Health Library

17-hydroxycorticosteroid (17-OHCS) is an inactive product formed when the liver and other body tissues break down the steroid hormone, cortisol. This article discusses the laboratory test to measure the amount of 17-OHCS in urine.

17-ketosteroids are substances that form when the body breaks down male steroid sex hormones called androgens and other hormones released by part of the adrenal gland in males and females, and in the testes in males. This article discusses the laboratory test used to measure the amount of ...

17-OH progesterone is a blood test that measures the amount of 17-OH progesterone, a hormone produced by the and gonads.

The 24-hour urinary aldosterone excretion rate test measures the amount of aldosterone removed in the urine in a day. Aldosterone is a hormone released by the adrenal gland that helps the kidney control salt and potassium balance. See also:

The 24-hour urine copper test measures the amount of copper in a urine sample.

24-hour urine protein measures the amount of protein excreted in urine over a 24-hour period. See also:

The 25-hydroxy vitamin D test is the most accurate way to measure how much vitamin D is in your body. In the kidney, 25-hydroxy vitamin D changes into an active form of the vitamin. The active form of vitamin D helps control calcium and phosphate levels in the body. This article discusses the ...

5’-nucleotidase (5’-NT) is a protein produced by the liver. A test can be done to measure the amount of this protein in your blood.

5-HIAA is a urine test that measures the amount of 5-hydroxyindoleacetic acid (5-HIAA) — a breakdown product of a hormone called serotonin. This test tells how much 5-HIAA the body is producing.

Aarskog syndrome is an inherited disease that affects a person’s height, muscles, skeleton, genitals, and appearance of the face. Inherited means that it is passed down through families.

Aase syndrome is a rare disorder that involves and certain joint and skeletal deformities.

A swollen abdomen is when your belly area is bigger than usual. See also:

An abdominal aortic is when the large blood vessel that supplies blood to the abdomen, pelvis, and legs becomes abnormally large or balloons outward.

Open abdominal aortic aneurysm repair is surgery to fix a widened part (aneurysm) in your aorta, the large artery that carries blood to your belly (abdomen), pelvis, and legs. An is when part of this artery becomes too large or balloons outward. Your surgeon opens up your belly and replaces the ...

Abdominal bloating is a condition in which the abdomen (belly) feels full and tight. The abdomen may be visibly swollen (distended).

An abdominal CT scan is an imaging method that uses x-rays to create cross-sectional pictures of the belly area. CT stands for computed tomography. See also:

Abdominal exploration is surgery to examine the contents of the abdomen. Surgery that opens the abdomen is called a laparotomy. Laparotomy may also be done to treat certain health problems and conditions.

Abdominal girth is the measurement of the distance around the abdomen at a specific point, usually at the level of the belly button (navel). Measuring abdominal girth is used to diagnose and monitor the following: Buildup of fluid in the abdomen, most often caused by liver failure or heart ...

An abdominal mass is swelling in one part of the belly area (abdomen).

A magnetic resonance imaging (MRI) scan of the abdomen is a method to create detailed pictures of the inside of the belly area. Unlike and computed tomographic () scans, which use radiation, MRI uses powerful magnets and radio waves. Signals from the magnetic field bounce off your body and are ...

Abdominal pain is pain that you feel anywhere between your chest and groin. This is often referred to as the stomach region or belly.

Abdominal rigidity is stiffness of the muscles in the belly area, which can be felt when touched or pressed.

Abdominal sounds are the noises made by the intestines.

An abdominal tap is a procedure used to remove fluid from the area between the belly wall and the spine. This space is called the abdominal cavity.

Abdominal is an imaging procedure used to examine the internal organs of the abdomen, including the liver, gallbladder, spleen, pancreas, and kidneys. The blood vessels that lead to some of these organs can also be looked at with ultrasound.

An abdominal wall fat pad biopsy is the removal of a small part of the abdominal wall fat pad. The procedure is done most often to test for .

Abdominal wall surgery is surgery that improves the appearance of flabby, stretched-out abdominal (belly) muscles and skin. It is often called a “tummy tuck.” It can range from a simple “mini-tummy tuck” to more complicated, extended surgery. Tummy tuck is not the same as ...

An abdominal x-ray is an imaging test to look at organs and structures in the belly area, including the spleen, stomach, and intestines. When the test is done to look at the bladder and kidney structures, it’s called a KUB (kidneys, ureters, bladder) x-ray. See:

Abnormal posturing is different from what is commonly called “bad posture” or “slouching.” Instead, it is a tendency to hold a particular body position, or to move one or more parts of the body in a particular way. This phenomenon is an important part of evaluating a person ...

ABO incompatibility is a reaction of the immune system that occurs if two different and not compatible blood types are mixed together.

A medical abortion is the use of certain medications to end a pregnancy. The drugs help remove the fetus and placenta from the mother’s womb (uterus). There are different types of medical abortion. Sometimes the woman has one for a health reason. This is called a therapeutic medical ...

A surgical abortion is a procedure that ends a pregnancy by removing the fetus and placenta from the mother’s womb (uterus). There are different types of surgical abortion. Sometimes the woman needs the procedure for a health reason. This is called a therapeutic abortion. Other times, ...

An abscess is a collection of pus in any part of the body that, in most cases, causes swelling and inflammation around it.

Radioactive abscess scan uses a radioactive substance to look for abscesses in the body. An is a collection of pus in any part of the body. Abscesses occur when an area of tissue becomes infected, most often with bacteria.

Absent pulmonary valve is a rare defect in which the pulmonary valve that carries oxygen-poor blood from the heart to the lungs is either missing or poorly formed. This condition is present at birth (congenital). See also:

Acanthosis nigricans is a skin disorder in which there is darker, thick, velvety skin in body folds and creases.

ACE levels is a blood test that measures the amount of angiotensin-converting (ACE).

Acetaminophen (Tylenol) and codeine is a prescription pain medicine. It is a narcotic, which means it has the potential to relieve pain while making you feel sleepy. Acetaminophen and codeine occurs when someone accidentally or intentionally takes more than the normal or recommended amount of ...

Acetaminophen overdose is one of the most common poisonings worldwide. People often think that acetaminophen, a pain-relieving medicine, is extremely safe. However, it may be deadly if taken in large doses. This is for information only and not for use in the treatment or management of an actual ...

Acetone is a chemical used in many household products. This article discusses poisoning from swallowing acetone-based products. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you should call your local emergency ...

Acetylcholine receptor antibody is a protein found in the blood of most people with myasthenia gravis. The attacks receptors for a chemical called acetylcholine, which sends signals from nerves to muscles and between nerves in the brain.

Achalasia is a disorder of the tube that carries food from the mouth to the stomach (esophagus), which affects the ability of the esophagus to move food toward the stomach.

Achilles tendinitis is when the Achilles tendon becomes swollen, inflamed, and painful at the heel. The Achilles tendon connects your calf muscles to your heel bone. It is used for walking, running, and jumping.

Achondrogenesis is a rare type of in which there is a defect in the development of bone and cartilage.

Achondroplasia is a disorder of bone growth that causes the most common type of dwarfism.

The acid loading test (pH) measures the ability of the kidney tubules to acidify urine when there is increased plasma acidity. See also:

Acid mucopolysaccharides is a test that measures the amount of released into the urine over a 24-hour period. Mucopolysaccharides are long chains of sugar molecules found throughout the body, often in mucus and in fluid around the joints.

The acid-fast stain is a laboratory test that determines if a sample of tissue, blood, or other body substance is infected with the bacteria that causes tuberculosis and other illnesses.

Acidosis is a condition in which there is excessive acid in the body fluids. It is the opposite of alkalosis (a condition in which there is excessive base in the body fluids).

ACL reconstruction is surgery to replace the ligament in the center of your knee with a new ligament. The anterior cruciate ligament (ACL) keeps your shin bone (tibia) in place. A tear of this ligament can cause your knee to give way during physical activity.

Acne is a skin condition that causes whiteheads, blackheads, and inflamed red growths (papules, pustules, and cysts) to form. These growths are commonly called pimples or “zits.”

An acoustic neuroma is a slow-growing tumor of the nerve that connects the ear to the brain. This nerve is located behind the ear right under the brain. An acoustic neuroma is benign, which means it does not spread to other parts of the body or invade the tissue around it. However, it can damage ...

Acoustic trauma is injury to the hearing mechanisms in the inner ear due to very loud noise.

Acquired platelet function defects are diseases or conditions that cause the blood elements needed for blood clotting () to not work properly. The term “acquired” means these diseases or conditions are not inherited, but instead develop independently in a person.

Acrodermatitis is a childhood skin condition that may be accompanied by mild symptoms of and . It may also be associated with hepatitis B and other viral infections.

Acrodysostosis is an extremely rare disorder that is present at birth (congenital). People with this condition have problems in the bones of the hands, feet, and nose, and mental retardation.

Acromegaly is a metabolic disorder in which there is too much growth hormone and the body tissues gradually enlarge.

An ACTH test measures ACTH, a hormone released from the anterior pituitary gland in the brain.

ACTH (cosyntropin) stimulation test measures how well the adrenal glands respond to the hormone . ACTH is a hormone produced in the pituitary gland that stimulates the to release cortisol.

Actinic keratosis is a small, rough, raised area found on skin that has been exposed to the sun over a long period of time. Over many years, some actinic keratoses may develop into a type of .

Actinomycosis is a long-term (chronic) bacterial infection that commonly affects the face and neck.

Acute means sudden or severe. Acute symptoms appear, change, or worsen rapidly. It is the opposite of .

Acute adrenal crisis is a life-threatening condition that occurs when there is not enough cortisol, a hormone produced by the .

Acute arterial occlusion of the kidney is a sudden, severe blockage of the artery that supplies blood to the kidney.

Acute bilateral obstructive uropathy is a sudden blockage of the flow of urine from both kidneys. The kidneys continue to produce urine in the normal manner, but because urine does not drain properly, the kidneys start to swell. See also:

Acute cerebellar ataxia is sudden onset of .

Acute cholecystitis is a sudden inflammation of the gallbladder that causes severe . See also:

Acute cytomegalovirus (CMV) infection is a condition caused by a member of the herpesvirus family. See also:

Acute HIV infection is caused by the human immunodeficiency virus (HIV), a virus that gradually destroys the immune system.

Acute (sudden) kidney failure is the sudden loss of the ability of the kidneys to remove waste and concentrate urine without losing .

Acute lymphocytic leukemia (ALL) is a fast-growing cancer in which the body produces a large number of immature white blood cells (lymphocytes). These cells are found in the blood, bone marrow, lymph nodes, spleen, and other organs.

Acute mountain sickness is an illness that can affect mountain climbers, hikers, skiers, or travelers at high altitude (typically above 8,000 feet or 2,400 meters).

Acute myeloid leukemia (AML) is cancer that starts inside bone marrow, the soft tissue inside bones that helps form blood cells. The cancer grows from cells that would normally turn into white blood cells. Acute means the disease develops quickly. See also:

Acute nephritic syndrome is a group of disorders that cause swelling or inflammation of the internal kidney structures (specifically, the glomeruli). Nephritic syndrome is a type of .

Acute pancreatitis is sudden swelling and inflammation of the pancreas.

Acute respiratory distress syndrome (ARDS) is a life-threatening lung condition that prevents enough oxygen from getting into the blood. See also:

Acute tubular necrosis is a kidney disorder involving damage to the tubule cells of the kidneys, resulting in .

Acute unilateral is a sudden blockage in one of the tubes (ureters) that drain urine from the kidneys. See also:

An acute upper airway obstruction is a blockage of the upper airway, which can be in the trachea, voice box (laryngeal), or throat (pharyngeal) areas.

Addison’s disease is a disorder that occurs when the do not produce enough of their hormones.

Adenoid removal is surgery to take out the adenoid glands. These glands are located between the airway you breathe into through your nose and the back of your throat. Often, adenoid removal is done at the same time as a , surgery to remove the tonsils. Adenoid removal is also called adenoidectomy. ...

Adenomyosis is uterine thickening that occurs when endometrial tissue, which normally lines the uterus, moves into the outer muscular walls of the uterus.

ADH is a test that measures the amount of antidiuretic hormone (ADH) in blood. ADH is found in the body, and it may be given as a medication.

Adhesions are bands of scar-like tissue that form between two surfaces inside the body and cause them to stick together. As the body moves, tissues or organs inside are normally able to shift around each other. This is because these tissues have slippery surfaces.

Adjustment disorder is an emotional and behavioral reaction that develops within 3 months of a life stress, and which is stronger or greater than what would be expected for the type of event that occurred.

Adolescent depression is a disorder that occurs during the teenage years, and involves ongoing sadness, discouragement, loss of self-worth, and loss of interest in usual activities. See also:

The development of children ages 12 through 18 years old is expected to include predictable physical and mental milestones.

Adolescent pregnancy is pregnancy in girls age 19 or younger.

Proper preparations for a test or procedure can reduce an adolescent’s anxiety, encourage cooperation, and help the adolescent develop coping skills.

Adrenal glands are triangle-shaped glands located on top of the kidneys. The outer part of the adrenal gland is called the cortex and produces steroid hormones such as , , and . The inner part of the adrenal gland is called the medulla and produces and , which are commonly called adrenaline and ...

Adrenalectomy is an operation in which one or both adrenal glands are removed. The adrenal glands are part of the endocrine system and are located just above the kidneys.

Adrenergic bronchodilators are inhaled medicines that help open up the air passages. They are used to treat asthma and chronic bronchitis. Adrenergic bronchodilator occurs when someone accidentally or intentionally takes more than the normal or recommended amount of this medication. This is for ...

Adrenocortical carcinoma is a cancer of the .

Adrenoleukodystrophy describes several closely related inherited disorders that disrupt the breakdown () of certain fats (very-long-chain fatty acids).

Adult Still’s disease is a rare illness that causes high fevers, rash, and joint pain. It may lead to long-term (chronic) arthritis. Still’s disease is a severe version of juvenile idiopathic arthritis (JIA), which occurs in children. Adults can have the same condition, though much ...

Advance care directives are specific instructions, prepared in advance, that are intended to direct a person’s medical care if he or she becomes unable to do so in the future.

Aerobic means oxygen is needed to survive, grow, or function properly. For example, bacteria that require oxygen to grow are called aerobic bacteria. Aerobic is the opposite of .

Aerobic bacteria are bacteria that can grow and live in the presence of oxygen.

Aflatoxins are produced by a mold that grows in nuts, seeds, and legumes.

Aftershave is a lotion, gel, or liquid applied to the face after shaving. It is often used by men. This article discusses the harmful effects from swallowing aftershave products. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have ...

Agammaglobulinemia is an inherited disorder in which there are very low levels of protective immune system proteins called immunoglobulins. People with this disorder repeatedly develop infections.

An age-appropriate diet is one that provides adequate nutrition and is appropriate for a child’s state of development.

Age-related hearing loss, or presbycusis, is the slow loss of hearing that occurs as people get older.

Aging changes in the skin are a group of common conditions and developments that occur as people grow older.

As a woman ages, a number of changes take place in the female reproductive system. For women, the cessation of menses (menopause) is an obvious sign of aging. But, it is by no means the only change. A transition period, called the climacteric, lasts for many years before and after a woman’s ...

Aging changes in the male reproductive system may include changes in testicular tissue, sperm production, and erectile function. These changes usually occur gradually.

Aging changes in the senses are perceptual changes related to growing older.

Agitation is an unpleasant state of extreme arousal (stirred up or excited), increased , and irritability.

Agranulocytosis means a failure of the bone marrow to make enough white blood cells (neutrophils). Bone marrow is the soft tissue inside bones that helps form blood cells.

Aicardi syndrome is a rare inherited (genetic) disorder in which the structure that connects the two sides of the brain (corpus callosum) is partly or completely missing.

AIDS (acquired immune deficiency syndrome) is the final stage of , which causes severe damage to the immune system.

Albinism is a defect of production that results in little or no color (pigment) in the skin, hair, and eyes.

Albumin is a protein made by the liver. A serum albumin test measures the amount of this protein in the clear liquid portion of the blood.

Alcohol comes from fermenting and . Alcohol has about 7 calories per gram. These are considered “empty” calories because alcohol contains no beneficial nutrients, such as vitamins and minerals.

Pregnant women are strongly urged not to drink alcohol during pregnancy. Drinking alcohol while you are pregnant has been shown to have damaging effects on the developing baby and may even lead to permanent disability and medical problems in the child after birth.

Alcohol use involves drinking beer, wine, or hard liquor. See also:

Alcohol withdrawal refers to symptoms that may occur when a person who has been drinking too much alcohol every day suddenly stops drinking alcohol.

Alcoholic ketoacidosis is the build up of ketones in the blood. Ketones are a type of acid that form when the body breaks down fat for energy. The condition is an form of .

Alcoholic liver disease is damage to the liver and its function due to alcohol abuse. See also:

Alcoholic neuropathy is damage to the nerves that results from excessive drinking of alcohol.

Alcoholism (alcohol dependence) and alcohol abuse are two different forms of problem drinking. Alcoholism occurs when a person shows signs of physical addiction to alcohol (for example, tolerance and withdrawal) and continues to drink, despite problems with physical health, mental health, and ...

Aldolase is a protein (called an enzyme) that helps break down certain sugars into energy. It is found in high amounts in muscle tissue. A test can be done to measure the amount of aldolase in your blood.

An aldosterone test measures the amount of the hormone aldosterone in blood.

Alkalosis is a condition in which the body fluids have excess base (alkali). This is the opposite of excess acid ().

Alkaptonuria is a rare condition in which a person’s urine turns a dark brownish-black color when exposed to air. See also:

An allergen is a substance that can cause an allergic reaction. Allergens are substances that, in some people, the immune system recognizes as “foreign” or “dangerous” but cause no response for most people.

Allergic conjunctivitis is inflammation of the tissue lining the eyelids (conjunctiva) due to a reaction from allergy-causing substances such as pollen and dander. See also:

Allergic reactions are sensitivities to substances, called , that come into contact with the skin, nose, eyes, respiratory tract, and gastrointestinal tract. They can be inhaled into the lungs, swallowed, or injected.

Allergic rhinitis is a collection of symptoms, mostly in the nose and eyes, which occur when you breathe in something you are allergic to, such as dust, dander, or pollen. This article focuses on allergic rhinitis due to outdoor triggers, such as plant pollen. This type of allergic rhinitis is ...

Allergic vasculitis is an extreme reaction to a drug, infection, or foreign substance that leads to inflammation and damage to blood vessels of the skin.

An allergy is an exaggerated or reaction to substances that are generally not harmful. See also: (eczema) (allergic rhinitis)

Allergy tests are any of several tests used to determine the substances to which a person is allergic.

Allergy-related symptoms can occur after you are around mold, certain animals or animal hair, dust, and other substances. These substances are usually found indoors and do not cause symptoms for most people. See also:

Aloe is an extract from the aloe plant that is used in many skincare products. Aloe poisoning occurs when someone swallows this substance. However, aloe is relatively nonpoisonous. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have ...

Alopecia areata is a condition that causes round patches of hair loss, and can lead to total hair loss.

Alkaline phosphatase (ALP) is a protein found in all body tissues. Tissues with particularly high amounts of ALP include the liver, ducts, and bone. A blood test can be done to measure the level of ALP. See also:

Alkaline phosphatase (ALP) is a substance found in all body tissues. There are many different forms of ALP. Each type has a different chemical structure, called an isoenzyme. Its structure depends on where in the body it is produced. For example, liver and bone ALP isoenzymes have different ...

Alpha fetoprotein (AFP) is a protein normally produced by the liver and yolk sac of a fetus. AFP levels decrease soon after birth. AFP probably has no normal function in adults. A test can be done to measure the amount of AFP in your blood. See also:

Alpha-1 antitrypsin (AAT) deficiency is a condition in which the body does not make enough of a protein that protects the lungs and liver from damage. The condition can lead to emphysema and .

Alpha-1 antitrypsin is a laboratory test to measure the amount of alpha-1 antitrypsin (A1AT) in your blood.

Alport syndrome is an inherited disorder that damages tiny blood vessels in the kidneys.

Alström syndrome is a very rare inherited disease that can lead to , , , and .

Alanine transaminase (ALT) is an found in the highest amounts in the liver. Injury to the liver results in release of the substance into the blood. This article discusses the test to measure the amount of ALT in the blood.

Alveolar abnormalities are changes in the tiny air sacs in the lungs, called alveoli. The alveoli allow oxygen to enter the blood. These air sacs may collapse, fuse together, or develop thickened membranes, making it difficult for oxygen to enter the blood.

is a loss of brain function that occurs with certain diseases. Alzheimer’s disease (AD), is one form of dementia that gradually gets worse over time. It affects memory, thinking, and behavior. Memory impairment, as well as problems with language, decision-making ability, judgment, and ...

Amaurosis fugax is loss of vision in one eye due to a temporary lack of blood flow to the . It may be a sign of an impending stroke. See:

Ambiguous genitalia is a birth defect where the outer genitals do not have the typical appearance of either a boy or a girl. See also:

Amblyopia, or “lazy eye,” is the loss of one eye’s ability to see details. It is the most common cause of vision problems in children.

Amebiasis is an infection of the intestines caused by the parasite Entamoeba histolytica.

Amebic liver abscess is a collection of pus in the liver brought on by an intestinal parasite.

Amelogenesis imperfecta is a tooth development disorder in which the teeth are covered with thin, abnormally formed enamel.

Amenorrhea is the absence of menstruation. Menstruation is a woman’s monthly period. Primary amenorrhea is when a girl has not yet started her monthly periods, and she: Has gone through other normal changes that occur during puberty Is older than 15 See also:

Aminoaciduria is an abnormal amount of in the urine. Amino acids are the building blocks for proteins in the body. This article discusses the test used to look for increased amounts of amino acids in the urine. See also:

Aminophylline or theophylline are medicines used to prevent and treat wheezing and other breathing difficulties caused lung diseases such as asthma. Aminophylline or theophylline occurs when someone accidentally or intentionally takes more than the normal or recommended amount of these ...

Amitriptyline and perphenazine is a combination drug that is sometimes prescribed for patients with depression, agitation, or anxiety. Amitriptyline and perphenazine occurs when someone accidentally or intentionally takes more than the normal or recommended amount of this medication. This is ...

Amitriptyline hydrochloride is a type of prescription medicine called a tricyclic antidepressant. Amitriptyline hydrochloride occurs when someone accidentally or intentionally takes more than the normal or recommended amount of this medication. This is for information only and not for use in the ...

Ammonia is a strong, colorless gas. If the gas is dissolved in water, it is called liquid ammonia. Poisoning may occur if you breathe in ammonia. Poisoning may also occur if you swallow or touch products that contain very large amounts of ammonia. This is for information only and not for use in ...

Ammonium hydroxide is a colorless liquid chemical solution that forms when ammonia dissolves in water. This article discusses poisoning due to ammonium hydroxide. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you ...

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

Amniocentesis is a test during pregnancy that removes a small amount of fluid from the sac around the baby to look for birth defects and chromosome problems.

Amniotic constriction bands are strands of the fluid-filled sac (amniotic sac) that surrounds a baby in the womb. They may cause a congenital (present from birth) deformity of the face, arms, legs, fingers, or toes.

Amniotic fluid is a clear, slightly yellowish liquid that surrounds the unborn baby (fetus) during pregnancy. It is contained in the amniotic sac.

Traumatic amputation is the loss of a body part — usually a finger, toe, arm, or leg — that occurs as the result of an accident or injury.

Amylase is an that helps digest carbohydrates. It is produced mainly in the pancreas and the glands that make saliva. When the pancreas is diseased or inflamed, amylase releases into the blood. A test can be done to measure the level of this enzyme in your blood. Amylase may also be measured ...

This is a test that measures the amount of amylase in urine. Amylase is an that helps digest carbohydrates. It is produced mainly in the pancreas and the glands that make saliva. Amylase may also be measured with a blood test. See:

Amyotrophic lateral sclerosis, or ALS, is a disease of the nerve cells in the brain and spinal cord that control voluntary muscle movement. ALS is also known as Lou Gehrig’s disease.

Anaerobic means “without oxygen.” Anaerobic bacteria are able to survive and grow in environments that have no oxygen. Anaerobic exercise, such as weight lifting, uses energy produced the body’s metabolism that does not require oxygen. Anaerobic is the opposite of .

Anaerobic bacteria are bacteria that do not live or grow in the presence of oxygen. In humans, this type of bacteria is most commonly found in the gastrointestinal tract. It plays a role in conditions such as , , and .

An anal fissure is a small split or tear in the thin moist tissue () lining the lower rectum (anus).

Analgesic nephropathy involves damage to one or both kidneys caused by overexposure to mixtures of medications, especially over-the-counter pain remedies (analgesics).

Anaphylaxis is a life-threatening type of .

Anaplastic thyroid carcinoma is a rare and aggressive form of cancer of the thyroid gland.

An anastomosis is a surgical connection between two structures. It usually means a connection that is created between tubular structures, such as blood vessels or loops of intestine. For example, when part of an intestine is surgically removed, the two remaining ends are sewn or stapled together ...

Androgen insensitivity syndrome (AIS) is when a person who is genetically male (has one X and one Y chromosome) is resistant to male hormones called androgens. As a result, the person has some or all of the physical characteristics of a woman, despite having the genetic makeup of a man.

Anemia is a condition in which the body does not have enough healthy red blood cells. Red blood cells provide oxygen to body tissues. See also:

Anemia is a condition in which the body does not have enough healthy red blood cells. Red blood cells provide oxygen to body tissues. Vitamin B12 deficiency anemia is a low red blood cell count due to a lack of . See also:

Anemia is a condition in which the body does not have enough healthy red blood cells. Red blood cells provide oxygen to body tissues. There are many types of anemia. Anemia of chronic disease is a blood disorder that results from a long-term (chronic) medical condition that affects the production ...

Anencephaly is the absence of a large part of the brain and the skull.

Anesthesia is the delivery of medicine to prevent you from feeling pain during surgery and other medical or dental procedures.

An aneurysm is an abnormal widening or ballooning of a portion of an artery due to weakness in the wall of the blood vessel. See also:

An aneurysm is a weak area in the wall of a blood vesel that causes the blood vessel to bulge or balloon out. When an aneurysm occurs in a blood vessel of the brain, it is called a cerebral aneurysm.

Angina is a type of chest discomfort due to poor blood flow through the blood vessels (coronary vessels) of the heart muscle (myocardium). Related topics:

Angiodysplasia of the colon is swollen, fragile blood vessels in the colon that occasionally result in blood loss from the gastrointestinal (GI) tract.

Angioedema is a swelling, similar to hives, but the swelling is beneath the skin rather than on the surface. Hives are often called welts. They are a surface swelling. It is also possible to have angioedema without hives. See also:

You have an artery on each side of your neck called the carotid artery. This artery brings needed blood to your brain and face. The blood flow in this artery can become partly or totally blocked by fatty material called plaque. A partial blockage is called carotid artery stenosis (narrowing). A ...

Angioplasty is a procedure to open narrowed or blocked blood vessels that supply blood to the heart. These blood vessels are called the coronary arteries. A coronary artery stent is a small, metal mesh tube that expands inside a coronary artery. A is often placed during or immediately after ...

Angioplasty (ballooning) is a procedure to open narrowed or blocked blood vessels that supply blood to your legs. These arteries can become blocked with fatty material that builds up inside them. This is called . A is a small, metal mesh tube that keeps the artery open. Angioplasty and stent ...

An animal bite can result in a break in the skin, a bruise, or a puncture wound.

Anisocoria is unequal pupil size. The pupil is the black part in the center of the eye. It gets larger in dim light and smaller in bright light.

Ankle pain involves any discomfort in one or both ankles.

Ankle replacement is surgery to replace the damaged parts of the three bones that make up the ankle joint. Artificial joint parts () are used to replace your own bones. They come in different sizes to fit different-size people.

Ankylosing spondylitis is a long-term disease that causes inflammation of the joints between the spinal bones, and the joints between the spine and pelvis. It eventually causes the affected spinal bones to join together. See also:

An annular pancreas is a ring of pancreatic tissue that encircles the (the first part of the small intestine). Normally, the pancreas sits next to, but does not surround, the duodenum.

Anomalous left coronary artery from the pulmonary artery (ALCAPA) is a heart defect in which the left coronary artery (which carries blood to the heart muscle) is connected to the pulmonary artery instead of to the aorta. ALCAPA is present at birth (congenital).

Anorchia is the absence of both at birth.

An anorectal abscess is a collection of pus in the area of the anus and rectum.

Anorexia nervosa is an eating disorder that involves an inability to stay at the minimum body weight considered healthy for the person’s age and height. Persons with this disorder may have an intense fear of weight gain, even when they are underweight. They may use extreme dieting, excessive ...

Anoscopy is a method to view the anus, anal canal, and lower rectum.

Anterior means “in front of” or “the front surface of.” The term usually refers to the front side of the body. For example, your knee caps and your face are on the anterior surfaces of your body.

An anterior cruciate ligament injury is the over-stretching or tearing of the anterior cruciate ligament (ACL) in the knee. A tear may be partial or complete.

Anterior knee pain is pain that occurs at the front and center of the knee.

Anterior vaginal wall repair is surgery that tightens the front () wall of the vagina.

Anthrax is an infectious disease caused by bacteria called Bacillus anthracis. Infection in humans most often involves the skin, the gastrointestinal tract, or the lungs. See also:

Anti-DNase B is a blood test to look for a substance produced by Group A Streptococcus, the bacteria that cause strep throat. See also:

The glomerular basement membrane is a part of the kidneys that helps filter waste and extra fluid from the blood. Anti-glomerular basement membrane antibodies are against this membrane. They can lead to kidney damage. This article describes the blood test to detect these antibodies.

The anti-insulin antibody test checks to see if your body has produced antibodies against insulin.

Anti-reflux surgery is surgery to correct a problem with the muscles at the bottom of the esophagus (the tube from your mouth to the stomach). Problems with these muscles allow (GERD) to happen. This surgery can also repair a .

Anti-reflux surgery is surgery to repair the muscles at the bottom of the esophagus (the tube that carries food from the mouth to the stomach). Problems with these muscles can lead to (GERD). This surgery can also repair a .

Anti-rust product poisoning occurs when someone breathes in or swallows anti-rust products. These products may be accidentally breathed in (inhaled) if they are used in a small, poorly ventilated area, such as a garage. This is for information only and not for use in the treatment or management of ...

Anti-smooth muscle antibody is a blood test that detects the presence of against smooth muscle.

An antibody is a protein produced by the body’s immune system when it detects harmful substances, called antigens. Examples of antigens include microorganisms (such as bacteria, fungi, parasites, and viruses) and chemicals. Antibodies are also produced when the immune system mistakenly ...

Antibody titer is a laboratory test that measures the presence and amount of in blood. The antibody level in the blood is a reflection of past exposure to an or to something that the body does not recognize as belonging to itself. The body uses antibodies to attack and remove foreign substances.

Anticoagulant rodenticides are poisons used to kill rats. Rodenticide means rodent killer. An anticoagulant is a blood thinner. Anticoagulant rodenticide poisoning occurs when someone swallows a product containing these chemicals. This is for information only and not for use in the treatment or ...

Antidiarrheal drugs are medications used to treat loose, watery, and frequent stools. This article discusses of antidiarrheal drugs containing diphenoxylate or atropine. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an ...

Antifreeze is a liquid used to cool engines. It is also called engine coolant. This article discusses poisoning caused by swallowing antifreeze. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you should call your ...

An antigen is any substance that causes your immune system to produce against it. An antigen may be a foreign substance from the environment such as chemicals, bacteria, viruses, or pollen. An antigen may also be formed within the body, as with bacterial or tissue cells.

Antimitochondrial antibodies (AMA) are substances () that form against mitochondria, an important part of cells. Mitochondria are the energy source inside all of the body’s cells. Mitochondria help cells work properly. This article discusses the blood test used to measure the amount of AMA ...

The antinuclear antibody panel is a blood test that looks at antinuclear antibodies (ANA). Antinuclear are substances produced by the immune system that attack the body’s own tissues. See also:

The antiparietal cells antibodies test measures the presence of against the parietal cells of the stomach. The parietal cells make and release and stomach acid. Intrinsic factor is needed to absorb vitamin B12.

Antisocial personality disorder is a mental health condition in which a person has a long-term pattern of manipulating, exploiting, or violating the rights of others. This behavior is often criminal.

Antistreptolysin O (ASO) titer is a blood test to measure against streptolysin O, a substance produced by group A Streptococcus bacteria.

Antithrombin III is a blood test that measures the amount of antithrombin III (AT III), a that helps control blood clotting.

Antithyroglobulin antibody is a test to measure to a protein called thyroglobulin, which is found in thyroid cells.

Antithyroid microsomal antibody is a test to measure antithyroid microsomal in the blood. Microsomes are found inside thyroid cells. The body produces antibodies to microsomes when there has been damage to thyroid cells.

Endovascular abdominal aortic aneurysm repair is surgery to fix a widened part (or aneurysm) in your aorta, the large artery that carries blood to your belly, pelvis, and legs. An is when a part of this artery becomes too large, or balloons outward, due to weakness in the wall of the artery. ...

Aortic angiography is a procedure that uses a special dye and x-rays to see how blood flows through the aorta, the major artery leading out of the heart, and through your abdomen or belly. Angiography is an imaging test that uses x-rays and a special dye to see inside the arteries. Arteries are ...

Aortic arch syndrome refers to a group of signs and symptoms associated with structural problems in the arteries that branch off the aortic arch. The aortic arch is the top part of the main artery carrying blood away from the heart.

Aortic dissection is a potentially life-threatening condition in which there is bleeding into and along the wall of the aorta, the major artery carrying blood out of the heart.

Aortic insufficiency is a heart valve disease in which the aortic valve weakens or balloons, preventing the valve from closing tightly. This leads to the backward flow of blood from the aorta (the largest blood vessel) into the left ventricle (the left lower chamber of the heart).

The aorta is the main artery carrying blood out of the heart. When blood leaves the heart, it flows through the aortic valve, into the aorta. In aortic stenosis, the aortic valve does not open fully. This decreases blood flow from the heart.

Aortic valve surgery is done to replace the aortic valve in your heart. Blood flows out of your heart and into the aorta through a valve. This valve is called the aortic valve. It opens up so blood can flow out. It then closes, keeping blood from flowing backwards. An aortic valve that does not ...

Aortopulmonary window is a rare heart defect in which there is a hole connecting the major artery taking blood from the heart to the body (the aorta) and the one taking blood from the heart to the lungs (pulmonary artery). The condition is congenital, which means it is present from birth.

Apert syndrome is a genetic disease in which the seams between the skull bones close earlier than normal. This affects the shape of the head and face.

APGAR is a quick test performed at 1 and 5 minutes after birth. The 1-minute score determines how well the baby tolerated the birthing process. The 5-minute score assesses how well the newborn is adapting to the new environment. The rating is based on a total score of 1 to 10, with 10 suggesting ...

Aplastic means: Did not grow or develop normally Did not fully mature Became incapable of forming new tissue

Apnea is breathing that slows down or stops from any cause. Apnea of prematurity refers to short episodes of stopped breathing in babies who were born before they were due.

Apolipoprotein B100 (apo B100) is a protein that plays a role in moving cholesterol around your body. It is a form of (LDL). This article discusses the test used to measure the level of apoB100 in the blood.

Apolipoprotein CII (apoCII) is a protein found in large fat particles absorbed from the gastrointestinal tract. It is also found in very low density lipoprotein (), which is made up of mostly triglycerides. This article discusses the test used to check for apoCII in a sample of your blood.

Apoplexy is bleeding into an organ or loss of blood flow to an organ. For example, adrenal apoplexy is bleeding into the , pituitary apoplexy is bleeding into the pituitary gland, and so on. When the word apoplexy (with no organ specified) is used alone, it often refers to stroke symptoms that ...

An appendectomy is surgery to remove the appendix. See also:

Appendicitis is inflammation of the appendix. The appendix is a small pouch attached to the beginning of your large intestine.

A decreased appetite is when you have a reduced desire to eat. The medical term for a loss of appetite is anorexia.

Increased appetite means you have an excess desire for food.

Appropriate for gestational age (AGA) describes a fetus or newborn infant whose size is within the normal range for his or her .

Apraxia is a disorder of the brain and nervous system in which a person is unable to perform tasks or movements when asked, even though: The request or command is understood They are willing to perform the task The muscles needed to perform the task work properly The task may have already been ...

Arachnodactyly is a physical condition in which the fingers are long, slender, and curved, resembling a spider’s legs.

A computed tomography (CT) scan of the arm is an imaging method that uses x-rays to create cross-sectional pictures of the arm.

A magnetic resonance imaging (MRI) scan of the arm is a method to create detailed pictures of the upper and lower arm, including the elbow, wrist, hands, fingers, and the surrounding muscles and other tissues. Unlike and computed tomographic () scans, which use radiation, MRI uses powerful ...

An armpit lump refers to enlargement of one or more lymph nodes under the arm.

Arrhenoblastoma of the ovary is an that releases the male hormone, , or other hormones. See also:

An arrhythmia is a disorder of the (pulse) or heart rhythm, such as beating too fast (tachycardia), too slow (bradycardia), or irregularly.

Arterial embolism is a sudden interruption of blood flow to an organ or body part due to a clot (embolus).

Arterial insufficiency is a lack of enough blood flow through the arteries. See also:

An arterial stick is the collection of blood from an artery for laboratory testing.

An arteriogram is an imaging test that uses x-rays and a special dye to see inside the arteries. It can be used to see arteries in the heart, brain, kidney, and many other parts of the body. The procedure is often called angiography. See also:

A cerebral arteriovenous malformation is an abnormal connection between the arteries and veins in the brain that usually forms before birth.

Arthritis is inflammation of one or more joints, which results in pain, swelling, stiffness, and limited movement. There are over 100 different types of arthritis. See also:

Arthroscopy is surgery that is done using a tiny camera on the end of a tube to check for and treat joint problems. See also:

Asbestos-related pleural effusion is a collection of fluid around the lung that generally develops a few years after asbestos exposure. The fluid collection is not harmful and usually goes away on its own. See:

Asbestosis is a disease brought on by inhaling asbestos fibers.

Ascariasis is infection with the parasitic roundworm Ascaris lumbricoides.

Ascites is excess fluid in the space between the tissues lining the abdomen and abdominal organs (the peritoneal cavity). See also:

Aseptic meningitis is an illness that appears similar to bacterial meningitis. However, bacteria do not grow in cultures of the fluid around the brain and spinal cord (cerebrospinal fluid). This may occur because there are no bacteria, or because the bacteria are difficult to grow. See also:

Asherman syndrome is the formation of intrauterine adhesions (scar tissue), which typically develop after uterine surgery.

Aspartic acid, also called asparaginic acid, is one of the nonessential . “Nonessential” means that our bodies produce it even if we don’t get this amino acid from the food we eat. Aspartic acid helps every cell in the body work. It plays a role in: Hormone production and ...

Asperger syndrome is often considered a high functioning form of autism. People with this syndrome have difficulty interacting socially, repeat behaviors, and often are clumsy. Motor milestones may be delayed.

Aspergillosis is an infection, growth, or due to the Aspergillus fungus.

Aspergillosis precipitin is a laboratory test to detect in the blood resulting from exposure to the fungus .

Asphalt is a brownish-black liquid petroleum material that hardens when it cools. Asphalt cement poisoning occurs when someone swallows asphalt. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you should call your ...

Aspiration means to draw in or out using a sucking motion. This medical term has two meanings, depending on how it is used: Aspiration can mean breathing in a foreign object (such as sucking food into the airway). The term can also refer to a medical procedure that removes harmful or misplaced ...

Aspiration pneumonia is inflammation of the lungs and airways to the lungs (bronchial tubes) from breathing in foreign material.

An overdose of aspirin means you have too much aspirin in your body. This can happen in two ways: If a person accidentally or intentionally takes a very large dose of aspirin at one time, it’s called an acute overdose. If a normal daily dose of aspirin builds up in the body over time and ...

AST (aspartate aminotransferase) is an found in high amounts in heart muscle and liver and skeletal muscle cells. It is also found in lesser amounts in other tissues. This article discusses the test to measure the amount of AST in the blood.

Asthma is an inflammatory disorder of the airways, which causes attacks of , shortness of breath, chest tightness, and coughing. See also:

is a disease of the respiratory system, which causes swelling and narrowing of the airways. Pediatric asthma refers to asthma in children.

Astigmatism is a type of refractive error of the eye. Refractive errors cause blurred vision and are the most common reason why a person goes to see an eye professional. Other types of refractive errors are:

Asymptomatic means there are no symptoms. You are considered asymptomatic if you: Have recovered from an illness or condition and no longer have symptoms Have an illness or condition (such as early stage high blood pressure or glaucoma) but do not have symptoms

Asymptomatic bacteriuria is a significant number of bacteria in the urine that occurs without usual symptoms such as burning during urination or frequent urination. Asymptomatic bacteriuria may not need treatment, which makes it different from a bacterial .

Asymptomatic HIV infection is a phase of infection with human immunodeficiency virus (HIV) during which there are no symptoms of HIV infection.

Ataxia-telangiectasia is rare childhood disease that affects the brain and other parts of the body. Ataxia refers to uncoordinated movements, such as walking. Telangiectasias are enlarged blood vessels (capillaries) just below the surface of the skin. Telangiectasias appear as tiny, red, ...

Atelectasis is the collapse of part or (much less commonly) all of a lung. See also:

Atheroembolic renal disease (AERD) is an inflammatory reaction in the small blood vessels of the kidneys.

Atherosclerosis is a condition in which fatty material collects along the walls of arteries. This fatty material thickens, hardens (forms calcium deposits), and may eventually block the arteries. Atherosclerosis is a type of arteriosclerosis. The two terms are often used to mean the same thing.

Athlete’s foot is an infection of the feet caused by fungus. The medical term is tinea pedis. Athlete’s foot may last for a short or long time and may come back after treatment.

Eczema is a skin disorder that involves scaly and itchy rashes. Atopic eczema is the most common type. See also:

Atrial fibrillation/flutter is a heart rhythm disorder (arrhythmia). It usually involves a rapid that is not regular.

An atrial myxoma is a noncancerous tumor in the upper left or right side of the heart. It grows on the wall (atrial septum) that separates the two sides of the heart.

Atrial septal defect (ASD) is a congenital heart defect in which the wall that separates the upper heart chambers (atria) does not close completely. Congenital means the defect is present at birth.

Atrophic vaginitis is inflammation of the vagina due to thinning tissue and decreased lubrication. It is related to reduced estrogen levels. For other types and causes of vaginitis, see:

ADHD is a problem with inattentiveness, over-activity, impulsivity, or a combination. For these problems to be diagnosed as ADHD, they must be out of the normal range for a child’s age and development.

Atypical pneumonia refers to pneumonia caused by certain bacteria, including Legionella pneumophila, Mycoplasma pneumoniae, and Chlamydophila pneumoniae. Pneumonia is a condition in which there is an infection of the lung.

An audiometry exam tests your ability to hear sounds. Sounds vary based on their loudness (intensity) and the speed of sound wave vibrations (tone). Hearing occurs when sound waves stimulates the nerves of the inner ear. Eventually the sound travels along nerve pathways to the brain. Sound waves ...

An aural polyp is a growth in the outside (external) ear canal. It may be attached to the eardrum (tympanic membrane), or it may grow from the middle ear space.

Auscultation is the method of listening to the sounds of the body during a .

Autism is a developmental disorder that appears in the first 3 years of life, and affects the brain’s normal development of social and communication skills.

Autoerythrocyte sensitivity means your body is sensitive to its own red blood cells (erythrocytes). This generally results in the destruction of red blood cells.

An autoimmune disorder is a condition that occurs when the immune system mistakenly attacks and destroys healthy body tissue. There are more than 80 different types of autoimmune disorders. See also:

Autoimmune hepatitis is inflammation of the liver that occurs when immune cells mistake the liver’s normal cells for harmful invaders and attack them.

An autoimmune liver disease panel is a series of tests performed when autoimmune is suspected. An autoimmune liver disease means that the body’s immune system attacks the liver. These tests include: Anti-liver/kidney microsomal antibodies Occasionally, the panel may also include additional ...

Autoinoculation is a procedure in which cells are removed from a person’s body, treated or medically changed, and then placed back into the body. The procedure is done to help prevent an immune reaction or to help diagnose a medical condition or illness. Autoinoculation can also refer to the ...

Automatic dishwasher soap poisoning refers to illness that occurs when you swallow soap used in automatic dishwashers or when the soap contacts the face. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you should ...

Autonomic hyperreflexia is a reaction of the autonomic (involuntary) nervous system to overstimulation. This reaction may include high blood pressure, change in heart rate, skin color changes (paleness, redness, blue-grey skin color), and excessive sweating.

Autonomic neuropathy is a group of symptoms that occur when there is damage to the nerves that manage every day body functions such as blood pressure, heart rate, bowel and bladder emptying, and digestion.

Autosomal dominant is one of several ways that a trait or disorder can be passed down through families. If a disease is autosomal dominant, it means you only need to get the abnormal from one parent in order for you to inherit the disease. One of the parents may often have the disease.

Autosomal recessive is one of several ways that a trait, disorder, or disease can be passed down through families. An autosomal recessive disorder means two copies of an abnormal must be present in order for the disease or trait to develop.

Avian influenza is infection in birds. The virus that causes the bird infectin can change (mutate) to infect humans. Such mutation could start a deadly worldwide epidemic.

Avoidant personality disorder is a mental health condition in which a person has a lifelong pattern of feeling very shy, inadequate, and sensitive to rejection.

Axillary nerve dysfunction is a loss of movement or sensation of the shoulder because of nerve damage.