Health Library

Labyrinthitis is an ear disorder that involves irritation and swelling of the inner ear. See also:

Intrinsic factor is a natural substance normally found in the stomach. You need this substance to absorb from foods. A lack of intrinsic factor leads to and vitamin B12 deficiency, which can cause anemia and brain and nervous system (neurological) problems.

Lacquer is a clear or colored coating (called a varnish) that is often used to give wooden surfaces a glossy look. Lacquers are dangerous to swallow. Breathing in the fumes for a long period of time is also harmful. This is for information only and not for use in the treatment or management of an ...

A lacrimal gland tumor is a in the glands that release tears. These glands are located above and to the side of each eye. The tumor can be harmless () or cancer ().

The lactate dehydrogenase (LDH) test measures the amount of LDH in the blood. See also:

Lactic acid is mainly produced in muscle cells and red blood cells. It forms when the body breaks down carbohydrates to use for energy during times of low oxygen levels. Your body’s oxygen level might drop during intense exercise or if you have an infection or disease. A test can be done to ...

Lactic acidosis is when builds ups in the bloodstream faster than it can be removed. Lactic acid is produced when oxygen levels in the body drop.

Lactose intolerance is the inability to digest lactose. Lactose is a type of sugar found in milk and other dairy products.

Lactose tolerance tests measure the ability of your intestines to break down lactose, a type of sugar found in milk and other dairy products. See also:

Lambert-Eaton syndrome is a disorder in which faulty communication between nerves and muscles leads to .

Lamellar ichthyosis is a rare skin condition that appears at birth and continues throughout a person’s life.

Laminectomy is surgery to remove the lamina, part of the bone that makes up a vertebra, or bone spurs in your back. The procedure can take pressure off your spinal nerves or spinal canal.

Language disorder in children refers to problems with either: Getting their meaning or message across to others (expressive language disorder), or Understanding the message coming from others (receptive language disorder) Some children only have an expressive language disorder. Others have a mixed ...

Lanolin is an oily substance taken from sheep’s wool. Lanolin poisoning occurs when someone swallows products that contain this substance. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you should call your ...

Laparoscopic gastric banding is surgery to help with weight loss. The surgeon places a band around the upper part of your stomach to create a small pouch to hold food. The band limits the amount of food you can eat by making you feel full after eating small amounts of food. After surgery, your ...

Laparoscopy describes a group of operations performed with the aid of a camera placed in the abdomen or pelvis. The laparoscope allows doctors to perform both minor and complex surgeries with a few small cuts in the abdomen. This technique is known as laparoscopic-assisted surgery. Laparoscopy ...

Large bowel resection is surgery to remove all or part of your large bowel. This surgery is also called colectomy. The large bowel is also called the large intestine or colon. Removal of the entire colon and the rectum is called a proctocolectomy. Removal of part or all of the colon but not the ...

Large for gestational age (LGA) means that a fetus or infant is larger or more developed than normal for the baby’s .

Laryngeal nerve damage is injury to one or both of the nerves that are attached to the voice box.

Laryngectomy is surgery to remove the larynx (voice box) in your throat. All or part of the larynx may be removed in a laryngectomy.

Laryngitis is swelling and irritation (inflammation) of the voice box (larynx) that is usually associated with or loss of voice.

Laryngoscopy is examination of the larynx (voice box) using a small mirror held just below the back of your palate, or a rigid or flexible viewing tube called a laryngoscope placed in your mouth. Depending on the circumstances, you may need anesthesia.

Laser surgery is a medical procedure that uses laser light to remove diseased tissues or treat bleeding blood vessels. Laser surgery may also be used for cosmetic purposes, such as removing wrinkles, sunspots, tattoos, or birthmarks.

Laser therapy is any treatment using intense beams of light to precisely cut, burn, or destroy tissue. The term laser is an acronym for “light amplification by stimulated emission of radiation.”

LASIK is eye surgery that permanently changes the shape of the cornea (the clear covering on the front of the eye) in order to improve vision and reduce a person’s dependency on glasses or contact lenses.

Lateral means to the side of, or away from, the middle of the body. The ears are lateral to the nose. The arms are lateral to the chest.

Lateral collateral ligament (LCL) injury is an injury to the ligament on the outer side of the knee. It can be a stretch, partial tear, or complete tear of the ligament.

Lateral traction is a technique in which tension is used to move a body part to the side or away from its original location.

The latex agglutination test is a laboratory method to check for certain or in a variety of bodily fluids including saliva, urine, cerebrospinal fluid, or blood.

Lavender oil is an oil made from the flowers of lavender. Lavender poisoning occurs when someone accidentally or intentionally swallows lavender oil. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you should call ...

A laxative is a medication used to produce bowel movements. Laxative occurs when someone accidentally or intentionally takes more than the normal or recommended amount of this medication. Most laxative overdoses in children are accidental. However, some people abuse laxatives by regularly taking ...

LDH isoenzymes is a test to check how much (LDH) is in the blood.

LDL stands for low-density lipoprotein. It’s also sometimes called “bad” cholesterol. Lipoproteins are made of fat and protein. They carry cholesterol, triglycerides, and other fats, called lipids, in the blood to various parts of the body. This article discusses the blood test ...

Nutritional considerations to reduce the risk of .

Blood lead level is a test that measures the amount of lead in the blood.

Lead is a very strong poison. When a person swallows a lead object or breathes in lead dust, some of the poison can stay in the body and cause serious health problems.

Left heart catheterization is the passage of a thin flexible tube (catheter) into the left side of the heart to diagnose or treat certain heart problems.

Left heart ventricular angiography is a procedure to look at the left side of the heart and, sometimes, the coronary arteries.

A computed tomography (CT) scan of the leg is an imaging method that uses x-rays to create cross-sectional pictures of the leg.

Leg lengthening and shortening are types of surgery to treat some children who have legs of unequal lengths. These procedures may: Lengthen an abnormally short leg Shorten an abnormally long leg Limit growth of a normal leg to allow a short leg to grow to a matching length

A magnetic resonance imaging () scan of the leg is a method to create detailed pictures of the leg, including the ankle, foot, and surrounding tissues. A leg MRI also creates pictures of the knee. However, the knee is discussed in a separate article. See also: . Unlike and computed tomographic ...

Leg or foot amputation is the removal of a leg, foot or toes from the body. These body parts are called extremities. Amputations are done either by surgery, or they occur by accident or trauma to the body.

Leg pain is a common symptom and complaint. For more specific information, see:

Legg-Calve-Perthes disease is when the ball of the thighbone in the hip doesn’t get enough blood, causing the bone to die.

Legionnaire’s disease is an acute infection caused by Legionella bacteria.

A leiomyosarcoma is a rare cancerous of the smooth muscle cells. It is most often found in the uterus or abdomen.

Leishmaniasis is a parasitic disease spread by the bite of the sandfly.

The lepromin skin test is used to determine what type of leprosy a person has.

Leprosy is an infectious disease that has been known since biblical times. It is characterized by disfiguring skin sores, nerve damage, and progressive debilitation.

Leptospirosis is a rare and severe bacterial infection that occurs when people are exposed to certain environments.

Lesch-Nyhan syndrome is an inheritable disorder that affects how the body builds and breaks down purines. Purines are a normal part of human tissue and help make up the body’s genetic blueprint. They are also found in many different foods.

Leucine aminopeptidase is a protein, called an , that is normally found in liver cells. Serum leucine aminopeptidase is a test that measures how much of this protein is in your blood. Your urine can also be checked for this protein. See:

Leucine aminopeptidase is a protein, called an , that is normally found in liver cells. This article discusses the test to measure how much of this protein appears in your urine. Your blood can also be checked for this protein. See also:

Leukemia is a group of cancers that begins in the blood forming cells of the bone marrow. The term “leukemia” literally means “white blood.” White blood cells (leukocytes) are used by the body to fight off infections and other foreign substances. They are made in the bone ...

A leukemoid reaction is an increase in white blood cell count similar to what occurs in people with . However, the reaction is actually due to an infection or another disease and is not a sign of cancer.

Leukocyte alkaline phosphatase is a test that tells how much of a protein called alkaline phosphatase (ALP) you have inside your white blood cells. Leukocyte means white blood cell. See also:

Leukocyte esterase is a urine test to look for white blood cells and other signs associated with infection.

Leukoplakia is a precancerous sore (lesion) that develops on the tongue or the inside of the cheek in response to irritation. Occasionally, leukoplakia patches develop on the external female genitals.

A Leydig cell tumor is a of the testicle. It develops from Leydig cells — the cells in the testicles that release the male hormone, .

The LH blood test measures the amount of luteinizing hormone (LH). LH is a hormone released by the . In women, an increase in LH levels at mid-cycle causes ovulation. In men, LH stimulates production of .

LH response to GnRH is a blood test to indirectly determine the pituitary gland’s ability to appropriately respond to gonadotropin releasing hormone (GnRH), a hormone produced in the .

An LH urine test detects a rise in lutenizing hormone (LH). Such a rise, or surge, signals the ovary to release the egg. This at-home test is often used by women to help predict ovulation.

Lichen planus is a disease in which there is an itchy on the skin or in the mouth.

Lichen simplex chronicus is a skin disorder that leads to itching and scratching.

Lichenified means the skin has become thickened and leathery. This often results from continuous rubbing or scratching on an area of skin. Chronic irritation due to conditions such as can cause lichenified skin.

Lighter fluid is a flammable liquid found in cigarette lighters and other types of lighters. Lighter fluid poisoning occurs when someone swallows this substance. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you ...

Lily of the valley is a flowering plant. Lily of the valley poisoning occurs when someone eats parts of this plant. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you should call your local emergency number (such ...

Limb plethysmography is a test that compares blood pressure in the legs and arms.

Limb-girdle muscular dystrophies include at least 18 different inherited disorders, which first affect the muscles around the shoulder girdle and hips. These diseases get worse, and may eventually involve other muscles.

Limited range of motion is a reduction in the normal distance and direction through which a joint can move.

This poisoning results from eating or swallowing lip moisturizers containing para-aminobenzoic acid. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you should call your local emergency number (such as 911) or the ...

Lipase is a protein () released by the pancreas into the small intestines. It triggers the breakdown of fat into fatty acids. This article discusses the test to measures the amount of the lipase in the blood.

Lipofuscin is a brownish pigment left over from the breakdown and absorption of damaged blood cells. Lipofuscin is found in heart muscle and smooth muscles and is also called the aging pigment.

Lipoproteins are molecules made of and fat. They carry cholesterol and similar substances through the blood. A blood test can be done to measure a specific type of lipoprotein called lipoprotein-a, or Lp(a). Lp(a) is considered a risk factor for heart disease.

Liposuction is the removal of excess body fat by suction using special surgical equipment. A plastic surgeon typically does the surgery.

Liquid nitrogen is a chemical that is super cold, about -200 degrees Celsius. Liquid nitrogen will instantly freeze anything it touches. It is used to kill cells that make up diseased or cancerous tissue. Tissue that has been frozen dries out and falls off.

Listeriosis is a dangerous infection caused by eating food contaminated with bacteria called Listeria monocytogenes (L. monocytogenes).

Lithium is a medication used to treat bipolar disorder (manic depression). This article focuses on lithium overdose, or toxicity. Acute toxicity occurs when you intentionally or accidentally swallow too much of a lithium prescription. Chronic toxicity occurs when you slowly take a little too much of ...

Lithotripsy is a medical procedure that uses shock waves to break up stones in the kidney, bladder, or ureter (tube that carries urine from your kidneys to your bladder). After the procedure, the tiny pieces of stones pass out of your body in your urine.

A liver is a test that takes a sample of tissue from the liver for examination.

The term “liver disease” applies to many diseases and disorders that cause the liver to function improperly or stop functioning. Abdominal pain, yellowing of the skin or eyes (), or abnormal results of suggest you have liver disease. See also:

Common tests that are used to evaluate how well the liver is working (liver function) include: Please see individual tests for details on how each is performed.

Liver metastases are cancerous tumors that have spread to the liver from somewhere else in the body. See also:

A liver scan uses a radioactive material to help determine how well the liver or spleen is working.

Liver spots are flat, brown-black spots that usually appear on the skin in sun-exposed areas of the body. They have nothing to do with the liver or liver function.

Liver transplant is surgery to replace a diseased liver with a healthy liver.

Lomotil is a prescription medicine used to treat diarrhea. Lomotil occurs when someone accidentally or intentionally takes more than the normal or recommended amount of this medication. This is for information only and not for use in the treatment or management of an actual poison exposure. If ...

Long bones are hard, dense bones that provide strength, structure, and mobility. The femur (thigh bone) is a long bone. A long bone has a shaft and two ends. There are also bones in the fingers that are classified as “long bones,” even though they are short in length. This is due to ...

Lordosis is an increased curving of the spine.

Low back pain refers to a shooting or stabbing pain felt in your lower back. You may also have back stiffness, decreased movement of the lower back, and difficulty standing straight. Acute back pain lasts from a few days to a few weeks. See also:

Back pain is one of the most common health complaints. Almost everyone will have back pain at some time in their life. Most of the time, the exact cause of the pain cannot be found. This article discusses long-term (chronic) low back pain. For information on other types of low back pain that occur ...

A low nasal bridge is a flattening of the top part of the nose.

A lower esophageal ring is an abnormal ring of tissue that forms where the esophagus (the tube from the mouth to the stomach) and stomach meet.

Ludwig’s angina is a bacterial infection of the floor of the mouth.

A lumbar magnetic resonance imaging (MRI) scan is a noninvasive way to create detailed pictures of the part of the spine that runs through the lower back. This area is called the lumbar spine. It consists of five vertebrae called L1 to L5. Unlike and computed tomographic () scans, which use ...

A computed tomography (CT) scan of the lumbar spine is an imaging method that uses x-rays to create cross-sectional pictures of the lower back (lumbar spine).

A lumbosacral spine CT is a scan of the lower spine and surrounding tissues.

A lumbosacral spine is a picture of the small bones (vertebrae) in the lower part of the spine (the lumbar region) and the sacrum, the area that connects the spine to the pelvis.

A lump in the abdomen is a soft bulge of tissue or a small, local area of swelling in the belly area. See also:

There are many causes for lumps in the breast. These range from normal changes in your body to abnormal breast disease. Breast lumps are either (noncancerous) or (cancerous). See also: Breast lumps and cancer

Lung cancer is cancer that starts in the lungs. The lungs are located in the chest. They help you breathe. When you breathe, air goes through your nose, down your windpipe (trachea), and into the lungs, where it spreads through tubes called bronchi. Most lung cancer begins in the cells that line ...

Non-small cell lung cancer (NSCLC) is the most common type of . It usually grows and spreads more slowly than . There are three forms of NSCLC: Adenocarcinomas are often found in an outer area of the lung. Squamous cell carcinomas are usually found in the center of the lung by an air tube ...

Small cell lung cancer (SCLC) is a fast-growing type of . It spreads much more quickly than . There are three different types of small cell lung cancer: Small cell carcinoma (oat cell cancer) Mixed small cell/large cell carcinoma Combined small cell carcinoma Most small cell lung cancers are the ...

Lung diffusion testing measures how well the lungs exchange gases. This is an important part of lung testing, because the major function of the lungs is to allow oxygen to “diffuse” or pass into the blood from the lungs, and to allow carbon dioxide to “diffuse” from the blood ...

Lung disease is any disease or disorder that occurs in the lungs or that causes the lungs to not work properly. There are three main types of lung disease: Airway diseases — These diseases affect the tubes (airways) that carry oxygen and other gases into and out of the lungs. These diseases ...

Lung gallium scan is a type of that uses radioactive gallium (Ga) to identify swelling (inflammation) in the lungs.

A lung needle biopsy is a method to remove a piece of lung tissue for examination. If it is done through the wall of your chest, it is called a transthoracic lung biopsy.

A lung positron emission tomography (PET) scan is an imaging test that uses a radioactive substance (called a tracer) to look for disease in the lungs, especially . Unlike magnetic resonance imaging () and computed tomography () scans, which reveal the structure of the lungs, a PET scan shows how ...

Lung plethysmography is a test used to measure how much air you can hold in your lungs. See also:

Volcanic smog (vog) is created when sulfur dioxide and other gases released from a volcano react with oxygen, moisture, dust, and sunlight in the atmosphere. Volcanic smog can irritate the lungs and worsen existing lung problems.

Lung surgery is surgery to repair or remove lung tissue. Several common lung surgeries are: Lobectomy, to remove one or more lobes of a lung Wedge resection, to remove part of a lobe in a lung Pneumonectomy, to remove a lung Surgery to remove an infection or blood in the chest cavity Surgery to ...

Lung transplant is surgery to replace one or both diseased lungs with healthy lungs from a human donor.

Lupus anticoagulants are antibodies against phospholipids (substances in the lining of cells) that prevent blood clotting in a test tube. Persons with these antibodies may have an abnormally high risk of blood clotting. See also:

Lupus nephritis is a kidney disorder that is a complication of .

Lyme disease is an inflammatory disease spread through a tick bite. This article offers a general overview on Lyme disease. For specific information, see: Lyme disease – primary Lyme disease – early disseminated

Chronic persistent Lyme disease is a late stage of an inflammatory disease caused by Borrelia burgdorferi bacteria. It is also called Stage 3, or tertiary, Lyme disease. See also: Lyme disease – early disseminated Lyme disease – primary

Lyme disease antibody tests are used to help diagnose .

A lymph node biopsy is the removal of lymph node tissue for examination under a microscope. The lymph nodes are small glands that make white blood cells (lymphocytes), which fight infection. Lymph nodes may trap the germs that are causing an infection. Cancer can spread to lymph nodes.

Lymph node culture is a laboratory test performed on a lymph node to identify microorganisms (bacteria, viruses, and fungi) that cause infection and lymph node swelling.

The lymph system is a network of organs, lymph nodes, lymph ducts, and lymph vessels that produce and transport lymph from tissues to the bloodstream. The lymph system is a major component of the body’s immune system.

Lymphadenitis is an infection of the (also called lymph glands). It is a common complication of certain bacterial infections.

A lymphangiogram is a special x-ray of the lymph nodes and lymph vessels. Lymph nodes produce white blood cells (lymphocytes) that help fight infections. The lymph nodes also filter and trap cells. The lymph nodes and vessels are not usually seen on a normal , so a dye or radioisotope ...

Lymphangitis is an infection of the lymph vessels (channels). It is a common complication of certain bacterial infections. See also:

Lymphatic obstruction is a blockage of the lymph vessels that drain fluid from tissues throughout the body and allow immune cells to travel where they are needed. Lymphatic obstruction may cause lymphedema, which means swelling due to a blockage of the lymph passages.

Lymphofollicular hyperplasia is an increase in the size of the lymph node follicles. These follicles contain normal white blood cells called lymphocytes. Your body produces more lymphocytes to help the lymph nodes prevent bacteria, viruses, and other types of germs from entering the bloodstream. ...

Lymphogranuloma venereum (LGV) is a sexually transmitted bacterial infection.

Lymphoid hyperplasia is a rapid increase in the number of normal cells (called lymphocytes) that are contained in lymph nodes. These cells increase in number to help lymph nodes prevent bacteria, viruses, and other types of germs from entering the bloodstream.