Definition Chronic kidney failure occurs when disease or disorder damages the kidneys so that they are no longer capable of adequately removing fluids and wastes from the body or of maintaining the proper level of certain kidney-regulated chemicals in the bloodstream. Description Chronic kidney failure, also known as chronic renal failure, affects over 250,000 Americans...

Definition Chronic granulomatous disease (CGD) is an inherited disorder in which white blood cells lose their ability to destroy certain bacteria and fungi. Description CGD is an X-linked genetic disease, meaning the defective gene is carried on the X chromosome (one of the sex chromosomes). Females have two copies of the X chromosome, whereas males have one X and one Y. CGD also is a recessive...

Definition Chronic fatigue syndrome (CFS) is a condition that causes extreme tiredness. People withCFS have debilitating fatigue that lasts for six months or longer. CFS does not have a known cause, but appears to result from a combination of factors. Description CFS is the most common name for this disorder, but it also has been called chronic fatigue and immune disorder syndrome (CFIDS),...

Definition Chorionic villus sampling (CVS), also known as chorionic villus biopsy, is a prenatal test that can detect genetic and chromosomal abnormalities of an unborn baby. Purpose Chorionic villus sampling is performed on pregnant women who are at risk for carrying a fetus with a genetic or chromosomal defect. Although it carries a slightly higher risk, CVS may be used in place of amniocentesis for women...

Definition A choriocarcinoma is type of cancer germ cell containing trophoblast cells. Description Choriocarcinomas are cancers that develop from germ cells, cells that ordinarily turn into sperm or eggs. Choriocarcinomas resemble the cells that surround an embryo in the uterus. Most of these cancers form inside the reproductive organs. Some originate in the testes or ovaries, especially in young adults....

Definition Chondromalacia patellae refers to the progressive erosion of the articular cartilage of the knee joint, that is the cartilage underlying the kneecap (patella) that articulates with the knee joint.   Description   Chondromalacia patellae (CMP), also known as patello-femoral pain syndrome or patello-femoral stress syndrome, is a syndrome that causes pain/discomfort...

Definition Cholinergic drugs are medications that produce the same effects as the parasympathetic nervous system. Purpose Cholinergic drugs produce the same effects as acetylcholine. Acetylcholine is the most common neurohormone of the parasympathetic nervous system, the part of the peripheral nervous system responsible for the everyday work of the body. While the sympathetic nervous system...

Definition The cholesterol test is a quantitative analysis of the cholesterol levels in a sample of the patient's blood. Total serum cholesterol (TC) is the measurement routinely taken. Doctors sometimes order a complete lipoprotein profile to better evaluate the risk for atherosclerosis (coronary artery disease, or CAD). The full lipoprotein profile also includes...

Definition Cholesterol-reducing drugs are medicines that lower the amount of cholesterol (a fat-like substance) in the blood. Purpose Cholesterol is a chemical that can both benefit and harm the body. On the good side, cholesterol plays important roles in the structure of cells and in the production of hormones. But too much cholesterol in the blood can lead to heart and blood vessel disease. To...

Definition Cholesterol is a fatty substance found in animal tissue and is an important component to the human body. It is manufactured in the liver and carried throughout the body in the bloodstream. Problems can occur when too much cholesterol forms an accumulation of plaque on blood vessel walls, which impedes blood flow to the heart and other organs. The highest cholesterol content is found in meat, poultry,...

Definition Cholestasis is a condition caused by rapidly developing (acute) or long-term (chronic) interruption in the excretion of bile (a digestive fluid that helps the body process fat). The term is taken from the Greek chole, bile, and stasis, standing still. Description Cholestasis is caused by obstruction within the liver (intrahepatic) or outside the liver (extrahepatic). The obstruction...

    Definition Cerebral amyloid angiopathy (CAA) is also known as congophilic angiopathy or cerebrovascularamyloidosis. It is a disease of small blood vessels in the brain in which deposits of amyloid protein in the vessel walls may lead to stroke, brain hemorrhage, or dementia. Amyloid protein resembles a starch and is deposited in tissues...

Definition Byssinosis is a chronic, asthma-like narrowing of the airways. Also called brown lungdisease, byssinosis results from inhaling particles of cotton, flax, hemp, or jute. Description Although inhaling cotton dust was identified as a source of respiratory disease more than 300 years ago, byssinosis has...

Definition Bursitis is a painful inflammation of a bursa, a fluid-filled sac located near a joint. Description There are approximately 150 bursae (plural of bursa) throughout the body. Bursae act like air-filled bubble wrap that cushions the movement of a joint. Located near the tendons of joints, bursae reduce friction between the bones and tendons, making joints flexible and easier to move. Bursae are...

Definition Burns are injuries to the tissues caused by heat, friction, electricity, radiation, or chemicals. Such injuries cause the breakdown of body proteins, death of cells, loss of body fluids, and edema. Description Burns vary depending on the cause, the intensity, and the body parts involved. They are classified by degree, based on the severity of the tissue damage: A first-degree burn...

Definition Bundle branch block (BBB) is a disruption in the normal flow of electrical pulses that drive the heart beat. Description Bundle branch block belongs to a group of heart problems called intraventricular conduction defects (IVCD). There are two bundle branches, right and left. The right bundle carries nerve impulses that cause contraction of the right...

Definition Bulimia nervosa is an eating disorder characterized by binge eating and engaging in inappropriate ways of counteracting the bingeing (using laxatives, for example) in order to prevent weight gain. The word "bulimia" is the Latin form of the Greek word boulimia, which means "extreme hunger." A binge is consuming a larger amount of food within a limited...

Definition Budd-Chiari syndrome is a rare problem that results from blood clotting in the veins flowing out of the liver (hepatic veins). The high pressure of blood in these veins leads to an enlarged liver, and to an accumulation of fluid in the abdomen, called ascites. Description The liver, the largest internal organ in the human body, is responsible for many vital physiologic processes. Blood...

Definition Bruxism is the habit of clenching and grinding the teeth. It most often occurs at night during sleep, but may also occur during the day. It is an unconscious behavior or habit perhaps performed to release anxiety, aggression, or anger. Description Bruxism is one of the oldest disorders known, and approximately one in four adults experience it. It can occur in children and adolescents...

Definition Bruises, or ecchymoses, are a discoloration and tenderness of the skin or mucous membranes due to the leakage of blood from an injured blood vessel into the tissues. Pupura refers to bruising as the result of a disease condition. A very small bruise is called a petechia. These often appear as many tiny red dots clustered together, and could indicate a serious problem. Description Bruises change...

Definition Bronchoscopy is a procedure in which a cylindrical fiberoptic scope is inserted into the airways. This scope contains a viewing device that allows the visual examination of the lower airways. Purpose During a bronchoscopy, a physician can visually examine the lower airways, including the larynx, trachea, bronchi, and bronchioles. The procedure is used to examine the mucosal surface of the...

Definition Bronchodilators are medicines that help open the bronchial tubes (airways) of the lungs, allowing more air to flow through them. Purpose People with asthma have trouble breathing, because their airways are inflamed and become narrowed. Normally, air moves smoothly from the mouth and nose through the airways and into the tiny air sacs of the lungs as a person breathes in. Breathing...

Definition Bronchiolitis is an acute viral infection of the small air passages of the lungs called the bronchioles. Description Bronchiolitis is extremely common. It occurs most often in children between the ages of two and 24 months, with peak infection occurring between three and six months of age. About 25% of infants have bronchiolitis during...

Definition Bronchiectasis is a condition in which an area of the bronchial tubes is permanently and abnormally widened (dilated), with accompanying infection. Description The bronchial tubes are the networks of branching tubes which deliver air to the tiny sacs of the lungs (alveoli). In bronchiectasis, the diameter of the bronchi is unusually large. Examination of the walls of the bronchial tubes...

Definition In a breech birth, the presenting part of the fetus, or the part that enters the woman's birth canal first, is the buttocks or leg(s). Description In almost 97% of vaginal births, the head is the part of the baby to be born first (i.e., vertex presentation). During a woman's pregnancy, the fetus moves freely inside the uterus, cushioned by the amniotic fluid....

Definition Breast ultrasound (or sonography) is an imaging technique for diagnosing breast disease, such as cancer. It uses harmless, high-frequency sound waves to form an image (sonogram). The sound waves pass through the breast and bounce back or echo from various tissues to form a picture of the internal structures. It is not invasive and involves no radiation.    Purpose Breast ultrasound may...

Definition A breast self-examination (BSE) is an inspection by a woman of her breasts to detect breast cancer. Purpose A BSE is one of three tests the American Cancer Society recommends to help detect breast cancer in its earliest stages. By regularly examining her own breasts, a woman is...

Definition Breast reduction is a surgical procedure performed to decrease the size of the breasts. Purpose Women with very large breasts (macromastia, or mammary hyperplasia) seek breast reduction for relief of back, shoulder, and neck pain. They may also feel uncomfortable about their breast size and have difficulty finding clothing that will fit properly. Breast reduction may...

Definition Botulism is caused by botulinum toxin, a natural poison produced by certain bacteria in the Clostridium genus. Exposure to the botulinum toxin occurs mostly from eating contaminated food, or in infants, from certain clostridia growing in the intestine. Botulinum toxin blocks motor nerves' ability to release acetylcho-line, the...

Definition Botulinum is a bacterium (Clostridium botulinum ) that produces seven different toxins that can cause botulism and is also medically used to block muscle contractions. Purpose Botulinum toxin (Botox) injection is used in conditions of excessive and inappropriate muscle contraction, spasticity (persistent states of muscle contraction), sphincter contraction, eye-movement...

  Definition A bone scan is a diagnostic procedure used to evaluate abnormalities involving bones and joints. A radioactive substance is injected intravenously, and the image of its distribution in the skeletal system is analyzed to detect certain diseases or conditions. Purpose Bone scans are most frequently ordered to check whether a cancer that originated elsewhere has spread...

Definition Bone marrow aspiration, which is also called bone marrow sampling, is the removal by suction of the soft, spongy semisolid tissue (marrow) that fills the inside of the long and flat bones. Bone marrow biopsy, or needle core biopsy, is the removal of a small piece (about 0.75 by 0.06 inch, or 2 by 0.16 cm) of intact bone marrow. The bone marrow is...

Definition Bone grafting is a surgical procedure that places new bone or a replacement material into spaces between or around broken bone (fractures) or in holes in bone (defects) to aid in healing.  Purpose Bone grafting is used to repair bone fractures that are extremely complex, pose a significant risk to the patient, or fail to heal properly. Bone grafting is...

  Definition Bone grafting is a surgical procedure that places new bone or a replacement material into spaces between or around broken bone (fractures) or in holes in bone (defects) to aid in healing.  Purpose Bone grafting is used to repair bone fractures that are extremely complex, pose a significant risk to the patient, or fail to heal...

  Definition Bone biopsy is the removal of a piece of bone for laboratory examination and analysis. Purpose Bone biopsy is used to distinguish between malignant tumors and benign bone disease such as osteoporosis and osteomyelitis. This test may be ordered to determine why a patient's bones ache or feel sore, or when a mass or deformity is found on an x ray,...

  Definition Boils and carbuncles are bacterial infections of hair follicles and surrounding skin that form pustules (small blister-like swellings containing pus) around the follicle. Boils are sometimes called furuncles. A carbuncle is formed when several furuncles merge to form a single deep abscess with several heads or drainage points. Description Boils and carbuncles are...

Definition Body dysmorphic disorder (BDD) is defined by the DSM-IV-TR (a handbook for mental health professionals) as a condition marked by excessive preoccupation with an imaginary or minor defect in a facial feature or localized part of the body. The diagnostic criteria specify that the condition must be sufficiently severe to cause a decline in the patient's social, occupational,...

Definition Blood urea nitrogen (BUN) is a chemical waste product of protein metabolism. Proteins are broken down into amino acids within the liver; these amino acids are metabolized, giving rise to nitrogen. Nitrogen is coupled with other molecules within the liver, producing the waste product urea that circulates in the bloodstream and goes to the kidneys. Healthy kidneys...

  Definition Blood typing is a laboratory test done to determine a person's blood type. If the person needs a blood transfusion, another test called crossmatching is done after the blood is typed to find blood from a donor that the person's body will accept. Purpose Blood typing and crossmatching are most commonly done to...

Definition Blood sugar tests include several different tests that measure the amount of sugar (glucose) in a person's blood. These tests are performed either on an empty stomach, or after consuming a meal or premeasured glucose drink. Blood sugar tests are done primarily to diagnose and evaluate a person with diabetes mellitus. Purpose The...

  Definition Blood gas analysis, also called arterial blood gas (ABG) analysis, is a procedure to measure the partial pressure of oxygen (O2) and carbon dioxide (CO2) gases and the pH (hydrogen ion concentration) in arterial blood. Purpose Blood gas analysis is used to diagnose and evaluate respiratory diseases and conditions that influence how effectively...

Definition Blood donation, also called blood banking, refers to the process of collecting, testing, preparing, and storing whole blood and blood components intended primarily for transfusion. Blood donors are typically unpaid volunteers, but they may also be paid by commercial blood donation and processing enterprises, such as independent blood banks...

Definition A blood culture is a lab test designed to detect the presence of bacteria, yeast, or fungi in the bloodstream. A routine blood culture involves injecting a sample of the patient's blood into two bottles of sterile nutrient broth (one for aerobes and one for anaerobes), incubating the bottles at 95°F (35°C), and monitoring the...

  Definition One of the most commonly ordered clinical laboratory tests, a blood count, also called a complete blood count (CBC), is a basic evaluation of the cells (red blood cells, white blood cells, and platelets) suspended in the liquid part of the blood (plasma). It involves determining the numbers, concentrations, and conditions of the different types...

Definition Blood clots are semi-solid clumps of coagulated blood. Blood clots that form in an uninjured blood vessel are not normal.    Description Clotting of blood is a natural process in which liquid blood thickens to a jelly-like consistency. Normally, a blood clot stops the flow of blood after an injury to a blood vessel,...

  Definition Blood-viscosity reducing drugs are medicines that improve blood flow by making the blood less viscous (sticky). Purpose The main use of blood-viscosity reducing drugs is to relieve painful leg cramps caused by poor circulation, a condition called intermittent claudication. Physicians also may prescribe this medicine for other conditions, including stroke,...

  Definition Bleeding time is a crude test of hemostasis (the arrest or stopping of bleeding). It indicates how well platelets interact with blood vessel walls to form blood clots. Purpose Bleeding time is used most often to detect qualitative defects of platelets, such as Von Willebrand's disease. The test helps identify people who have defects in their platelet function....

Definition Bleeding varices are bleeding, dilated (swollen) veins in the esophagus (gullet), or the upper part of the stomach, caused by liver disease. Description Engorged veins are called varices (plural of varix). Varices may occur in the lining of the esophagus, the tube that connects the mouth to the stomach, or in the upper part of the stomach. Such varices are...

  Definition Bleeding time is a crude test of hemostasis (the arrest or stopping of bleeding). It indicates how well platelets interact with blood vessel walls to form blood clots. Purpose Bleeding time is used most often to detect qualitative defects of platelets, such as Von Willebrand's disease. The test helps identify people who have defects in their platelet function....