Facts on File Encyclopedia of Health and Medicine

• infants born to infected mothers


• people who received organ transplants before
  1992 or blood transfusions before 1987 (before
  stringent screening practices became available)


• people who work in health care and public
  safety

The most effective measures for protecting
against infectious hepatitis are diligent PERSONAL
HYGIENE(especially HAND WASHING) and vaccination.
Vaccines are available to prevent infection with
hepatitis A and hepatitis B. The hepatitis B VACCINE
also protects against hepatitis D, which requires
the hepatitis B virus to replicate. Hepatitis A and
hepatitis E infection confer lifelong immunity.
Measures to reduce the risk for noninfectious hep-
atitis center on eliminating or limiting exposure to
hepatotoxic substances including alcohol. The
herb MILK THISTLE(silymarin) helps to protect the
liver from damage and to recover from damage
that occurs. Many health experts recommend that
people who have hepatitis or have exposure to
hepatotoxins take milk thistle.
See also FOOD SAFETY; HEPATITIS PREVENTION; LIVER
CANCER; LIVER DISEASE OF ALCOHOLISM; SHORT BOWEL
SYNDROME.

hepatomegaly An enlarged LIVER. Hepatomegaly
is a symptom of numerous conditions involving
the liver. Its presence or absence has no correla-
tion to the seriousness of the underlying liver dis-
ease. Because hepatomegaly is a symptom rather
than a condition, it often resolves when the
underlying condition comes under control.
Chronic liver conditions may result in long-term
hepatomegaly.

CONDITIONS THAT CAN RESULT IN HEPATOMEGALY
AMYLOIDOSIS ANEMIA
CIRRHOSIS congestiveHEART FAILURE
HEMATOCHROMATOSIS HEPATITIS
INFECTION infectious mononucleosis
LEUKEMIA LIVER CANCER
LIVER DISEASE OF ALCOHOLISM LIVER FAILURE
REYE’S SYNDROME SARCOIDOSIS
sclerosing cholangitis STEATOHEPATITIS

See also: HEPATOTOXINS; JAUNDICE; MONONUCLEOSIS,
INFECTIOUS; PORTAL HYPERTENSION; SPLENOMEGALY.

hepatotoxins Substances that damage the LIVER.

A key role of the liver is to metabolize chemicals

that it filters from the BLOOD. In the case of med-

ications, this releases the therapeutic components

into the bloodstream and channels the waste

byproducts for appropriate elimination. Often the

chemical interactions of these metabolic processes

generate substances that poison the cells of the

liver. Most drugs affect liver function to some

degree; hundreds of them have short-term toxic

effects and dozens cause permanent liver damage.

The most common are ALCOHOL, acetaminophen,

and NONSTEROIDAL ANTI-INFLAMMATORY DRUGS

(NSAIDS). Recreational drugs such as hallucino-

genic mushrooms are especially hazardous to the

liver. Industrial chemicals such as carbon tetra-

chloride and numerous environmental pollutants

also cause the death of liver cells (hepatonecrosis).

Elevated levels of key liver enzymes in the

blood provide early indication of hepatotoxicity.

These include aspartate aminotransferase (AST),

alanine aminotransferase (ALT), and glutamate

oxaloacetate transaminase (GOT). Hepatotoxicity

may also result in symptoms similar to those of

HEPATITIS, such as JAUNDICE, NAUSEA, vomiting, and

occasionally FEVER. Damage can be fairly immedi-

ate (within days to weeks of ingestion) or manifest

months later. Regular alcohol consumption

reduces the capacity of the liver to handle toxins,

lowering the threshold at which damage occurs.

Liver function often returns to normal when

ingestion of the toxic substance ends and the liver

completes all metabolic functions related to it,

though hepatotoxic consequences can cause irre-

versible loss of liver function and even LIVER FAIL-

URE. Many substances that damage the liver also

damage the KIDNEYS. The herb MILK THISTLE, which

contains silymarin, helps protect the liver from

toxins.

See also ANALGESIC MEDICATIONS; CIRRHOSIS; HAL-

LUCINOGENS; LIVER DISEASE OF ALCOHOLISM; OVERDOSE;

POISON PREVENTION; RENAL FAILURE.

hereditary nonpolyposis colorectal cancer

(HNPCC) A form of COLORECTAL CANCERpredis-

posed by a mutation in the mlh1and msh1genes.

These genes direct DNA repair mechanisms, the

processes cells follow to correct mistakes that

occur when they replicate their DNA codes during

hereditary nonpolyposis colorectal cancer (HNPCC) 57