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Glossaries - D

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

Danaparoid (DAN-uh-puh-roid)

generic name for a naturally occurring heparinoid antithrombotic agent (Orgaran, Organon International) indicated in the prevention of deep vein thrombosis and sometimes used in the treatment of HAT type II.

Deep Vein Thrombosis (DVT)

the formation of a thrombus in the deep veins of the leg; associated with a high risk of pulmonary embolism.

Delayed Gastric Emptying (dee-LAYD GA-strik EM-tee-ing)

Dendritic cell

immune cell with threadlike tentacles called dendrites used to enmesh antigen, which they present to T cells. Langerhans cells, found in the skin, and follicular dendritic cells, found in lymphoid tissues, are both types of dendritic cells. (See also antigen-presenting cell.)

Dermatitis Herpetiformis (dur-muh-TY-tis hur-PEH-tee-for-mis)

A skin disorder associated with celiac disease. See also Celiac Disease.

Descending Colon (dee-SEND-ing KOH-lun)

The part of the colon where stool is stored. Located on the left side of the abdomen.

Diabetes mellitus


A method to reduce or stop a response such as an allergic reaction to something. For instance, if a person with diabetes has a bad reaction to taking a full dose of beef insulin, the doctor gives the person a very small amount of the insulin at first. Over a period of time, larger doses are given until the person is taking the full dose. This is one way to help the body get used to the full dose and to avoid having the allergic reaction.

Diabetes insipidus

A disease of the pituitary gland or kidney, not diabetes mellitus. Diabetes insipidus is often called "water diabetes" to set it apart from "sugar diabetes." The cause and treatment are not the same as for diabetes mellitus. "Water diabetes" has diabetes in its name because most people who have it show most of the same signs as someone with diabetes mellitus -they have to urinate often, get very thirsty and hungry, and feel weak. However, they do not have glucose (sugar) in their urine.

Diabetes mellitus

A disease that occurs when the body is not able to use sugar as it should. The body needs sugar for growth and energy for daily activities. It gets sugar when it changes food into glucose (a form of sugar). A hormone called insulin is needed for the glucose to be taken up and used by the body. Diabetes occurs when the body cannot make use of the glucose in the blood for energy because either the pancreas is not able to make enough insulin or the insulin that is available is not effective. The beta cells in areas of the pancreas called the islets of Langerhans usually make insulin.

There are two main types of diabetes mellitus: insulin-dependent (Type I) and noninsulin-dependent (Type II). In insulin-dependent diabetes (IDDM), the pancreas makes little or no insulin because the insulin-producing beta cells have been destroyed. This type usually appears suddenly and most commonly in younger people under age 30. Treatment consists of daily insulin injections or use of an insulin pump, a planned diet and regular exercise, and daily self- monitoring of blood glucose.

In noninsulin-dependent diabetes (NIDDM), the pancreas makes some insulin, sometimes too much. The insulin, however, is not effective (see Insulin Resistance). NIDDM is controlled by diet and exercise and daily monitoring of glucose levels. Sometimes oral drugs that lower blood glucose levels or insulin injections are needed. This type of diabetes usually develops gradually, most often in people over 40 years of age. NIDDM accounts for 90 to 95 percent of diabetes.

The signs of diabetes include having to urinate often, losing weight, getting very thirsty, and being hungry all the time. Other signs are blurred vision, itching, and slow healing of sores. People with untreated or undiagnosed diabetes are thirsty and have to urinate often because glucose builds to a high level in the bloodstream and the kidneys are working hard to flush out the extra amount. People with untreated diabetes often get hungry and tired because the body is not able to use food the way it should.

In insulin-dependent diabetes, if the level of insulin is too low for a long period of time, the body begins to break down its stores of fat for energy. This causes the body to release acids (ketones) into the blood. The result is called ketoacidosis, a severe condition that may put a person into a coma if not treated right away.

The causes of diabetes are not known. Scientists think that insulin- dependent diabetes may be more than one disease and may have many causes. They are looking at hereditary (whether or not the person has parents or other family members with the disease) and at factors both inside and outside the body, including viruses.

Noninsulin-dependent diabetes appears to be closely associated with obesity and with the body resisting the action of insulin.

Diabetic Retinopathy

A disease of the small blood vessels of the retina of the eye. When retinopathy first starts, the tiny blood vessels in the retina become swollen, and they leak a little fluid into the center of the retina. The person's sight may be blurred. This condition is called background retinopathy. About 80 percent of people with background retinopathy never have serious vision problems, and the disease never goes beyond this first stage.

However, if retinopathy progresses, the harm to sight can be more serious. Many new, tiny blood vessels grow out and across the eye. This is called neovascularization. The vessels may break and bleed into the clear gel that fills the center of the eye, blocking vision. Scar tissue may also form near the retina, pulling it away from the back of the eye. This stage is called proliferative retinopathy, and it can lead to impaired vision and even blindness. See also: Photocoagulation or vitrectomy for treatments.


A method for removing waste such as urea from the blood when the kidneys can no longer do the job. The two types of dialysis are: hemodialysis and peritoneal dialysis. In hemodialysis, the patient's blood is passed through a tube into a machine that filters out waste products. The cleansed blood is then returned to the body.

In peritoneal dialysis, a special solution is run through a tube into the peritoneum, a thin tissue that lines the cavity of the abdomen. The body's waste products are removed through the tube. There are three types of peritoneal dialysis. Continuous ambulatory peritoneal dialysis (CAPD), the most common type, needs no machine and can be done at home. Continuous cyclic peritoneal dialysis (CCPD) uses a machine and is usually performed at night when the person is sleeping. Intermittent peritoneal dialysis (IPD) uses the same type of machine as CCPD, but is usually done in the hospital because treatment takes longer. Hemodialysis and peritoneal dialysis may be used to treat people with diabetes who have kidney failure.

Diaphragm (DY-uh-fram)

The muscle wall between the chest and the abdomen. It is the major muscle that the body uses for breathing.

Diarrhea (DY-uh-REE-uh)

Frequent, loose, and watery bowel movements. Common causes include gastrointestinal infections, irritable bowel syndrome, medicines, and malabsorption.

Diastolic Blood Pressure

Diathesis (di-ATH-e-sis)

a constitution or condition of the body which makes the tissues react in special ways to certain extrinsic stimuli and thus tends to make the person unusually susceptible to certain diseases.

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Digestants (dy-JES-tants)

Medicines that aid or stimulate digestion. An example is a digestive enzyme such as Lactaid for people with lactase deficiency.

Digestive System

Digestive System (dy-JES-tuv sis-tum)

The organs in the body that break down and absorb food. Organs that make up the digestive system are the mouth, esophagus, stomach, small intestine, large intestine, rectum, and anus. Organs that help with digestion but are not part of the digestive tract are the tongue, glands in the mouth that make saliva, pancreas, liver, and gallbladder.

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Digestive Tract (dy-JES-tuv trakt)


A drug that is given by injection to treat cluster headaches. It is a form of the antimigraine drug ergotamine tartrate.

Direct Thrombin Inhibitor

an agent that inactivates thrombin by binding directly to it.

Distention (dis-TEN-shun)

Bloating or swelling of the abdomen.



A drug that increases the production of urine.


Diverticula (dy-vur-TIK-yoo-lah)

Plural form of diverticulum. See Diverticulum.


Diverticulitis (dy-vur-tik-yoo-LY-tis)

A condition that occurs when small pouches in the colon (diverticula) become infected or irritated. Also called left-sided appendicitis.

Although the diverticula themselves do not cause symptoms, complications such as bleeding and infection may occur. Bleeding is an uncommon symptom and is usually not severe. Sometimes the pouches become infected and inflamed, a more serious condition known as diverticulitis.

When inflammation is present, there may be fever and an increased white blood cell count, as well as acute abdominal pain. Diverticulitis also may result in large abscesses (infected areas of pus), bowel blockage, or breaks and leaks through the bowel wall.


Diverticulosis (dy-vur-tik-yoo-LOH-sis)

A condition that occurs when small pouches (diverticula) push outward through weak spots in the colon.

Diverticulosis is a condition in which outpouchings form in the walls of the intestines. These pouches, known as diverticula, are about the size of large peas. They form in weakened areas of the bowels, most often in the lower part of the colon (large intestine).

Most people with diverticula do not have any symptoms from them. They may never know they have the condition. Some people feel tenderness over the affected area or muscle spasms in the abdomen. Pain may be felt on the lower left side of the abdomen or, less often, in the middle or on the right side.


Diverticulum (dy-vur-TIK-yoo-lum)

A small pouch in the colon. These pouches are not painful or harmful unless they become infected or irritated.


DNA (Deoxyribonucleic Acid)

A chemical substance in plant and animal cells that tells the cells what to do and when to do it. DNA is the information about what each person inherits from his or her parents.

the double-stranded, helical molecular chain found within the nucleus of each cell. DNA carries the genetic information that encodes proteins and enables cells to reproduce and perform their functions.


pertaining to the back.

Dose-ranging study

a clinical trial in which two or more doses (starting at a lower dose and proceeding to higher doses) of a vaccine are tested against each other to determine which dose works best and has acceptable side effects.

Dose-response relationship

the relationship between the dose of a vaccine and an immune or physiologic response. In vaccine research, a dose-response effect means that as the dose of the vaccine increases, so does the level of the immune response (antibodies and CTL activity).

Double-blinded, Double-blind study

A doubled-blinded trial is a clinical trial in which neither the medical staff nor the patient knows if the patient is receiving the investigational drug or the placebo.

a clinical trial in which neither the study staff nor the participants know which participants are receiving the experimental vaccine and which are receiving a placebo or another therapy. Double-blind trials are thought to produce objective results, since the researcher's and volunteers expectations about the experimental vaccine do not affect the outcome.

Dry Mouth

Dubin-Johnson Syndrome (DOO-bun JAWN-sun sin-drohm)

An inherited form of chronic jaundice (yellow tint to the skin and eyes) that has no known cause.

Dumping Syndrome (DUM-peeng sin-drohm)

A condition that occurs when food moves too fast from the stomach into the small intestine. Symptoms are nausea, pain, weakness, and sweating. This syndrome most often affects people who have had stomach operations. Also called rapid gastric emptying.

Duodenal Ulcer (doo-AW-duh-nul UL-sur)

An ulcer in the lining of the first part of the small intestine (duodenum).

Small Duodenitis (doo-AW-duh-NY-tis)

An irritation of the first part of the small intestine (duodenum).

Duodenum (doo-AW-duh-num)

The first part of the small intestine.

Dysentery (DIS-un-tair-ee)

An infectious disease of the colon. Symptoms include bloody, mucus-filled diarrhea; abdominal pain; fever; and loss of fluids from the body.

Dysphoria (DIS-for-e-uh)

Excessive pain, anguish, agitation, disquiet, restlessness or malaise (extreme fatigue).

Dyspepsia (dis-PEP-see-uh)

Dysphagia (dis-FAY-jee-uh)

Problems in swallowing food or liquid, usually caused by blockage or injury to the esophagus.


Abnormal changes in the way tissue cells look under a microscope.

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