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Glossaries - L

We've defined thousands of terms related to health care. This page discusses glossary terms with the letter L.

Lactase (LAK-tayss)

An enzyme in the small intestine needed to digest milk sugar (lactose).

Lactic Acid

An acid produced during the fermentation of milk sugar (LACTOSE). To make cheese and yogurt, to sour cabbage into sauerkraut, even to leaven sourdough bread, food processors capitalize on the lactic-acid-forming capabilities of certain BACTERIA (lactobacilli) to break down a variety of different sugars, among them lactose, sucrose (table sugar), GLUCOSE and variety of different sugars, among them lactose, sucrose (table sugar), MALTOSE.

Lactase Deficiency (LAK-tayss duh-FISH-en-see)

Lack of the lactase enzyme. Causes lactose intolerance.


A type of sugar found in milk and milk products (cheese, butter, etc.). It is considered a nutritive sweetener because it has calories.

Lactose Intolerance (LAK-tohss in-TAH-luh-runs)

Being unable to digest lactose, the sugar in milk. This condition occurs because the body does not produce the lactase enzyme.

Lactose Tolerance Test (LAK-tohss TAH-luh-runs test)

A test for lactase deficiency. The patient drinks a liquid that contains milk sugar. Then the patient's blood is tested; the test measures the amount of milk sugar in the blood.

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Laparoscope (LAP-uh-ruh-skohp)

A thin tube with a tiny video camera attached. Used to look inside the body and see the surface of organs. See also Endoscope.

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Laparoscopic Cholecystectomy (LAP-uh-ruh-SKAWP-ik KOH-luh-sis-TEK-tuh-mee)

An operation to remove the gallbladder. The doctor inserts a laparoscope (see above) and other surgical instruments through small holes in the abdomen. The camera allows the doctor to see the gallbladder on a television screen. The doctor removes the gallbladder through the holes.


Laparoscopy (LAP-uh RAW-skuh-pee)

A test that uses a laparoscope to look at and take tissue from the inside of the body.

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Laparotomy (LAP-uh-RAW-tuh-mee)

An operation that opens up the abdomen.

Large intestine

Large Intestine (LARJ in-TES-tin)

The part of the intestine that goes from the cecum to the rectum. The large intestine absorbs water from stool and changes it from a liquid to a solid form. The large intestine is 5 feet long and includes the appendix, cecum, colon, and rectum. Also called colon.

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Lavage (lah-VAJ)

A cleaning of the stomach and colon. Uses a special drink and enemas. See also Bowel Prep.

Laxatives (LAK-suh-tivz)

Medicines to relieve long-term constipation. Used only if other methods fail. Also called cathartics.

Lazy Colon (LAY-zee KOH-lun)

Lepirudin (leh-puh-ROO-din)

Generic name for a recombinant hirudin. Chemical designation: [Leu1, Thr2]-63- desulfohirudin. Trade name: Refludan.

Levator Syndrome (luh-VAY-tur sin-drohm)

Feeling of fullness in the anus and rectum with occasional pain. Caused by muscle spasms.


Stretchy bands of cordlike tissue that connect bone to bone.


A term for fat. The body stores fat as energy for future use just like a car that has a reserve fuel tank. When the body needs energy, it can break down the lipids into fatty acids and burn them like glucose (sugar).

Lithotripsy, Extracorporeal Shock Wave (ESWL) (LITH-uh-trip-see, EK-struh-cor-POH-ree-ul SHAHK wayv)

A method of breaking up bile stones and gallstones. Uses a specialized tool and shock waves.

Liver (LIH-vur)

The largest organ in the body. The liver carries out many important functions, such as making bile, changing food into energy, and cleaning alcohol and poisons from the blood.

Liver Enzyme Tests (LIH-vur EN-zym tests)

Blood tests that look at how well the liver and biliary system are working. Also called liver function tests. Also called liver function tests.

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Low Molecular Weight Heparin (LMWH)

Parenteral anticoagulants prepared by depolymerization of standard heparin to form molecules with an average of one third the molecular weight of heparin. Low molecular weight heparins have relatively more anti-Xa activity and a more predictable anticoagulant response than heparin.

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Lower Esophageal Ring (LOH-wur uh-saw-fuh-JEE-ul Ring)

An abnormal ring of tissue that may partially block the lower esophagus. Also called Schatzki's ring.

Lower Esophageal Sphincter

Lower Esophageal Sphincter (LOH-wur uh-saw-fuh-JEE-ul SFEENK-tur)

The muscle between the esophagus and stomach. When a person swallows, this muscle relaxes to let food pass from the esophagus to the stomach. It stays closed at other times to keep stomach contents from flowing back into the esophagus.

Lower GI Series (LOH-wur jee-eye SEER-eez)

X-rays of the rectum, colon, and lower part of the small intestine. A barium enema is given first. Barium coats the organs so they will show up on the x-ray. Also called barium enema x-ray.


a type of white blood cell produced in the lymphoid organs that is primarily responsible for immune responses. Present in the blood, lymph and lymphoid tissues. (See also B cell and T cell).

Lymphoid tissue

tonsils, adenoids, lymph nodes, spleen and other tissues that act as the body's filtering system, trapping invading microorganisms and presenting them to squadrons of immune cells that congregate there.

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