Inflammation of Crohn's disease may involve different areas in different people. In some people, just the small intestine is affected. In others, it's confined to the colon (part of the large intestine). The most common areas affected by Crohn's disease are the last part of the small intestine (ileum) and the colon. Inflammation may be confined to the bowel wall, which can lead to scarring (stenosis), or inflammation may spread through the bowel wall (fistula).

Signs and symptoms of Crohn's disease can range from mild to severe and may develop gradually or come on suddenly, without warning. You may also have periods of time when you have no signs or symptoms (remission). When the disease is active, signs and symptoms may 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. Diarrhea is a common problem for people with Crohn's.
  • 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 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 include nausea and vomiting.
  • Blood in your stool. Food moving through your digestive tract may 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).
  • Ulcers. Crohn's disease can cause small sores on the surface of the intestine that eventually 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.

Other signs and symptoms

People with severe Crohn's disease may also experience:

  • Fever
  • Fatigue
  • Arthritis
  • Eye inflammation
  • Mouth sores
  • Skin disorders
  • Inflammation of the liver or bile ducts
  • Delayed growth or sexual development, in children

When to see a doctor

See your doctor if you have persistent changes in your bowel habits or if you have any of the signs and symptoms of Crohn's disease, such as:

  • Abdominal pain
  • Blood in your stool
  • Ongoing bouts of diarrhea that don't respond to over-the-counter (OTC) medications
  • Unexplained fever lasting more than a day or two
Aug. 09, 2011

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