Definition Tzanck preparation is a rapid test used to help physicians diagnose infections caused by herpes viruses. This test cannot detect the virus, but can detect the characteristic changes in cells that herpes infection produces. Purpose Herpes viruses are responsible for several superficial infections. Varicella zoster virus causes chickenpox and shingles, herpes simplex type 1...

Resources Typhus is a disease caused by a group of bacteria called Rickettsia. Three forms of typhus are recognized: epidemic typhus, a serious disease that is fatal if not treated promptly; rat-flea or endemic typhus, a milder form of the disease; and scrub typhus, another fatal form. The Rickettsiaspecies of bacteria that cause all three forms of typhus are...

Definition Typhoid fever is a severe infection caused by a bacterium, Salmonella typhi. S. typhi is in the same family of bacteria as the type spread by chicken and eggs, commonly known as salmonella poisoning or food poisoning. S. typhi bacteria do not have vomiting and diarrhea as the most prominent symptoms of their...

Definition 2,3-diphosphoglycerate (2,3-DPG) is a substance made in the red blood cells. It controls the movement of oxygen from red blood cells to body tissues. 2,3-DPG testing is done to help investigate both a deficiency in red blood cells (anemia) and an unexplained increase of red blood cells, called erythrocytosis. Purpose Hemoglobin, the protein in the blood that carries oxygen, uses 2,3-DPG to control...

Definition Turner syndrome is a chromosomal disorder affecting females wherein one of the two X-chromosomes is defective or completely absent. Description Chromosomes are structures in the nucleus of every cell in the human body. Chromosomescontain the genetic information necessary to direct the growth and normal functioning...

Definition A tumor is an abnormal growth caused by the uncontrolled division of cells. Benign tumors do not have the potential to spread to other parts of the body (a process called metastasis) and are curable by surgical removal. Malignant or cancerous tumors, however, may metastasize to other parts of the body and will ultimately result in death if not successfully treated by surgery and/or...

Definition Tumor markers are measurable biochemicals that are associated with a malignancy. They are either produced by tumor cells (tumor-derived) or by the body in response to tumor cells (tumor-associated). They are typically substances that are released into the circulation and thus measured in the blood. There are a few exceptions to this, such as tissue-bound receptors that...

Definition Tularemia is an illness caused by a bacterium. It results in fever, rash, and greatly enlarged lymph nodes. Description Tularemia infects a variety of wild animals, including rabbits, deer, squirrels, muskrat, and beaver. Humans can acquire the bacterium directly from contact with the blood or body fluids of these animals, from the bite of a tick...

Resources Tuberculosis is a disease caused by the bacterium Mycobacterium tuberculosis. The organism infects the lungs and causes a debilitating condition that historically was known as consumption. In the 1970s, scientists considered tuberculosis as largely defeated following the widespread use of antibiotics. Today, multi-drug resistant Mycobacterium tuberculosis has developed,...

Definition Tuberculosis (TB) is an airborne infectious disease caused by the bacteria Mycobacterium tuberculosis. Besides culturing in the laboratory, the two most common types of tests to screen for exposure to this disease are the Mantoux PPD tuberculin skin test, which is generally considered more reliable, and the older TB tine test, which is now rarely used. These tests are...

Definition Tube feeding is a procedure used for placing food, fluids, and drugs directly into the stomach or small intestine through a tube inserted through the nose or abdomen. Tube feeding is also called enteral feeding or enteral nutrition . Purpose Tube feeding is used with people who have normally functioning digestive systems, but who cannot or will not take food...

Definition Tube compression of the esophagus and stomach is an emergency procedure used to stop bleeding from the upper digestive tract. Purpose Vomiting blood is both frightening and life-threatening. Among its causes are: bleeding from the nose and throat peptic ulcers stomach cancer esophageal cancer a tear in the esophagus caused by violent vomiting (Mallory-Weiss...

Definition Tubal ligation is a permanent voluntary form of birth control (contraception ) in which a woman's Fallopian tubes are surgically cut or blocked off to prevent pregnancy. Purpose Tubal ligation is performed in women who definitely want to prevent future pregnancies. It is frequently chosen by women who do not want more children, but who are still sexually active and...

Definition Troponins are specific proteins found in heart muscle. Troponin testing is done to diagnose heart attacks (myocardial infarctions). Purpose When heart muscle is damaged, as in a myocardial infarction (MI), troponins leak out of cells and into the bloodstream. Increased troponin levels indicate myocardial infarction or injury in a person with chest pain or pressure. Some MIs...

Definition Tropical spastic paraparesis (TSP) is a slowly progressive spastic paraparesis caused by the human T-cell lymphotropic virus-1 (HTLV-1), with an insidious onset in adulthood. It has been found all around the world (except in the poles), mainly in tropical and subtropical regions. Description For several decades the term tropical spastic paraparesis (TSP) was used to describe a...

Definition Triple screen is a blood test offered to pregnant women during the 16th-18th week of pregnancy to help identify if the unborn baby is at risk for birth defects. Purpose Researchers have found that women carrying a fetus with Down syndrome tend to have three substances in their blood in a distinctive abnormal pattern. Both alpha-fetoprotein (AFP), a protein produced by...

Definition Triglycerides test is a blood test to determine the amount of triglycerides, a form of fat, in the blood. Purpose The triglycerides test is one of the screening tests for excess lipids (fats) in the blood. It is usually part of an evaluation of risk factors for heart disease. Description Triglycerides are a form of fat that comes from foods. They can also...

Definition Trigger finger is the popular name of stenosing tenosynovitis, a painful condition in which a finger or thumb locks when it is bent (flexed) or straightened (extended). Description Tendons are tough, fibrous cords that connect muscles to bones. Tendons must slide easily through their protective coverings (tendon sheaths). The finger and thumb bones have tendons that are responsible...

Definition Trigeminal neuralgia is a disorder of the trigeminal nerve that causes severe facial pain . It is also known as tic douloureux, Fothergill syndrome, or Fothergill's syndrome. Description Trigeminal neuralgia is a rare disorder of the sensory fibers of the trigeminal nerve (fifth cranial nerve), which innervate the face and jaw. The neuralgia is...

Definition Tricuspid valve stenosis is a narrowing or stiffening of the opening in the valve. This stenosis causes increased resistance to blood flow through the valve. Description The tricuspid valve is located between the right atrium and the right ventricle of the heart. It is the largest of the four valves in the heart. When the tricuspid valve is...

Definition Tricuspid valve insufficiency occurs when a tricuspid valve does not close tightly enough to prevent leakage. This condition is also called tricuspid valve regurgitation and tricuspid incompetence. Description The tricuspid valve is located between the right atrium and the right ventricle of the heart. When the right ventricle contracts,...

Definition Trichomoniasis refers to an infection of the genital and urinary tract. It is the most commonsexually transmitted disease, affecting about 120 million women worldwide each year. Description Trichomoniasis is caused by a protozoan (the smallest, single-celled members of the animal kingdom). Trichomonas vaginalis is...

Definition Trichinosis is a disease caused by a roundworm (nematode) called Trichinella spiralis. Anindividual worm of this species is called a trichina, from the Greek word meaning "hairlike." Trichinae can be readily avoided by proper handling and cooking of certain meats, particularly pork products. Description The life cycle of T. spiralis includes several different stages. The adult...

Definition Trench fever is a bacterial infection that causes repeated cycles of high fever. Description The term trench fever refers to the crowded conditions in which troops fought in during World War I and World War II. Because the causative bacteria are passed among humans through contact with body lice, overcrowding, and conditions which interfere with good hygiene (including...

Definition Tremor is an unintentional (involuntary) rhythmical alternating movement that may affect the muscles of any part of the body. Tremor is caused by the rapid alternating contraction and relaxation of muscles and is a common symptom of diseases of the nervous system (neurologic disease). Description Occasional tremor is felt by almost everyone, usually as a result of fear or excitement. However, uncontrollable...

Definition Traveler’s diarrhea is an increase in loose, watery stools that often occurs when travelers from industrialized countries travel to developing or underdeveloped countries. Traveler’s diarrhea has many nicknames such as Montezuma’s revenge, Tut’s tummy, or tourista. Description Traveler’s diarrhea is a common disease. It is a form...

Definition Traumatic amputations is the accidental severing of some or all of a body part. A complete amputation totally detaches a limb or appendage from the rest of the body. In a partial amputation, some soft tissue remains attached to the site. Description Trauma is the second leading cause of amputation in the United States. About 30,000 traumaticamputations occur in this country every...

Definition Transverse myelitis is an inflammation of the full width of the spinal cord that disrupts communication to the muscles, resulting in pain , weakness, and muscle paralysis. Description The symptoms of transverse myelitis are due to damage and/or destruction of the myelin sheath, the fatty white covering of nerve fibers that serves both to insulate the nerve fibers...

Definition Transvaginal ultrasound is a imaging technique used to create a picture of the genital tract in women. The hand-held device that produces the ultrasound waves is inserted directly into the vagina, close to the pelvic structures, thus often producing a clearer and less distorted image than obtained through transabdominal ultrasound technology, where the probe is located...

Definition Transurethral bladder resection is a surgical procedure used to view the inside of the bladder, remove tissue samples, and/or remove tumors. Instruments are passed through a cystoscope (a slender tube with a lens and a light) that has been inserted through the urethra into the bladder.  Purpose Transurethral resection is the initial form of treatment for bladder cancers....

Definition Transposition of the great arteries (TGA) is a birth defect causing a fatal condition in which there is a reversal, or switch, in the primary connections of the two main (great) blood vessels to the heart, the aorta and pulmonary artery. Description There are two great arteries that transport blood away from the heart, the pulmonary artery and the aorta. Normally,...

Definition Transient ischemic attacks or TIAs are brief stroke-like episodes, sometimes called mini-strokes or transient stroke , that occur when a blood clot temporarily blocks an artery and prevents blood from flowing normally in the brain. Description A transient ischemic attack (TIA) is not an actual stroke but gives the individual a serious warning of increased risk...

Definition Transhepatic biliary catheterization is a surgical procedure during which a catheter is inserted into the bile duct to relieve an obstruction. Purpose Bile is a fluid made in the liver and stored in the gall bladder. The function of bile is to break down fats during digestion. When fatty foods move into the intestine, bile is released from the gall bladder, travels through the bile...

Definition Transfusion is the process of transferring whole blood or blood components from one person (donor) to another (recipient). Purpose Transfusions are given to restore lost blood, to improve clotting time, and to improve the ability of the blood to deliver oxygen to the body's tissues. Precautions For donors, the process of giving blood is very safe. Only sterile equipment is used and there...

Definition Transesophageal echocardiography is a diagnostic test using an ultrasound device that is passed into the esophagus of the patient to create a clear image of the heart muscle and other parts of the heart. A tube with a device called a transducer is passed down into the patient's throat and into the esophagus (the food tube that connects the mouth to the stomach). The transducer directs...

Definition Transcranial Doppler ultrasonography is a noninvasive method of analyzing blood flow in the brain. Purpose The blood that flows through the brain distributes nutrients to the brain and removes wastes. This flow maintains the high rate of metabolism necessary for the brain to function. Restrictions in blood flow may occur from vessel narrowing (stenosis), clot formation (thrombosis),...

Definition Trager psychophysical integration therapy, also known as the Tragerwork system of physical integration, is a combination of hands-on tissue mobilization, relaxation, and movement reeducation called Mentastics. The underlying principle of psychophysical integration is that clients learn to be lighter, easier, and freer by experiencing lightness, ease, and freedom of movement...

Definition Traditional Chinese medicine (TCM) is based on a set of interventions designed to restore balance to human beings. The therapies usually considered under the heading of classic Chinese medicine include: acupunture and moxibustion dietary regulation herbal remedies massage therapeutic exercise These forms of treatments are based upon beliefs that differ from the disease...

Definition Traction is the use of a pulling force to treat muscle and skeleton disorders. Purpose Traction is usually applied to the arms and legs, the neck, the backbone, or the pelvis. It is used to treat fractures, dislocations, and long-duration muscle spasms, and to prevent or correct deformities. Traction can either be short-term, as at an accident scene, or long-term, when...

Definition Trachoma, also called granular conjunctivitis or Egyptian ophthalmia, is a contagious, chronic inflammation of the mucous membranes of the eyes, caused by the bacterium Chlamydia trachomatis. It is characterized by swelling of the eyelids, sensitivity to light, and eventual scarring of the conjunctiva and cornea of the eye. Description Trachoma is a disease associated with poverty...

Definition A tracheotomy is a surgical procedure in which a cut or opening is made in the windpipe (trachea). The surgeon inserts a tube into the opening to bypass an obstruction, allow air to get to the lungs, or remove secretions. The term tracheostomy is sometimes used interchangeably with tracheotomy. Strictly speaking, however, tracheostomy usually refers to the opening itself while a tracheotomy is...

Definition Tracheoesophageal fistula (TEF) is commonly a birth defect, with the trachea connected to the esophagus. In most cases, the esophagus is discontinuous, causing immediate feeding difficulties. TEFs may develop in adult life, secondary to the invasion of cancer in the area. In addition, TEFs may be deliberately constructed with surgery to aid talking in a patient who has the larynx...

Definition Trabeculectomy is a surgical procedure that removes part of the trabeculum in the eye to relieve pressure caused by glaucoma. Purpose Glaucoma is a disease that injures the optic nerve, causing progressive loss of vision. Presently, glaucoma is a major cause of blindness in the United States If caught early, glaucoma-related blindness is easily prevented. However, since it does not produce...

Definition Toxoplasmosis is an infectious disease caused by the one-celled protozoan parasiteToxoplasma gondii. Although most individuals do not experience any symptoms, the disease can be very serious, and even fatal, in individuals with weakened immune systems. Description Toxoplasmosis is caused by a one-celled protozoan parasite known...

Definition Toxic shock syndrome (TSS) is an uncommon, but potentially serious, illness that occurs when poisonous substances (toxins) produced by bacteria enter the bloodstream. The toxins cause a type of blood poisoning that results in high fever , symptoms of shock, and potentially organ failure. Description Initially toxic shock syndrome was associated with...

Definition Toxic epidermal necrolysis is a rare condition that causes large portions of the epidermis, the skin's outermost layer, to detach from the layers of skin below. A reaction to a medication is the primary cause. Description Toxic epidermal necrolysis (TEN) begins with fever, cough, and other nonspecific symptoms, and is soon followed by purplish, bloody-looking...

Definition Tourette syndrome (TS) is an inherited disorder of the nervous system, characterized by a variable expression of unwanted movements and noises (tics). Description The first references in the literature to what might today be classified as Tourette syndrome largely describe individuals who were wrongly believed to be possessed by the devil. In 1885 Gilles de laTourette, a French...

Definition Torticollis (cervical dystonia or spasmodic torticollis) is a type of movement disorder in which the muscles controlling the neck cause sustained twisting or frequent jerking. Description In torticollis, certain muscles controlling the neck undergo repetitive or sustained contraction, causing the neck to jerk or twist to the side. Cervical dystonia causes forward twisting, and is called...

Definition The TORCH test, sometimes called the TORCH panel, belongs to a category of blood tests called infectious-disease antibody titers. A titer is the serial dilution of antibodies (protein molecules or immunoglobulins produced by the immune system in response to specific disease agents) found in blood serum that determines their level of concentration. Antibodies are proteins produced...

Definition Topical anesthesia is a condition of temporary numbness caused by applying a substance directly to a surface of the body. Loss of feeling occurs in the specific areas touched by the anesthetic substance. Purpose Topical anesthesia typically either relieves existing pain from a body surface or prevents pain during medical examinations or procedures. Body surfaces...