trophoblastic tumourA growth aris-
ing from the tissues that develop into
the placenta. The most common type of
trophoblastic tumour is a hydatidiform
mole. (See also choriocarcinoma.)
tropical diseasesDiseases prevalent
in the tropics because of living condi-
tions and diet include malnutrition,
measles, diphtheria, tuberculosis, typhoid
fever, shigellosis, cholera, amoebiasis,
and tapeworm infestation. Diseases
spread through the tropics by insects
include malaria, yellow fever, sleeping
sickness, and leishmaniasis. Exposure to
strong sunlight in the tropics causes an
increased tendency to skin cancer, and
may lead to pingueculaand pterygium.
tropical ulcerAn area of persistent skin
and tissue loss caused by infection with
1 or more organisms. The condition is
most common in malnourished people
living in the tropics. Treatment is clean-
ing and dressing of the ulcer, a course of
antibiotic drugs, and a high protein diet.
The ulcer usually heals but may scar.
tropicamideA drug used to dilate the
pupil. Adverse effects of the drug include
blurred vision, increased sensitivity to
light, stinging, and, rarely, dry mouth,
flushing, and glaucoma.
trunkThe central part of the body, com-
prising the chest and abdomen. The
term also refers to any large blood ves-
sel or nerve, from which smaller vessels
or nerves branch off.
trussAn elastic, canvas, or padded metal
appliance used to hold an abdominal
herniain place. Trusses are only used if
corrective surgery cannot be undertaken.
trypanosomiasisA tropical disease cau-
sed by TRYPANOSOMAparasites. (See also
sleeping sickness; Chagas’ disease.)
tsetse fly bitesThe bites of tsetse flies,
which are found in Africa, can be painful.
The flies, resembling brown houseflies,
spread sleeping sickness.
T-tube cholangiographyAn imaging
techniqueperformed to check that there
are no gallstonesleft in the bile duct
after a cholecystectomy. A T-shaped rub-
ber tube is inserted into the bile duct
during the surgery. A week or so later,
contrast mediumis inserted into the
tube and X-raysare taken.
tubal ligationSee sterilization, female.
tubal pregnancySee ectopic pregnancy.
tubercleA grey, nodular mass found in
tissues affected by tuberculosis. The
term also refers to a small rounded pro-
trusion on the surface of a bone.
tuberculin testsSkin tests used to
determine whether or not a person has
been exposed to the bacterium that
causes tuberculosis. Tuberculin tests are
carried out for diagnosis of tuberculosis,
and before BCG vaccination. A small
amount of tuberculin (purified protein
from the bacteria) is injected into the
skin. A few days later, the skin reaction,
if any, is noted. A reaction indicates
previous exposure.
tuberculosisAn infectious disease, com-
monly called TB, caused in humans by
the bacterium MYCOBACTERIUM TUBER-
CULOSIS. TB is usually transmitted in
airborne droplets expelled when an infec-
ted person coughs or sneezes. An
inhaled droplet enters the lungs and
the bacteria begin multiplying. The
immune system usually seals off the
infection at this point, but in about 5 per
cent of cases the infection spreads to the
lymph nodes. It may also spread to
other organs through the bloodstream,
which may lead to miliary tuberculosis,
a potentially fatal form of the disease.
In about another 5 per cent of cases,
bacteria held in a dormant state by the
immune system become reactivated
months, or even years, later. The infec-
tion may then progressively damage the
lungs, forming cavities.
The primary infection is usually with-
out symptoms. Progressive infection in
the lungs causes coughing (sometimes
bringing up blood), chest pain, short-
ness of breath, fever and sweating, poor
appetite, and weight loss. Pleural effu-
sionor pneumothoraxmay develop. The
lung damage may be fatal.
A diagnosis is made from the symp-
toms and signs, from a chest X-ray, and
from tests on the sputum. Alternatively,
a bronchoscopymay also be carried out
to obtain samples for culture.
Treatment is usually with a course of 3
or 4 drugs, taken daily for 2 months, fol-
lowed by daily doses of isoniazidand
rifampicinfor 4–6 months. However, TB
bacteria are increasingly resistant to theTROPHOBLASTIC TUMOUR TUBERCULOSIS
T