The cause of IBD is not well understood, but may be related to the response of the body’s immune system against bacteria in the colon. The bacteria cause the lining of the intestinal tract to become inflamed (red and swollen). IBD is thought of as an autoimmune disease. An autoimmune disease is a disease in which the immune system attacks itself rather than bacteria and other infections.
Ulcerative colitis starts in the rectum and can affect the entire colon or only part of it. The inflammation is chronic, which means that it is always present, although the symptoms may come and go. Symptoms "flare" when the colon is severely inflamed.
Ulcerative colitis may be called proctitis if only the rectum is involved, or it may be called left-sided colitis if only the lower half of the colon is affected. If most of the colon is involved, it may be called extensive colitis or pancolitis. The inflammation is continuous which means that the inflammation does not stop and then start again in a different part of the colon.
Crohn’s disease can affect any part of the digestive tract — the mouth, the esophagus, the stomach, the duodenum, the jejunum, the ileum, the ileocecal valve, the cecum, the ascending or right colon, the transverse colon, the descending or left colon, the sigmoid colon, and the rectum, to the anus. The most common area affected is the part of the small bowel called the ileum. The inflammation usually occurs in segments, with healthy segments of bowel in-between inflamed segments.
All types of IBD affect men and women about equally. It can occur at any age, but often starts between the ages of 15 to 25. Crohn’s disease is more common among people who have a family history of the disease. Ulcerative colitis affects about 600,000 people in the United States; Crohn’s disease affects about 700,000 people.
Diet can affect the symptoms of Crohn’s disease, but it is not likely that it is caused by diet. Research suggests that Crohn’s disease results from the way the body’s immune system reacts to the bacteria in the digestive tract. An overactive immune system may be genetic in families that have multiple members with Crohn’s disease.
The symptoms of IBD partly depend on where the inflammation occurs. Inflammation in the colon often causes diarrhea and bloody stools. Inflammation in the rectum often causes urgency (the need to have a bowel movement quickly) and tenesmus (frequent urges to have a bowel movement, but passing very little stool). If the colitis is severe, the inflammation may extend deep into the wall of the intestine and cause abdominal pain and cramping.
Crohn’s disease often causes abdominal pain, tenderness, and cramping. These symptoms occur as the muscles in the intestine push food through narrowed areas. Stomach cramps and bowel obstruction may lead to nausea and vomiting. In addition to bowel symptoms, you may have other symptoms such as severe fatigue, weight loss, loss of appetite, fever, sore or red eyes, skin rashes, and pain in the large joints, such as knees. People with IBD tend to have flares with active symptoms and periods of remission with no symptoms.
Scar tissue may result as the inflamed tissue heals. This scarring can narrow or even block the intestine. The narrowed area is called a stricture. If food can’t move through your intestine, you may have nausea and vomiting. Long-term obstruction raises the pressure in the part of the intestine before the narrowed or blocked area. This pressure can cause the inflamed intestinal wall to burst (perforation). An untreated perforation lets intestinal contents out into the abdomen. This is quite painful and requires immediate surgery. More commonly, the perforation forms a small hole and a tunnel to another organ as a way to release the pressure that builds up from the blockage. This tunnel is called a fistula. A fistula most commonly connects to another part of the intestine, to the skin, to the bladder, or to the vagina. If a fistula does not connect to an exit site, it can form a cavity filled with infected intestinal contents and pus. This is called an abscess.
Long-term inflammation of the colon can lead to colon dysplasia (abnormal or pre-cancerous cells) and colon cancer. Long-term inflammation of the small intestine rarely leads to cancer. However, inflammation of the small intestine can decrease the body’s ability to absorb iron and vitamin B12. This is called malabsorption. A lack of iron or B12 can cause anemia. Blood loss in the stool over time can also cause anemia. People with IBD also often have decreased vitamin D, which can lead to bone loss (osteopenia; osteoarthritis) Steroid use can make bone loss worse. In addition to the intestinal inflammation, you may have inflamed joints, arthritis, skin problems (sore red bumps or ulcers on the skin) and inflammation of the eyes or mouth. If your eyes suddenly become very red and sensitive to light, you need to have eye exam right away.
Crohn’s disease in the small intestine increases the risk for kidney stones and gallstones. The risk is higher if part of the small intestine has been removed. A decreased ability to absorb fat may lead to a specific type of kidney stones called oxalate. People with an ileostomy have no colon and do not develop oxalate kidney stones. A low oxalate diet may be helpful for someone who keeps getting oxalate kidney stones. To see the oxalate content of different foods go to this web site: http://www.lowoxalate.info/food_lists/alph_oxstat_chart.pdf.
Crohn’s disease also lowers the ability to absorb bile salts, which can lead to gallstones. Poor absorption of bile salts leads to an increase in cholesterol in the bile, which may cause gallstones.
Your will have a complete physical exam. You may need some tests, such as blood tests, stool tests, CT or MRI scans, and colonoscopy with biopsy. The colonoscopy is to look for sores or inflammation in the intestine. Because most of the treatments for IBD have risks, you need to be completely sure that you have IBD before it is treated. Your intestinal tissue will be looked at very closely under a microscope to be sure you have IBD and not an infection or another illness.