I
DOGS, DISEASES FROM
Diverticulosis of the colon
Diverticula (pouches) are clearly visible in this
endoscopic view of the wall of the colon. The
condition is thought to be due to a low-fibre diet.
the
colon
.
Complications of diverticulo-
sis may include intestinal bleeding and
diverticulitis
.
The cause is believed to be
a lack of fibre in the diet (see
fibre,
dietary
) .
Diverticulosis is very rare in
developing countries, where high-fibre
foods make up much of the diet.
SYMPTOMS
Symptoms occur in only a m inority
of people w ho have diverticulosis. They
usually result from spasm or cramp of
the intestinal muscle near diverticula.
Many patients have symptoms similar
to
those
of
irritable bowel syndrome
,
including abdominal pain, a bloated
sensation, and changes in bowel habits.
In severe cases of diverticulosis, intesti-
nal haemorrhage can lead to bleeding
from the rectum.
TREATMENT
In people with cramps, a high-fibre
diet, fibre supplements, and
antispas-
modic drugs
may relieve the symptoms.
A high-fibre diet also reduces the inci-
dence of complications. Bleeding from
diverticula
usually
subsides
without
treatment, but surgery is an option.
diving medicine
See
scuba-diving medicine
;
decompression
sickness
.
Dixarit
A brand name for
clonidine
,
an
anti-
hypertensive drug
that is also used in the
treatment of
migraine
and, in meno-
pausal women,
hot flushes
.
dizziness
A sensation of unsteadiness and light-
headedness. Dizziness may be a mild,
brief symptom that occurs by itself, or
it may be part of a more severe, pro-
longed attack of
vertigo
(a condition
typified by a spinning sensation) with
nausea, vomiting, sweating, or fainting.
CAUSES
Most attacks are harmless and are due
to a fall in the pressure of blood to the
brain. This can occur when getting up
quickly from a sitting or lying position
(called
postural hypotension
) .
Similar
symptoms may result from a
transient
ischaemic attack,
in w hich there is a
temporary, partial blockage in the arter-
ies that supply the brain.
Other possible causes include tired-
ness, stress, fever,
anaemia
,
heart block
(impairment of electrical activity in the
heart muscle),
hypoglycaemia
(low blood
sugar levels), and
subdural haemorrhage
(bleeding between the outer two mem-
branes that cover the brain).
Dizziness as part of vertigo is usually
due to a disorder of the inner ear,
the
acoustic nerve
,
or the
brainstem
.
The
principal disorders of the inner ear
that can cause dizziness and vertigo
are
labyrinthitis
and
Meniere’s disease
.
Disorders of the acoustic nerve, such
as
acoustic neuroma
,
are rare causes of
dizziness and vertigo. Brainstem dis-
orders that can cause
dizziness and
vertigo include a type of
migraine
,
brain
tumours
,
and
vertebrobasilar insufficiency
.
TREATMENT
Brief episodes of m ild dizziness usually
clear up after taking a few deep breaths
or after resting for a short time.
Severe, prolonged, or recurrent dizzi-
ness should be investigated by a doctor.
Treatment depends on the underlying
cause. For example, certain cases of
dizziness and vertigo due to a disorder
of the inner ear are treated w ith
anti-
emetic drugs
or
antihistamine drugs
.
dizygotic twins
Nonidentical
twins
,
also called fraternal
twins. Dizygotic twins are the result of
the simultaneous
fertilization
of two egg
cells
(
ovum
) .
They each have a
placenta
of their own and may be of different
sexes. (See also
monozygotic twins
. )
DLE
Discoid
lupus erythematosus
.
DMARDs
See
disease-modifying anti-rheumatic drugs
.
DMSA scan
A type of
kidney imaging
technique (see
radionuclide scanning
).
DNA
The abbreviation for deoxyribonucleic
acid. DNA is the principal molecule
carrying genetic information in almost
all organisms; the exceptions are cer-
tain viruses that use
RNA
.
DNA is found in the
chromosomes
of
cells; its double-helix structure allows
the chromosomes to be copied exactly
during the process of cell division. A
special form of DNA exists in m ito-
chondria,
the
tiny
energy-producing
structures within cells (see
mitochondrial
DNA
) .
Sections of DNA can also be cre-
ated artificially (see
recombinant DNA
)
during genetic engineering. (See also
meiosis
;
mitosis
;
nucleic acids
. )
DNA fingerprinting
See
genetic fingerprinting
.
dobutamine
A drug that is used in the treatment of
heart failure
and
shock
,
and sometimes
after
cardiac arrest
(a halt in the pum p-
ing action of the heart). The drug may
be given by intravenous drip.
Dobutamine stimulates nerve cells in
the heart to increase the heart rate and
raise the blood pressure. For this rea-
son, the drug may be used in a
cardiac
stress test
to investigate potential
coro-
nary artery disease
in cases where the
patient is unable to exercise on a tread-
m ill (see
exercise ECG
) .
doctor
A qualified medical practitioner who is
licensed to practise by the appropriate
medical authority in his or her country,
such as the General Medical Council in
the UK.
dogs, diseases from
Infectious or parasitic diseases that are
acquired from contact with dogs. They
may be caused by viruses, bacteria,
fungi,
protozoa,
worms,
insects,
or
mites living in or on a dog.
Many parasites that live on dogs can
be transferred to humans, for example
through stroking the dog’s fur.
The most serious disease from dogs
is the viral infection
rabies
.
The UK is
free of rabies, but travellers to countries
in w hich rabies exists should treat any
dog bite w ith suspicion. Dog bites can
cause serious bleeding and shock and
may become infected.
Toxocariasis
and
hydatid disease
are
potentially serious diseases caused by
the ingestion of worm eggs from dogs.
D
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