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Glossaries - E

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

ECL Cell (Enterochromaffin-like Cell)

A histamine-secreting endocrine cell of the stomach.

Edema (eh-DEE-mah)

excess fluid buid up in cells or tissue.


in drug research, the ability of a drug to produce a desired clinical effect, such as protection against a specific infection, at the optimal dosage and schedule in a given population. A drug may be tested for efficacy in Phase 3 trials if it appears to be safe and shows some promise in smaller Phase 1 and Phase 2 trials.

Electrocoagulation (ee-LEK-troh-koh-ag-yoo-LAY-shun)

A procedure that uses an electrical current passed through an endoscope to stop bleeding in the digestive tract and to remove affected tissue.

Electroencephalogram (EEG)

A technique for recording electrical activity in the brain.

Electrolytes (ee-LEK-troh-lyts)

Chemicals such as salts and minerals needed for various functions in the body.

Elimination half-life

the time it takes for the body to eliminate or breakdown half of a dose of a pharmacologic agen.

ELISA (enzyme-linked immunoabsorbent assay) (EN-zym linkt IM-yoo-nohSOR-bent ASS-ay)

a blood test that detects antibodies to viruses (eg, HIV) or bacteria (eg,Helicobacter pylori ) based on a reaction that leads to a detectable color change in the test tube. The HIV ELISA is commonly used as the initial screening test because it is relatively easy and inexpensive to perform. Because the HIV ELISA is designed for optimal sensitivity -- that is, it detects all persons with HIV antibodies as well as some who don't have them (false positives) -- a positive HIV ELISA test must be confirmed by a second, more specific test such as an HIV Western Blot.

Embolism (EM-buh-liz-em)

the sudden blocking of an artery by a clot or foreign material that has been brought to the site by the blood flow.

Embolus (EM-buh-lus)

a mass of clotted blood or other material brought by the blood from another vessel and forced into a smaller one, thus obstructing the circulation.

Emetogenic (eh-MET-oh-gen-ik)

induces vomiting.


based on experience or observational information and not necessarily on proven scientific data. In the past, vaccine trials have been performed based exclusively on empirical data and without a full understanding of the disease processes or correlates of immunity.


a suspension of droplets of one liquid in another liquid (such as oil and water). The two liquids do not actually combine but are instead suspended within one another.

Encopresis (en-koh-PREE-sis)

Accidental passage of a bowel movement. A common disorder in children.

Endocrine glands

Glands that release hormones into the bloodstream. They affect how the body uses food (metabolism). They also influence other body functions. One endocrine gland is the pancreas. It releases insulin so the body can use sugar for energy.


A doctor who treats people who have problems with their endocrine glands. Diabetes is an endocrine disorder. See also: Endocrine glands.


Grown or made inside the body. Insulin made by a person's own pancreas is endogenous insulin. Insulin that is made from beef or pork pancreas or derived from bacteria is exogenous because it comes from outside the body and must be injected.

Endometrium (en-doh-MEE-tree-um)

the inner mucous membrane of the uterus.

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Naturally occurring painkilling chemicals. Substances produced in the brain or nervous system that stops pain naturally.

Some scientists theorize that people who suffer from severe headache have lower levels of endorphins than people who are generally pain free.


Endoscope (EN-doh-skohp)

A small, flexible tube with a light and a lens on the end. It is used to look into the esophagus, stomach, duodenum, colon, or rectum. It can also be used to take tissue from the body for testing or to take color photographs of the inside of the body. Colonoscopes and sigmoidoscopes are types of endoscopes.

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Endoscopic Papillotomy (en-doh-SKAW-pik pah-pih-LAW-tuh-mee)

Endoscopic Retrograde Cholangiopancreatography (ERCP) (en-doh-SKAW-pik REH-troh-grayd koh-LAN-jee-oh-PANG-kree-uh-TAW-gruh-fee)

A test using an x-ray to look into the bile and pancreatic ducts. The doctor inserts an endoscope through the mouth into the duodenum and bile ducts. Dye is sent through the tube into the ducts. The dye makes the ducts show up on an x-ray.

Endoscopic Sphincterotomy (en-doh-SKAW-pik sfeenk-tuh-RAW-tuh-mee)

An operation to cut the muscle between the common bile duct and the pancreatic duct. The operation uses a catheter and a wire to remove gallstones or other blockages. Also called endoscopic papillotomy.

Endoscopy (en-DAW-skuh-pee)

A procedure that uses an endoscope to diagnose or treat a condition.


the results of an intervention such as vaccination compared among different study groups in a clinical trial. In early vaccine trials, common endpoints are safety and specific types and intensities of immune responses (neutralizing antibodies, CTL responses).

Enhancing antibody

a type of binding antibody, detected in the test tube and formed in response to viral (eg, HIV) infection, that may enhance the ability of the virus to produce disease. Theoretically, enhancing antibodies could attach to virions and enable macrophages to engulf the viruses. However, instead of being destroyed, the engulfed virus may remain alive within the macrophage, which then can carry the virus to other parts of the body. It is currently unknown whether enhancing antibodies have any effect on the course of HIV infection. Enhancing antibodies can be thought of as the opposite of neutralizing antibodies.

Enema (EN-uh-muh)

A liquid put into the rectum to clear out the bowel or to administer drugs or food.

Enteral Nutrition (EN-tuh-rul noo-TRISH-un)

A way to provide food through a tube placed in the nose, the stomach, or the small intestine. A tube in the nose is called a nasogastric or nasoenteral tube. A tube that goes through the skin into the stomach is called a gastrostomy or percutaneous endoscopic gastrostomy (PEG). A tube into the small intestine is called a jejunostomy or percutaneous endoscopic jejunostomy (PEJ) tube. Also called tube feeding. See also Gastrostomy and Jejunostomy.

Enteritis (en-tuh-RY-tis)

An irritation of the small intestine.

Enterocele (EN-tuh-roh-seel)

A hernia in the intestine.

Enteroscopy (en-tuh-RAW-skuh-pee)

An examination of the small intestine with an endoscope. The endoscope is inserted through the mouth and stomach into the small intestine.

Enterostomy (en-tuh-RAW-stuh-mee)

An ostomy, or opening, into the intestine through the abdominal wall.

Enzyme (EN-zime)

a protein produced by cells to accelerate a specific chemical reaction without itself being altered. Enzymes are generally named by adding the ending "-ase" to the name of the substance on which the enzyme acts (for example, protease is an enzyme that acts on proteins). (see catalyze).

Enzyme cofactors

Many enzymes require the presence of an additional, nonprotein, cofactor.

Some of these are metal ions such as Zn2+ (the cofactor for carbonic anhydrase), Cu2+, Mn2+, K+, and Na+.

Some cofactors are small organic molecules called coenzymes. The B vitamins thiamine (B1), riboflavin (B2) and nicotinamide are precursors of coenzymes.

Eosinophilic Gastroenteritis (ee-oh-sin-oh-FIL-ik gah-stroh-en-tuh-RY-tis)

Infection and swelling of the lining of the stomach, small intestine, or large intestine. The infection is caused by white blood cells (eosinophils).


The study of a disease that deals with how many people have it, where they are, how many new cases develop, and how to control the disease.


One of the secretions of the adrenal glands. It helps the liver release glucose (sugar) and limit the release of insulin. It also makes the heart beat faster and can raise blood pressure; also called adrenalin.

Epithelial Cells (eh-puh-THEE-lee-ul selz)

One of many kinds of cells that form the epithelium and absorb nutrients. See also epithelium.

Epithelium (eh-puh-THEE-lee-um)

the cellular layer without blood vessels covering free surfaces of the body such as the skin.


a specific site on an antigen that stimulates specific immune responses, such as the production of antibodies or activation of immune cells.

Eructation (ee-ruk-TAY-shun)


Erythema Nodosum (EH-rih-THEE-muh noh-DOH-sum)

Red swellings or sores on the lower legs during flareups of Crohn's disease and ulcerative colitis. These sores show that the disease is active. They usually go away when the disease is treated. For detailed information on Crohn's disease click here.

Escherichia coli (eh-shuh-RIK-ee-uh KOH-ly)

Bacteria that cause infection and irritation of the large intestine. The bacteria are spread by unclean water, dirty cooking utensils, or undercooked meat. See also Gastroenteritis.

Esophagitis (E-sof-ah-ji-tis)

inflammation of the esophagus.

Esophageal Atresia (eh-saw-fuh-JEE-uhl uh-TREEZ-ya)

A birth defect. The esophagus lacks the opening to allow food to pass into the stomach.

Esophageal Manometry (eh-saw-fuh-JEE-ul mah-NAW-muh-tree)

A test to measure muscle tone in the esophagus.

Esophageal Reflux (eh-saw-fuh-JEE-ul REE-fluks)

See Gastroesophageal Reflux Disease. For detailed information click here.


Esophageal Stricture (eh-saw-fuh-JEE-ul STRIK-sher)

A narrowing of the esophagus often caused by acid flowing back from the stomach. This condition may require surgery.


Esophageal Ulcer (eh-saw-fuh-JEE-ul UL-sur)

A sore in the esophagus. Caused by long-term inflammation or damage from the residue of pills. The ulcer may cause chest pain.


Esophagogastroduodenoscopy (EGD) (eh-SAW-fuh-goh-GAH-stroh-doo-AW-duh-NAW-skuh-pee)

Exam of the upper digestive tract using an endoscope. See Endoscopy.

Esophagus (eh-SAW-fuh-gus)

The organ that connects the mouth to the stomach. Also called gullet.


Describes a substance that the body requires which must be obtained through diet, since the body cannot independently produce it. Many fatty acids, amino acids, minerals, and vitamins are essential.

Etiology (ee-tee-OL-oh-gee)

the science of the causes and modes of operation of disease.

Excrete (ek-SKREET)

To get rid of waste from the body.

Exfoliate (eks-FO-lee-ate)

to shed cells from the epithelium layer of the skin or mucosa


Grown or made outside the body; for instance, insulin made from pork or beef pancreas is exogenous insulin for people.

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