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Glossaries - B

We've defined thousands of terms related to health care. This page discusses glossary terms with the letter B.

B lymphocyte (B cell)

one of the two major classes of lymphocytes, B lymphocytes are white blood cells of the immune system that are derived from the bone marrow and spleen. B cells develop into plasma cells, which produce antibodies.

Background retinopathy

Early stage of diabetic retinopathy; usually does not impair vision. Also called "nonproliferative retinopathy."

Bacterial Toxin

A poison made by a bacteria that kills specific tumor cells without harming normal cells.

Barium (BAIR-ee-um)

A chalky liquid used to coat the inside of organs so that they will show up on an x-ray.

Barium Enema X-Ray (BAIR-ee-um EN-uh-muh EKS-ray)

Barium Meal

Barrett's Esophagus (BAH-ruts eh-SAW-fuh-gus)

Peptic ulcer of the lower esophagus. It is caused by the presence of cells that normally stay in the stomach lining.

Basal rate

Refers to a continuous supply of low levels of insulin, as in insulin pump therapy.


the time point in a study just before initiation of intervention (vaccination) when starting measurements are taken. Measurements taken at later time points may be compared with those taken at baseline to study variations.

Basilar artery migraine

Migraine, occurring primarily in young women and often associated with the menstrual cycle, that involves a disturbance of a major brain artery. Symptoms include vertigo, double vision, and poor muscular coordination.


Not cancer; does not invade or spread to other parts of the body.

Benign exertional headache

headache brought on by running, lifting, coughing, sneezing, or bending.

Beta cell

A type of cell in the pancreas in areas called the islets of Langerhans. Beta cells make and release insulin, a hormone that controls the level of glucose (sugar) in the blood.

Bernstein Test (BURN-styn test)

A test to find out if heartburn is caused by acid in the esophagus. The test involves dripping a mild acid, similar to stomach acid, through a tube placed in the esophagus.

Beta-adrenergic Antagonist (BAY-tah ah-dren-ER-jik)

also known as beta-blockers, these drugs inhibit the action of certain types of neurons that stimulate beta receptors (see Chemoreceptor).

Bezoar (BEE-zor)

A ball of food, mucus, vegetable fiber, hair, or other material that cannot be digested in the stomach. Bezoars can cause blockage, ulcers, and bleeding.

Bile (BY-ul)

Fluid made by the liver and stored in the gallbladder. Bile helps break down fats and gets rid of wastes in the body.

Bile Acids (BY-ul ASS-idz)

Acids made by the liver that work with bile to break down fats.

Bile Ducts (BY-ul dukts)

Tubes that carry bile from the liver to the gallbladder for storage and to the small intestine for use in digestion.

Biliary Atresia (BILL-ee-air-ee uh-TREEZ-ya)

A condition present from birth in which the bile ducts inside or outside the liver do not have normal openings. Bile becomes trapped in the liver, causing jaundice and cirrhosis. Without surgery the condition may cause death.

Biliary Stricture (BILL-ee-air-ee STRIK-sher)

A narrowing of the biliary tract from scar tissue. The scar tissue may result from injury, disease, pancreatitis, infection, or gallstones. See also Stricture.


Biliary Tract

The gallbladder and the bile ducts. Also called biliary system or biliary tree. (see image).


Bilirubin (BILL-ee-ROO-bin)

The substance formed when hemoglobin breaks down. Bilirubin gives bile its color. Bilirubin is normally passed in stool. Too much bilirubin causes jaundice.



a technique in which patients are trained to gain some voluntary control over certain physiological conditions, such as blood pressure and muscle tension, to promote relaxation. Thermal biofeedback helps patients consciously raise hand temperature, which can sometimes reduce the number and intensity of migraines.

A way to enhance a body signal so that one is aware of something that usually occurs at a level below consciousness. An electronic device provides information about a body function (such as heart rate) so that the person using biofeedback can learn to control that function. Biofeedback can help people with arthritis learn to relax their muscles. In this case, an electronic device amplifies the sound of a muscle contracting, so the arthritis patient knows that the muscle is not relaxed.

Bioavailability (bi-oh-ah-vale- ah-BILL-i-tee)

the amount of drug that is available to the target tissue after administration; this may not be 100% due to degradation or alteration before reaching the target tissue.


The removal of tissue, which is then examined under a microscope to check for cancer cells. When only a sample of tissue is removed, the procedure is called incisional biopsy or core biopsy. When the whole tumor is removed, it is called excisional biopsy. Removing tissue or fluid with a needle for microscopic examination is called needle biopsy or needle aspiration.

Biphasic Insulin

A type of insulin that is a mixture of intermediate- and fast-acting insulin.

Bismuth Subsalicylate (BIZ-muth SUB-sal-ih-SIL-ayt)

A nonprescription medicine such as Pepto-Bismol. Used to treat diarrhea, heartburn, indigestion, and nausea. It is also part of the treatment for ulcers caused by the bacterium Helicobacter pylori (HELL-uh-koh-BAK-tur py-LOH-ree).

Blinded study

a clinical trial in which participants are unaware as to whether or not they are in the experimental or control arm of the study. (See also Double-blind study.

Bloating (BLO-ting)

Fullness or swelling in the abdomen that often occurs after meals.


Blood Glucose

The main sugar that the body makes from the three elements of food-proteins, fats, and carbohydrates-but mostly from carbohydrates. Glucose is the major source of energy for living cells and is carried to each cell through the bloodstream. However, the cells cannot use glucose without the help of insulin.

Blood Glucose Meter

A machine that helps test how much glucose (sugar) is in the blood. A specially coated strip containing a fresh sample of blood is inserted in a machine, when then calculates the correct level of glucose in the blood sample and shows the result in a digital display. Some meters have a memory that can store results from multiple tests.

Blood Glucose Monitoring

A way of testing how much glucose (sugar) is in the blood. A drop of blood, usually taken from the fingertip, is placed on the end of a specially coated strip, called a testing strip. The strip has a chemical on it that makes it change color according to how much glucose is in the blood. A person can tell if the level of glucose is low, high, or normal in one of two ways. The first is by comparing the color on the end of the strip to a color chart that is printed on the side of the test strip container. The second is by inserting the strip into a small machine, called a meter, which "reads" the strip and shows the level of blood glucose in a digital window display. Blood testing is more accurate than urine testing in monitoring blood glucose levels because it shows what the current level of glucose is, rather than what the level was an hour or so previously.

Blood Pressure

The force of the blood on the walls of arteries. Two levels of blood pressure are measured-the higher, or systolic, pressure, which occurs each time the heart pushes blood into the vessels, and the lower, or diastolic, pressure, which occurs when the heart rests. In a blood pressure reading of 120/80, for example, 120 is the systolic pressure and 80 is the diastolic pressure. A reading of 120/80 is said to be the normal range. Blood pressure that is too high can cause health problems such as heart attacks and strokes.

Blood Sugar

Blood Urea Nitrogen (BUN)

A waste product of the kidneys. Increased levels of BUN in the blood may indicate early kidney damage.

Blood Vessel

Tubes that act like a system of roads or canals to carry blood to and from all parts of the body. The three main types of blood vessels are arteries, veins, and capillaries. The heart pumps blood through these vessels so that the blood can carry with it oxygen and nutrients that the cells need or take away waste that the cells do not need.

Body mechanics

Correct positioning of the body for a given task, such as lifting a heavy object or typing.


A concentrated mass given as a single dose; Diabetes: An extra boost of insulin given to cover expected rise in blood glucose (sugar) such as the rise that occurs after eating.

Bone marrow

The soft sponge-like material inside some bones. Blood cells are formed in the bone marrow. Bone marrow may be autologous (the patient's own marrow saved earlier), allogeneic (marrow from someone else), or syngeneic (marrow from an identical twin).

Bone marrow transplantation

A procedure in which doctors replace marrow destroyed by treatment with high doses of anticancer drugs or radiation. The replacement marrow may be taken from the patient before treatment or may be donated by another person. When the patient's own marrow is used, the procedure is called autologous (aw-TOL-o-gus) bone marrow transplantation.

Bone resorption

The wearing away of bone tissue, which can eventually lead to osteoporosis, spinal deformities ("dowager's hump"), and fractures.

Borborygmi (BOR-boh-RIG-mee)

Rumbling sounds caused by gas moving through the intestines (stomach "growling").

Borderline diabetes

A term no longer used. See: glycosylated hemoglobin.

Bowel (BAH-wul)

Another word for the small and large intestines.

Bowel Prep

The process used to clean the colon with enemas and a special drink. Used before surgery of the colon, colonoscopy, or barium x-ray. See also Lavage.

Brittle diabetes

A term used when a person's blood glucose (sugar) level often swings quickly from high to low and from low to high. Also called labile and unstable diabetes.


A procedure in which a flexible lighted tube is inserted through the throat to allow doctors to see the lungs. Bronchoscopy may be used to detect lung cancer or to see the lungs during some treatment procedures.

Branched DNA (bDNA) assay

laboratory test for measuring the amount of virus in blood plasma. The test detects an amplified luminescent signal whose brightness depends on the amount of viral RNA present.

Breakthrough infection

an infection, which the vaccine is intended to prevent, that occurs in a volunteer during the course of a vaccine trial. Such an infection is caused by exposure to the infectious agent and may occur before or after the vaccine has taken effect or all doses have been given.


A large passageway for air in the lungs.

Bronze Diabetes

A genetic disease of the liver in which the body takes in too much iron from food. Also called "hemocromatosis.".

Budd-Chiari Syndrome (BUD kee-AH-ree sin-drohm)

A rare liver disease in which the veins that drain blood from the liver are blocked or narrowed.

Bulking Agents (BUL-king AY-jents)

Laxatives that make bowel movements soft and easy to pass.

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