shunt An abnormal or surgically created
passage between two normally uncon-
nected body parts.
Shy-Drager syndrome A rare degener-
ative disorder of unknown cause that
progressively damages the
It begins gradually at
age 60-70 and is more common in men.
Symptoms include dizziness and fainting
due to postural
continence, impotence, reduced ability to
eventually leads to disability, and some-
times premature death. There is no cure
or means of slowing degeneration, but
many symptoms are relieved by drugs.
SIADH The abbreviation for syndrome of
inappropriate antidiuretic hormone (se-
cretion), associated with certain lung or
brain disorders and some types of cancer.
Siamese twins See
sibling rivalry A term that describes
the intense competition that sometimes
occurs between siblings.
sibutramine A centrally acting
drug used to treat obesity
in people who have not responded to
other methods of weight loss, such as
dieting. Common side effects include
constipation, dry mouth, and
People taking this drug should
have regular follow-ups and have their
blood pressure and pulse monitored.
sick building syndrome A collection
of symptoms reported by some workers
in office buildings. Symptoms include
loss of energy, headaches, and dry, itch-
ing eyes, nose, and throat. The cause is
unknown, but various factors are invol-
ved, including air conditioning, passive
smoking, lack of natural ventilation and
light, and psychological factors.
sickle cell anaemia An inherited blood
disease in which the red blood cells con-
tain haemoglobin S, an abnormal type of
. This crystallizes in the cap-
illaries, making red cells sickle-shaped
and fragile, and leading to haemolytic
. The abnormal cells are unable
to pass easily through tiny blood vessels.
The blood supply to organs is blocked
intermittently, causing sickle cell crises.
The disease affects mainly black people.
Symptoms usually appear after age
months, often beginning with painful
swelling of the hands and feet. Chronic
headaches, shortness of breath on exer-
tion, pallor, and
. Sickle cell
crises start suddenly; they are sometimes
brought on by an infection, cold wea-
ther, or dehydration, but may also occur
for no apparent reason. The sufferer may
bones), blood in the urine (from kidney
damage) or damage to the lungs or intes-
tines. If the brain is affected,
, or unconsciousness may result.
In some affected children, the
enlarges and traps red cells at a particu-
larly high rate, causing a life-threatening
form of anaemia. After adolescence, the
spleen usually stops functioning, increas-
ing the risk of infection in those affected.
Diagnosis is made from examination of
a blood smear and
portive treatment may include
nization to protect against infection.
Life-threatening crises are treated with
the crisis still does not respond, an
may be per-
formed. This may be done regularly for
people who suffer frequent severe crises.
sick sinus syndrome Abnormal func-
tion of the heart's
leads to episodes of
heart-rate), alternating bradycardia and
(fast heart-rate), or very short
. The cause is
coronary artery disease
, but may
include lightheadedness, fainting, and
palpitations. The diagnosis is confirmed
by a 24-hour
is usually by
the fitting of an artificial
side effect A reaction or consequence of
medication or therapy that is additional
to the desired effect. The term usually
refers to an unwanted or adverse effect,
usually following a normal dose, rather
than the toxic effects, of a
siderosis Any of a variety of conditions
in which there is too much iron in the
body. (See also
SIDS An abbreviation for