(a kidney disorder), and
c i r r h o s i s .
also given for
h y p e r t e n s i o n
pressure). Adverse effects include leg
cramps, dizziness, rash, and impotence.
The drug may rarely, cause
g o u t
d i a b e t e s m e l l i t u s .
h y d ro c o rtis o n e
Also called cortisol, a
h o r m o n e
naturally by the
a d r e n a l g l a n d s .
hydrocortisone is used as a
c o r t i c o s t e r o i d
d r u g
to treat severe allergic conditions;
for example, it is given by injection to
a n a p h y l a c t i c s h o c k .
It is also used as a
replacement treatment when the adrenal
glands fail to function (see
A d d i s o n ’s d i s -
e a s e ) .
Hydrocortisone is widely given in
the form of a cream or ointment, to treat
inflammatory skin conditions, such as
heat rash, and is effective at reducing
itching; however, used to excess, hydro-
cortisone creams may cause thinning of
the skin, wrinkles or loss pigmentation.
h y d ro g e n p e ro x id e
A substance used as m ild
a n t i s e p t i c
ution or cream to treat infections of the
skin or mouth, or used to bleach hair.
Hydrogen peroxide combines with cata-
lase, an enzyme present in the skin and
mouth, to release oxygen. This reaction
kills bacteria. Solutions used to treat the
skin and mouth usually contain three
per cent hydrogen peroxide; those used
for bleaching hair are stronger. Occa-
sionally, solutions containing hydrogen
peroxide may irritate the skin.
h y d ro n e p h ro s is
A condition in w hich a
k i d n e y
swollen with urine due to an obstruc-
tion in the
u r i n a r y t r a c t . T h e
causes pressure to build up inside the
kidney and prevents it from functioning
one or both kidneys.
In some cases, hydronephrosis may be
due to a
c o n g e n i t a l
narrowing of the
u r e -
t e r .
In other cases, the obstruction of a
ureter may be caused by a stone (see
c a l -
c u l u s , u r i n a r y t r a c t ) ,
k i d n e y t u m o u r ,
blood clot. Occasionally, hydronephrosis
is caused by obstruction to the outflow
enlarged prostate gland
p r o s t a t e ,
e n l a r g e d
) in men, or by enlargement of
the uterus in pregnant women. In such
cases, both kidneys are affected.
Acute hydronephrosis, in which there
is a sudden blockage of the ureter, causes
severe pain in the abdomen and the
small of the back. Chronic hydronephro-
sis, in which the obstruction develops
slowly, may cause no symptoms until
total blockage results in
k i d n e y f a i l u r e .
Hydronephrosis also increases the risk of
kidney infection because bacteria can
multiply more easily in stagnant urine.
using X-rays (see
i n t r a v e n o u s u r o g r a p h y ) ,
C T s c a n n i n g
M R I
(techniques that pro-
duce cross-sectional or three-dimensional
images of body structures). Following
diagnosis, it is usually possible to relieve
pressure by draining urine through a
tube either directly onto the surface of
the skin or by bypassing the blockage.
Further treatment w ill then be needed to
treat the cause of the blockage.
If the blockage can be removed surgi-
cally, the kidney is likely to function
normally again. Occasionally, however, a
kidney is so badly damaged that it
requires removal (see
n e p h r e c t o m y ) .
h y d ro p h o b ia
A popular term, now almost obsolete,
r a b i e s
h y d ro p s
An abnormal accumulation of fluid in a
body tissue (see
o e d e m
), cavity, or sac
(a baglike body structure).
h y d ro p s fe ta lis
o e d e m a
(swelling of the body
tissues) that occurs in a
f e t u s
birth. Hydrops fetalis is often the result
of Rhesus incompatibility (see
h a e m o l y t -
i c d i s e a s e o f t h e n e w b o r n ) .
women who are affected by Rhesus
u l t r a s o u n d
s c a n n i n g
may be carried out to detect
any swelling and help doctors to deter-
mine whether any treatment w ill be
necessary for the fetus.
h y d ro th e ra p y
A form of
p h y s i o t h e r a p y
in which exercis-
es are performed in water to aid recovery
or to improve mobility.
Hydrotherapy includes the use of exer-
cise pools, whirlpool baths, and showers.
People w ho cannot bear their full
body weight on a limb (such as people
with arthritis or those who have frac-
tured a limb) may undergo exercises in
a hydrotherapy pool. The buoyancy of
the water supports the person’s body; in
resistance that helps to improve muscle
strength. Warm w hirlpool baths can also
provide a gentle massage to stimulate
areas of the body and relieve stiffness.
h y d ro u s o in tm e n t
preparation that is used to treat dry or
scaling skin conditions such as
e c z e m a
p s o r i a s i s .
Such ointment hydrates
the affected area and can provide relief
h y d ro x o c o b a la m in
A long-acting synthetic preparation of
v i t -
a m i n B 12.
Hydroxocobalamin is given by
injection to treat disorders involving vita-
min B12 deficiency, particularly pernicious
a n a e m i a , m e g a l o b l a s t i c ) ,
which vitamin B12 cannot be absorbed
from the intestines.
h y d ro x y a p a tite
A complex crystalline form of calcium
phosphate that occurs naturally in the
body as a major component of bones and
teeth. A synthetic form of hydroxyapatite
is used as a
c a l c i u m
supplement to reduce
bone loss when the intake of dietary cal-
cium is inadequate.
5 -h y d ro x y try p ta m in e
Another name for
s e r o t o n i n .
h y d ro x y z in e
a n t i h i s t a m i n e d r u g
relieve itching and, occasionally, in the
a n x i e t y .
h y g ie n e
The science and practice of preserving
health. The word “hygiene” is commonly
used of personal cleanliness. It can also
p u b l i c h e a l t h
- the scientific study
of various environmental influences on
health, such as safe sanitation and good
housing. The terms “industrial hygiene”
and “occupational hygiene” refer to the
scientific discipline of assessing and regu-
lating the work environment in order to
o c c u p a t i o n a l d i s e a s e a n d i n j u r y .
h y g ie n e , o ra l
o r a l h y g i e n e
h y g ro m a , c y s tic
l y m p h a n g i o m a
(a type of noncancerous
tumour) that occurs around the head
and neck, the armpits, or the groin and
contains clear fluid. Cystic hygromas are
usually present from birth, reach their
maximum size by the time the child is
about two years old, then gradually dis-
appear. The tumour may be surgically
removed if it is obstructing the airway,
but the final appearance is usually better
if surgery can be avoided.