Gastrointestinal Tract

Selenium is an essential trace mineral. Small amounts of selenium are good for your health.

Diet - selenium

Selenium has a variety of functions. It helps make special proteins, called antioxidant enzymes, which play a role in preventing cell damage. Some medical information suggests that selenium may help prevent certain cancers, but better studies are needed.

There have also been mixed results regarding selenium's impact on cardiovascular disease.

Selenium seems to stimulate antibodies after you receive a vaccination. It also may help protect the body from the poisonous effects of heavy metals and other harmful substances.

Selenium may boost fertility, especially among men. The mineral has been shown to improve the production of sperm and sperm movement.

Plant foods, such as vegetables, are the most common dietary sources of selenium. How much selenium is the vegetables you eat depends on how much of the mineral was in the soil where the plants grew.

Fish, shellfish, red meat, grains, eggs, chicken, liver, and garlic are all good sources of selenium. Meats produced from animals that ate grains or plants found in selenium-rich soil have higher levels of selenium.

Brewer's yeast, wheat germ, and enriched breads are also good sources of selenium.

Selenium deficiency is rare in people in the United States. However, selenium deficiency may occur when a person is fed through a vein (IV line) for long periods of time.

Keshan disease is caused by a deficiency of selenium. This leads to an abnormality of the heart muscle. Keshan disease caused many childhood deaths in China until the link to selenium was discovered and selenium supplements were provided.

Two other diseases have been linked to selenium deficiency:

• Kashin-Beck disease, which results in joint and bone disease
• Myxedematous endemic cretinism, which results in mental retardation

Severe gastrointestinal disorders may also affect the body's ability to absorb selenium.

Too much selenium in the blood can cause a condition called selenosis. Selenosis can cause loss of hair, nail problems, nausea, irritability, fatigue, and mild nerve damage. However, selenium toxicity is rare in the United States.

Selenium is often available in multivitamin and mineral supplements.

The Food and Nutrition Board at the Institute of Medicine recommends the following dietary intake for selenium:

Infants

• 0 - 6 months: 15 micrograms per day (mcg/day)
• 7 - 12 months: 20 mcg/day

Children

• 1 - 3 years: 20 mcg/day
• 4 - 8 years: 30 mcg/day
• 9 - 13 years: 40 mcg/day

Adolescents and Adults

• Males age 14 and older: 55 mcg/day
• Females age 14 and older: 55 mcg/day

The best way to get the daily requirement of essential vitamins is to eat a balanced diet that contains a variety of foods from the food guide pyramid.

Specific recommendations depend on age, gender, and other factors (such as pregnancy). Women who are pregnant or producing breast milk (lactating) need higher amounts. Ask your health care provider which amount is best for you.

Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes: Vitamin C, Vitamin E, Selenium, and Carotenoids. National Academy Press, Washington, DC, 2000.

Rakel D, ed. Integrative Medicine. 2nd ed. Philadelphia, Pa: Saunders Elsevier; 2007.

Hamrick I, Counts SH. Vitamin and mineral supplements. Wellness and Prevention. December 2008:35(4);729-747.

Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007.

Ammonium ion test measures the amount of ammonium ions in a blood sample.

NH4+ test; Ammonia nitrogen level

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

Fast for 8 - 12 hours. The health care provider may advise you to withhold drugs that may affect test results.

Drugs that can interfere with the test include thiazide or loop diuretics, barbiturates, acetazolamide, neomycin, and oral kanamycin. Consult the health care provider before this test if you are taking any of these medications.

When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.

This test may be performed when a condition that may cause toxic accumulation of ammonia is present or suspected. It is most commonly used to diagnose and monitor hepatic encephalopathy, a severe liver disease.

Ammonia (NH4+) is produced by cells throughout the body, especially the intestines, liver, and kidneys. Most of the ammonia produced in the body is used by the liver in the production of urea. Urea is also a waste product but is much less toxic than ammonia.

Ammonia is especially toxic to the brain and can cause confusion, lethargy, and sometimes coma.

The normal range is 15 - 45 micrograms per deciliter (mcg/dL).

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

Conditions that can increase ammonia levels include:

• Liver failure
• Severe congestive heart failure
• Erythroblastosis fetalis
• Gastrointestinal (GI) bleeding - usually in the upper GI tract
• Genetic diseases of the urea cycle
• Leukemia
• Pericarditis
• Reye syndrome
• Certain drugs

There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

Patients with liver disease may have clotting problems. After the venipuncture, pressure should be applied to the puncture site for several minutes to ensure that bleeding has stopped.

Berk PD, Korenblat KM. Approach to the patient with jaundice or abnormal liver test results. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 150.

Delta agent is a type of virus called hepatitis D that causes symptoms only in people who have a hepatitis B infection.

Hepatitis D virus

Hepatitis D virus (HDV) is only found in people who carry the hepatitis B virus. HDV may make a hepatitis B infection or existing hepatitis B liver disease worse. It can cause symptoms in people with hepatitis B virus who never had symptoms.

Hepatitis D infects about 15 million people worldwide. It occurs in 5% of people with hepatitis B.

Risk factors include:

• Abusing intravenous (IV) drugs
• Being infected while pregnant (the mother can pass the virus to the baby)
• Carrying the hepatitis B virus
• Having had a hepatitis B infection in the past
• Men having intercourse with other men
• Receiving many blood transfusions

Hepatitis D may make the symptoms of hepatitis B more severe.

Symptoms may include:

• Abdominal pain
• Dark-colored urine
• Fatigue
• Jaundice
• Joint pain
• Loss of appetite
• Nausea
• Vomiting

• Anti-delta agent antibody
• Liver biopsy
• Liver enzymes

Many of the medicines used to treat hepatitis B are not helpful for treating hepatitis D. See hepatitis B.

Persons with long-term HDV infection may receive a medicine called alpha interferon for up to 12 months. A liver transplant for end-stage chronic hepatitis B may be effective.

Persons with an acute HDV infection usually get better over 2 to 3 weeks. Liver enzyme levels return to normal within 16 weeks.

About 10% of those who are infected may develop long-term (chronic) liver inflammation (hepatitis).

• Chronic active hepatitis
• Fulminant hepatitis

Call for an appointment with your health care provider if you have symptoms of hepatitis B.

Prompt recognition and treatment of hepatitis B infection can help prevent hepatitis D.

Avoid intravenous drug abuse. If you use IV drugs, avoid sharing needles.

A vaccine is available to prevent hepatitis B. It should be considered by people who are at high risk for hepatitis B infection.

Dienstag JL. Chronic viral hepatitis. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 6th ed. Philadelphia, Pa: Elsevier Churchill Livingstone;2005:chap 112.