The pleura is the membrane that lines the lungs and chest cavity. A pleural biopsy is the removal of pleural tissue for examination. Pleural biopsy is done to differentiate between benign and malignant disease, to diagnose viral, fungal, or parasitic diseases, and to identify a condition called collagen vascular disease of the pleura. It is also ordered when a chest x ray indicates a pleural-based…
Pleural effusion occurs when too much fluid collects in the pleural space (the space between the two layers of the pleura). It is commonly known as "water on the lungs." It is characterized by shortness of breath, chest pain, gastric discomfort (dyspepsia), and cough. There are two thin membranes in the chest, one (the visceral pleura) lining the lungs, and the other (the parietal pl…
Pleurisy is an inflammation of the membrane that surrounds and protects the lungs (the pleura). Inflammation occurs when an infection or damaging agent irritates the pleural surface. As a consequence, sharp chest pains are the primary symptom of pleurisy. Pleurisy, also called pleuritis, is a condition that generally stems from an existing respiratory infection, disease, or injury. In people who h…
Pneumococcal pneumonia is a common but serious infection and inflammation of the lungs. It is caused by the bacterium Streptococcus pneumoniae. The gram-positive, spherical bacteria, Streptococcus pneumoniae, is the cause of many human diseases, including pneumonia. Although the bacteria can normally be found in the nose and throat of healthy individuals, it can grow and cause infection when the i…
Pneumocystis pneumonia is a lung infection that occurs primarily in people with weakened immune systems—especially people who are HIV-positive. The disease agent is an organism whose biological classification is still uncertain. Pneumocystis carinii was originally thought to be a one-celled organism (a protozoan), but more recent research suggests that it is a fungus. Although its life cycl…
Pneumonia is an infection of the lung, and can be caused by nearly any class of organism known to cause human infections. These include bacteria, viruses, fungi, and parasites. In the United States, pneumonia is the sixth most common disease leading to death. It is also the most common fatal infection acquired by already hospitalized patients. In developing countries, pneumonia ties with diarrhea …
Pneumothorax is a collection of air or gas in the chest or pleural space that causes part or all of a lung to collapse. Normally, the pressure in the lungs is greater than the pressure in the pleural space surrounding the lungs. However, if air enters the pleural space, the pressure in the pleura then becomes greater than the pressure in the lungs, causing the lung to collapse partially or complet…
Poisoning occurs when any substance interferes with normal body functions after it is swallowed, inhaled, injected, or absorbed. Poisonings are a common occurrence. About 10 million cases of poisoning occur in the United States each year. In 80% of the cases, the victim is a child under the age of five. About 50 children die each year from poisonings. Curiosity, inability to read warning labels, a…
Polarity therapy is a holistic, energy-based system that includes bodywork, diet, exercise, and lifestyle counseling for the purpose of restoring and maintaining proper energy flows throughout the body. The underlying concept of polarity therapy is that all energy within the human body is based in electromagnetic force and that disease results from improperly dissipated energy. Polarity therapy un…
Poliomyelitis, also called polio or infantile paralysis, is a highly infectious viral disease that may attack the central nervous system and is characterized by symptoms that range from a mild nonparalytic infection to total paralysis in a matter of hours. There are three known types of polioviruses (called 1,2, and 3), each causing a different strain of the disease and all are members of the vira…
Polycystic kidney disease (PKD) is one of the most common of all life-threatening human genetic disorders. It is an incurable genetic disorder characterized by the formation of fluid-filled cysts in the kidneys of affected individuals. These cysts multiply over time. It was originally believed that the cysts eventually caused kidney failure by crowding out the healthy kidney tissue. It is now thou…
Polycystic ovary syndrome (PCOS) is a condition characterized by the accumulation of numerous cysts (fluid-filled sacs) on the ovaries associated with high male hormone levels, chronic anovulation (absent ovulation), and other metabolic disturbances. Classic symptoms include excess facial and body hair, acne, obesity, irregular menstrual cycles, and infertility. PCOS, also called Stein-Leventhal s…
Polycythemia vera (PV) is a chronic blood disorder marked by an abnormal increase in three types of blood cells produced by bone marrow: red blood cells (RBCs), white blood cells (WBCs), and platelets. PV is called a myeloproliferative disorder, which means that the bone marrow is producing too many cells too quickly. Most of the symptoms of PV are related to the increased volume of the patient&#x…
Polydactyly and syndactyly are congenital irregularities of the hands and feet. Polydactyly is the occurrence of extra fingers or toes, and syndactyly is the webbing or fusing together of two or more fingers or toes. Syndactyly is the webbing or fusing together of two or more fingers or toes. (Photograph by Keith, Custom Medical Stock Photo. Reproduced by permission.) Polydactyly can vary f…
Polyglandular deficiency syndromes are disorders characterized by the failure of more than one endocrine gland to make hormones in sufficient quantities for the body to function normally. The endocrine system is a diverse group of glands located all over the body that work together to regulate the body's metabolic activities. It includes: There are over a dozen different syndromes that invo…
Polyhydramnios is a high level and oligohydramnios is low level of amniotic fluid. Amniotic fluid is the liquid that surrounds the developing fetus during pregnancy. It is contained within the amniotic membrane that forms the amniotic sac (bag of waters). During the first three months after conception (first trimester), amniotic fluid is mainly derived from the blood plasma that diffuses through t…
Polymyalgia rheumatica is a syndrome that causes pain and stiffness in the hips and shoulders of people over the age of 50. Allthough the major characteristics of this condition are just pain and stiffness, there are reasons to believe it is more than just old-fashioned rheumatism. Patients are commonly so afflicted that their muscles atrophy from disuse. A similar complaint of such weakness is al…
Polymyositis is an inflammatory muscle disease causing weakness and pain. Dermatomyositis is identical to polymyositis with the addition of a characteristic skin rash. Polymyositis (PM) is an inflammatory disorder in which muscle tissue becomes inflamed and deteriorates, causing weakness and pain. It is one of several types of inflammatory muscle disease, or myopathy. Others include dermatomyositi…
The word polysomnography, derived from the Greek roots "poly," meaning many, "somno," meaning sleep, and "graphy" meaning to write, refers to multiple tests performed on patients while they sleep. Polysomnography is an overnight test to evaluate sleep disorders. Polysomnography generally includes monitoring of the patient's airflow through the nose …
The porphyrias are disorders in which the body produces too much porphyrin and insufficient heme (an iron-containing nonprotein portion of the hemoglobin molecule). Porphyrin is a foundation structure for heme and certain enzymes. Excess porphyrins are excreted as waste in the urine and stool. Overproduction and overexcretion of porphyrins causes low, unhealthy levels of heme and certain important…
Portal vein bypass surgery diverts blood from the portal vein into another vein. It is performed when pressure in the portal vein is so high that it causes internal bleeding from blood vessels in the esophagus. The portal vein carries blood from the stomach and abdominal organs to the liver. It is a major vein that splits into many branches. High pressure in the portal vein causes swelling and ble…
Positron emission tomography (PET) is a scanning technique used in conjunction with small amounts of radiolabeled compounds to visualize brain anatomy and function. A PET scan showing brain activity while patient recognizes faces—left sides at left/right sides at right. Activity is prevalent in temporal lobe (bottom scans). (Photo Researchers. Reproduced by permission.) PET was the f…
Post-concussion syndrome (PCS) is a common but controversial disorder that presents with variety of symptoms including—but not limited to—headache, dizziness, fatigue, and personality changes. PCS occurs in approximately 23–93% of persons with mild to severe head injuries. It is estimated that a neurologist (a physician who specializes in nerve and brain disorders) sees five p…
Postmenopausal bleeding is bleeding from the reproductive system that occurs six months or more after menstrual periods have stopped due to menopause. Menopause, the end of ovulation and menstrual periods, naturally occurs for most women at age 40–55 years. The process of ending ovulation and menstruation is gradual, spanning one to two years. Postmenopausal bleeding is bleeding that occurs…
Postpartum depression is a mood disorder that begins after childbirth and usually lasts beyond six weeks. The onset of postpartum depression tends to be gradual and may persist for many months, or develop into a second bout following a subsequent pregnancy. Postpartum depression affects approximately 15% of all childbearing women. Mild to moderate cases are sometimes unrecognized by women themselv…
Postpolio syndrome (PPS) is a condition that strikes survivors of the disease polio. PPS occurs about 20–30 years after the original bout with polio, and causes slow but progressive weakening of muscles. Polio is a disease caused by the poliovirus. It most commonly infects younger children, although it can also infect older children and adults. About 90% of people infected by poliovirus dev…
Post-traumatic stress disorder (PTSD) is a debilitating condition that affects people who have been exposed to a major traumatic event. PTSD is characterized by upsetting memories or thoughts of the ordeal, "blunting" of emotions, increased arousal, and sometimes severe personality changes. Once called "shell shock" or battle fatigue, PTSD is most well known as a proble…
Prader-Willi syndrome (PWS) is a genetic condition caused by the absence of chromosomal material from chromosome 15. The genetic basis of PWS is complex. Characteristics of the syndrome include developmental delay, poor muscle tone, short stature, small hands and feet, incomplete sexual development, and unique facial features. Insatiable appetite is a classic feature of PWS. This uncontrollable ap…
Sexual development before the age of eight in girls, and age 10 in boys. Not every child reaches puberty at the same time, but in most cases it's safe to predict that sexual development will begin at about age 11 in girls and 12 or 13 in boys. However, occasionally a child begins to develop sexually much earlier. Between four to eight times more common in girls than boys, precocious puberty…
Preeclampsia and eclampsia are complications of pregnancy. In preeclampsia, the woman has dangerously high blood pressure, swelling, and protein in the urine. If allowed to progress, this syndrome will lead to eclampsia. Blood pressure is a measurement of the pressure of blood on the walls of blood vessels called arteries. The arteries deliver blood from the heart to all of the tissues in the body…
The period from conception to birth. After the egg is fertilized by a sperm and then implanted in the lining of the uterus, it develops into the placenta and embryo, and later into a fetus. Pregnancy usually lasts 40 weeks, beginning from the first day of the woman's last menstrual period, and is divided into three trimesters, each lasting three months. Pregnancy is a state in which a woman…
Premature ejaculation occurs when male sexual climax (orgasm) occurs before a man wishes it or too quickly during intercourse to satisfy his partner. Premature ejaculation is the most commonly reported sexual complaint of men and couples. The highest number of complaints is among teenage, young adult, and sexually inexperienced males. Increased risk is associated with sexual inexperience and lack …
Premature labor is the term to describe contractions of the uterus that begin at 20–36 weeks of a pregnancy. The usual length of a human pregnancy is 38–42 weeks after the first day of the last menstrual period. Labor is a natural series of events that indicate that the birth process is starting. Premature labor is defined as contractions that occur after 20 weeks and before 37 weeks…
The average age at which American women go through menopause is 51 years. If menopause (hormonal changes at the end of the female reproductive years) occurs before age 40, it is said to be premature menopause. Possible causes include autoimmune problems and common cancer treatments. About half of all women will go through menopause before age 51 and the rest will go through it after. Most women wi…
Premature rupture of membranes (PROM) is an event that occurs during pregnancy when the sac containing the developing baby (fetus) and the amniotic fluid bursts or develops a hole prior to the start of labor. During pregnancy, the unborn baby (fetus) is surrounded and cushioned by a liquid called amniotic fluid. This fluid, along with the fetus and the placenta, is enclosed within a sac called the…
The length of a normal pregnancy or gestation is considered to be 40 weeks (280 days) from the date of conception. Infants born before 37 weeks gestation are considered premature and may be at risk for complications. More than one out of every ten infants born in the United States is born prematurely. Advances in medical technology have made it possible for infants born as young as 23 weeks gestat…
Premenstrual dysphoric disorder (PMDD) is a collection of physical and emotional symptoms that occurs 5 to 11 days before a woman's period begins, and goes away once menstruation starts. The most severe form of premenstrual syndrome (PMS) is PMDD. PMS is estimated to affect 70–90% of women of childbearing age. The more severe form of the disorder, PMDD, affects 3–5% of women o…
Premenstrual syndrome (PMS) refers to symptoms that occur between ovulation and the onset of menstruation. The symptoms include both physical symptoms, such as breast tenderness, back pain, abdominal cramps, headache, and changes in appetite, as well as psychological symptoms of anxiety, depression, and unrest. Severe forms of this syndrome are referred to as premenstrual dysphoric disorder (PMDD)…
Prepregnancy counseling is advice supplied by an obstetrician, nurse, certified nurse-midwife, or childbirth educator about those steps a mother-to-be and father-to-be can take in preparation for pregnancy. Basically, it is a checklist for people to see if they are living lives that are most accommodating to having a healthy pregnancy. Prepregnancy counseling gives time for one to make changes bef…
The term presbyopia means "old eye" and is a vision condition involving the loss of the eye's ability to focus on close objects. Presbyopia is a condition that occurs as a part of normal aging and is not considered to be an eye disease. The process occurs gradually over a number of years. Symptoms are usually noticeable by age 40–45 and continue to develop until the pro…
Priapism is a rare condition that causes a persistent, and often painful, penile erection. Priapism is drug induced, injury related, or caused by disease, not sexual desire. As in a normal erection, the penis fills with blood and becomes erect. However, unlike a normal erection that dissipates after sexual activity ends, the persistent erection caused by priapism is maintained because the blood in…
Also known as sweat retention syndrome or miliaria rubra, prickly heat is a common disorder of the sweat glands. The skin contains two types of glands: one produces oil and the other produces sweat. Sweat glands are coilshaped and extend deep into the skin. They are capable of plugging up at several different depths, producing four distinct skin rashes. There are two requirements for each of these…
Primary biliary cirrhosis is the gradual destruction of the biliary system for unknown reasons. Although the cause of this serious condition is not known, it has many features to suggest that it is an autoimmune disease. Autoimmunity describes the process whereby the body's defense mechanisms are turned against itself. The immune system is supposed to recognize and attack only dangerous for…
Proctitis is an inflammation of the rectum. Proctitis affects mainly adolescents and adults. It is most common in men around age 30. Proctitis is caused by several different sexually transmitted diseases. Male homosexuals and people who practice anal intercourse are more likely to suffer from proctitis. Patients who have AIDS or who are immunocompromised are also more at risk. Proctitis is caused …
Progressive multifocal leukoencephalopathy (PML) is a rapidly progressive neuromuscular disease caused by opportunistic infection of brain cells (oligodendrocytes and astrocytes) by the JC virus (JCV). PML is an opportunistic infection associated with AIDS and certain cancers. It occurs in people with inadequate immune response and carries a poor prognosis. The incidence of PML, once quite rare, i…
Progressive supranuclear palsy (PSP; also known as Steele-Richardson-Olszewski syndrome) is a rare disease that gradually destroys nerve cells in the parts of the brain that control eye movements, breathing, and muscle coordination. The loss of nerve cells causes palsy, or paralysis, that slowly gets worse as the disease progresses. The palsy affects ability to move the eyes, relax the muscles, an…
Prolactin is a hormone secreted by the anterior portion of the pituitary gland (sometimes called the "master gland"). Its role in the male has not been demonstrated, but in females, prolactin promotes lactation, or milk production, after childbirth. The prolactin test is used to diagnose pituitary dysfunction that might be caused by a tumor called an adenoma. In some circumstances, t…
Prolonged QT syndrome, also known as long QT syndrome (LQTS), refers to a group of disorders that increase the risk for sudden death due to an abnormal heartbeat. Abnormal heartbeats (cardiac arrhythmias) are a primary cause of sudden death, especially in the young population. In the United States, an estimated 1 in 300,000 individuals per year die suddenly due to irregular heart rhythms. One of t…
A prophylaxis is a measure taken to maintain health and prevent the spread of disease. Antibiotic prophylaxis is the focus of this article and refers to the use of antibiotics to prevent infections. Antibiotics are well known for their ability to treat infections. But some antibiotics also are prescribed to prevent infections. This usually is done only in certain situations or for people with part…
Prostate biopsy is a surgical procedure that involves removing a small piece of prostate tissue for microscopic examination. This test is usually done to determine whether the patient has prostate cancer. Occasionally, it may also be used to diagnose a condition called benign prostatic hyperplasia that causes enlargement of the prostate. In the United States, prostate cancer is the most common can…
Prostate cancer is a disease in which cells of the prostate become abnormal and start to grow uncontrollably, forming tumors. Prostate cancer is a malignancy of one of the major male sex glands. Along with the testicles and the seminal vesicles, the prostate secretes the fluid that makes up semen. The prostate is about the size of a walnut and lies just behind the urinary bladder. A tumor in the p…
Prostate-specific antigen, or PSA, is a protein produced by the prostate gland that may be found in elevated levels in the blood when a person develops certain diseases of the prostate, notably prostate cancer. PSA is specific, because it is present only in prostate tissue. It is not specific for prostate cancer, however, as it may also be elevated in men with benign enlargement of this organ. The…
A prostate ultrasound is a diagnostic test used to detect potential problems with a man's prostate. An ultrasound test uses very high frequency sound waves that are passed through the body. The pattern of reflected sound waves, or "echoes," shows the outline of the prostate. This test can show whether the prostate is enlarged, and whether an abnormal growth that might be cance…
Prostatectomy is surgical removal of part of the prostate gland (transurethral resection, a procedure performed to relieve urinary symptoms caused by benign enlargement), or all of the prostate (radical prostatectomy, the curative surgery most often used to treat prostate cancer). When men reach their mid-40s, the prostate gland begins to enlarge. This condition, benign prostatic hyperplasia (BPH)…
Prostatitis is an inflammation of the prostate gland, a common condition in adult males. Often caused by infection, prostatitis may develop rapidly (acute) or slowly (chronic). Prostatitis may be the symptom-producing disease of the genitourinary tract for which men most often seek medical help. About 40% of visits to a specialist in genitourinary problems (urologist) are for prostatitis. Forms of…
A protease inhibitor is a type of drug that cripples the enzyme protease. An enzyme is a substance that triggers chemical reactions in the body. The human immunodeficiency virus (HIV) uses protease in the final stages of its reproduction (replication) process. The drug is used to treat selected patients with HIV infection. Blocking protease interferes with HIV reproduction, causing it to make copi…
Protein components tests measure the amounts and types of protein in the blood. Proteins are constituents of muscle, enzymes, hormones, transport proteins, hemoglobin, and other functional and structural elements of the body. Albumin and globulin make up most of the protein within the body and are measured in the total protein of the blood and other body fluids. Thus, the serum (blood) protein com…
Electrophoresis is a technique used to separate different elements (fractions) of a blood sample into individual components. Serum protein electrophoresis (SPEP) is a screening test that measures the major blood proteins by separating them into five distinct fractions: albumin, alpha1, alpha2, beta, and gamma proteins. Protein electrophoresis can also be performed on urine. Protein electrophoresis…
Protein-energy malnutrition (PEM) is a potentially fatal body-depletion disorder. It is the leading cause of death in children in developing countries. PEM is also referred to as protein-calorie malnutrition. It develops in children and adults whose consumption of protein and energy (measured by calories) is insufficient to satisfy the body's nutritional needs. While pure protein deficiency…
The prothrombin time test belongs to a group of blood tests that assess the clotting ability of blood. The test is also known as the pro time or PT test. The PT test is used to monitor patients taking certain medications as well as to help diagnose clotting disorders. Patients who have problems with delayed blood clotting are given a number of tests to determine the cause of the problem. The proth…
