.
Blood in your stool. Food moving through your digestive tract can cause inflamed tissue to bleed, or your bowel may also bleed on its own. You might notice bright red blood in the toilet bowl or darker blood mixed with your stool. You can also have bleeding you don't see (occult blood). In severe disease, bleeding is often serious and ongoing.
Ulcers. Crohn's disease begins as small, scattered sores on the surface of the intestine. Eventually these sores may become large ulcers that penetrate deep into — and sometimes through — the intestinal walls. You may also have ulcers in your mouth similar to canker sores.
Reduced appetite and weight loss. Abdominal pain and cramping and the inflammatory reaction in the wall of your bowel can affect both your appetite and your ability to digest and absorb food.
Fistula or abscess. Inflammation from Crohn's disease may tunnel through the wall of the bowel into adjacent organs, such as the bladder or vagina, creating an abnormal connection called a fistula. This can also lead to an abscess, a swollen, pus-filled sore. The fistula may also tunnel out through your skin. A common place for this type of fistula is in the area around the anus. When this occurs, it's called perianal fistula.
Other signs and symptomsPeople with severe Crohn's disease may experience fever and fatigue as well as problems that occur outside the digestive tract, including arthritis, eye inflammation, skin disorders, and inflammation of the liver or bile ducts. Children with Crohn's disease may have delayed growth or sexual development.
The course of Crohn's disease varies greatly. You may have long periods without signs and symptoms, or you may have recurrent episodes of abdominal pain, diarrhea, and sometimes fever or bleeding.

Causes
Crohn's disease begins with inflammation, most often in the lower part of the small intestine (ileum) or in the colon, but sometimes in the rectum, stomach, esophagus or mouth. Unlike ulcerative colitis, in which inflammation occurs uniformly throughout an affected area, Crohn's disease can develop in several places simultaneously, with healthy tissue in between. In time, large ulcers that extend deep into the intestinal wall may develop in the inflamed areas.
No one is quite sure what triggers inflammation in Crohn's disease, but there's a consensus as to what doesn't cause it. Researchers no longer believe that stress and diet are the main culprits, although both factors can often aggravate symptoms. Instead, current thinking focuses on the following possibilities:
Immune system. It's possible that a virus or bacterium may cause Crohn's disease. When your immune system tries to fight off the invading microorganism, the digestive tract becomes inflamed. One microorganism that may be involved in the development of Crohn's is Mycobacterium avium subspecies paratuberculosis (MAP), a bacterium that causes intestinal disease in cattle. Researchers have found MAP in the blood and intestinal tissue of many people with Crohn's disease, but only rarely in people with ulcerative colitis.
There's no clear evidence that MAP causes Crohn's disease. Some researchers believe that a genetic susceptibility may trigger an abnormal response to the bacterium in some people. Currently, most investigators believe that some people with the disease develop it because of an abnormal immune response to bacteria that normally live in the intestine.
Heredity. About 20 percent of people with Crohn's disease have a parent, sibling or child who also has the disease. Mutations in a gene called NOD2/CARD15 tend to occur frequently in people with Crohn's disease and seem to be associated with an early onset of symptoms as well as a high risk of relapse after surgery for the disease. Scientists continue to search for other genetic mutations that might play a role in Crohn's.

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