Most of the nutrient absorption that takes place in the small intestine occurs in the jejunum and the ileum. Disorders of the small intestine are usually related to problems with breaking down and absorbing nutrients.
Lactose intolerance is the inability to digest lactose, the sugar found in milk. It is caused by a deficiency of lactase, the enzyme needed to break down lactose during digestion. Symptoms of lactose intolerance include nausea, cramps, bloating, gas, and diarrhea. In general, symptoms appear about a half hour to 2 hours after a person eats or drinks food that contains lactose. Not all people with lactase deficiency experience symptoms, and the severity of symptoms varies from person to person. The disorder is especially common among adults of Asian, African, and Native American descent.
If you regularly experience symptoms of lactose intolerance when you consume dairy products, you may be lactose intolerant. To avoid these symptoms, your doctor may recommend that you consume smaller portions of your favorite dairy foods, eat only those dairy products that contain added lactase, or take over-the-counter lactase supplements (in liquid or tablets). He or she may recommend that you follow a dairy-free diet. Because not all dairy products cause symptoms in all people who are lactose intolerant, you may find some dairy foods easy to digest, and others intolerable.
Concerns interferes with its ability to absorb nutrients from food. Most cases of this rare disorder are diagnosed in infancy or early childhood. It is possible, however, for celiac disease to appear for the first time in an adult.
Gastrointestinal symptoms of celiac disease include recurring abdominal swelling and pain; fatty, yellow stools; and gas. Weight loss and unexplained anemia (characterized by fatigue and weakness) often occur. Other possible symptoms include bone or joint pain, muscle cramps, tooth discoloration, tingling and numbness in the legs, mouth sores, a painful skin rash, and behavior changes (such as depression). To diagnose celiac disease, doctors perform special blood tests and use an endoscope (viewing tube) to help remove tissue samples from the small intestine for microscopic examination.
Treatment for celiac disease is to follow a strict gluten-free diet. You will need to avoid wheat, rye, barley, and other grains that contain gluten. You also will need to watch for hidden gluten in foods such as pasta and beer. Rice and corn are safe to eat, and gluten-free flour and other food products also are available. Symptoms will begin to improve within a few days of beginning the diet, though full recovery may take up to 2 years. If left untreated, celiac disease can lead to intestinal cancer, osteoporosis (see page 301), and seizures.
Absorption of nutrients in the small intestine can be impaired by bacteria, viruses, parasites, and other microorganisms in food or fluids (including water). Symptoms of food poisoning usually come on suddenly and include vomiting, diarrhea, cramps, bloating, weakness, and loss of appetite. Symptoms also can occur 12 to 48 hours after consuming contaminated food or fluid, when the infectious microorganisms have multiplied to toxic levels in the digestive tract.
Treatment for food poisoning depends on the microorganism that is causing the problem. In most cases all that is needed is bed rest and plenty of clear fluids (such as water, a glucose-electrolyte solution, bouillon, or a sports drink). However, if you have diarrhea that contains blood or mucus or that lasts more than 3 days and a fever that lasts more than 2 days, see your doctor as soon as possible. Also, symptoms of dehydration—excessive thirst, infrequent urination, dry skin, fatigue, rapid heart rate, dizziness—require immediate medical treatment.
Keeping Your Digestive System Healthy
[ost digestive system disorders can be prevented by following a healthy lifestyle. The following tips can help you keep your digestive system healthy:
• Consume at least 20 to 25 grams of fiber daily.
• Exercise regularly.
• Drink at least eight glasses of water (8 ounces each) every day.
• Avoid using laxatives except under your doctor's supervision.
• Reduce the amount of fat in your diet.
• Do not smoke or use other tobacco products.
• Use safe food handling and storage procedures.
• Avoid drinking, washing, or cooking with water that may be contaminated by microorganisms.
Crohn's disease is a type of chronic inflammatory bowel disease that can occur anywhere in the gastrointestinal tract, although it most commonly occurs in the ileum. Crohn's disease causes inflammation that extends deep into the intestinal walls, causing pain in the lower right abdominal area (where the small intestine and the large intestine meet) and chronic diarrhea. There may be blood, mucus, or pus in the stool. Symptoms also may include rectal bleeding, weight loss, and fever. In some people with Crohn's disease, abnormal connecting channels called fistulas develop between the intestines and the skin in the genital area. If this happens, intestinal contents may leak through the skin. For reasons that are not known, symptoms also can occur in areas outside the gastrointestinal tract. For example, inflammation and redness may occur in the irises of the eyes, and inflammation and swelling may occur in the joints. An abnormal immune response may be the cause of these symptoms. Crohn's disease increases the risk of cancer and makes it more difficult to screen for cancer due to disease-related tissue changes. The cause of Crohn's disease is unknown, although it appears to run in families.
A doctor can confirm a diagnosis of Crohn's disease by examining the ileum and the colon with an endoscope (viewing tube) in a procedure called colon-oscopy (see "Diagnostic Procedures," page 282). There is no cure for Crohn's disease. Medications such as cortisone and sulfasalazine are used to control the inflammation. Drugs also may be used to treat fistulas and the body's abnormal immune response. Your doctor may recommend that you avoid drinking milk or alcohol or eating spicy or high-fiber foods to help prevent worsening of your symptoms. If you are losing weight because your body is not absorbing enough nutrients, your doctor may recommend that you drink a high-calorie liquid nutritional supplement every day. This type of nutritional supplement is available in single-serving cans. In severe cases of weight loss, diarrhea, or bleeding, the doctor may recommend intravenous (directly into a vein) feeding in the hospital until the tissue has recovered sufficiently to permit normal absorption of nutrients. If treatment with medication is ineffective, surgery may be performed to repair a fistula or to remove severely damaged sections of the intestine. Surgery also may be required if the doctor finds precancerous changes in the cells in the intestine. However, surgery will not cure the disease or prevent recurrence of symptoms.
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