According to the Centers for Disease Control and Prevention, approximately 1.4 million Americans suffer from inflammatory bowel disease. This term primarily refers to Crohn's disease and ulcerative colitis. Both diseases affect the intestines, and both affect other organs in the body as well. But there are some distinct differences between the two.
Effects Within the Intestines
In ulcerative colitis, the inflammation is confined to two layers of the intestines; that is, to the mucosa and submucosa. The intestines become swollen and develop ulcers and pseudopolyps (pieces of mucosa that hang off the intestines). In Crohn's disease, the inflammation goes through all of the layers. This gives it what is referred to as a "cobblestone" appearance, and causes the formation of fistulas. A fistula is an abnormal opening that leads from one part of the body to another. The fistulas in Crohn's can go from one part of the intestines to another part of the intestines. But fistulas may also go from the intestines to the vagina, bladder or skin.
Pattern of Inflammation
The inflammation in ulcerative colitis can affect any part of the intestines, but it always starts at the rectum and migrates upward, in a continuous manner. Crohn's can also affect any part of the intestines, but it has a different pattern. It does not start at the rectum, and most of the time the rectum is not affected. And it is not a continuous inflammation; the inflammation skips, says Sonia Friedman, M.D., assistant professor of medicine at Harvard Medical School, in "Harrison's Principles of Internal Medicine." Normal intestinal tissue is in between the areas of inflammation.
Symptoms
Ulcerative colitis and Crohn's have symptoms that include abdominal pain and diarrhea. But in ulcerative colitis, it is a bloody diarrhea. Crohn's has a watery diarrhea, unless the rectum is involved. Then the diarrhea is bloody. People with Crohn's may also have fevers, abscesses and be able to feel a mass. Friedman writes they can also develop steatorrhea (fatty, smelly diarrhea), dermatitis (inflammation of the skin) and fractures in their vertebrae. If the jejunum and ileum are affected by the inflammation, the intestines cannot absorb fats, niacin, calcium and vitamin D. Fats will be lost in the bowel movement, causing steatorrhea. Niacin deficiency can cause dermatitis and diarrhea, while low calcium and vitamin D affect the bones.
Effects Outside of the Intestines
Both diseases can cause pyoderma gangrenosum (a skin disease), erythema nodosum (the inflammation of the fat beneath the skin), arthritis, ankylosing spondylitis (the inflammation of the spine and pelvis) and primary sclerosing cholangitis (the inflammation of the biliary structures). But Crohn's can also cause kidney stones and gallstones if the jejunum and ileum are diseased. The jejunum absorbs fats. If it is inflamed, it cannot absorb at the normal level and too much fat will result in kidney stones. The ileum absorbs bile. If there is too much bile, it hardens and forms gallstones.
References
- Centers for Disease Control and Prevention: Inflammatory Bowel Disease (IBD)
- "Harrison's Principles of Internal Medicine"; Anthony Fauci, M.D., Dennis Kasper, M.D., Dan Longo, M.D. et al.; 2008
