Dictionary

helical CAT scan See spiral CAT scan.

Helicobacter heilmannii A bacterium that infects most cats, dogs, and pigs and causes them stomach inflammation (gastritis). H. heilmannii is not usually transmitted from animals to people, but people who have been infected by H. heilmannii are known to have developed gastric and duodenal ulcers. Antibiotics can cure H. heilmannii infections. H. heilmannii is closely…

Helicobacter pylori A bacterium that causes stomach inflammation (gastritis) and ulcers in the stomach and duodenum. This bacterium is the most common cause of ulcers worldwide. H. pylori infection may be acquired from contaminated food and water or through person-to-person contact. It is common in people who live in crowded conditions with poor sanitation. This…

HELLP syndrome A combination of the breakdown of red blood cells (hemolysis; the H in the acronym), elevated liver enzymes (EL), and low platelet count (LP) occurring in pregnancy. HELLP syndrome has been considered to be a complication of preeclampsia and eclampsia (toxemia) of pregnancy, but the syndrome can also occur on its own. Common…

helper T cell See T-4 cell.

helper/supressor ratio The ratio of T-helper (T-4; cells expressing the CD4 antigen) cells to supressor (T-8; cells expressing the CD8 antigen) cells in the bloodstream. This value is used in the diagnosis and management of conditions that affect immune functioning, including HIV infection.

hemangioma A benign tumor formed by a collection of excess blood vessels. A hemangioma may be visible through the skin as a birthmark, known colloquially as a “strawberry mark.” Most hemangiomas that occur at birth disappear after a few months or years.

hemangioma, capillary A type of hemangioma that is composed almost entirely of tiny capillary vessels. Capillary hemangiomas may appear anywhere on the body but are most common on the face, scalp, back, and chest. They may be evident at birth or become noticeable several weeks later. They usually grow quickly and then remain fixed in…

hemangioma, cavernous A type of hemangioma composed of blood-filled “lakes” and channels. A cavernous henangioma is raised and red or purplish. Small cavernous hemangiomas on the surface of the body may be removed or treated by electrocoagulation. Surgery is sometimes needed.

hemangiosarcoma See angiosarcoma.

health, child See child health.

health care proxy An advance medical directive in the form of a legal document that designates another person (a proxy) to make health care decisions in case a person is rendered incapable of making his or her wishes known. The health care proxy has, in essence, the same rights to request or refuse treatment that…