Leptospirosis is a febrile disease (fever) caused by infection with the bacteria Leptospira interrogans. The disease can range from very mild and symptomless to a more serious, even life threatening form, that may be associated with kidney (renal) failure. An infection by the bacterium Leptospira interrogans goes by different names in different regions. Alternate names for leptospirosis include mu…
Lesch-Nyhan syndrome is a rare genetic disorder that affects males. Males with this syndrome develop physical handicaps, mental retardation, and kidney problems. It is caused by a total absence of an enzyme. Self injury is a classic feature of this genetic disease. Lesch-Nyhan syndrome was first described in 1964 by Dr. Michael Lesch and Dr. William Nyhan. The syndrome is caused by a severe change…
Leukemia stains are laboratory tests done on bone marrow or blood samples to help diagnose specific types of leukemia. Leukemia stains are done to diagnose and classify leukemia. Blood contains red cells, several varieties of white cells, and platelets. Cancerous overproduction of any one type of cell produces one of many types of leukemia. A patient's specific type of leukemia must be clas…
Leukemia is a cancer that starts in the organs that make blood, namely the bone marrow and the lymph system. Depending on their characteristics, leukemias can be divided into two broad types. Acute leukemias are the rapidly progressing leukemias, while the chronic leukemias progress more slowly. The vast majority of the childhood leukemias are of the acute form. The cells that make up blood are pr…
Chronic leukemia is a disease in which too many white blood cells are made in the bone marrow. Depending on the type of white blood cell that is involved, chronic leukemia can be classified as chronic lymphocytic leukemia or chronic myeloid leukemia. Chronic leukemia is a cancer that starts in the blood cells made in the bone marrow. The bone marrow is the spongy tissue found in the large bones of…
Leukocytosis is a condition characterized by an elevated number of white cells in the blood. Leukocytosis is a condition that affects all types of white blood cells. Other illnesses, such as neutrophilia, lymphocytosis, and granulocytosis, target specific types of white blood cells. Normal white blood cell counts are 4,300-10,800 white blood cells per microliter. Leukocyte or white blood cell leve…
Lice infestations (pediculosis) are infections of the skin, hair, or genital region caused by lice living directly on the body or in hats or other garments. Lice are small wingless insect-like parasites with sucking mouthparts that feed on human blood and lay their eggs on body hairs or in clothing. The name pediculosis comes from the Latin word for louse (singular) or lice (plural). Lice infestat…
Lichen planus is a skin condition of unknown origin that produces small, shiny, flat-topped, itchy pink or purple raised spots on the wrists, forearms or lower legs, especially in middle-aged patients. One example of lichen planus on the tongue. (Custom Medical Stock Photo. Reproduced by permission.) Lichen planus affects between 1-2% of the population, most of whom are middle-aged women. T…
Lichen simplex chronicus is a chronic inflammation of the skin (dermatitis) characterized by small, round itchy spots that thicken and become leathery as a result of scratching. Also termed neurodermatis, lichen simplex chronicus is the result of chronic skin irritation. It occurs in 4-5 out of every thousand people. Initial irritation causes itching, and in turn, itching causes scratching. Scratc…
Life support refers to a spectrum of techniques used to maintain life after the failure of one or more vital organs. A patient requires life support when one or more vital organs fail, due to causes such as trauma, infection, cancer, heart attack, or chronic disease. Among the purposes of life support are to: Patients and families need to recognize that life support is an extremely painful, expens…
The lipase test is a blood test performed to determine the serum level of a specific protein (enzyme) involved in digestion. Lipase is an enzyme produced by the pancreas, which is a large gland situated near the stomach. Lipase works to break down a certain type of blood lipid (triglycerides) into fatty acids. Lipase appears in the blood together with another enzyme called amylase following damage…
Lipidoses are heredity disorders, passed from parents to their children, characterized by defects of the digestive system that impair the way the body uses fat from the diet. When the body is unable to properly digest fats, lipids accumulate in body tissues in abnormal amounts. The digestion, storage, and use of fats from foods is a complex process that involves hundreds of chemical reactions in t…
Lipoproteins are the "packages" in which cholesterol and triglycerides travel throughout the body. Measuring the amount of cholesterol carried by each type of lipoprotein helps determine a person's risk for cardiovascular disease (disease that affects the heart and blood vessels, also called CVD). Cholesterol and triglycerides are fat-like substances called lipids. Cholesterol…
Liposuction, also known as lipoplasty or suction-assisted lipectomy, is cosmetic surgery performed to remove unwanted deposits of fat from under the skin. The doctor sculpts and recontours the patient's body by removing excess fat deposits that have been resistant to reduction by diet or exercise. The fat is permanently removed from under the skin with a suction device. Liposuction is inten…
Listeriosis is an illness caused by the bacterium Listeria monocytogenes that is acquired by eating contaminated food. The organism can spread to the blood stream and central nervous system. During pregnancy, listeriosis often causes miscarriage or stillbirth. Listeriosis is caused by an infection with the bacterium Listeria monocytogenes. This bacteria can be carried by many animals and birds, an…
Lithotripsy is the use of high-energy shock waves to fragment and disintegrate kidney stones. The shock wave, created by using a high-voltage spark or an electromagnetic impulse, is focused on the stone. This shock wave shatters the stone and this allows the fragments to pass through the urinary system. Since the shock wave is generated outside the body, the procedure is termed extracorporeal shoc…
A liver biopsy is a medical procedure performed to obtain a small piece of liver tissue for diagnostic testing. Liver biopsies are sometimes called percutaneous liver biopsies, because the tissue sample is obtained by going through the patient's skin. A liver biopsy is usually done to diagnose a tumor, or to evaluate the extent of damage that has occurred to the liver because of chronic dis…
Liver cancer is a form of cancer with a high mortality rate. Liver cancers can be classified into two types. They are either primary, when the cancer starts in the liver itself, or metastatic, when the cancer has spread to the liver from some other part of the body. Primary liver cancer is a relatively rare disease in the United States, representing about 2% of all malignancies and 4% of newly dia…
Liver encephalopathy is a potentially life-threatening disease in which toxic substances accumulate in the blood. Also known as hepatic encephalopathy or hepatic coma, this condition can cause confusion, disorientation, abnormal neurological signs, loss of consciousness, and death. A normally functioning liver metabolizes and detoxifies substances formed in the body during the digestive process. I…
Liver function tests, or LFTs, include tests for bilirubin, a breakdown product of hemoglobin, and ammonia, a protein byproduct that is normally converted into urea by the liver before being excreted by the kidneys. LFTs also commonly include tests to measure levels of several enzymes, which are special proteins that help the body break down and use (metabolize) other substances. Enzymes that are …
A liver scan is a diagnostic procedure to evaluate the liver for suspected disease. A radioactive substance that concentrates in the liver is injected intravenously and the image of its distribution in the body is analyzed to diagnose certain abnormalities. In the past, liver scans were used to evaluate the liver in a wide variety of situations. It was considered a useful study to detect abnormali…
Liver transplantation is a surgery that removes a diseased liver and replace it with a healthy donor liver. The liver is the body's principle chemical factory. It receives all nutrients, drugs, and toxins absorbed from the intestines and performs the final stages of digestion, converting food into energy and replacement parts for the body. The liver also filters the blood of all waste produ…
Low back pain is a common musculoskeletal symptom that may be either acute or chronic. It may be caused by a variety of diseases and disorders that affect the lumbar spine. Low back pain is often accompanied by sciatica, which is pain that involves the sciatic nerve and is felt in the lower back, the buttocks, and the backs of the thighs. Low back pain is a symptom that affects 80% of the general …
Lower esophageal ring is a condition in which there is a ring of tissue inside the lower part of the esophagus (the tube connecting the throat with the stomach). This tissue causes narrowing and partial blockage of the esophagus. Lower esophageal ring can also refer to the ring itself. Lower esophageal ring (also called Schatzki's ring and B-ring) affects about 10-14% of the population. Nor…
A lumpectomy is a type of surgery for breast cancer. It is considered "breast-conserving" surgery because in a lumpectomy, only the malignant tumor and a surrounding margin of normal breast tissue are removed. Lymph nodes in the armpit (axilla) may also be removed. This procedure is called lymph node dissection. Lumpectomy is a surgical treatment for newly diagnosed breast cancer. It…
Lung abscess is an acute or chronic infection of the lung, marked by a localized collection of pus, inflammation, and destruction of tissue. Lung abscess is the end result of a number of different disease processes ranging from fungal and bacterial infections to cancer. It can affect anyone at any age. Patients who are most vulnerable include those weakened by cancer and other chronic diseases; pa…
Lung biopsy is a medical procedure performed to obtain a small piece of lung tissue for examination under a microscope. Biopsy examinations are usually performed by pathologists, who are doctors with special training in tissue abnormalities and other signs of disease. Lung biopsies are useful, first of all, in confirming a diagnosis of cancer, especially if malignant cells are detected in the pati…
Non-small cell lung cancer is a disease in which the cells of the lung tissues grow uncontrollably and form tumors. There are two kinds of lung cancers, primary and secondary. Primary lung cancer starts in the lung itself, and is divided into small cell lung cancer and non-small cell lung cancer. Small cell lung cancers are shaped like an oat and called oat-cell cancers; they are aggressive, sprea…
Small cell lung cancer is a disease in which the cells of the lung tissues grow uncontrollably and form tumors. Lung cancer is divided into two main types: small cell and non-small cell. Small cell lung cancer is the least common of the two, accounting for only about 20% of all lung cancers. In the past, the disease was called oat cell cancer because, when viewed under a microscope, the cancer cel…
Lung diseases due to gas or chemical exposure are conditions that can be acquired from indoor and outdoor air pollution and from ingesting tobacco smoke. The lungs are susceptible to many airborne poisons and irritants. Mucus present in the airways blocks foreign particles of a certain size, however it is unable to filter all airborne particulates. There are hundreds of substances that can pollute…
A lung perfusion scan is a nuclear medicine test that produces a picture of blood flow to the lungs. A lung ventilation scan measures the ability of the lungs to take in air and uses radiopharmaceuticals to produce a picture of how air is distributed in the lungs. Lung perfusion scans and lung ventilation scans are usually performed in the same session. They are done to detect pulmonary embolisms,…
Lung surgery includes a variety of procedures used to diagnose or treat diseases of the lungs. Biopsies are performed to extract a small amount of tissue for diagnosis, resections remove a portion of lung tissue, and other surgeries are aimed at reducing the volume of the lungs, removing cancerous tumors, or improving lung function. The type of lung surgery performed will depend upon the underlyin…
Lung transplantation involves removal of one or both diseased lungs from a patient and the replacement of the lungs with healthy organs from a donor. Lung transplantation may refer to single, double, or even heart-lung transplantation. The purpose of lung transplantation is to replace a lung that no longer functions, or is cancerous, with a healthy lung. In order to qualify for lung transplan…
The luteinizing hormone (LH) test is a test of the blood or urine to measure the level of luteinizing hormone (lutropin). This hormone level is highest immediately before a woman ovulates during her menstrual cycle. The LH test is frequently used to determine the timing of ovulation. Couples who are trying to become pregnant may use information about the timing of ovulation to improve their chance…
Lyme disease is an infection transmitted by the bite of ticks carrying the spiral-shaped bacterium Borrelia burgdorferi. The disease was named for Lyme, Connecticut, the town where it was first diagnosed in 1975 after a puzzling outbreak of arthritis. The organism was named for its discoverer, Willy Burgdorfer. The effects of this disease can be long-term and disabling unless it is recognized and …
A lymph node biopsy is a procedure in which all or part of a lymph node is removed and examined to determine if there is cancer within the node. Lymph node biopsy is a procedure in which a sample of lymph node tissue is removed for laboratory analysis. It is generally performed on an outpatient basis. (Illustration by Electronic Illustrators Group.) The lymph system is the body's pri…
Lymphadenitis is the inflammation of a lymph node. It is often a complication of a bacterial infection of a wound, although it can also be caused by viruses or other disease agents. Lymphadenitis may be either generalized, involving a number of lymph nodes; or limited to a few nodes in the area of a localized infection. Lymphadenitis is sometimes accompanied by lymphangitis, which is the inflammat…
Lymphangiography, or lymph node angiogram, is a test which utilizes x-ray technology, along with the injection of a contrast agent, to view lymphatic circulation and lymph nodes for diagnostic purposes. The lymphatic system is a one way circulation that channels tissue fluid back into the heart. The watery fluid called lymph seeps out of the blood into tissues, and while journeying back to the hea…
Lymphedema is the swelling of tissues (edema), usually the feet and legs, due to lymphatic obstruction. Lymphatic fluid seeps out of the blood circulation into the tissues. It returns to the heart through separate channels called lymphatics, carrying waste products and germs. On its way to the heart, it passes through lymph nodes, where infecting germs (including some cancers) are attacked by the …
Lymphocyte typing focuses on identifying the numbers and relative percentages of lymphocytes in an individual's bloodstream. Lymphocytes, primarily T cells and B cells, are types of white blood cells, the underlying supports of the immune system in the bloodstream. A lymphocyte cell. (Photograph by Lester V. Bergman, Corbis Images. Reproduced by permission.) Determining the numbers a…
Lymphocytic choriomeningitis (LCM) is a viral infection of the membranes surrounding the brain and spinal cord and of the cerebrospinal fluid. Lymphocytic choriomeningitis virus infection is relatively rare and recovery usually occurs spontaneously within a couple of weeks. Many cases are probably not even identified because the symptoms range from extremely mild to those resembling severe flu. A …
Lymphocytopenia is a condition marked by an abnormally low level of lymphocytes in the blood. Lymphocytes are a specific type of white blood cell with important functions in the immune system. Lymphocytes normally account for 15-40% of all white cells in the bloodstream. They help to protect the body from infections caused by viruses or fungi. They also coordinate the activities of other cells in …
Lymphogranuloma venereum (LGV) is a sexually transmitted systemic disease (STD) caused by a parasitic organism closely related to certain types of bacteria. It affects the lymph nodes and rectal area, as well as the genitals, in humans. The name comes from two Latin words that mean a swelling of granulation tissue in the lymph nodes resulting from sexual intercourse. Granulation tissue is tissue t…
Lysergic acid diethylamide (LSD), also known as "acid," belongs to a class of drugs known as hallucinogens, which distort perceptions of reality. LSD is the most potent mood-and perception-altering drug known: doses as small as 30 micrograms can produce effects lasting six to 12 hours. In the United States, LSD has no accepted medical use and its manufacture is illegal. LSD is produc…
Macular degeneration is the progressive deterioration of a critical region of the retina called the macula. The macula is a 3-5 mm area in the retina that is responsible for central vision. This disorder leads to irreversible loss of central vision, although peripheral vision is retained. In the early stages, vision may be gray, hazy, or distorted. Macular degeneration is the most common cause of …
A mineral found in the fluid that surrounds cells, magnesium (Mg) is an essential component of more than 300 enzymes that regulate many body functions. Imbalances occur when the blood contains more or less magnesium than it should. Magnesium is necessary for the formation and functioning of healthy bones, teeth, muscles, and nerves. It converts food into energy, builds proteins, and is instrumenta…
Magnetic therapy is the use of magnets to relieve pain in various areas of the body. Some of the benefits that magnetic therapy claims to provide include: Sir William Gilbert's 1600 treatise, De Magnete, was the first scholarly attempt to explain the nature of magnetism and how it differed from the attractive force of static electricity. Gilbert allegedly used magnets to relieve the arthrit…
Magnetic resonance imaging (MRI) is the newest, and perhaps most versatile, medical imaging technology available. Doctors can get highly refined images of the body's interior without surgery, using MRI. By using strong magnets and pulses of radio waves to manipulate the natural magnetic properties in the body, this technique makes better images of organs and soft tissues than those of other…
Malabsorption syndrome is an alteration in the ability of the intestine to absorb nutrients adequately into the bloodstream. Protein, fats, and carbohydrates (macronutrients) normally are absorbed in the small intestine; the small bowel also absorbs about 80% of the eight to ten liters of fluid ingested daily. There are many different conditions that affect fluid and nutrient absorption by the int…
Malaria is a serious, infectious disease spread by certain mosquitoes. It is most common in tropical climates. It is characterized by recurrent symptoms of chills, fever, and an enlarged spleen. The disease can be treated with medication, but it often recurs. Malaria is endemic (occurs frequently in a particular locality) in many third world countries. Isolated, small outbreaks sometimes occur wit…
Lymphomas are a group of cancers in which cells of the lymphatic system become abnormal and start to grow uncontrollably. Because there is lymph tissue in many parts of the body, lymphomas can start in almost any organ of the body. The lymph system is made up of ducts or tubules that carry lymph to all parts of the body. Lymph is a milky fluid that contains the lymphocytes or white blood cells. Th…
Malignant Melanoma is a type of cancer arising from the melanocyte cells of the skin. The melanocytes are cells in the skin that produce the pigment melanin. Malignant melanoma develops when the melanocytes no longer respond to normal control mechanisms of cellular growth and are capable of invasion locally or spread to other organs in the body (metastasis), where again they invade and compromise …
In the context of medicine, malingering is the act of intentionally feigning or exaggerating physical or psychological symptoms for personal gain. People may feign physical or psychological illness for any number of reasons. Faked illness can get them out of work, military duty, or criminal prosecution. It can also help them obtain financial compensation through insurance claims, lawsuits, or work…
Mallet finger refers to the involuntary flexion of the distal phalanx of a finger caused by the disruption or tearing of its extensor tendon. Tendons are the strong "cables" between muscles and bones that help control movements of the body. They consist of white, glistening, fibrous cords, of various length and thickness, either round or flattened, and lacking in elasticity. In malle…
Mallory-Weiss syndrome is bleeding from an arterial blood vessel in the upper gastrointestinal tract, caused by a mucosal gastric tear at or near the point where the esophagus and stomach join. Mallory-Weiss syndrome causes about 5% of all upper gastrointestinal bleeding. The condition was originally diagnosed in alcoholics and is associated with heavy alcohol use, although it can also be found in…
Malnutrition is the condition that develops when the body does not get the right amount of the vitamins, minerals, and other nutrients it needs to maintain healthy tissues and organ function. Malnutrition occurs in people who are either under-nourished or over-nourished. Undernutrition is a consequence of consuming too few essential nutrients or using or excreting them more rapidly than they can b…
Malocclusion is a problem in the way the upper and lower teeth fit together in biting or chewing. The word malocclusion literally means "bad bite." The condition Orthodontia treatments usually include the use of braces and retainers. (Photograph by Lester V. Bergman, Corbis Images. Reproduced by permission). may also be referred to as an irregular bite, crossbite, or overbite.…
MALT lymphomas are solid tumors that originate from cancerous growth of immune cells that are recruited to secretory tissue such as the gastrointestinal tract, salivary glands, lungs, and the thyroid gland. The digestive tract is generally not associated with lymphoid tissue, with the exception of small collections of lymphocytes such as Peyer's patches. A specific kind of white blood cell,…
Mammography is the study of the breast using x ray. The actual test is called a mammogram. There are two types of mammograms. A screening mammogram is ordered for women who have no problems with their breasts. It consists of two x-ray views of each breast. A diagnostic mammogram is for evaluation of new abnormalities or of patients with a past abnormality requiring follow-up (i.e. a woman with bre…
Mania is an abnormally elated mental state, typically characterized by feelings of euphoria, lack of inhibitions, racing thoughts, diminished need for sleep, talkativeness, risk taking, and irritability. In extreme cases, mania can induce hallucinations and other psychotic symptoms. Mania typically occurs as a symptom of bipolar disorder (a mood disorder characterized by both manic and depressive …
