A chronic inflammatory disease that can affect any part of the gastrointestinal tract from the mouth to the anus. Crohn’s disease can occur at any age, but people in their mid-twenties are most likely to be affected.
The most common site of inflammation is the terminal ileum (the end of the small intestine where it joins the large intestine). The wall of the intestine becomes extremely thick due to continued chronic inflammation, and deep, penetrating ulcers may form. The disease tends to be patchy; areas of the intestine that lie between the diseased parts may appear to be normal, but are usually mildly affected.
The cause is unknown, but genetic and environmental factors seem to be involved. It is possible that the disease is caused by an abnormal immune response to an antigen (foreign protein). Smoking increases the risk, and worsens the condition once developed. The risk of developing Crohns disease is higher in people who have a close relative with the disorder.
In young people, the ileum is usually involved. The disease causes spasms of abdominal pain, diarrhea and chronic sickness, loss of appetite, anemia, and weight loss. The ability of the small intestine to absorb nutrients from food is reduced. In elderly people, it is more common for the disease to affect the rectum and cause rectal bleeding.
Crohns disease can also affect the colon (the major part of the large intestine), causing bloody diarrhea. In rare cases, it also affects the mouth, esophagus, stomach, and duodenum (the upper part of the small intestine).
Complications may affect the intestines or may develop elsewhere in the body. The thickening of the intestinal wall may narrow the inside of the intestine so much that an obstruction occurs.
About three in ten affected people develop a fistula (abnormal passageway). Internal fistulas may form between loops of intestine. External fistulas, from the intestine to the skin of the abdomen of around the anus, may cause leakage of faces.
Abscesses (pus-filled pockets of infection) form in about one in five people. Many abscesses occur around the anus, but some occur within the abdomen. Complication in other parts of the body may include inflammation of various parts of the eye, severe arthritis affecting various joints of the body, ankylosing spondylitis (an inflammation of the spine), skin disorders, liver disease, and gallstones.
A physical examination may reveal tender abdominal swellings that indicate thickening of the intestinal walls. Sigmoidoscopy (examination of the lower, or sigmoid, colon and the rectum with a viewing instrument) may confirm the diagnosis. X-rays using barium follow through or barium enemas will show thickened loops of intestine with deep fissures.
It may be difficult to differentiate between Crohns disease when it is affecting the colon and ulcerative colitis, an inflammatory bowel disease limited to the large intestine. However, colonoscopy (examination of the colon using a flexible viewing instrument) and biopsy (the removal of a sample of tissue for microscopic examination) can confirm the diagnosis.