Glossary

Find definitions for thousands of medical terms, treatments, and tests -- even health-related abbreviations, prefixes, and suffixes.

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Radiation therapy is the use of high-dose X-rays to destroy cancer cells and shrink tumors. Radiation may come from a machine outside the body (external radiation therapy) or from the placement of thin plastic tubes containing radiation (radioisotopes) into the area where the cancer cells are found (internal radiation therapy, or brachytherapy).

Radiation therapy is standard treatment for many types of cancer. It may be used in combination with surgery, chemotherapy, or hormonal therapy.

Last Revised: July 27, 2011

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Matthew I. Kim, MD - Endocrinology

Radioactive tracers are used in imaging tests that help find problems inside the body. These tracers give off particles that can be detected and turned into a picture to help find problems in organs or other structures.

The tracer is usually given through an intravenous (IV) line placed in a vein. But the tracer also may be given by mouth or by inhaling it into the lungs. The tracer then travels through the body and may collect in a certain organ or area.

The types of tests that use radioactive tracers include positron emission tomography (PET) and nuclear medicine scans to look at specific organs such as the liver, lungs, kidneys, and gallbladder.

Last Revised: October 1, 2012

Author: Healthwise Staff

Medical Review: Anne C. Poinier, MD - Internal Medicine & Myo Min Han, MD - Nuclear Medicine

Radiologic technologists perform imaging tests such as X-rays, computed tomography (CT) scans, and magnetic resonance imaging (MRI). They are also called radiographers. They work under the direction of a radiologist, who interprets the images to diagnose illness.

Training programs in radiography lead to a certificate, associate degree, or bachelor's degree. State requirements for licensing vary. And radiologic technologists may be registered through the American Registry of Radiologic Technologists.

Last Revised: August 17, 2012

Author: Healthwise Staff

Medical Review: Anne C. Poinier, MD - Internal Medicine & E. Gregory Thompson, MD - Internal Medicine

Radiologists are medical doctors who specialize in performing and interpreting diagnostic imaging tests. They read X-rays and scans, such as chest X-rays, ultrasounds, or magnetic resonance imaging (MRI).

Another specialist or primary care doctor may base treatment decisions on findings reported by the radiologist. Radiologists may also supervise people who perform special tests, such as barium enemas or computed tomography (CT) scans.

Diagnostic radiologists further specialize in performing tests to diagnose diseases. People might see a diagnostic radiologist to get a test such as an ultrasound.

Radiologists can be board-certified through the Board of Radiology, which is recognized by the American Board of Medical Specialties.

Last Revised: August 17, 2012

Author: Healthwise Staff

Medical Review: Anne C. Poinier, MD - Internal Medicine & E. Gregory Thompson, MD - Internal Medicine

Range of motion is the degree of movement a joint has when it is extended, flexed, and rotated through all of its possible movements. A joint becomes stressed or overextended if it is moved past its natural range.

A person may increase a joint's range of motion through regular, gentle stretching exercises as directed by a health professional. Often these exercises are recommended after an injury or surgery to help prevent joint stiffness.

Last Revised: February 16, 2011

Author: Healthwise Staff

Medical Review: Anne C. Poinier, MD - Internal Medicine & Nancy Greenwald, MD - Physical Medicine and Rehabilitation

Recreational therapists are health and rehabilitation professionals who provide treatment services and recreation activities to people who have disabilities or illnesses. They are also called therapeutic recreation specialists.

Recreational therapists use arts and crafts, animals, sports, games, dance and movement, drama, music, and community outings to help people who have disabilities and illnesses. These activities not only help people be more independent but also reduce the depression, stress, and anxiety caused by being disabled or ill.

After recreational therapists complete their undergraduate work, they can be certified through the National Council for Therapeutic Recreation Certification.

Last Revised: August 17, 2012

Author: Healthwise Staff

Medical Review: Anne C. Poinier, MD - Internal Medicine & E. Gregory Thompson, MD - Internal Medicine

Red blood cells, or erythrocytes, travel through circulating blood carrying oxygen to body tissues and organs while removing waste. These blood cells make up the largest part of the blood system.

As the red blood cells in blood travel through the lungs, oxygen molecules from the lungs attach to the hemoglobin, a protein in the blood cells that contains iron. The oxygen is then released to tissues and organs, and the hemoglobin bonds with carbon dioxide and other waste gases. These waste products are transported away and removed as blood continues to circulate.

Millions of red blood cells are contained in a single drop of blood. Red blood cells are constantly being produced in the bone marrow to replenish those that gradually wear out and die. The average life of a red blood cell is about 120 days.

A significant decrease in the number of red blood cells causes anemia and shortness of breath.

Last Revised: August 6, 2012

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Joseph O'Donnell, MD - Hematology, Oncology

Registered dietitians (RDs) are health professionals who teach people about nutrition or develop diets to promote health. They can also specialize in nutritional counseling to help treat food-related psychological problems, such as anorexia or bulimia.

Dietitians work in hospitals, nursing homes, and schools. Registered dietitians also work in government, restaurant management, fitness, food companies, and private practices.

Registered dietitians complete a bachelor's degree. They also must complete a supervised practice program and pass a national examination given by the Commission on Dietetic Registration (CDR). Some RDs hold additional certifications in specialized areas of practice, such as pediatric or renal nutrition, nutrition support, or diabetes education. These certifications are awarded through the CDR or other medical and nutrition groups.

Last Revised: January 25, 2013

Author: Healthwise Staff

Medical Review: Kathleen Romito, MD - Family Medicine & Rhonda O'Brien, MS, RD, CDE - Certified Diabetes Educator

Multiple sclerosis (MS) is a chronic neurological disease that involves the central nervous system—specifically the brain, spinal cord, and optic nerves. Relapsing-remitting multiple sclerosis is a form of MS in which symptoms randomly flare up (relapse) and then improve or fade (remission).

This relapsing-remitting pattern emerges with the onset of the disease and may last for many years. MS can cause problems with muscle control and strength, vision, balance, sensation, and mental functions.

The disease does not advance during the remissions. But loss of nerve function that can occur during relapses may be permanent. After repeated relapse episodes, the loss of nerve function may cause symptoms that do not improve.

There is no cure for MS, but medicines can reduce the number, frequency, and severity of relapses and may slow the progression of the disease.

Last Revised: February 15, 2012

Author: Healthwise Staff

Medical Review: Adam Husney, MD - Family Medicine & Anne C. Poinier, MD - Internal Medicine & Barrie J. Hurwitz, MD - Neurology

Respiratory therapists (RTs) are health professionals who evaluate, treat, and care for people who have breathing problems. Respiratory therapists use oxygen, medicines, and mechanical measures such as chest percussion to help people breathe more effectively.

Most respiratory therapists work under the direct supervision of a doctor. Respiratory therapists treat people of all ages, from premature babies with undeveloped lungs to older adults with respiratory disease. Most respiratory therapists work in hospitals. But some work in nursing homes and doctor's offices.

Respiratory therapists can be certified as RTs after they complete a college-level, accredited RT program. The National Board for Respiratory Care (NBRC) offers voluntary certification and registration to graduates of accredited programs. Two credentials are awarded to respiratory therapists who satisfy the requirements: registered respiratory therapist (RRT) and certified respiratory therapist (CRT). Either the CRT or RRT examination is the standard in the states that require licensure.

Last Revised: August 17, 2012

Author: Healthwise Staff

Medical Review: Anne C. Poinier, MD - Internal Medicine & E. Gregory Thompson, MD - Internal Medicine

Restrictive cardiomyopathy is a problem in which the heart muscle becomes stiff and cannot fully expand to let enough blood enter its chambers. Blood that would normally enter the heart backs up in the circulatory system instead of getting pumped out to the body.

In most cases, restrictive cardiomyopathy leads to heart failure. Heart failure means that your heart can't pump enough blood to meet your body's needs.

The cause of restrictive cardiomyopathy is often not known. But a number of diseases can lead to restrictive cardiomyopathy. Symptoms of restrictive cardiomyopathy happen if a person gets heart failure. Heart failure symptoms include shortness of breath, feeling weak and tired, and swollen legs and feet.

The treatment of restrictive cardiomyopathy includes medicine and lifestyle changes. Treatment focuses on relieving the symptoms of heart failure and slowing its progression.

Last Revised: July 24, 2012

Author: Healthwise Staff

Medical Review: Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology & Robert A. Kloner, MD, PhD - Cardiology

The retina is a thin nerve membrane that detects light entering the eye. Nerve cells in the retina send signals of what the eye sees along the optic nerve to the brain.

The retina lines the back two-thirds of the eye and is made up of two layers: the sensory retina and the retinal pigment epithelium (RPE).

The macula, near the center of the retina at the back of the eyeball, provides the sharp, detailed, central vision a person uses for focusing on what is directly in the line of sight. The rest of the retina provides side (peripheral) vision, which lets a person see shapes but not fine details.

Last Revised: August 7, 2011

Author: Healthwise Staff

Medical Review: Adam Husney, MD, MD - Family Medicine & Carol L. Karp, MD - Ophthalmology

Reye syndrome is a very rare but serious disease that is most likely to occur in children younger than 15 years of age. The exact cause is not known, but it is linked with children who have recently had chickenpox (varicella), a cold, or flu (influenza) and taken aspirin.

The disease primarily targets the brain and liver and can cause drowsiness, confusion, seizures, coma, and in severe cases, death. The symptoms usually develop 3 to 7 days after the viral illness starts. Reye syndrome is not contagious.

All children with Reye syndrome are treated in a hospital intensive care unit, and most recover in a few weeks. But some children develop lasting brain damage. Early treatment increases the chance for full recovery.

Aspirin or aspirin products should not be given to anyone younger than 20, unless they are specifically prescribed by a doctor. Aspirin is also called acetyl salicylate, acetylsalicylic acid, salicylic acid, salicylate, or subsalicylate. Aspirin products are found in over-the-counter medicines such as Pepto-Bismol, Kaopectate, and Alka Seltzer.

Last Revised: May 16, 2012

Author: Healthwise Staff

Medical Review: John Pope, MD - Pediatrics & Chuck Norlin, MD - Pediatrics

Rh sensitization happens when a pregnant woman with Rh-negative blood is exposed to blood from her Rh-positive baby, usually during delivery. This isn't a problem in her first pregnancy, but if she gets pregnant again with an Rh-positive baby, antibodies in her blood can attack the baby's blood cells and cause serious problems.

A blood test is the only way to know you have Rh sensitization or are at risk for it.

Last Revised: October 9, 2012

Author: Healthwise Staff

Medical Review: Sarah Marshall, MD - Family Medicine & William Gilbert, MD - Maternal and Fetal Medicine

Rhabdomyolysis is a process in which dying muscle cells cause the toxic buildup of certain substances in the blood. Some of these substances are creatine, myoglobin, aldolase, potassium, and lactate dehydrogenase. Left untreated, rhabdomyolysis can cause life-threatening damage to body organs, including kidney failure.

Rhabdomyolysis can be caused by a variety of problems, including:

  • Severe muscle injury, such as that caused by prolonged pressure on muscle tissue, heat exhaustion, extreme physical exertion, seizures, and electrical burns.
  • Medicines, such as statins, salicylates, gemfibrozil, phenothiazines, corticosteroids, and phenytoin.
  • Toxins, such as alcohol, cocaine, hornet stings, snakebites, and carbon monoxide.
  • Salmonella and infections such as influenza, Legionnaires' disease, and blood infections caused by gram-negative bacteria.

Early symptoms are often subtle. Muscle weakness, pain, tenderness, and stiffness may develop along with fever, nausea, confusion, and a general ill feeling (malaise). Urine may also be noticeably dark.

Treatment for rhabdomyolysis includes removing the cause of the muscle cell destruction whenever possible, such as by stopping certain medicines. Measures to help the kidneys remove the buildup of toxins and other chemicals, such as providing plenty of fluids, is also important. Other treatment (such as dialysis) may be needed if rhabdomyolysis is severe.

Last Revised: June 29, 2012

Author: Healthwise Staff

Medical Review: Kathleen Romito, MD - Family Medicine & Robert A. Kloner, MD, PhD - Cardiology & Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology

Rheumatic fever results from an infection caused by certain strains of streptococcal bacteria and may be triggered by a strep infection (most often strep throat) that has not been treated. Proper treatment of strep infection can prevent rheumatic fever.

Rheumatic fever affects the joints and heart, causing symptoms similar to arthritis as well as heart problems (rheumatic heart disease). Rheumatic fever may also affect the skin, brain, and other organs and tissues. Most of the damage caused by rheumatic fever is temporary. But if any heart damage occurs, it is usually permanent.

Last Revised: August 2, 2012

Author: Healthwise Staff

Medical Review: Kathleen Romito, MD - Family Medicine & Donald R. Mintz, MD - Otolaryngology

Rheumatic heart disease is inflammation and damage to the heart muscle and heart valves that develop as a result of rheumatic fever. A strep throat infection that is not properly treated can trigger rheumatic fever.

Not all people who have rheumatic fever develop rheumatic heart disease. But any heart damage that occurs is usually permanent.

Last Revised: August 2, 2012

Author: Healthwise Staff

Medical Review: Kathleen Romito, MD - Family Medicine & Donald R. Mintz, MD - Otolaryngology

Rheumatoid arthritis is a type of arthritis in which your body's immune system attacks healthy tissue in your joints. This makes the joints swollen, stiff, and painful. Over time, it may destroy the joint tissues and make it hard for you to walk and use your hands.

Medicine may help control rheumatoid arthritis or keep it from getting worse.

Last Revised: October 9, 2012

Author: Healthwise Staff

Medical Review: Anne C. Poinier, MD - Internal Medicine & Nancy Ann Shadick, MD, MPH - Internal Medicine, Rheumatology

Rubella, also called German measles, is a contagious infection caused by a virus. It usually causes a mild illness with a fine, red rash over most of the body, swollen glands, and low fever.

Rubella is not common in the United States because most children are vaccinated (immunized) against it. Most people who get rubella are young adults who have not been vaccinated. A person can develop immunity to rubella by having the disease or being vaccinated.

Rubella is a mild illness in adults. But if a woman gets rubella during pregnancy, her baby is at risk for birth defects, such as heart defects, deafness, and cataracts. The illness can also result in miscarriage or stillbirth. The earlier the infection occurs in a woman's pregnancy, the greater the risk that her baby will have severe defects. Women who are not immune to rubella should be vaccinated before becoming pregnant.

Last Revised: August 31, 2012

Author: Healthwise Staff

Medical Review: John Pope, MD - Pediatrics & W. David Colby IV, MSc, MD, FRCPC - Infectious Disease