young people is usually caused by
migraine. In older people, it occurs in
transient ischaemic attacks. Permanent
homonymous hemianopia is usually
caused by a stroke, but it may result
from brain damage by a tumour, injury,
or infection. Hemianopia may also be
caused by pressure on the optic nerve
from a pituitary tumour.
hemiballismusIrregular and uncon-
trollable flinging movements of the arm
and leg on 1 side of the body, caused by
disease of the basal ganglia. (See also
athetosis; chorea.)
hemicolectomyThe surgical removal
of half, or a major portion, of the colon.
(See also colectomy.)
hemiparesisMuscular weakness or par-
tial paralysisaffecting only 1 side of the
body (see hemiplegia).
hemiplegiaParalysisor weakness on 1
side of the body, caused by damage or
disease affecting the motor nerve tracts
in the opposite side of the brain. A com-
mon cause is a stroke. Others include
head injury, brain tumour, brain haemor-
rhage, encephalitis, multiple sclerosis,
complications of meningitis, or a con-
version disorder. Treatment is for the
underlying cause, and is carried out in
conjunction with physiotherapy.
Henoch–Schönlein purpuraInflam-
mation of small blood vessels, causing
leakage of blood into the skin, joints,
kidneys, and intestine. The disease is
most common in young children, and
may occur after an infection such as a
sore throat. The condition may also be
due to an abnormal allergic reaction.
The main symptom is a raised purplish
rash on the buttocks and backs of the
limbs. The joints are swollen and often
painful, and colicky abdominal pain may
occur. In some cases, there is intestinal
bleeding, leading to blood in the faeces.
The kidneys may become inflamed, resul-
ting in blood and protein in the urine.
The only treatment usually required is
bed rest and analgesic drugs. Complica-
tions may arise if kidney inflammation
persists. In severe cases, corticosteroid
drugsmay be given.
heparinAn anticoagulant drugused to
prevent and treat abnormal blood clot-
ting. Heparin is given by injection and isused as an immediate treatment for
deep vein thrombosis or for pulmonary
embolism. Newly developed “low molec-
ular weight heparins”, for example
tinzaparin, which need to be injected
once a day, are now widely used and
can be self-administered at home.
Adverse effects of heparin include rash,
aching bones, and abnormal bleeding
in different parts of the body. Long-term
use may cause osteoporosis.
hepatectomy, partialSurgical removal
of part of the liver. Surgery may be need-
ed to remove a damaged area of liver
following injury, or to treat noncancer-
ous liver tumours and hydatid disease.
Rarely, liver canceris treated in this way.
hepatectomy, totalSurgical removal of
the liver. Hepatectomy is the 1st stage
in a liver transplantoperation.
hepaticRelating to the liver.
hepatitisInflammation of the liver, with
accompanying damage to liver cells. The
condition may be acute (see hepatitis,
acute) or chronic (see hepatitis, chronic)
and have various causes. (See also hep-
atitis A; hepatitis B; hepatitis C; hepatitis
D; hepatitis E; hepatitis, viral.)
hepatitis A Also known as epidemic
hepatitis, this disorder is caused by the
hepatitis A virus, which is transmitted
to people in contaminated food or drink.
The incubation period lasts for 15–40
days, after which nausea, fever and jaun-
dicedevelop. Recovery usually occurs
within 3 weeks. Serious complications
are rare. Active immunizationprovides
the best protection against hepatitis A,
and an attack can confer immunity.
hepatitis, acute Short-term inflamma-
tion of the liver, which usually recovers
in 1–2 months. In some cases, acute
hepatitis may progress to chronic hep-
atitis (see hepatitis, chronic), but it
rarely leads to acute liver failure.
Acute hepatitis is fairly common. The
most frequent cause is infection with one
of the hepatitis viruses (see hepatitis,
viral), but it can arise as a result of other
infections such as cytomegalovirus infec-
tion or Legionnaires’ disease. It may also
occur as a result of overdose of halothane
or paracetamolor exposure to toxic
chemicals including alcohol (see liver
disease, alcoholic). Symptoms range fromHEMIBALLISMUS HEPATITIS, ACUTEH