Ventricular fibrillation is a very rapid, uncoordinated, ineffective series of contractions throughout the lower chambers of the heart. Unless stopped, these chaotic impulses are fatal. When the ventricles begin to quiver, and do not employ coordinated contractions, the heart is said to be fibrillating. In this condition the ventricles cannot pump blood from the heart. Ventricular fibrillation (V-…
A ventricular septal defect is a hole in the wall of the heart (septum) that separates the left lower chamber (left ventricle) from the right lower chamber (right ventricle). The hole allows blood to flow from the left ventricle to the right ventricle instead of entering the aorta for distribution throughout the body. Ventricular septal defect is one of a group of heart problems found in newborn b…
Ventricular shunt is a surgical procedure in which a tube is placed in one of the fluid-filled chambers inside the brain (ventricles). The fluid around the brain and the spinal column is called the cerebrospinal fluid. When infection or disease causes an excess of this cerebrospinal fluid in the ventricles, the shunt is placed to drain it and thereby relieve excess pressure. Ventricular shunt reli…
Ventricular tachycardia (V-tach) is a rapid heart beat that originates in one of the lower chambers (the ventricles) of the heart. To be classified as tachycardia, the heart rate is usually at least 100 beats per minute. A rapid heart rate can originate in either the left or right ventricle. Ventricular tachycardia which lasts more than 30 seconds is referred to as sustained ventricular tachycardi…
Vesicoureteral reflux (VUR) refers to a condition in which urine flows from the bladder, back up the ureter, and back into the kidneys. The normal flow of urine begins in the collecting system of each kidney. Urine then flows out of each kidney and into a tube called the ureter. Each ureter leads into the bladder, where the urine collects until it is passed out of the body. Normally, urine should …
Vibriosis is a disease caused by an infection with bacteria of the Vibrio genus, most commonly Vibrio parahemolyticus or Vibrio vulnificus. Vibrio bacteria cause diarrhea, skin infections, and/or blood infections. The diarrhea-causing Vibrio parahemolyticus is a relatively harmless infection, but Vibrio vulnificus infection, though rare, can lead to blood poisoning and death in many cases. Vibrios…
Vision training, also known as vision therapy or orthoptics, consists of a variety of programs to enhance visual performance. It includes treatments for focusing, binocularity, and eye movement problems. Vision training is generally provided by an optometrist (O.D.). While visual acuity refers to how clearly each eye can see, vision training addresses how well the two eyes work together as a team.…
Total blindness is the inability to tell light from dark, or the total inability to see. Visual impairment or low vision is a severe reduction in vision that can't be corrected with standard glasses or contact lenses and reduces a person's ability to function at certain or all tasks. Legal blindness (which is actually a severe visual impairment) refers to a best-corrected central vis…
Vitamin A deficiency exists when the chronic failure to eat sufficient amounts of vitamin A or beta-carotene results in levels of blood-serum vitamin A that are below a defined range. Beta-carotene is a form of pre-vitamin A, which is readily converted to vitamin A in the body. Night blindness is the first symptom of vitamin A deficiency. Prolonged and severe vitamin A deficiency can produce total…
Vitamin B6 is used by the body as a catalyst in reactions that involve amino acids. Vitamin B6 deficiency is rare, since most foods eaten contain the vitamin. Vitamin B6 is a water-soluble vitamin. The recommended dietary allowance (RDA) for vitamin B6 is 2.0 mg/day for the adult man and 1.6 mg/day for the adult woman. Vitamin B6 in the diet generally occurs as a form called pyridoxal phosphate. I…
Vitamin D deficiency exists when the concentration of 25-hydroxy-vitamin D (25-OH-D) in the blood serum occurs at 12 ng/ml (nanograms/milliliter), or less. The normal concentration of 25-hydroxy-vitamin D in the blood serum is 25-50 ng/ml. When vitamin D deficiency continues for many months in growing children, the disease commonly referred to as rickets will occur. A prolonged deficiency of the v…
Vitamin E deficiency is a very rare problem that results in damage to nerves. When vitamin E deficiency does occur, it strikes people with diseases that prevent the absorption of dietary fats and fat-soluble nutrients. Since vitamin E is a fat-soluble vitamin, it has some of the properties of fat. The recommended dietary allowance (RDA) for vitamin E is 10 mg/day for the adult man, 8 mg/day for th…
Vitamin K deficiency exists when chronic failure to eat sufficient amounts of vitamin K results in a tendency for spontaneous bleeding or in prolonged and excessive bleeding with trauma or injury. Vitamin K deficiency occurs also in newborn infants, as well as in people treated with certain antibiotics. The protein in the body most affected by vitamin K deficiency is a blood-clotting protein calle…
Vitamin tests measure the levels of certain vitamins in an individual's blood. They are generally used to aid in the diagnosis of vitamin deficiencies or in detecting toxic amounts of a vitamin in a patient's system. Vitamins are components of food that are needed for growth, reproduction, and maintaining good health. The vitamins include vitamin D, vitamin E, vitamin A, and vitamin …
Vitamin toxicity is a condition in which a person develops symptoms as side effects from taking massive doses of vitamins. Vitamins vary in the amounts that are required to cause toxicity and in the specific symptoms that result. Vitamin toxicity, which is also called hypervitaminosis or vitamin poisoning, is becoming more common in developed countries because of the popularity of vitamin suppleme…
Vitamins are organic components in food that are needed in very small amounts for growth and for maintaining good health. The vitamins include vitamin D, vitamin E, vitamin A, and vitamin K, or the fat-soluble vitamins, and folate (folic acid), vitamin B12, biotin, vitamin B6, niacin, thiamin, riboflavin, pantothenic acid, and vitamin C (ascorbic acid), or the water-soluble vitamins. Vitamins are …
Vitiligo is a condition in which a loss of cells that give color to the skin (melanocytes) results in smooth, white patches in the midst of normally pigmented skin. Vitiligo is a common, often inherited disorder characterized by areas of well-defined, milky white skin. People with vitiligo may have eye abnormalities and also have a higher incidence of thyroid disease, diabetes mellitus, and pernic…
Vitrectomy is the surgical removal of the vitreous (transparent gel that fills the eye from the iris to the retina). The bulk of the contents of the eyeball is a clear jelly-like substance that is susceptible to several afflictions that impair vision by damaging its transparency. The retina is the light-sensitive membrane that receives images and transmits them to the brain. It covers Vitrecto…
Vocal cord nodules and polyps are noncancerous growths on the vocal cords that affect the voice. The vocal cords, located in the voice box in the middle of the neck, are two tough, fibrous bands that vibrate to produce sound. They are covered with a layer of tissue that is similar to skin. With use, this layer thickens. With heavy use, the thickening may localize, producing a nodule. Unlike skin, …
Vocal cord paralysis is the inability to move the vocal cords and the resulting loss of vocal cord function. The vocal cords are a pair of tough, fibrous bands that lie across the air column in the middle of the voice box. They assist three functions: breathing, swallowing, and speaking. When vocal cords vibrate, they produce sound, allowing us to speak. Vocal cords temporarily stop breathing to a…
Von Willebrand disease is caused by a deficiency or an abnormality in a protein called von Willebrand factor and is characterized by prolonged bleeding. The Finnish physician Erik von Willebrand was the first to describe von Willebrand disease (VWD). In 1926 Dr. von Willebrand noticed that many male and female members of a large family from the Aland Islands had increased bruising (bleeding into t…
Vulvar cancer refers to an abnormal, cancerous growth in the external female genitalia. Vulvar cancer is a rare disease that occurs mainly in elderly women. The vulva refers to the external female genitalia, which includes the labia, the opening of the vagina, the clitoris, and the space between the vagina and anus (perineum). There are two pairs of labia (a Latin term meaning lips). The labia mee…
Inflammation of the vagina and vulva most often caused by a bacterial, fungal, or parasitic infection. Vulvovaginitis, vulvitis, and vaginitis are general terms that refer to the inflammation of the vagina and/or vulva (the external genital organs of a woman).These conditions can be caused by bacterial, fungal, or parasitic infections. Also, vulvovaginitis can be caused by low estrogen levels (cal…
Waldenström's macroglobulinemia is a rare, chronic cancer of the immune system that is characterized by hyperviscosity, or thickening, of the blood. Waldenström's (Waldenstrom, Waldenstroem's) macroglobulinemia (WM) is a lymphoma, or cancer of the lymphatic system. It was first identified in 1944, by the Swedish physician Jan Gosta Waldenström, in patients…
Warts are small, benign growths caused by a viral infection of the skin or mucous membrane. The virus infects the surface layer. The viruses that cause warts are members of the human papilloma virus (HPV) family. Warts are not cancerous but some strains of HPV, usually not associated with warts, have been linked with cancer formation. Warts are contagious from person to person and from one area of…
The Wechsler Intelligence Scales are a series of standardized tests used to evaluate cognitive abilities and intellectual abilities in children and adults. The Wechsler Intelligence Scales for Children (regular, revised, and third edition) and Wechsler Preschool and Primary Scale of Intelligence are used as tools in school placement, in determining the presence of a learning disability or a develo…
Wegener's granulomatosis is a very rare disease that affects many different organs and systems of the body. It mainly attacks the respiratory system (sinuses, nose, windpipe, and the lungs) and the kidneys. One of the main features of the disease is an inflammation of the blood vessels (vasculitis). The inflammation narrows the blood vessels and reduces the blood flow to the affected organs…
Wheezing is a high-pitched whistling sound associated with labored breathing. Wheezing occurs when a child or adult tries to breathe deeply through air passages that are narrowed or filled with mucus as a result of: Wheezing is most common when exhaling. It is sometimes accompanied by a mild sensation of tightness in the chest. Anxiety about not being able to breathe easily can cause muscle tensio…
Whiplash is a sudden, moderate-to-severe strain affecting the bones, discs, muscles, nerves, or tendons of the neck. The neck is composed of seven small bones. Known as the cervical spine, these bones: About 1,000,000 whiplash injuries occur in the United States every year. Most are the result of motor vehicle accidents or collisions involving contact sports. When unexpected force jerks the head b…
The white blood cell count and differential determine the number of white blood cells and the percentage of each type of white blood cell in a person's blood. These tests are included in general health examinations and help investigate a variety of illnesses, including infection, allergy, and leukemia. The white blood cell count provides a clue to the presence of illness. White cells protec…
Whooping cough, also known as pertussis, is a highly contagious disease which causes classic spasms A magnified image of a pertussis toxin crystal that causes whooping cough. (National Institutes of Health/Custom Medical Stock Photo. Reproduced by permission.) (paroxysms) of uncontrollable coughing, followed by a sharp, high-pitched intake of air which creates the characteristic "who…
Wilderness medicine encompasses the prevention, diagnosis, and treatment of injuries and medical conditions that may occur during activities in remote territories. Activities that may require wilderness medicine include backpacking, cross-country skiing, mountaineering, white water rafting, scuba diving, and exploration in undeveloped regions such as deserts or jungles. Wilderness medicine has evo…
Wilms' tumor is a cancerous tumor of the kidney that usually occurs in young children. When an unborn baby is developing, the kidneys are formed from primitive cells. Over time, these cells become more specialized. The cells mature and organize into the normal kidney structure. Sometimes, clumps of these cells remain in their original, primitive form. If these cells begin to multiply after …
Wilson disease is a rare, inherited disorder that causes excess copper to accumulate in the body. Steadily increasing amounts of copper circulating in the blood are deposited primarily in the brain, liver, kidneys, and the cornea of the eyes. Under normal conditions, copper that finds its way into the body through the diet is processed within the liver. This processed form of copper is then passed…
Wiskott-Aldrich syndrome (WAS) is a rare inherited disorder marked by a low level of blood platelets, eczema, recurrent infections, and a high risk of leukemia or lymph node tumors. WAS was named for the two physicians who first reported the disorder. In 1937, Dr. A. Wiskott, a physician working in Munich, described two affected boys of German ancestry who had repeated infections, a skin rash, and…
Withdrawal syndrome occurs in drug and alcohol addicted individuals who discontinue or reduce the use of their drug of choice. This process of eliminating drugs and alcohol from the body is known as detoxification. Anxiety, insomnia, nausea, perspiration, body aches, and tremors are just a few of the physical and psychological symptoms of drug and alcohol withdrawal that may occur during detoxific…
Wolff-Parkinson-White syndrome is an abnormality in the electrical functioning of the heart which may cause rapid heart rates. The abnormality affects the electrical signal between the atria and ventricles. Blood is circulated through the heart and body by a muscular pump and valve system involving the atria and ventricles. The right atrium receives oxygen-lacking blood returning to the heart from…
Women's health is the effect of gender on disease and health that encompasses a broad range of biological and psychosocial issues. Women's health is the concept that examines gender differences in health and disease states. The average life expectancy has almost doubled for women (79 years for women and 73 years for men), when compared with averages during the turn of the century. Be…
A wound culture is a laboratory test in which microorganisms from a wound are grown in a special growth medium. It is done to find and identify the microorganism causing an infection in a wound or an abscess. If a microorganism is found, more testing is done to determine the antibiotics that will be effective in treating the infection. Wounds are injuries to body tissues caused by disease processe…
Wound flushing is a method of cleaning a wound by applying pressurized water or antiseptic solutions to the tissues. Wound flushing is used to help flush debris from a wound, lessening the risk of infection or treating an infection that already exists. If the wound is flushed with an antiseptic, it is more likely to heal correctly; flushing the wound can help prevent the surface from healing over …
A wound occurs when the integrity of any tissue is compromised (e.g. skin breaks, muscle tears, burns,or bone fractures). A wound may be caused by an act, such as a gunshot, fall, or surgical procedure; by an infectious disease; or by an underlying condition. Types and causes of wounds are wide ranging, and health care professionals have several different ways of classifying them. They may be chro…
X-linked agammaglobulinemia (XLA) or Bruton's agammaglobulinemia is present at birth (congenital) and is characterized by low or completely absent levels of immunoglobulins in the bloodstream. Immunoglobulins are protein molecules in blood serum that function like antibodies. Without them, the body lacks a fully functioning immune system. Persons with XLA are vulnerable to repeated, potenti…
Orbital x rays are studies of the area and structures containing the eye. The orbit is the circle of thin bones that houses and protects the eye, even extending behind the eye and nearly wrapping around it. The orbit includes the eyebrow, the bridge of the nose and the cheekbone. X rays are a form of radiation (like light) that can penetrate body tissues. Orbital x ray, or orbital radiography, is …
Yaws is a chronic illness which first affects the skin, and then affects the bones. Yaws tends to strike children, particularly between the ages of two and five. It is common in areas where poverty and overcrowding interfere with good hygiene practices. The most common locations are in rural areas throughout Africa, Southeast Asia, and in locations bordering the equator in the Americas. Yaws is ca…
Yellow fever is a severe infectious disease, caused by a virus called a "flavivirus." This flavivirus can cause outbreaks of epidemic proportions throughout Africa and tropical America. The first written evidence of such an epidemic occurred in the Yucatan in 1648. Since that time, much has been learned about the interesting transmission patterns of this devastating illness. In order…
Yersinosis refers to infection by a genus of bacteria known as Yersinia. The two sub-types that are responsible for yersinosis are Yersinia enterocolitica and Yersinia pseudotuberculosis. The diseases produced by these organisms are called "zoonoses," because the bacteria is passed to humans from animal sources. The name Yersinia comes from Dr. Alexandre Yersin, who was the first per…
The term yoga comes from a Sanskrit word which means yoke or union. Traditionally, yoga is a method joining the individual self with the Divine, Universal Spirit, or Cosmic Consciousness. Physical and mental exercises are designed to help achieve this goal, also called self-transcendence or enlightenment. On the physical level, yoga postures, called asanas, are designed to tone, strengthen, and al…
Zoonosis, also called zoonotic disease refers to diseases that can be passed from animals, whether wild or domesticated, to humans. Although many diseases are species specific, meaning that they can only occur in one animal species, many other diseases can be spread between different animal species. These are infectious diseases, caused by bacteria, viruses, or other disease causing organisms that…
