Definition An embolism is an obstruction in a blood vessel due to a blood clot or other foreign matter that gets stuck while traveling through the bloodstream. The plural of embolism is emboli. Description Emboli have moved from the place where they were formed through the bloodstream to another part of the body, where they obstruct an artery and block the flow of blood. The emboli are usually formed from...

Definition The word elephantiasis is a vivid and accurate term for the syndrome it describes: the gross (visible) enlargement of the arms, legs, or genitals to elephantoid size. Description True elephantiasis is the result of a parasitic infection caused by three specific kinds of round worms. The long, threadlike worms block the body’s lymphatic system–a network of channels, lymph nodes, and organs...

Definition An electrophysiology (EP) study of the heart is a nonsurgical analysis of the electrical conduction system (normal or abnormal) of the heart. The test employs cardiac catheters and sophisticated computers to generate electrocardiogram (EKG) tracings and electrical measurements with exquisite precision from within the heart chambers. The EP study can be performed solely for diagnostic purposes....

Definition Electronic fetal monitoring (EFM) is a method for examining the condition of a baby in the uterus by noting any unusual changes in its heart rate. Electronic fetal monitoring is performed late in pregnancy or continuously during labor to ensure normal delivery of a healthy baby. EFM can be utilized either externally or internally in the womb. Electronic fetal monitoring (EFM) is performed late in...

Definition Electromyography (EMG) is an electrical recording of muscle activity that aids in the diagnosis of neuromuscular disease. Purpose Muscles are stimulated by signals from nerve cells called motor neurons. This stimulation causes electrical activity in the muscle, which in turn causes contraction. This electrical activity is detected by a needle electrode inserted into the muscle and connected...

Definition Electrolytes are positively and negatively charged molecules, called ions, that are found within cells, between cells, in the bloodstream, and in other fluids throughout the body. Electrolytes with a positive charge include sodium, potassium, calcium, and magnesium; the negative ions are chloride, bicarbonate, and phosphate. The concentrations of these ions in the bloodstream remain fairly constant...

Definition Electrolyte supplements are a varied group of prescription and nonprescription preparations used to correct imbalances in the body’s electrolyte levels. Electrolytes themselves are substances that dissociate into ions (electrically charged atoms or atom groups) when they melt or are dissolved, thus serving to conduct electricity. In the human body, electrolytes are thus critical to the proper...

Definition An electrolyte disorder is an imbalance of certain ionized salts (i.e., bicarbonate, calcium, chloride, magnesium, phosphate, potassium, and sodium) in the blood. Description Electrolytes are ionized molecules found throughout the blood, tissues, and cells of the body. These molecules, which are either positive (cations) or negative (anions), conduct an electric current and help to balance pH and...

Definition Electroencephalography, or EEG, is a neurological test that uses an electronic monitoring device to measure and record electrical activity in the brain.       This woman is undergoing an electroencephalogram (EEG) to diagnose Alzheimer’s disease. On the computer screen at the right are the colored scans of the electrical activity in her brain. Alzheimer’s patients show...

Definition Electroconvulsive therapy (ECT) is a medical treatment for severe mental illness in which a small, carefully controlled amount of electricity is introduced into the brain. This electrical stimulation, used in conjunction with anesthesia and muscle relaxant medications, produces a mild generalized seizure or convulsion.While used to treat a variety of psychiatric disorders, it is most effective...

Definition Electrocardiography is a commonly used, noninvasive procedure for recording electrical changes in the heart. The record, which is called an electrocardiogram (ECG or EKG), shows the series of waves that relate to the electrical impulses which occur during each beat of the heart. The results are printed on paper or displayed on a monitor. The waves in a normal record are named P, Q, R, S, and T and...

Definition Electrical stimulation of the brain (ESB) is a relatively new technique used to treat chronic pain and tremors associated with Parkinson disease. ESB is administered by passing an electrical current through an electrode implanted in the brain. Purpose While the implantation of electrodes in the brain is used to treat or diagnose several disorders, the term ESB is limited here to the treatment of...

Definition Electrical nerve stimulation, also called transcutaneous electrical nerve stimulation (TENS), is a noninvasive, drug-free pain management technique. By sending electrical signals to underlying nerves, the battery-powered TENS device can relieve a wide range of chronic and acute pain. Purpose TENS is used to relieve pain caused by a variety of chronic conditions, including:  neck and lower...

Definition Electric shock injuries are caused by lightning or electric current from a mechanical source passing through the body. Description Electric shocks are responsible for about 1,000 deaths in the United States each year, or about 1% of all accidental deaths. Causes and symptoms The severity of injury depends on the current’s pressure (voltage), the amount of current (amperage), the type of current...

Definition  Elder abuse is a general term used to describe harmful acts toward an elderly adult, such as physical abuse, sexual abuse, emotional or psychological abuse, financial exploitation, and neglect, including self-neglect. Description  Results from the National Elder Abuse Incidence Study, funded in part by the Administration on Aging, suggest that over 500,000 people 60 years of age and older...

Definition Ehrlichiosis is a bacterial infection that is spread by ticks. Symptoms include fever, chills, headache, muscle aches, and tiredness. Description Ehrlichiosis is a tick-borne disease caused by infection with Ehrlichia bacteria. Ticks are small, blood-sucking arachnids. Although some ticks carry disease-causing organisms, most do not. When an animal or person is bitten by a tick that carries bacteria,...

Definition The Ehlers-Danlos syndromes (EDS) refer to a group of inherited disorders that affect collagen structure and function. Genetic abnormalities in the manufacturing of collagen within the body affect connective tissues, causing them to be abnormally weak.     Description Collagen is a strong, fibrous protein that lends strength and elasticity to connective tissues such as the skin, tendons,...

Definition Edwards’ syndrome is caused by an extra copy of chromosome 18. For this reason, it is also called trisomy 18 syndrome. The extra chromosome is lethal for most babies born with this condition. It causes major physical abnormalities and severe mental retardation, and very few children afflicted with this disease survive beyond a year. Description Humans normally have 23 pairs of chromosomes....

Definition Echocardiography is a diagnostic test that uses ultrasound waves to create an image of the heart muscle. Ultrasound waves that rebound or echo off the heart can show the size, shape, and movement of the heart’s valves and chambers as well as the flow of blood through the heart. Echocardiography may show such abnormalities as poorly functioning heart valves or damage to the heart tissue from...

Definition Echinococcosis (Hydatid disease) refers to human infection by the immature (larval) form of tapeworm, Echinococcus. One of three forms of the Echinococcus spp., E. granulosus, lives on dogs and livestock, and infects humans through contact with these animals. Allergic reactions and damage to various organs from cyst formation are the most common forms of disease in humans. Infection with the larva...

Definition Echinacea, or purple coneflower, is a perennial herb of the Composite family, commonly known as the daisy family. Most often referred to as the purple coneflower, this hardy plant also known as Sampson root, Missouri snakeroot, and rudbeckia. The prominent, bristly seed head inspired the generic name of the plant, taken from the Greek word echinos meaning hedgehog.         Description Echinacea...

Definition Ear surgery is the treatment of diseases, injuries, or deformations of the ear by operation with instruments. Purpose Ear surgery is performed to correct certain types of hearing loss, and to treat diseases of, injuries to, or deformities of the ear’s auditory tube, middle ear, inner ear, and auditory and vestibular systems. Ear surgery is commonly performed to treat conductive hearing loss,...

Definition An otoscope is a hand-held instrument with a tiny light and a cone-shaped attachment called an ear speculum, which is used to examine the ear canal. An ear examination is a normal part of most physical examinations by a doctor or nurse. It is also done when an ear infection or other type of ear problem is suspected.     Purpose An otoscope is used to look into the ear canal to see the ear...

Definition Personality disorders are a group of mental disturbances defined by the fourth edition, text revision (2000) of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) as ‘‘enduring pattern[s] of inner experience and behavior’’ that are sufficiently rigid and deep-seated to bring a person into repeated conflicts with his or her social and occupational environment....

Definition Peroxisomal disorders are a group of congenital (existing from birth) diseases characterized by the absence of normal peroxisomes in the cells of the body. Peroxisomes are special parts (organelles) within a cell that contain enzymes responsible for critical cellular processes, including oxidation of fatty acids, biosynthesis of membrane phospholipids (plasmalogens), cholesterol, and bile acids,...

Definition Pernicious anemia is a disease in which the red blood cells are abnormally formed, due to an inability to absorb vitamin B12. True pernicious anemia refers specifically to a disorder of atrophied parietal cells leading to absent intrinsic factor, resulting in an inability to absorb B12.     Description Vitamin B12, or cobalamin, plays an important role in the development of red blood cells....

Definition Peritonitis is an inflammation of the membrane which lines the inside of the abdomen and all of the internal organs. This membrane is called the peritoneum. Description Peritonitis may be primary (meaning that it occurs spontaneously, and not as the result of some other medical problem) or secondary (meaning that it results from some other condition). It is most often due to infection by bacteria,...

Definition Peripheral vascular disease is a narrowing of blood vessels that restricts blood flow. It mostly occurs in the legs, but is sometimes seen in the arms. Description Peripheral vascular disease includes a group of diseases in which blood vessels become restricted or blocked. Typically, the patient has peripheral vascular disease from atherosclerosis. Atherosclerosis is a disease in which fatty...

Definition The term peripheral neuropathy encompasses a wide range of disorders in which the nerves outside of the brain and spinal cord—peripheral nerves—have been damaged. Peripheral neuropathy may also be referred to as peripheral neuritis, or if many nerves are involved, the terms polyneuropathy or polyneuritis may be used. Description Peripheral neuropathy is a widespread disorder, and there...

Definition Radiation injuries are caused by ionizing radiation emitted by sources such as the sun, x-ray and other diagnostic machines, tanning beds, and radioactive elements released in nuclear power plant accidents and detonation of nuclear weapons during war and as terrorist acts.  Description Ionizing radiation is made up of unstable atoms that contain an excess amount of energy. In an attempt to...

Definition Radial keratotomy (RK) is a type of eye surgery used to correct myopia (nearsightedness). It works by changing the shape of the cornea–the transparent part of the eye that covers the iris and the pupil. Purpose  About 25–30% of all people in the world are nearsighted and need eyeglasses or contact lenses for distance vision to be clear. For a number of reasons, some people don’t...

Definition Rabies is an acute viral disease of the central nervous system that affects humans and other mammals but is most common in carnivores (flesh-eaters). It is sometimes referred to as a zoonosis, or disease of animals that can be communicated to humans. Rabies is almost exclusively transmitted through saliva from the bite of an infected animal. Another name for the disease is hydrophobia, which literally...

Definition Periodontal diseases are a group of diseases that affect the tissues that support and anchor the teeth. Left untreated, periodontal disease results in the destruction of the gums, alveolar bone (the part of the jaws where the teeth arise), and the outer layer of the tooth root. Description Periodontal disease is usually seen as a chronic inflammatory disease. An acute infection of the periodontal...

Definition Periodic paralysis (PP) is the name for several rare, inherited muscle disorders marked by temporary weakness, especially following rest, sleep, or exercise. Description Periodic paralysis disorders are genetic disorders that affect muscle strength. There are two major forms, hypokalemic and hyperkalemic, each caused by defects in different genes. In hypokalemic PP, the level of potassium in...

 Definition An infection caused by a bacteria or virus that can be passed from a mother to her baby during pregnancy or delivery is called a perinatal infection. Description Perinatal infections include bacterial or viral illnesses that can be passed from a mother to her baby either while the baby is still in the uterus, during the delivery process, or shortly after birth. Maternal infection can, in...

Definition Pericarditis is an inflammation of the two layers of the thin, sac-like membrane that surrounds the heart. This membrane is called the pericardium, so the term pericarditis means inflammation of the pericardium. Description Pericarditis is fairly common. It affects approximately one in 1,000 people. The most common form is caused by infection with a virus. People in their 20s and 30s who have had...

Definition Pericardiocentesis is the removal by needle of pericardial fluid from the sac surrounding the heart for diagnostic or therapeutic purposes. Purpose The pericardium, the sac (or membrane) that surrounds the heart muscle, normally contains a small amount of fluid that cushions and lubricates the heart as the heart expands and contracts. When too much fluid gathers in the pericardial cavity, the...

Definition A perforated septum is a hole in the nasal septum, the vertical plane of tissue that separates the nostrils. Description The nasal septum is a thin structure in the middle of the nose. In front, it is cartilage, further back it is bone. On either side, it is covered with mucus membranes. The cartilage depends upon the blood vessels in the mucus membranes on either side for its nutrition. If that blood...

Definition A perforated eardrum exists when there is a hole or rupture in the eardrum, the thin membrane that separates the outer ear canal from the middle ear. A perforated eardrum may cause temporary hearing loss and occasional discharge. A perforated eardrum is caused by a hole or rupture in the eardrum, the thin membrane that separates the outer ear canal from the middle ear. It may result in temporary...

Definition Percutaneous transhepatic cholangiography (PTHC) is an x-ray test used to identify obstructions either in the liver or bile ducts that slow or stop the flow of bile from the liver to the digestive system. Purpose Because the liver and bile ducts are not normally seen on x rays, the doctor injects the liver with a special dye that will show up on the resulting picture. This dye distributes evenly to...

Definition Penile prostheses are semirigid or inflatable devices that are implanted into penises to alleviate impotence. The inflatable implant is a common penile prosthesis. This device connects through a tube to a flexible fluid reservoir and a pump. The pump is shaped like a testicle and inserted in the scrotum. When the pump is squeezed, the fluid is forced into the inflatable cylinders implanted inside...

Definition Penile cancer is the growth of malignant cells on the external skin and in the tissues of the penis. Description Penile cancer is a disease in which cancerous cells appear on the penis. If left untreated, this cancer can grow and spread from the penis to the lymph nodes in the groin and eventually to other parts of the body. Demographics Penile cancer is a rare form of cancer that develops in...

Definition Penicillins are medicines that kill bacteria or prevent their growth. Purpose Penicillins are antibiotics (medicines used to treat infections caused by microorganisms). There are several types of penicillins, each used to treat different kinds of infections, such as skin infections, dental infections, ear infections, respiratory tract infections, urinary tract infections, gonorrhea, and other infections...

Definition Pelvic ultrasound is a procedure where harmless, high-frequency sound waves are projected into the abdomen. These waves reflect off of the internal structures and create shadowy black and white pictures on a display screen.   An ultrasound image of Anabelle Ashlyn Longe at 20 weeks. (Courtesy of Jacqueline Longe.) Purpose Ultrasound is performed routinely during pregnancy. Early in the...

Definition Pelvic relaxation is a weakening of the supportive muscles and ligaments of the pelvic floor. This condition, which affects women and is usually caused by childbirth, aging, and problems with support, causes the pelvic floor to sag and press into the wall of the vagina. Description The pelvic floor normally holds the uterus and the bladder in position above the vagina. When the pelvic floor becomes...

Definition Pelvic inflammatory disease (PID) is a term used to describe any infection in the lower female reproductive tract that spreads to the upper female reproductive tract. The lower female genital tract consists of the vagina and the cervix. The upper female genital tract consists of the body of the uterus, the fallopian or uterine tubes, and the ovaries.   Description PID is the most common...

Definition A pelvic fracture is a break in one or more bones of the pelvis. Description The pelvis is a butterfly-shaped group of bones located at the base of the spine. The pelvis consists of the pubis, ilium, and ischium bones (among others) held together by tough ligaments. With a cavity in its center, the pelvis forms one major ring and two smaller rings of bone that support and protect internal organs such...

Definition A pelvic examination is a routine procedure used to assess the well being of the female patients’ lower genito-urinary tract. This is done as part of a usual health screening and prevention tool, and is an element of the total health care for the female patient. Purpose Pelvic exams are useful as a screening tool for sexually transmitted diseases such as gonorrhea, chlamydia, genital warts,...

Definition Pellagra is a disorder brought on by a deficiency of the nutrient called niacin or nicotinic acid, one of the B-complex vitamins. Description Nicotinic acid plays a crucial role in the cellular process called respiration. Respiration is the process by which nutrients (specifically sugar, or glucose) and oxygen are taken in, chemical reactions take place, energy is produced and stored, and carbon dioxide...

Definition Patent ductus arteriosus (PDA) is a heart defect that occurs when the ductus arteriosus (the temporary fetal blood vessel that connects the aorta and the pulmonary artery) does not close at birth. Description The ductus arteriosus is a temporary fetal blood vessel that connects the aorta and the pulmonary artery before birth. The ductus arteriosus should be present and open before birth while the...