may increase to a dangerous level, caus-
ing a risk of kernicterus(a type of brain
damage). Severely affected babies have
marked anaemia while still in the uterus.
They become swollen (hydrops fetalis)
and are often stillborn.
In mild cases, no treatment is neces-
sary. In other cases, the aim is to deliver
the baby before the anaemia becomes
severe, usually by induction of labourat
35–39 weeks’ gestation. If the baby is
too young to be delivered safely, fetal
blood transfusions may be necessary.
After birth, phototherapy (light treat-
ment that converts bilirubin in the skin
into a water-soluble form that is more
easily excreted from the body) can help
to reduce jaundice. An exchange blood
transfusion may be needed.
haemolytic–uraemic syndromeA rare
disease in which red blood cellsare
destroyed prematurely and the kidneys
are damaged, causing acute kidney fail-
ure. Thrombocytopeniacan also occur.
Haemolytic–uraemic syndrome most
commonly affects young children and
may be triggered by a serious bacterial
or viral infection. Symptoms include
weakness, lethargy, and a reduction in
the volume of urine. Seizures may occur.
Blood and urine tests can determine
the degree of kidney damage. Dialysis
may be needed until the kidneys have
recovered. Most patients recover nor-
mal renal function.
haemophiliaAn inherited bleeding dis-
ordercaused by deficiency of a blood
protein, factor VIII, which is essential
for blood clotting. Haemophiliacs suffer
recurrent bleeding, usually into their
joints, which may occur spontaneously
or after injury. The lack of factor VIII is
due to a defective gene, which shows a
pattern of sex-linked inheritance; haem-
ophilia affects males in most cases.
Episodes of bleeding are painful and,
unless treated promptly, can lead to
joint deformity. Injury, and even minor
operations such as tooth extraction,
may lead to profuse bleeding. Internal
bleeding can lead to blood in the urine
or extensive bruises.
Haemophilia is diagnosed by blood-
clotting tests, and by amniocentesisor
chorionic villus sampling in a fetus.Bleeding can be prevented or controlled
by infusions of factor VIII concentrates.
haemophilus influenzaeA bacterium
(see bacteria) responsible for numerous
cases of the infectious diseases epiglot-
titisand meningitis.
haemoptysisThe medical term for cough-
ing up blood.
haemorrhageThe medical term for
bleeding. (See also haematoma.)
haemorrhoidectomyThe surgical re-
moval of haemorrhoids. The procedure
is used to treat large, prolapsing, or
bleeding haemorrhoids.
haemorrhoidsSwollen veins in the
lining of the anus. Sometimes these
veins protrude outside the anal canal,
in which case they are called prolapsing
haemorrhoids. Straining repeatedly to
pass hard faeces is one of the main
causes of haemorrhoids. Haemorrhoids
are also common during pregnancy and
just after childbirth.
Rectal bleeding and discomfort on
defaecation are the most common fea-
tures. Prolapsing haemorrhoids often
produce a mucous discharge and itch-
ing around the anus. A complication of
prolapse is thrombosisand strangula-
tion; this can cause extreme pain.
Diagnosis is usually by proctoscopy.
Mild cases are controlled by drinking
plenty of fluids, eating a high-fibre diet,
and establishing regular toilet habits.
Rectal suppositories and creams con-
taining corticosteroid drugsand local
anaestheticsreduce pain and swelling.
More troublesome haemorrhoids may
be treated by sclerotherapy, cryosurg-
ery, or by banding, in which a band is
tied around the haemorrhoid, causing it
to wither and drop off. A haemorrh-
oidectomy is generally required for
prolapsing haemorrhoids.
haemosiderosisA general increase in
ironstores in the body. Haemosiderosis
may occur after repeated blood transfu-
sions or, more rarely, as a result of
excessive intake of iron.
haemospermiaThe medical term for
blood in the semen (see semen, blood
in the).
haemostasisThe arrest of bleeding.
There are 3 main natural mechanisms
by which bleeding is stopped afterHAEMOLYTIC–URAEMIC SYNDROME HAEMOSTASISH