Prostate cancer

Introduction

disease characterized by uncontrolled growth of cells within the prostate gland, a walnut-sized organ surrounding the urethra just below the bladder in males. Worldwide among males, the incidence of prostate cancer is surpassed only by lung and stomach cancers; among North American men, only skin cancer occurs more often. Prostate cancer is rare in men below the age of 50, and in North America the disease is twice as common in black men as it is in whites. Prostate cancer should not be confused with benign prostate hyperplasia, which has similar symptoms and occurs often in older men but is not a type of cancer.

 

Causes and symptoms

When the prostate gland becomes cancerous, it can put pressure on the urethra, causing frequent or painful urination. Such pressure can also cause difficulty in urinating, a weak and intermittent urine flow, or blood in the urine. The cancerous growth may also put pressure on the nerves required for erection, causing impotence or sexual dysfunction. Other symptoms of prostate cancer include swollen lymph nodes in the groin and pain in the pelvis, hips, back, or ribs. As in most cancers, the causes of prostate cancer are varied, though most cases are thought to be related to the male hormone androgen. The likelihood of a man's developing prostate cancer doubles if a parent or sibling has had prostate cancer; this suggests that genetic factors play a role. Two genes, known as BRCA1 (breast cancer type 1) and BRCA2 (breast cancer type 2), have been linked to prostate cancer. As their names imply, they are commonly found in mutated forms in some women with breast cancer. However, studies have shown that men carrying mutations in BRCA2 have an increased risk of developing prostate cancer, and mutations in either gene can significantly reduce survival.

 

Diagnosis

Prostate cancers usually grow very slowly, and individuals may not display symptoms for some time. If the prostate is enlarged, preliminary diagnosis can be made by rectal examination or transrectal ultrasound (TRUS). A blood test for prostate-specific antigen (PSA) is used to detect prostate tumours in their earliest stages. If any of these tests suggest cancer, a biopsy is done to confirm the diagnosis. When caught early, prostate cancer is treatable. A large majority of prostate cancers are diagnosed either before they have spread or when they have spread only locally. Survival rates in these cases are very high.

 

Treatment

Because prostate cancers usually progress slowly, a physician may recommend a “watchful waiting” approach rather than immediate treatment. This is especially true for patients who are elderly or in otherwise poor health. If treatment is required, the physician may use surgery, radiation, hormone therapy, chemotherapy, or a combination of two or more of these approaches. Surgery is usually done only if the cancer has not spread from the prostate. The removal of the entire prostate plus some surrounding tissues (radical prostectomy) may be considered if examination of the pelvic lymph nodes reveals that they are not cancerous. Surgical risks include impotence and urinary incontinence. A second surgical procedure, transurethral resection of the prostate (TURP), is used to relieve symptoms but does not remove all of the cancer. TURP is often used in men who cannot have a radical prostectomy because of advanced age or illness or in men who have a noncancerous enlargement of the prostate. In men who are unable to have traditional surgery, cryosurgery may also be used. In this procedure, a metal probe is inserted into the cancerous regions of the prostate; liquid nitrogen is then used to freeze the probe, killing the surrounding cells.

If the cancer has spread from the prostate, radiation therapy may be used. Hormone therapy attacks the male hormones (androgens) that often stimulate the growth of prostate cancer. A form of hormone therapy involves drugs called LHRH analogs, or LHRH agonists, that chemically block the production of androgens. Side effects of hormone therapy may include reduced libido, abnormal growth or sensitivity of the breasts, and hot flashes. Orchiectomy, or removal of the testes, cuts off the tumour's supply of testosterone. This surgery can delay or stop tumour growth and eliminates the need for hormone therapy. If surgery or hormone therapy fails, chemotherapy may be used. Chemotherapy employs drugs that kill dividing cells (i.e., cancer cells) but is not highly effective in treating prostate cancer. It can, however, slow the growth of the tumour.

Other drugs, called antiandrogens, block the activity of androgens and are often used in combination with other forms of hormone therapy. An antiandrogen called abiraterone inhibits the activity of an enzyme involved in testosterone synthesis in the testes and adrenal glands. In clinical trials, abiraterone has shown promise in treating patients with aggressive end-stage prostate cancer, which is usually refractory to hormone therapy and is often fatal. Treatment with abiraterone is associated with reductions in tumour size and PSA levels. Its side effects appear to be limited primarily to hypertension, edema, and potassium deficiency.

 

Prevention

Risk factors for prostate cancer such as age, race, or family history cannot be avoided. However, studies have suggested that a diet low in fats and high in fruits and vegetables decreases prostate cancer risk. Compounds called lycopenes, which are present in grapefruit, tomatoes, and watermelon, have been linked to reduced risk, as has the nutrient selenium, which is found in nuts, oranges, and wheat germ.

Physicians disagree on the usefulness of routine screening for prostate cancer. Most medical societies and government agencies feel that screening has not proved to reduce prostate cancer mortality and therefore do not recommend screening. Some medical societies, however, recommend an annual PSA test and digital rectal examination at age 50 for most men and at age 45 for men at higher risk .

Breast cancer

Introduction

disease characterized by the growth of malignant cells in the mammary glands. Breast cancer can strike males and females, although women are about 100 times more likely to develop the disease than men. Most cancers in female breasts form shortly before, during, or after menopause, with three-quarters of all cases being diagnosed after age 50. Generally, the older a woman is, the greater is her likelihood of developing breast cancer. Worldwide, breast cancer is the most common cancer among women, and in North America and Western Europe, where life spans are longer, the incidence is highest. For instance, it is estimated that over 10 percent of all women in the United States will develop the disease at some point in their lives.

 

Causes and symptoms

The exact causes of breast cancer are largely unknown, but both environmental and genetic factors are involved. A family history of breast cancer increases risk. Specific mutations in genes called HER2, BRCA1, BRCA2, and p53 have been linked to breast cancer; these mutations may be inherited or acquired. Prolonged exposure to the hormone estrogen, as when menstruation starts before age 12 and continues beyond age 50, favours development of cancer, and women who have had certain kinds of benign tumours are also more prone to developing breast cancer. Other risk factors may include lack of exercise, use of oral contraceptives, alcohol consumption, and previous medical treatments involving chest irradiation.

The most common symptom of breast cancer is an abnormal lump or swelling in the breast, but lumps may also appear beside the breast or under the arm. Other symptoms may include unexplained breast pain, abnormal nipple discharge, changes in breast texture, or changes in the skin on or around the breast.

 

Diagnosis

Early diagnosis greatly improves the odds of survival. When detected early, breast cancer has a very high five-year survival rate, and patients who reach this stage often go on to live long, healthy lives. Survival rates are lower for cancers that have spread locally, and they are very low for cancers that have metastasized, or spread, to distant parts of the body.

Breast cancer may be first discovered by the patient as the result of a regular breast self-examination. A breast X ray (mammogram) is often used for initial diagnosis, but in order to confirm the presence of cancer, a tissue sample (biopsy) usually must be taken. If cancer is suspected to have spread to nearby lymph nodes, they must also be sampled.

Once cancer has been diagnosed, the tumour's type and degree of invasiveness is assessed. Several imaging methods may be used to determine the degree of metastasis, including X rays, computed tomography (CT) scans, or magnetic resonance imaging (MRI). The presence of receptors for the hormones estrogen and progesterone is also determined because these receptors play an important role in the cancer's development and in decisions regarding the appropriate treatment.

Almost all cases of breast cancer begin in the glandular tissues that either produce milk (lobular tissue) or provide a passage for milk (ductal tissue) to the nipple. Cancers of these tissues are called lobular carcinomas and ductal carcinomas. Because these tissues are glandular, both cancers are called adenocarcinomas. The most common type of tumour, called infiltrating ductal carcinoma, is a single hard, barely movable lump. This type of tumour accounts for about 70 percent of all cases. Fewer than 15 percent of all cases are lobular carcinomas.

There are several other types and subtypes of tumour classified and named according to several criteria, including their outward appearance, cellular composition, cellular origin, and activity.

Paget disease is an uncommon type of breast cancer that begins at the nipple and initially causes a burning, itching, or tender sensation. Eventually the lesion becomes enlarged, cracks, oozes, and forms crusts.

Inflammatory carcinoma is a rare type of breast cancer that results in swelling and reddening of the affected area. The area then becomes purplish, and the skin is hot, with the nipple usually becoming crusted and retracted.

 

Treatment

Any lump found in the breast should be examined by a physician for the possibility of cancer. If it is found to be malignant, treatment may entail surgery, radiation, or chemotherapy. Biological treatment is also an option.

Surgery is often the first method of treatment, and a range of procedures are used depending on the type and progression of the cancer. A lumpectomy removes only the cancerous mass and a small amount of surrounding tissue; a simple mastectomy removes the entire breast; and a modified radical mastectomy removes the breast along with adjacent lymph nodes. Radical mastectomies involving removal of the breast, underlying muscle, and other tissue are rarely performed. Side effects of surgery may include changes in arm or shoulder mobility, swelling, infection, and numbness. When lymph nodes are removed, fluid may build up in the region they were taken from. Partial or complete breast removal is often followed by cosmetic or reconstructive surgery.

Radiation is usually employed—either before surgery to shrink tumours or following surgery to destroy small amounts of remaining cancerous tissue. Side effects of radiation include swelling or thickening of the breast, vomiting, fatigue, diarrhea, or skin irritations resembling sunburn. Chemotherapy, the use of chemicals to destroy cancerous cells, is commonly employed. Chemotherapeutic agents also attack normal cells to some degree, causing side effects that include hair loss, immune suppression, mouth sores, fatigue, and nausea.

Breast cancer can also be treated through biological therapy, in which chemical inhibitors are used to block the hormones that stimulate growth of cancer cells. Tamoxifen, for instance, is a common drug that blocks the ability of estrogen to stimulate tumour growth, and Megace blocks the action of progesterone by partially mimicking the hormone. Herceptin is a manufactured antibody that binds to growth factor receptors on the surface of cancer cells and thereby blocks cell proliferation.

 

Prevention

Breast cancer cannot be completely prevented, but the risk of developing advanced disease can be greatly reduced by early detection. Medical societies recommend a monthly breast self-examination for all women over the age of 20, a breast exam by a health care professional every three years for women 20–39 years old, and a yearly mammogram for all women 40 and older. Women at high risk of developing breast cancer may benefit from taking tamoxifen to reduce their risk. Women who are at extreme risk, as determined by a very strong family history or the presence of mutated BRCA genes, may opt for preventive mastectomy.

Stomach cancer

Stomach cancer

Introduction

also called  gastric cancer 

a disease characterized by abnormal growth of cells in the stomach. The incidence of stomach cancer has decreased dramatically since the early 20th century in countries where refrigeration has replaced other methods of food preservation such as salting, smoking, and pickling. Stomach cancer rates remain high in countries where these processes are still used extensively.

 

Causes and symptoms

Ninety-five percent of malignant stomach cancers develop from epithelial cells lining the stomach. These tumours are called adenocarcinomas. Other stomach cancers can develop from the surrounding immune cells, hormone-producing cells, or connective tissue. Multiple risk factors have been identified that increase a person's probability of developing this cancer. These include a diet high in salted, smoked, or pickled foods, tobacco and alcohol use, or a family history of stomach cancer. Infection by the bacterium Helicobacter pylori, which can cause significant damage to gastric tissues and is a cause of peptic ulcers, can also lead to stomach cancer. Other factors that may increase the risk of stomach cancer to varying degrees are previous stomach surgery, blood type A, advanced age (60–70 years), or chronic stomach inflammation. Males develop stomach cancer at approximately twice the rate of females. Rare disorders such as pernicious anemia or Menetrier disease and congenital disorders that lead to increased risk for colorectal cancer may also increase stomach cancer risk.

The symptoms of stomach cancer are prevalent in many other illnesses and may include abdominal pain or discomfort, unexplained weight loss, vomiting, poor digestion, or visible swelling in the abdomen.

 

Diagnosis

No specific laboratory test for stomach cancer exists, and the disease is therefore usually diagnosed through a combination of visual means. A physician can inspect the lining of the stomach with a flexible, lens-containing tube called an endoscope. The endoscope can also be used to take samples from potentially cancerous tissues for biopsy. These samples are examined under a microscope for signs of cancer. An endoscope may also be modified with a special probe that emits sound waves in the stomach, which allows the physician to create an image of the stomach wall. X rays are also employed, usually after the patient has swallowed a barium compound that coats the stomach and provides better image contrast. Other imaging techniques such as computed tomography (CT) scans and magnetic resonance imaging (MRI) are also used, especially when the cancer is believed to have spread.

Once stomach cancer has been diagnosed, its stage is determined. The stage is an indicator of how far the cancer has progressed. Staging for stomach cancer is complicated and is based on a combination of how far the cancer has grown through the stomach wall and on the number of lymph nodes affected, if any. Stage 0 stomach cancer is also called carcinoma in situ and is confined to the epithelial cells that line the stomach. Stage I and stage II cancers have spread into the connective tissue or muscle layers that underlie the epithelial cells, but they have reached fewer than six nearby lymph nodes. Stage III and IV cancers are more advanced and may have metastasized to distant tissues.

A very high percentage of individuals survive stomach cancer for at least five years if the cancer is diagnosed very early, and many of them go on to live long, healthy lives. Unfortunately, only a small percentage of stomach cancers are identified and treated at such an early stage. At the time when most lower-stomach cancers are diagnosed, roughly half the patients survive for at least five years. Cancers of the upper stomach have a lower survival rate, and if the cancer has spread to distant tissues in the body, the survival rate is extremely low.

 

Treatment

Surgery is the only method available for curing stomach cancer, although radiation or chemotherapy may be used in conjunction with surgery or to relieve symptoms. If the cancer is localized, the cancerous portions of the stomach are removed in a procedure called a partial gastrectomy. In some cases, the entire stomach must be removed along with the spleen and nearby lymph nodes. Repair of the stomach generally requires permanent changes in dietary habits and may demand intravenous administration of vitamin supplements. If a cancer cannot be cured, surgery may still be used to relieve symptoms or digestive discomfort. Radiation therapy is sometimes used in conjunction with surgery to destroy any remaining cancer cells. When stomach cancer has spread to distant organs, chemotherapy may be required so that as many cancer cells as possible can be sought out and destroyed. Both radiation therapy and chemotherapy may produce several side effects such as vomiting and diarrhea.

 

Prevention

Stomach cancer cannot be completely prevented, but people can decrease their risk of disease by adopting a diet that is low in salted, smoked, and pickled foods and high in fruits and vegetables. Elimination of tobacco use and reduction in alcohol consumption also help lower risk. Research has indicated that prompt treatment of H. pylori infection can reverse gastric tissue damage, thereby reducing stomach cancer risk.

Empyema

Empyema

accumulation of pus in a cavity of the body, usually in the pleura, which are the serous membranes covering the lungs. Empyema is the result of a microbial, usually bacterial, infection in a body cavity. Thoracic empyema may be characterized by fever, coughing, shortness of breath, and weight loss, and the presence of fluid as ascertained by a chest X-ray. Treatment is directed at drainage of small amounts of pus through a needle or larger amounts through a drainage tube. Video-assisted thoracic surgery or open-chest surgery is sometimes needed to eviscerate thick or compartmentalized pus from the pleural space. Antibiotics are used to treat the underlying infection. Empyemas may also result from the infection of an obstructed gallbladder with a bacterial organism, in which case the high risk of perforation and systemic infection requires the immediate removal of the infected organ.

Flying doctor service

method for supplying medical service by airplane to areas where doctors are few and communications difficult. The plan for the first service of this type was conceived in 1912 by the Rev. John Flynn, superintendent of the Australian Inland Mission of the Presbyterian Church. Flynn's plan came to fruition in May 1928, when the first base of what is now the Royal Flying Doctor Service of Australia began operating at Cloncurry, Queensland, under Dr. K. St. Vincent Welch. An Adelaide electrical engineer, A.H. Traeger, developed a low-powered, portable, pedal-driven, Morse radio transmitter-receiver with a range of 300 miles. This transceiver, with the use of airplanes, made possible a system of regular long-distance medical consultations and the flying of doctors to patients in emergencies.

More than a dozen bases, run by state branches, came to cover two-thirds of the Australian continent and part of Tasmania. The Australian state governments contribute one-third of the finances; the rest is derived from voluntary and outpost subscriptions and message charges. The flying doctor service is free.

Other parts of the world regularly use aircraft for the assistance of the isolated sick. In Canada the Saskatchewan Air Ambulance Service was inaugurated in 1947. Newfoundland operates from the International Grenfell Association at St. Anthony an air ambulance service, likewise begun in 1947, covering northern Newfoundland and Labrador. The Royal Canadian Air Force operates a search and rescue service for Eskimos and Indians in the Arctic.

In East Africa the African Medical and Research Foundation, established in 1957 by joint British and American enterprise, was enabled in 1961 to begin a flying doctor service with a single airplane provided by private United States benefaction. In collaboration with this body, the Flying Doctor Service of Africa, Ltd., registered in the United Kingdom, planned a pilot scheme to be based at Gusau, northern Nigeria.

ABO blood group system

method of classifying human blood on the basis of the inherited properties of red blood cells (erythrocytes) as determined by their possession or lack of the antigens A and B, which are carried on the surface of the red cells. Persons may thus have type A, type B, type O, or type AB blood. The A, B, and O blood groups were first identified by Austrian immunologist Karl Landsteiner in 1901. See blood group.

Blood containing red cells with type A antigen on their surface has in its serum (fluid) antibodies against type B red cells. If, in transfusion, type B blood is injected into persons with type A blood, the red cells in the injected blood will be destroyed by the antibodies in the recipient's blood. In the same way, type A red cells will be destroyed by anti-A antibodies in type B blood. Type O blood can be injected into persons with type A, B, or O blood unless there is incompatibility with respect to some other blood group system also present. Persons with type AB blood can receive type A, B, or O blood, as shown in the table.

Blood group O is the most common blood type throughout the world, particularly among peoples of South and Central America. Type B is prevalent in Asia, especially in northern India. Type A also is common all over the world; the highest frequency is among the Blackfoot Indians of Montana and in the Sami people of northern Scandinavia.

The ABO antigens are developed well before birth and remain throughout life. Children acquire ABO antibodies passively from their mother before birth, but by three months infants are making their own—it is believed the stimulus for such antibody formation is from contact with ABO-like antigenic substances in nature. Erythroblastosis fetalis (hemolytic disease of the newborn) is a type of anemia in which the red blood cells of the fetus are destroyed by the maternal immune system because of a blood group incompatibility between the fetus and its mother, particularly in matings where the mother is type O and the father type A.

surgery

Introduction

branch of medicine that is concerned with the treatment of injuries, diseases, and other disorders by manual and instrumental means. Surgery basically involves the management of acute injuries and illnesses as differentiated from chronic, slowly progressing diseases, except when patients with the latter type of disease must be operated upon.

A general treatment of surgery follows. For further treatments, see Diagnosis and Therapeutics; Medicine.

 

History

Surgery is as old as humanity, for anyone who has ever stanched a wound has acted as a surgeon. In some ancient civilizations surgery reached a rather high level of development, as in India, China, Egypt, and Hellenistic Greece. In Europe during the Middle Ages, the practice of surgery was not taught in most universities, and ignorant barbers instead wielded the knife, either on their own responsibility or upon being called into cases by physicians. The organization of the United Company of Barber Surgeons of London in 1540 marked the beginning of some control of the qualifications of those who performed operations. This guild was the precursor of the Royal College of Surgeons of England.

In the 18th century, with increasing knowledge of anatomy, such operative procedures as amputations of the extremities, excision of tumours on the surface of the body, and removal of stones from the urinary bladder had helped to firmly establish surgery in the medical curriculum. Accurate anatomical knowledge enabled surgeons to operate more rapidly; patients were sedated with opium or made drunk with alcohol, tied down, and a leg amputation, for example, could then be done in three to five minutes. The pain involved in such procedures, however, continued to limit expansion of the field until the introduction of ether anesthesia in 1846. The number of operations thereafter increased markedly, but only to accentuate the frequency and severity of “surgical infections.” In the mid-19th century the French microbiologist Louis Pasteur developed an understanding of the relationship of bacteria to infectious diseases, and the application of this theory to wound sepsis by the British surgeon Joseph Lister from 1867 resulted in the technique of antisepsis, which brought about a remarkable reduction in the mortality rate from wound infections after operations. The twin emergence of anesthesia and antisepsis marked the beginning of modern surgery.

Wilhelm Conrad Röntgen's discovery of X-rays at the turn of the 20th century added an important diagnostic tool to surgery, and the discovery of blood types in 1901 by the Austrian biologist Karl Landsteiner made transfusions safer. New techniques of anesthesia involving not only new agents for inhalation but also regional anesthesia accomplished by nerve blocking (spinal and local anesthesia) were also introduced. The use of positive pressure and controlled respiration techniques (to prevent the lung from collapsing when the pleural cavity was opened) made chest surgery practical and relatively safe for the first time. The intravenous administration (injection into the veins) of anesthetic agents was also adopted. In the period from the 1930s to the 1960s, the replenishment of body fluids by intravenous infusion, the introduction of chemicals and antibiotics to fight infection and to treat the metabolically disturbed body, and the development of heart-lung machines helped bring surgery to a state in which every body cavity, system, organ, and area could safely be operated on.

 

Present-day surgery

Contemporary surgical therapy is greatly helped by monitoring devices that are used during surgery and during the postoperative period. Blood pressure and pulse rate are monitored during an operation because a fall in the former and a rise in the latter give evidence of a critical loss of blood. Other items monitored are the heart contractions as indicated by electrocardiograms; tracings of brain waves recorded by electroencephalograms, which reflect changes in brain function; the oxygen level in arteries and veins; carbon dioxide partial pressure in the circulating blood; and respiratory volume and exchange. Intensive monitoring of the patient usually continues into the critical postoperative stage.

Asepsis, the freedom from contamination by pathogenic organisms, requires that all instruments and dry goods coming in contact with the surgical field be sterilized. This is accomplished by placing the materials in an autoclave, which subjects its contents to a period of steam under pressure. Chemical sterilization of some instruments is also used. The patient's skin is sterilized by chemicals, and members of the surgical team scrub their hands and forearms with antiseptic or disinfectant soaps. Sterilized gowns, caps, and masks that filter the team's exhaled air and sterilized gloves of disposable plastic complete the picture. Thereafter, attention to avoiding contact with nonsterilized objects is the basis of maintaining asepsis.

During an operation, hemostasis (the arresting of bleeding) is achieved by use of the hemostat, a clamp with ratchets that grasps blood vessels or tissue; after application of hemostats, suture materials are tied around the bleeding vessels. Absorbent sterile napkins called sponges, made of a variety of natural and synthetic materials, are used for drying the field. Bleeding may also be controlled by electrocautery, the use of an instrument heated with an electric current to cauterize, or burn, vessel tissue. The most commonly used instruments in surgery are still the scalpel (knife), hemostatic forceps, flexible tissue-holding forceps, wound retractors for exposure, crushing and noncrushing clamps for intestinal and vascular surgery, and the curved needle for working in depth.

The most common method of closing wounds is by sutures. There are two basic types of suture materials; absorbable ones such as catgut (which comes from sheep intestine) or synthetic substitutes; and nonabsorbable materials, such as nylon sutures, steel staples, or adhesive tissue tape. Catgut is still used extensively to tie off small blood vessels that are bleeding, and since the body absorbs it over time, no foreign materials are left in the wound to become a focus for disease organisms. Nylon stitches and steel staples are removed when sufficient healing has taken place.

There are three general techniques of wound treatment; primary intention, in which all tissues, including the skin, are closed with suture material after completion of the operation; secondary intention, in which the wound is left open and closes naturally; and third intention, in which the wound is left open for a number of days and then closed if it is found to be clean. The third technique is used in badly contaminated wounds to allow drainage and thus avoid the entrapment of microorganisms. Military surgeons use this technique on wounds contaminated by shell fragments, pieces of clothing, and dirt.

The 20th century witnessed several new surgical technologies to supplement the techniques of manual incision. Lasers are now widely used to destroy tumours and other pigmented lesions, some of which are inaccessible by conventional surgery. They are also used to surgically weld detached retinas back in place and to coagulate blood vessels to stop them from bleeding. Stereotaxic surgery uses a three-dimensional system of coordinates obtained by X-ray photography to accurately focus high-intensity radiation, cold, heat, or chemicals on tumours located deep in the brain that could not otherwise be reached. Cryosurgery uses extreme cold to destroy warts and precancerous and cancerous skin lesions and to remove cataracts. In the late 20th century, some traditional techniques of open surgery were being replaced by the use of a thin, flexible fibre-optic tube equipped with a light and a video connection; the tube, or endoscope, is inserted into various bodily passages and provides views of the interior of hollow organs or vessels. Accessories added to the endoscope allow small surgical procedures to be executed inside the body without making a major incision.

Preoperative and postoperative care both have the same object: to restore patients to as near their normal physiologic state as possible. Blood transfusions, intravenous administration of fluids, and the use of measures to prevent common complications such as lung infection and blood clotting in the legs are the principal features of postoperative care.

There are four major categories of surgery: (1) wound treatment, (2) extirpative surgery, (3) reconstructive surgery, and (4) transplantation surgery. The technical aspects of wound surgery, already partly discussed, centre on procuring good healing and the avoidance of infection. Extirpative surgery involves the removal of diseased tissue or organs. Cancer surgery usually falls into this category, with mastectomy (removal of the breast), cholecystectomy (removal of the gallbladder), and hysterectomy (removal of the uterus) among the most frequent procedures. Reconstructive surgery deals with the replacement of lost tissues, whether from fractures, burns, or degenerative-disease processes, and is especially prominent in the practice of plastic surgery and orthopedic surgery. Grafts from the patient or from others are frequently used to replace lost tissues. Reconstructive surgery also uses artificial devices (prostheses) to replace damaged or diseased organs or tissues. Common examples are the use of metal in reconstructing hip joints and the use of plastic valves to replace heart valves. Transplantation surgery involves the use of organs transplanted from other bodies to replace diseased organs in patients. Kidneys are the most commonly transplanted organs.

The major medical specialties involving surgery are general surgery, plastic surgery, orthopedic surgery, obstetrics and gynecology, neurosurgery, thoracic surgery, colon and rectal surgery, otolaryngology, ophthalmology, and urology. General surgery is the parent specialty and now centres on operations involving the stomach, intestines, breast, blood vessels in the extremities, endocrine glands, tumours of soft tissues, and amputations. Plastic surgery is concerned with the bodily surface and with reconstructive work of the face and exposed parts. Orthopedic surgery deals with the bones, tendons, ligaments, and muscles; fractures of the extremities and congenital skeletal defects are common targets of treatment. Obstetricians perform cesarean sections, while gynecologists operate to remove tumours from the uterus and ovaries. Neurosurgeons operate to remove brain tumours, treat injuries to the brain resulting from skull fractures, and treat ruptured intravertebral disks that affect the spinal cord. Thoracic surgeons treat disorders of the lungs; the subspecialty of cardiovascular surgery is concerned with the heart and its major blood vessels and has become a major field of surgical endeavour. Colon and rectal surgery deals with disorders of the large intestine. Otolaryngologic surgery is performed in the area of the ear, nose, and throat (e.g., tonsillectomy), while ophthalmologic surgery deals with disorders of the eyes. Urologic surgery treats diseases of the urinary tract and, in males, of the genital apparatus.

Health

in human beings, the extent of an individual's continuing physical, emotional, mental, and social ability to cope with his environment.

This definition, just one of many that are possible, has its drawbacks. The rather fragile individual who stays “well” within the ordinary environment of his or her existence may succumb to a heart attack from heavy shovelling after a snowstorm; or a sea-level dweller may move to a new home in the mountains, where the atmosphere has a lower content of oxygen, and suffer from shortness of breath and anemia until his red blood cell count adjusts itself to the altitude. Thus, even by this definition, the conception of good health must involve some allowance for change in the environment.

Bad health can be defined as the presence of disease, good health as its absence—particularly the absence of continuing disease, because the person afflicted with a sudden attack of seasickness, for example, may not be thought of as having lost his good health as a result of such a mishap.

Actually, there is a wide variable area between health and disease. Only a few examples are necessary to illustrate the point: (1) It is physiologically normal for an individual, 15 to 20 minutes after eating a meal, to have a high blood sugar content. If, however, the sugar content remains elevated two hours later, this condition is abnormal and may be indicative of disease. (2) A “healthy” individual may have developed an allergy, perhaps during early childhood, to a single specific substance. If he never again comes in contact with the antigen that causes the allergy, all other factors remaining normal, he will remain in that state of health. Should he, however, come in contact with that allergen, even 20 or 30 years later, he may suffer anything from a mild allergic reaction—a simple rash—to severe anaphylactic shock, coma, or even death, depending upon the circumstances. Thus it can be seen that, unlike disease, which is frequently recognizable, tangible, and rather easily defined, health is a somewhat nebulous condition, and somewhat difficult to define.

Moreover, physical condition and health are not synonymous terms. A seven-foot-tall basketball player may be in excellent physical condition (although outside the range of normality for height) but may or may not be in good health—depending, for example, on whether or not he has fallen victim to an attack of influenza.

There are further problems in settling upon a definition of human health. A person may be physically strong, resistant to infection, able to cope with physical hardship and other features of his physical environment, and still be considered unhealthy if his mental state, as measured by his behaviour, is deemed unsound. What is mental health? Some say that a person is mentally healthy if he is able to function reasonably well. Others hold that a person is healthy mentally if his behaviour is like that of a majority of his fellows.

In the face of this confusion, it is most useful, perhaps, to define health, good or bad, in terms that can be measured, can be interpreted with respect to the ability of the individual at the time of measurement to function in a normal manner and with respect to the likelihood of imminent disease. These measurements can be found in tables of “reference values” printed in textbooks of clinical medicine, diagnosis, and other references of this type. When an individual is given a health examination, the examination is likely to include a series of tests. Some of these tests are more descriptive than quantitative and can indicate the presence of disease in a seemingly healthy person. Such tests include the electrocardiogram to detect some kinds of heart disease; electromyogram for primary muscle disorders; liver and gall bladder function tests; and X-ray techniques for determining disease or malfunction of internal organs.

Other tests give numerical results (or results that can be assigned numerical values—such as photometric colour determinations) that can be interpreted by the examiner. These are physical and chemical tests, including blood, urine, and spinal-fluid analyses. The results of the tests are compared with the reference values; and the physician receives clues as to the health of his patient and, if the values are abnormal, for the methods of improving his health.

A major difficulty in the interpretation of test results is that of biological variability. Almost without exception these reference values for variables are means or adjusted means of large group measurements. For these values to have significance, they must be considered as lying somewhere near the centre point of a 95 percent range—i.e., the so-called ordinary range or, with reservations, the range from normal to the upper and lower borderline limits. Thus, the 2.5 percent below the lower limit and the 2.5 percent above the upper limit of the 95 percent range are considered areas of abnormality or, perhaps, illness. Some areas have wide 95 percent ranges—blood pressure, for example, may vary considerably throughout the day (e.g., during exercise, fright, or anger) and remain within its range of normality. Other values have ranges so narrow that they are termed physiological constants. An individual's body temperature, for example, rarely varies (when taken at the same anatomical site) by more than a degree (from time of rising until bedtime) without being indicative of infection or other illness.

Hepatitis

inflammation of the liver that results from a variety of causes, both infectious and noninfectious. Infectious agents that cause hepatitis include viruses and parasites; noninfectious substances include certain drugs and toxic agents. In some instances hepatitis results from an autoimmune reaction directed against the liver cells of the body. Most cases of hepatitis are caused by viral infection. The viruses that give rise to liver inflammation include cytomegalovirus; yellow-fever virus; Epstein-Barr virus; herpes simplex viruses; measles, mumps, and chickenpox viruses; and a number of hepatitis viruses. The term viral hepatitis, however, usually is applied only to those cases of liver disease caused by the hepatitis viruses. There are seven known hepatitis viruses, which are labeled A, B, C, D, E, F, and G. Hepatitis A, E, and F viruses are transmitted through the ingestion of contaminated food or water (called the fecal-oral route); the spread of these agents is aggravated by crowded conditions and poor sanitation. The B, C, D, and G viruses are transmitted mainly by blood or bodily fluids; sexual contact or exposure to contaminated blood are common modes of transmission. The signs and symptoms of acute viral hepatitis result from damage to the liver and are similar regardless of the hepatitis virus responsible. Patients may experience a flulike illness, and general symptoms include nausea, vomiting, abdominal pain, fever, fatigue, loss of appetite, and, less commonly, rash and joint pain. Sometimes jaundice, a yellowing of the skin and eyes, will develop. The acute symptomatic phase of viral hepatitis usually lasts from a few days to several weeks; the period of jaundice that may follow can persist from one to three weeks. Complications of acute viral hepatitis include fulminant hepatitis, which is a very severe, rapidly developing form of the disease that results in severe liver failure, impaired kidney function, difficulty in the clotting of blood, and marked changes in neurological function. Such patients rapidly become comatose; mortality is as high as 90 percent. Another complication is chronic hepatitis, which is characterized by liver cell death and inflammation over a period greater than six months. Hepatitis A, caused by the hepatitis A virus (HAV), is the most common worldwide. The onset of hepatitis A usually occurs 15 to 45 days after exposure to the virus, and some infected individuals, especially children, exhibit no clinical manifestations. In the majority of cases, no special treatment other than bed rest is required; most recover fully from the disease. Hepatitis A does not give rise to chronic hepatitis. The severity of the disease can be reduced if the affected individual is injected within two weeks of exposure with immune serum globulin obtained from persons exposed to HAV. This approach, called passive immunization, is effective because the serum contains antibodies against HAV. An effective vaccine against HAV is available and is routinely administered to children over two years of age living in communities with high rates of HAV. The vaccine is also recommended for people who travel to areas where HAV is common, homosexuals, people with chronic liver disease, hemophiliacs, and people who have an occupational risk for infection. Hepatitis B is a much more severe and longer-lasting disease than hepatitis A. It may occur as an acute disease, or, in about 5 to 10 percent of cases, the illness may become chronic and lead to permanent liver damage. Symptoms usually appear from 40 days to 6 months after exposure to the hepatitis B virus (HBV). Those persons at greatest risk for contracting hepatitis B include intravenous drug users, sexual partners of individuals with the disease, health care workers who are not adequately immunized, and recipients of organ transplants or blood transfusions. A safe and effective vaccine against HBV is available and provides protection for at least five years. Passive immunization with hepatitis B immune globulin can also provide protection. Approximately 1 in 10 patients with HBV infection becomes a carrier of the virus and may transmit it to others. Those who carry the virus are also 100 times more likely to develop liver cancer than persons without HBV in their blood. Hepatitis C virus (HCV) was isolated in 1988. Symptoms of hepatitis C usually appear within six to nine weeks after exposure. HCV appears to be transmitted in a manner similar to HBV. Hepatitis C has a greater propensity than hepatitis B to develop into chronic liver disease. Alcoholics who are infected with hepatitis C are more prone to develop cirrhosis. The treatment for hepatitis C is a combination of alpha interferon and ribivarin; only about half of those receiving these drugs respond. Infection with hepatitis D virus (HDV), also called the delta agent, can occur only in association with HBV infection, because HDV requires HBV to replicate. Infection with HDV may occur at the same time infection with HBV occurs, or HDV may infect a person already infected with HBV. The latter situation appears to give rise to a more serious condition, leading to cirrhosis or chronic liver disease. Alpha interferon is the only treatment for HDV infection. Preventing infection with HBV also prevents HDV infection. Discovered in the 1980s, the hepatitis E virus (HEV) is similar to HAV. HEV is transmitted in the same manner as HAV, and it, too, only causes acute infection. However, the effects of infection with HEV are more severe than those caused by HAV, and death is more common. The risk of acute liver failure from infection with HEV is especially great for pregnant women. In less-developed countries, including Mexico, India, and those in Africa, HEV is responsible for widespread epidemics of hepatitis that occur as a result of ingestion of contaminated water or food (enteric transmission). Some cases of hepatitis transmitted through contaminated food or water are attributed to the hepatitis F virus (HFV), which was first reported in 1994. Another virus isolated in 1996, the hepatitis G virus (HGV), is believed to be responsible for a large number of sexually transmitted and bloodborne cases of hepatitis. HGV causes acute and chronic forms of the disease and often infects persons already infected with HCV. Most cases of chronic hepatitis are caused by the hepatitis viruses B, C, and D, but other factors such as alcoholism, reaction to certain medications, and autoimmune reactions lead to development of the disease. Chronic hepatitis may also be associated with some illnesses, such as Wilson disease and alpha-1-antitrypsin deficiency. Chronic hepatitis B primarily affects males, whereas chronic hepatitis C arises in equal numbers in both sexes. Autoimmune hepatitis, a disorder associated with a malfunction of the immune system, generally occurs in young women. Treatment for autoimmune hepatitis includes corticosteroids, which help to reduce symptoms. Alcoholic hepatitis results from sustained consumption of excessive amounts of alcohol. The condition can be reversed if it is caught in its early stages and if the individual either significantly reduces or entirely curtails intake of alcohol. If untreated, it can result in alcoholic cirrhosis.