Glossary

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

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A pacemaker is a small, battery-powered device that sends out small electrical impulses to make the heart muscle to contract. The pacemaker itself is a waterproof object about the size of a silver dollar. A pacemaker consists of a pulse generator and battery that create the electrical impulses, and wires (leads) that transmit electricity to the heart.

Pacemakers help your heart beat in a regular rhythm and at a normal speed. They are inserted to treat a heart rate that is too slow, too fast, or irregular.

Pacemakers are typically placed under the skin of the chest. These pacemakers are permanent. But sometimes, pacemakers are needed for only a short time to help a person in the hospital with heart rhythm problems. A temporary pacemaker is not surgically inserted but is worn outside the body. Temporary pacemakers are used only while a person is in the hospital.

Last Revised: June 2, 2011

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Rakesh K. Pai, MD, FACC

Palliative care is a kind of medical care for people who have serious and chronic illnesses. Palliative care provides an extra layer of support that can improve quality of life for the person who is sick and for his or her family.

Many people combine palliative care with other types of treatment.

Palliative care can help manage symptoms, pain, or side effects from treatment. It can help people cope with their feelings about living with a serious illness. It can also help with communication, so all the health professionals providing care for a person understand their shared goals. It may even help with planning for future medical care.

Palliative care can help a person of any age, whether or not his or her illness is terminal. More and more health professionals are using palliative care, and many are specially trained to provide it.

Last Revised: December 29, 2011

Author: Healthwise Staff

Medical Review: Anne C. Poinier, MD - Internal Medicine & Shelly R. Garone, MD, FACP - Palliative Medicine

Heart palpitations are an uncomfortable awareness of the heart beating rapidly or irregularly. Palpitations can be caused by stress, fatigue, or overuse of alcohol or stimulants such as caffeine or nicotine, and they usually are not a serious problem.

Heart palpitations can feel like:

  • Pounding or fluttering in your chest.
  • Your heart is doing a flip-flop.
  • Your heart is skipping or missing a beat.
  • Your heart is racing.
  • You have an extra heartbeat.
  • Your heart is beating in your neck.

If palpitations persist or occur with fainting, near fainting, or lightheadedness, they may be a sign of a heart problem.

Last Revised: September 13, 2012

Author: Healthwise Staff

Medical Review: William H. Blahd, Jr., MD, FACEP - Emergency Medicine & David Messenger, MD & H. Michael O'Connor, MD - Emergency Medicine

The pancreas is an organ in the upper abdomen, behind the stomach and close to the spine, that produces substances (digestive enzymes) needed to break down and use food. The pancreas also produces insulin, the hormone that regulates sugar (glucose) in the blood.

Last Revised: May 25, 2011

Author: Healthwise Staff

Medical Review: Kathleen Romito, MD - Family Medicine & Peter J. Kahrilas, MD - Gastroenterology

Pancreatitis is inflammation of the pancreas, an organ in your belly that makes insulin and enzymes that help you digest food. Pancreatitis can cause sudden, severe belly pain. It's usually caused by alcohol abuse or gallstones.

Most people recover fully from pancreatitis.

Last Revised: September 27, 2012

Author: Healthwise Staff

Medical Review: Kathleen Romito, MD - Family Medicine & Peter J. Kahrilas, MD - Gastroenterology

A panic attack is a sudden feeling of extreme anxiety. Symptoms include feelings of dying or losing control of oneself, rapid breathing (hyperventilation), and a racing heart.

A person having a panic attack may feel dizzy, sweaty, or shaky. Other symptoms include trouble breathing, chest pain or tightness, and an irregular heartbeat.

A panic attack can be triggered by a stressful event, or it can occur unexpectedly. An attack starts suddenly and usually lasts from 5 to 20 minutes but may last even longer, up to a few hours. You have the most anxiety about 10 minutes after the attack starts. Panic attacks can be successfully treated with counseling and medicine.

Last Revised: September 7, 2012

Author: Healthwise Staff

Medical Review: Anne C. Poinier, MD - Internal Medicine & Lisa S. Weinstock, MD - Psychiatry

Paralysis is a loss of nerve function or muscle power resulting in an inability to move. When nerve cells in the brain or other parts of the body are damaged by injury or disease, the body parts controlled by those nerve or brain cells do not function.

The damage may cause mild or severe loss of function and may be temporary or permanent. The degree of paralysis depends on:

  • Which nerve cells are damaged and, when paralysis is caused by brain damage, how much of the brain is involved.
  • How quickly the blood supply returns to the area, how quickly pressure is taken off the nerve, or how soon the disease causing the problem is corrected.

Last Revised: October 14, 2011

Author: Healthwise Staff

Medical Review: William H. Blahd, Jr., MD, FACEP - Emergency Medicine & H. Michael O'Connor, MD - Emergency Medicine

Parkinson's disease happens when there is a problem with certain nerve cells in the brain that control movement. The classic symptoms are shaking (tremor), stiff muscles (rigidity), and slow movement (bradykinesia). It may also cause problems with balance or walking, as well as confusion and memory loss.

Parkinson's gets worse over time. But usually this happens slowly, over many years.

Last Revised: December 5, 2012

Author: Healthwise Staff

Medical Review: Anne C. Poinier, MD - Internal Medicine & G. Frederick Wooten, MD - Neurology

Paroxysmal atrial fibrillation are episodes of atrial fibrillation, an irregular heart rhythm, that go away on their own. They may last anywhere from a few seconds to a few weeks and may not cause symptoms. Sometimes paroxysmal atrial fibrillation is related to other things, such as alcohol use, stress, or activity.

Last Revised: December 14, 2012

Author: Healthwise Staff

Medical Review: Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology & John M. Miller, MD, FACC - Cardiology, Electrophysiology

The ductus arteriosus is a blood vessel in a fetus that connects the pulmonary artery, which carries blood to the lungs, and the aorta, which carries blood to the body, so that blood flow bypasses the lungs. Normally, this blood vessel closes at birth as the baby starts breathing. But if the vessel does not close, it is known as a patent (open) ductus arteriosus (PDA).

A patent ductus arteriosus allows some oxygen-rich blood to flow from the aorta back into the pulmonary artery and to the lungs instead of to the rest of the body. Because some of the blood intended for the body returns to the lungs, the left side of the heart has to pump harder to get enough blood to the body. This can enlarge and weaken the heart.

Some babies do not have symptoms from a patent ductus arteriosus. But this abnormality often causes symptoms, such as poor feeding and shortness of breath. An older child may develop heart failure or an infection of the heart's inner lining (infective endocarditis). How bad the symptoms get and whether complications develop depend on how much blood flows through the ductus.

Treatment for a patent ductus arteriosus might be medicine that helps close the blood vessel. Or a doctor will insert a small closure device into the heart during a heart catheterization. This prevents blood from flowing into the lungs. If a heart catheterization can't be done, a surgeon might operate to close the PDA.

Last Revised: October 11, 2011

Author: Healthwise Staff

Medical Review: John Pope, MD - Pediatrics & Larry A. Latson, MD - Pediatric Cardiology

The foramen ovale is an opening in the part of the heart that separates the upper right and left chambers (atria). In a fetus, this opening has a flap of tissue that acts like a one-way door—it allows blood to flow to the left side of the heart without going to the lungs, and it is kept open by the pressure of the blood that passes through it.

Normally, when the baby is born and takes his or her first breath, blood begins to flow through the lungs, and the foramen ovale closes within a few days. Sometimes, this opening remains open (patent) and is called a patent foramen ovale. A patent foramen ovale is also called a PFO. A PFO happens in about 2 out of 10 people.

A patent foramen ovale is typically not treated and does not cause problems. But it might be treated if other heart defects are present or you had a stroke caused by a blood clot. Treatment includes a catheter procedure or surgery to close the opening in the heart.

Last Revised: October 11, 2011

Author: Healthwise Staff

Medical Review: John Pope, MD - Pediatrics & Larry A. Latson, MD - Pediatric Cardiology

PDF stands for portable document format. Forms available in PDF allow a person to view, navigate, enter text, and print the completed form using free software called Adobe Reader from Adobe Systems, Inc. Versions of Adobe Reader run on Windows, Macintosh, and UNIX systems.

Adobe Reader is available at: http://get.adobe.com/reader.

Last Revised: April 19, 2011

Author: Healthwise Staff

Medical Review: Kathleen Romito, MD - Family Medicine & Brian D. O'Brien, MD - Internal Medicine

Pediatricians are medical doctors who specialize in the care of children.

Pediatricians can treat children who have any type of problem, or they may specialize in specific areas, such as:

  • Adolescent medicine (conditions and diseases common to teenagers).
  • Cardiology (diseases and conditions of the heart and blood vessels).
  • Developmental disorders (behavior, communication, and mental disorders in children).
  • Endocrinology (diseases of the endocrine glands, which regulate hormones).
  • Gastroenterology (diseases of the digestive system).
  • Infectious disease (complex infections).
  • Nephrology (diseases of the kidney and urinary system).
  • Oncology (cancer).

Pediatricians can be board-certified through the Board of Pediatrics, 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

A peptic ulcer is a sore in the lining of your stomach or upper small intestine. Ulcers form when the protective layer in the lining has broken down, often because of a bacterial infection or frequent use of aspirin or similar medicine.

Peptic ulcers can cause pain in the belly, above the belly button. Ulcers can also bleed.

Last Revised: October 9, 2012

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Jerome B. Simon, MD, FRCPC, FACP - Gastroenterology

Perforating veins are blood vessels in the legs that connect the superficial leg veins just under the skin to the deep leg veins under the muscles. Perforating veins are sometimes called communicating veins.

Damage or disease in the perforating vein system can lead to varicose veins, which are twisted, enlarged veins that can occur anywhere a vein is close to skin, but which occur most often in the legs.

Last Revised: February 1, 2012

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & David A. Szalay, MD - Vascular Surgery

Pericardial effusion is a buildup of fluid in the space between the heart and the sac around the heart (pericardium).

Pericardial effusion can be caused by pericarditis, an inflammation of the pericardium. Pericarditis may be caused by heart attack, kidney failure, bacterial or viral infection, or cancer treatment.

Pericarditis can also cause chest pain and, rarely, increased pressure on the heart (cardiac tamponade).

Pericardial effusion may be drained in a procedure called pericardiocentesis, which involves using a needle and sometimes a thin tube called a catheter to drain the fluid. If the fluid buildup is gradual and the heart is tolerating the increased fluid around it, treatment of the underlying cause may be tried first.

Last Revised: April 5, 2011

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Stephen Fort, MD, MRCP, FRCPC - Interventional Cardiology

Pericarditis is inflammation of the sac that surrounds and protects the heart (pericardium). Pericarditis can cause an abnormal buildup of fluid between the pericardium and the heart (pericardial effusion).

Pericarditis often improves without causing any damage to the heart. But if pericarditis causes excess fluid to build up quickly, pressure on the heart increases (cardiac tamponade), and the heart may fail.

The most common cause of pericarditis is infection with a virus. Other causes include bacterial infection, heart attack, chest injury, and medicine side effects.

Symptoms of pericarditis include:

  • Severe, sudden pain in the center or the left side of the chest that may spread to the neck, back, shoulders, or arms. Breathing deeply, moving, or lying down often makes the pain worse. Sitting up and leaning forward may relieve the pain.
  • Mild fever.
  • A general feeling of weakness or fatigue.

Treatment for pericarditis may include medicines to reduce inflammation and relieve pain and antibiotics if the cause is a bacterial infection. If there is any fluid buildup, it may be drained.

Last Revised: April 5, 2011

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Stephen Fort, MD, MRCP, FRCPC - Interventional Cardiology

The pericardium is a membrane like a sac that surrounds the heart and its major blood vessels. Normally there is a small amount of fluid between the pericardium and the heart that helps cushion the heart and reduces friction between the heart and the pericardium when the heart beats.

Last Revised: April 5, 2011

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Stephen Fort, MD, MRCP, FRCPC - Interventional Cardiology

Peripheral arterial disease (PAD) is a narrowing or blockage of arteries that causes poor blood flow to your legs or arms. When you walk or exercise, your leg muscles don't get enough blood and you can get painful cramps.

Last Revised: October 9, 2012

Author: Healthwise Staff

Medical Review: Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology & David A. Szalay, MD - Vascular Surgery

Peripheral neuropathy is a condition that affects the nerves that control the sense of touch, how a person feels pain and temperature, and muscle strength. A person who has peripheral neuropathy may find it hard to do things that require coordination, such as walking or fastening buttons.

Peripheral neuropathy is often caused by other health problems such as diabetes, kidney problems, vitamin deficiencies and alcoholism, HIV, or Guillain-Barré syndrome. It can happen after exposure to toxic substances, such as arsenic, or by certain medicines such as those used for chemotherapy.

Last Revised: November 21, 2011

Author: Healthwise Staff

Medical Review: William H. Blahd, Jr., MD, FACEP - Emergency Medicine & Barry L. Scurran, DPM - Podiatry and Podiatric Surgery

Peritonitis is an infection of the lining of the abdominal wall (peritoneum) caused by bacteria or irritating substances. Peritonitis causes pain and swelling in the abdomen and can be very serious if it is not treated.

Symptoms of peritonitis include:

  • Swelling of the abdomen, which may feel hard (rigid).
  • Severe pain and tenderness in the abdomen that becomes worse with moving, coughing, or pressing on the abdomen. The pain sometimes reaches into the shoulder.
  • Nausea and vomiting.
  • A rapid pulse.
  • Chills and fever.
  • Rapid breathing.

A person with these symptoms requires immediate medical attention. Treatment typically involves surgery and antibiotics. Without treatment, the illness gets worse rapidly and can become life-threatening.

Last Revised: May 10, 2012

Author: Healthwise Staff

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

Persistent atrial fibrillation means that episodes of the irregular heart rhythm last longer and often don't go away on their own. If an episode lasts more than 7 days, it is called persistent atrial fibrillation.

Treatment with medicine or cardioversion can restore a normal rhythm. This normal rhythm may last for several weeks or longer before atrial fibrillation happens again.

Last Revised: December 14, 2012

Author: Healthwise Staff

Medical Review: Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology & John M. Miller, MD, FACC - Cardiology, Electrophysiology

Positron emission tomography (PET) is a test that uses a special type of camera and a tracer (radioactive chemical) to look at organs in the body.

During a PET scan, a radioactive substance called a tracer is typically injected into a vein (usually in the arm), but sometimes it may be inhaled. The tracer usually is a special form of a substance (such as glucose) that can be used (metabolized) by cells in the body.

A PET scan is often used to evaluate cancer, such as of the lung or colon. It also can be used to evaluate the heart's metabolism and blood flow and examine brain function.

PET scan pictures do not show as much detail as computed tomography (CT) scans or magnetic resonance imaging (MRI).

Last Revised: July 28, 2011

Author: Healthwise Staff

Medical Review: Adam Husney, MD, MD - Family Medicine & Howard Schaff, MD - Diagnostic Radiology

pH is a measure of the acidic or basic (alkaline) nature of a solution. The pH scale ranges from 0 (most acidic) to 14 (most basic).

  • A neutral solution (pure water) has a pH of 7.
  • Solutions with a pH less than 7 are acidic, with 0 being the most acidic.
  • Solutions with a pH greater than 7 are basic (alkaline), with 14 being the most basic.

Last Revised: May 30, 2012

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Robert L. Cowie, MB, FCP(SA), MD, MSc, MFOM - Pulmonology

Phenylketonuria (PKU) is an inherited disorder in which the body cannot break down an amino acid called phenylalanine, which is a part of protein. If treatment is not started soon after birth, phenylalanine levels rise and can cause lasting brain and nervous system damage, such as intellectual disability.

Symptoms of PKU usually appear within a few months of birth, after a baby has started drinking formula or breast milk and phenylalanine has built up in his or her blood. Before birth, the mother's body filters out the excess phenylalanine for the baby (fetus).

Early symptoms may include:

  • A musty odor to the skin, hair, and urine.
  • Weight loss from vomiting and frequent diarrhea.
  • Irritability.
  • Skin problems.
  • Sensitivity to light.

Screening for PKU is routinely done shortly after birth, making early diagnosis and treatment possible. Starting treatment within the first few weeks of birth may prevent lasting brain damage. In rare cases, some children who receive treatment will have learning or behavior problems. Left untreated, PKU causes progressively more severe intellectual disability.

People with PKU must follow a diet low in protein throughout life. Women of childbearing age with PKU must carefully manage their phenylalanine levels to prevent harm to their baby should they become pregnant. Babies born to mothers who have high phenylalanine levels during pregnancy are at risk for intellectual disability and other developmental problems.

Last Revised: September 8, 2011

Author: Healthwise Staff

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

Pheochromocytoma is a tumor usually found in the adrenal glands (located on the kidneys). The tumor usually is not cancerous, but it can be fatal if left untreated.

Pheochromocytoma is rare and occurs most often in young adults. It causes attacks of high blood pressure, headaches, excessive sweating, nausea and vomiting, anxiety, and loss of consciousness.

Treatment for pheochromocytoma involves surgery to remove the tumor.

Last Revised: June 29, 2012

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Avery L. Seifert, MD - Urology

During a physical exam, a health professional looks at, listens to, and touches or gently presses on (palpates) the body. This exam helps the health professional determine the cause of symptoms, what other conditions may be present, and what medical tests may be needed. During a physical exam, the health professional may:

  • Take the person's temperature.
  • Listen to the heart and lungs.
  • Examine the eyes with an ophthalmoscope.
  • Examine the ears with an otoscope.
  • Touch or gently press on (palpate) the neck, underarms, abdomen, and groin.
  • Look at the skin.
  • Check the person's balance and coordination.

Last Revised: August 13, 2012

Author: Healthwise Staff

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

Physical therapists are health professionals who evaluate physical problems and injuries, then provide education and treatment to promote health and physical function. Physical therapists also develop programs that include exercise and stretching to increase fitness and prevent injury.

A physical therapist provides hands-on treatment to help return normal movement to joints and muscles and gives instruction about exercises to help heal and strengthen the body. Treatment may include physical or mechanical means, such as exercise, heat, or mild electrical current. Physical therapists also use devices such as prosthetics (artificial limbs), orthotics (braces and supports), and equipment to help a person in daily life.

Some physical therapists treat a wide range of ailments. Others specialize in areas such as pediatrics, geriatrics, orthopedics, sports physical therapy, neurology, cardiovascular, pulmonary, oncology, and women's health. Physical therapists work for hospitals, nursing homes, home health agencies, rehabilitation facilities, fitness facilities, and schools.

Physical therapists earn a master's degree or entry-level doctorate in physical therapy from an accredited physical therapist educational program that includes a period of clinical work. All states require physical therapists to pass a licensure exam before they can practice.

Last Revised: August 17, 2012

Author: Healthwise Staff

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

Physical therapy is treatment to improve mobility (such as walking, going up stairs, or getting in and out of bed), to relieve pain, and to restore physical function and overall fitness. The physical therapist uses exercise, manual therapy, education, and modalities such as heat, cold, and electrical stimulation to work toward these goals.

Depending on the injury, disease, or condition, physical therapy may include work on flexibility, strength, endurance, coordination, and/or balance. Treatment may focus on preventing problems or treating problems that affect:

  • Your muscles, tendons, ligaments, and bones (musculoskeletal system).
  • Your nerves and related muscles (neuromuscular system).
  • Your heart and related blood vessels (cardiovascular system).
  • Your lungs and breathing (pulmonary system).
  • Your skin, including wounds and burns.
  • Any combination of two or more of these.

Last Revised: March 4, 2011

Author: Healthwise Staff

Medical Review: Adam Husney, MD - Family Medicine & David A. Fleckenstein, MPT - Physical Therapy

Physician assistants (PAs) are health professionals who practice medicine under a doctor's supervision in medical and surgical settings. They can perform routine exams, order lab work and X-rays, prescribe medicines, and counsel people about their health.

A physician assistant completes an accredited PA program after college. Then he or she is eligible to take the Physician Assistant National Certification Examination (PANCE).

Last Revised: August 17, 2012

Author: Healthwise Staff

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

Some medical tests report results in picograms per milliliter (pg/mL).

  • A picogram is one-trillionth of a gram. A gram is about 1/30 of an ounce.
  • A milliliter measures fluid volume equal to one-thousandth of a liter. A liter is a little bigger than a quart.

Last Revised: May 6, 2011

Author: Healthwise Staff

Medical Review: Anne C. Poinier, MD - Internal Medicine & Thomas M. Bailey, MD - Family Medicine

Some medical tests report results in picomoles per liter (pmol/L).

  • A mole is an amount of a substance that contains a large number (6 followed by 23 zeros) of molecules or atoms. A picomole is one-trillionth of a mole.
  • A liter measures fluid volume. It is a little bigger than a quart.

Last Revised: May 6, 2011

Author: Healthwise Staff

Medical Review: Anne C. Poinier, MD - Internal Medicine & Thomas M. Bailey, MD - Family Medicine

The pituitary gland is a small gland located beneath the brain. The pituitary gland produces substances (hormones) that enter the bloodstream and help control many processes of the body.

Hormones produced in the pituitary gland help manage these body functions:

  • Growth
  • Blood pressure
  • Some aspects of pregnancy
  • Breast milk production
  • Sex organ functions in both women and men
  • Thyroid gland function
  • The conversion of food into energy (metabolism)
  • Water balance in the body

Last Revised: June 8, 2012

Author: Healthwise Staff

Medical Review: Sarah Marshall, MD - Family Medicine & Kirtly Jones, MD - Obstetrics and Gynecology

The placenta is a large organ that develops in the uterus during pregnancy and is connected to the fetus by the umbilical cord. Through the blood vessels in the umbilical cord and placenta, the fetus receives oxygen and nutrients from the mother and gets rid of wastes.

The placenta is delivered soon after the baby is born. (This is sometimes called the afterbirth.)

Last Revised: July 23, 2012

Author: Healthwise Staff

Medical Review: Sarah Marshall, MD - Family Medicine & Kirtly Jones, MD - Obstetrics and Gynecology

Plantar fasciitis (say "PLAN-ter fash-ee-EYE-tus") is pain in your heel or the bottom of your foot. It happens when the flat band of tissue (ligament) that supports the arch of your foot is inflamed or irritated.

Plantar fasciitis is common in middle-aged people. It also occurs in younger people who are on their feet a lot, like athletes or soldiers. It can happen in one foot or both feet.

Last Revised: October 9, 2012

Author: Healthwise Staff

Medical Review: William H. Blahd, Jr., MD, FACEP - Emergency Medicine & Barry L. Scurran, DPM - Podiatry and Podiatric Surgery

Plaque is a buildup of cholesterol, white blood cells, calcium, and other substances in the walls of arteries. Over time, plaque narrows the artery, and the artery hardens (atherosclerosis).

Plaque sometimes reduces blood flow to the heart muscle, which can cause chest pain (angina). Plaque in the large artery in the neck (carotid artery stenosis) may block blood flow to the brain and is a common cause of transient ischemic attack (sometimes called "mini-stroke") and stroke.

Plaques are covered with a fibrous cap, which may rupture if some trigger causes a surge in blood pressure or causes the artery to constrict. A person may have a heart attack or stroke if a plaque breaks open, creating a blood clot that completely blocks blood flow through the artery.

Last Revised: January 3, 2013

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Karin M. Lindholm, DO - Neurology

Plastic surgeons are medical doctors who specialize in surgery that improves a person's appearance, surgery for a birth defect such as cleft palate, or surgery following an injury or the removal of cancer, such as breast implant surgery after breast removal (mastectomy).

Plastic surgeons can further specialize in hand surgery.

Plastic surgeons can be board-certified through the Board of Plastic Surgery, 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

A platelet is the smallest type of blood cell. Platelets are the body's first defense against bleeding, helping the blood to clot (coagulate) by collecting at the site of a wound and clumping together to help stop the flow of blood.

People with very low levels of platelets or who have bleeding disorders may need to have transfusions of platelets to prevent excessive bleeding.

Last Revised: August 6, 2012

Author: Healthwise Staff

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

A pleural effusion is the buildup of fluid between the outer lining of the lungs (visceral pleura) and the inner lining (parietal pleura) of the chest cavity. This fluid buildup has many causes, including infection, inflammation, heart failure, pancreatitis, or cancer.

A minor pleural effusion may not cause any symptoms. A large amount of fluid may prevent the complete expansion of a lung, making it hard for the person to breathe. Possible symptoms of a pleural effusion may include:

  • Difficulty breathing.
  • Chest pain.
  • Fever.
  • A cough.

A doctor may diagnose a pleural effusion during a physical exam and then confirm the diagnosis with a chest X-ray.

Small pleural effusions often heal on their own. If treatment is needed, it may involve removal of the fluid using a needle inserted through the chest wall (thoracentesis). The fluid may be sent to a lab to find out what is causing the fluid to build up.

Last Revised: July 15, 2011

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Robert L. Cowie, MB, FCP(SA), MD, MSc, MFOM - Pulmonology

Pneumonia is a lung infection that can make you very sick. You may cough, run a fever, and have a hard time breathing. It can usually be treated at home, but some people need to go to the hospital.

Pneumonia can be caused by bacteria or a virus. Antibiotics are used to treat pneumonia caused by bacteria.

Last Revised: October 9, 2012

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & R. Steven Tharratt, MD, MPVM, FACP, FCCP - Pulmonology, Critical Care Medicine, Medical Toxicology

A pneumothorax (collapsed lung) results from a buildup of air in the space between the lung and the chest wall (pleural space). This prevents the lung from expanding properly when the person tries to breathe in, causing shortness of breath and chest pain.

A pneumothorax is usually caused by an injury to the chest, such as a broken rib or a puncture wound. It may also occur suddenly without an injury (spontaneous pneumothorax). Spontaneous pneumothorax can result from damage to the lungs caused by conditions such as chronic obstructive pulmonary disease (COPD), asthma, cystic fibrosis, and pneumonia. Spontaneous pneumothorax can also occur in people who don't have lung disease.

Symptoms of pneumothorax often include:

  • Shortness of breath (dyspnea), which may be mild to severe, depending on how much of the lung is collapsed.
  • Sudden, severe, and sharp chest pain on the same side as the collapsed lung.

A small pneumothorax may improve without treatment. But a more serious pneumothorax usually is treated by inserting a needle or a chest tube into the chest cavity. This relieves the pressure on the lung and allows it to re-expand.

Last Revised: April 13, 2011

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & R. Steven Tharratt, MD, MPVM, FACP, FCCP - Pulmonology, Critical Care Medicine, Medical Toxicology

Podiatrists are health professionals who diagnose and treat medical and surgical problems and injuries of the feet and ankles, such as corns, warts, plantar fasciitis, bunions, or hammer toes. They also perform reconstructive surgery.

Podiatrists provide extended care for people who need it, such as those who have foot problems caused by diabetes.

A podiatrist completes a degree at a college of podiatric medicine after undergraduate college. After receiving his or her podiatry degree, a podiatrist typically spends time in a hospital-based residency program.

Podiatrists can be board-certified through the Council on Podiatric Medical Education. Certification is not required in every state.

Last Revised: August 17, 2012

Author: Healthwise Staff

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

Polycystic ovary syndrome (say "pah-lee-SIS-tik OH-vuh-ree SIN-drohm") is a hormone imbalance in women that can affect ovulation. It can cause problems with a woman's periods and make it harder to get pregnant.

Last Revised: October 9, 2012

Author: Healthwise Staff

Medical Review: Patrice Burgess, MD - Family Medicine & Kirtly Jones, MD - Obstetrics and Gynecology

Polycythemia is an abnormal increase in the number of red blood cells produced by the bone marrow. The extra numbers of red blood cells cause blood to thicken and may increase the risk of blood clots that may cause heart attacks or strokes.

Treatment for polycythemia (also called erythrocythemia) sometimes involves removing red blood cells (much like donating blood) from the blood. But this procedure may decrease iron levels in the body.

Last Revised: October 15, 2012

Author: Healthwise Staff

Medical Review: Kathleen Romito, MD - Family Medicine & Brian Leber, MDCM, FRCPC - Hematology

Postherpetic neuralgia is pain, headaches, and nerve problems that occur as a complication of shingles (herpes zoster). Postherpetic neuralgia lasts for at least 30 days and can continue for months to years.

People who develop shingles after age 50 and who have severe pain and rash during shingles have the greatest risk for having postherpetic neuralgia. It most commonly occurs on the forehead or chest. The pain linked with postherpetic neuralgia may make it difficult to eat, sleep, and do daily activities. It may also increase the risk for depression.

Early treatment of shingles with antiviral medicines may prevent postherpetic neuralgia. If postherpetic neuralgia does occur, certain over-the-counter and prescription medicines can relieve pain.

Last Revised: December 18, 2012

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Christine Hahn, MD - Epidemiology

The postmenopausal phase of a woman's life begins at menopause, which is 1 year after her last menstrual period. While postmenopause usually begins around age 50, some women become postmenopausal in their mid-40s, and others do so in their later 50s.

In early postmenopause, a woman's estrogen stabilizes at a low level. Although low estrogen helps reduce the risk of various types of cancer, it also leads to bone thinning, which sometimes results in osteoporosis. A variety of hormonal and nonhormonal treatments are available for postmenopausal women who have menopausal symptoms. Women are generally encouraged to try nonhormonal treatment to avoid the cancer, heart, and dementia risks of hormone replacement therapy.

Menopause can begin early and suddenly after removal of the ovaries or after cancer treatment that damages the ovaries.

Last Revised: April 26, 2012

Author: Healthwise Staff

Medical Review: Anne C. Poinier, MD - Internal Medicine & Carla J. Herman, MD, MPH - Geriatric Medicine

Post-thrombotic syndrome (also called postphlebitic syndrome) is a complication of a blood clot that forms in a deep vein. Post-thrombotic syndrome occurs because of damage to the vein caused by the blood clot (thrombosis).

Post-thrombotic syndrome can be a long-term problem that lasts for years. It can cause sores that are painful and hard to treat.

The symptoms include:

  • Brownish discoloration of the skin.
  • Itching, swelling, slow-healing sores, and pain in the area.
  • Fragile skin on the area that bruises easily. The skin may be dry and may peel.

Compression stockings may be used to reduce swelling and relieve symptoms.

Last Revised: December 28, 2011

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Jeffrey S. Ginsberg, MD - Hematology

Potassium is a mineral in the body that helps maintain fluid balance, nerve function, and muscle contraction, as well as the proper transmission of electrical impulses in the heart. Potatoes and bananas are especially good sources of potassium, which also is found in many meats, milks, fruits, vegetables, and grains.

Both low and high potassium levels can disrupt the normal electrical impulses in the heart, which leads to irregular heartbeats (arrhythmias).

Last Revised: April 26, 2012

Author: Healthwise Staff

Medical Review: Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology & Stephen Fort, MD, MRCP, FRCPC - Interventional Cardiology

Prediabetes is a condition in which your blood sugar is too high, but not high enough to call it diabetes. Having prediabetes makes you at risk for type 2 diabetes.

Last Revised: October 9, 2012

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & David C.W. Lau, MD, PhD, FRCPC - Endocrinology

Preeclampsia is high blood pressure that some women get during pregnancy. It affects the kidneys, liver, brain, and placenta. It can cause a headache that won't go away, vision problems, belly pain, and swollen hands and face.

Preeclampsia can be treated with bed rest, medicine, and close monitoring. If not treated, it can be deadly for the mother and baby.

Preeclampsia usually goes away after the baby is born.

Last Revised: November 5, 2012

Author: Healthwise Staff

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

A pressure sore (bed sore) is an injury to the skin and/or the tissues under the skin, caused primarily by constant pressure. People confined to a bed or chair and unable to move are at greatest risk for developing pressure sores, which form most often in bony areas such as the hips, heels, or tailbone.

Pressure sores develop when constant pressure reduces blood supply to an area of skin and tissue. Oxygen and nutrients carried by the blood cannot reach the cells in the tissue, causing the cells to die. Pressure sores can range from mild reddening of the skin to severe tissue damage that extends into muscle and bone. These sores are difficult to treat and slow to heal.

For people who are confined to a bed or chair or are unable to move, changing positions frequently and distributing body weight evenly will relieve pressure on any one area of skin. Eating a balanced diet with adequate protein promotes healthy skin, as does keeping skin clean and free of body fluids or feces. Moisturizing dry skin with good-quality lotions will keep the skin from drying out and cracking, which makes it vulnerable to pressure sores.

Healing a pressure sore depends on relieving the pressure on the area. Treatment for pressure sores includes changing positions frequently to restore blood flow to the tissue and washing the sore daily. Unaffected tissue around the sore should be kept clean and dry to prevent further damage. Removing dead tissue and applying medicated ointments or creams will help reduce the risk of infection.

Last Revised: February 15, 2011

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Margaret Doucette, DO - Physical Medicine and Rehabilitation, Wound Care, Hyperbaric Medicine

Priapism is a painful condition in which the penis stays erect without sexual stimulation. Priapism can occur in short, repeated episodes, or it may last for days or weeks.

Priapism can be a serious problem. It can cause unbearable pain and may damage the penis, making it impossible to get a normal erection (erectile dysfunction). Erectile dysfunction is the main long-term result of priapism, and it can occur after just one episode of priapism.

Priapism can affect males of any age. Although the cause is often unknown, it can result from sickle cell disease, diabetes, leukemia, or the use of certain medicines.

Ice packs may ease the pain. Any episode of priapism that lasts for more than 3 hours requires urgent medical treatment.

Last Revised: March 1, 2011

Author: Healthwise Staff

Medical Review: Kathleen Romito, MD - Family Medicine & David Messenger, MD

Progestin is a synthetic hormone used to affect a woman's body in the same ways as the hormone progesterone. The ovaries produce progesterone during the second half of the menstrual cycle to help prepare the uterus for pregnancy; at the time of menopause, the level of progesterone declines.

Progesterone regulates the cyclic growth and breakdown of the uterine lining (endometrium). When a woman's progesterone levels are low, progestin can be used to treat endometrial problems such as heavy, irregular menstrual bleeding. Women with an intact uterus who take estrogen are also prescribed progestin, which prevents the estrogen from causing cancerous cell growth in the endometrium.

Last Revised: November 29, 2010

Author: Healthwise Staff

Medical Review: Sarah Marshall, MD - Family Medicine & Ross Berkowitz, MD - Obstetrics and Gynecology

Prolactin is a hormone secreted by the pituitary gland in both men and women. In women, it prepares breasts to produce milk (lactate); in men, prolactin's function is not well understood.

In a lactating woman, more prolactin is produced when her breasts are emptied frequently, resulting in more milk production. Less frequent emptying of the breasts reduces the amount of prolactin produced, which in turn reduces the milk supply. Above-normal prolactin levels in women can cause ovulation to stop.

Above-normal levels of prolactin can indicate a problem with the pituitary gland that may affect reproductive functions.

Last Revised: April 14, 2011

Author: Healthwise Staff

Medical Review: Sarah Marshall, MD - Family Medicine & Kirtly Jones, MD - Obstetrics and Gynecology

Protein is an essential nutrient made up of building-block chemicals called amino acids. Protein provides energy and is needed for the body to make new cells, to maintain and rebuild muscles, to carry other nutrients, to act as messengers in the body, and to support the immune system.

Last Revised: August 29, 2011

Author: Healthwise Staff

Medical Review: John Pope, MD - Pediatrics & Rhonda O'Brien, MS, RD, CDE - Certified Diabetes Educator

Psoriasis (say "suh-RY-uh-sus") is a long-term (chronic) skin problem that causes skin cells to grow too quickly and form thick, white, silvery, or red patches. They're most often found on the knees, elbows, scalp, tailbone, and back.

Psoriasis isn't contagious. It tends to run in families. There are many types of treatment that can help keep it under control.

Last Revised: October 9, 2012

Author: Healthwise Staff

Medical Review: Adam Husney, MD - Family Medicine & Amy McMichael, MD - Dermatology

Psychologists are health professionals who have training and expertise in human behavior and psychological health. Psychologists are not medical doctors, but they hold a doctor of psychology (PsyD degree) or doctor of philosophy (PhD degree) in clinical psychology, counseling, or school psychology.

Psychologists evaluate and treat people who have mental health problems, such as depression. Psychologists also provide counseling and other mental health services. Some states allow psychologists to prescribe medicine.

Psychologists are licensed in the state in which they practice.

Last Revised: August 17, 2012

Author: Healthwise Staff

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

The pulmonary artery carries oxygen-depleted blood from the right side of the heart to the lungs, where it is re-oxygenated. The freshly oxygenated blood then travels to the left side of the heart through the pulmonary vein to be pumped to the rest of the body.

Last Revised: November 18, 2011

Author: Healthwise Staff

Medical Review: Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology & John A. McPherson, MD, FACC, FSCAI - Cardiology

Pulmonary edema is the buildup of fluid in the lungs, usually resulting from the heart's inability to pump blood through the body effectively. It can be caused by heart or kidney failure, poisoning, widespread infection, stroke, or near-drowning.

Symptoms of pulmonary edema include difficulty breathing, restlessness, shortness of breath that is worse when lying down, rapid heart rate, and a cough that sometimes produces foamy pink fluid.

Although pulmonary edema can be a life-threatening condition, it is treatable, depending on the cause. Treatment may include oxygen given through the nose or a face mask. In severe cases, relief may require a breathing tube placed into the windpipe (intubation) and use of a breathing machine (ventilator). Medicines to strengthen the heart muscle or to relieve the pressure on the heart may also be given as needed.

Last Revised: February 22, 2012

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Robert L. Cowie, MB, FCP(SA), MD, MSc, MFOM - Pulmonology

Pulmonary embolism happens when an artery in the lung is suddenly blocked. It's usually caused by a blood clot in a leg vein that breaks loose, travels to a lung (pulmonary) artery, and blocks blood flow. This is very serious and can be deadly.

Last Revised: January 10, 2013

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Jeffrey S. Ginsberg, MD - Hematology

Pulmonary hypertension is a condition of abnormally high pressure within the lungs or respiratory system. This pressure can eventually lead to progressive heart failure.

Last Revised: January 10, 2013

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Jeffrey S. Ginsberg, MD - Hematology

Pulmonary valve stenosis is a narrowing of the valve between the lower right heart chamber and the pulmonary artery, which carries blood from the heart to the lungs. It is a structural problem that develops before a baby is born (congenital heart defect).

Because the valve is narrow, the heart pumps harder to try to get enough blood through it. The narrower the valve, the more symptoms the baby will have.

Treatment for pulmonary valve stenosis is typically a minimally invasive catheter-based procedure called a percutaneous balloon pulmonary dilation (valvuloplasty) to open up the valve.

Surgical repair of the defect (heart valve surgery) may be needed if the valve is badly deformed.

Before these treatments, medicines may be given to maintain the blood flow or to otherwise improve heart function and blood flow.

Last Revised: October 11, 2011

Author: Healthwise Staff

Medical Review: John Pope, MD - Pediatrics & Larry A. Latson, MD - Pediatric Cardiology

Pulmonologists are medical doctors who further specialize in the diagnosis and treatment of lung disease, such as asthma, emphysema, or pneumonia. Pulmonologists perform tests to check how well a person is breathing. And they may use procedures such as bronchoscopy to diagnose a breathing problem.

Pulmonologists can be board-certified through the Board of Internal Medicine, 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

Pulse is the regular expansion of the arteries caused by the surge of blood that occurs each time the heart beats (contracts). It can be felt by gently pressing the fingers on certain blood vessels that are close to the skin's surface.

Pulse is also called heart rate, which is the number of times the heart beats per minute (bpm). The wrist and neck are common places to take a pulse.

Doctors usually check a person’s pulse at checkups or in an emergency. A weak pulse or a change in pulse rate or rhythm may be a sign of heart disease or other problem.

One way to know how hard you are exercising is to use your target heart rate. Your target heart rate is a percentage of your maximum heart rate. One way to find your maximum heart rate is to subtract your age from 220. After you know your maximum heart rate, you can find your target heart rate for moderate and vigorous aerobic activity.

  • Moderate aerobic activity is 60% to 70% of your maximum heart rate.
  • Vigorous aerobic activity is 70% to 80% of your maximum heart rate.

Target heart rate is only a guide. When you exercise, pay attention to how you feel, how hard you breathe, how fast your heart beats, and how much you feel the exertion in your muscles.

Chronic health problems and certain heart medicines affect a person's target heart rate range.

Last Revised: October 25, 2011

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Heather Chambliss, PhD - Exercise Science

A pulse oximeter is a device that checks how much oxygen is in the blood.

A small clip is put on a finger, toe, or earlobe. The light beam in the clip measures the oxygen of the red blood cells that move through the cells in the finger, toe, or earlobe. The person's oxygen level can be read on the display.

The pulse oximeter often has an alarm for blood oxygen levels that fall below a safe level.

Last Revised: September 30, 2011

Author: Healthwise Staff

Medical Review: Adam Husney, MD, MD - Family Medicine & John M. Freedman, MD, MD - Anesthesiology

The pupil is the black area in the center of the iris, the colored part of the eye. The iris controls the size of the pupil in response to light outside the eye so that the proper amount of light is let into the eye.

Light passes through the pupil to the back of the eye, where an image is formed of what the eye is looking at.

Last Revised: June 9, 2011

Author: Healthwise Staff

Medical Review: Kathleen Romito, MD - Family Medicine & Christopher J. Rudnisky, MD, MPH, FRCSC - Ophthalmology