and is protected by, the
age adult bladder can hold about 0.5
litres of urine before the need to pass
urine is felt.
The bladder walls consist of muscle
and an inner lining. Two tubes called
carry urine to the bladder from
the kidneys. At the lowest point of the
bladder is the opening into the
(outflow tube), known as the bladder
neck. This is normally kept closed by a
ring of muscle (the urethral sphincter).
The bladder’s function is to collect and
store urine until it can be expelled from
the body. Full control over bladder func-
tion takes several years to develop. In
infants, emptying of the bladder is an
entirely automatic, or
When the bladder fills with urine and is
stretched beyond a certain point, nerve
signals are sent to the spinal cord. Sig-
nals from the spinal cord then cause the
urethral sphincter to relax and the prin-
cipal bladder muscle to contract, thereby
expelling urine via the urethra.
Children develop complete bladder
control at varying ages. Most are dry at
night by the age of five years, but some
take longer (see
Defective bladder function, leading to
problems such as incontinence
can have a variety of causes. (See
bladder outflow obstruction
Growths originating in the inner lining
of the bladder.
like growths) often recur and eventually
become cancerous. Other, more malig-
nant, growths may extend not only into
the bladder cavity, but also through the
bladder wall to involve nearby organs,
such as the colon, rectum, prostate
gland, or uterus. Bladder cancer is more
common in smokers and workers in the
dye and rubber industries.
(blood in the urine) is the
main symptom of bladder cancer. A
tumour may obstruct the point at which
a ureter enters the bladder, causing back
pressure and pain in the kidney region,
or the urethral exit, causing difficulty in
passing, or retaining, urine.
DIAGNOSIS AND TREATMENT
Bladder tumours are diagnosed using
(passage of a viewing tube up
the urethra into the bladder) and biopsy
(tissue sampling for microscopic analy-
sis) of the abnormal area.
If they are small, the tumours can be
treated by heat or removed surgically.
Tumours tend to recur within the blad-
der, so regular follow-up cystoscopy is
usually necessary. Bladder tumours that
have spread through the bladder wall
may be treated by
or by the
removal of part or all of the bladder.
A surgical procedure in which a con-
nection is made between one of the
two subclavian arteries (which normally
deliver oxygen-rich blood to the neck
and arms) and one of the pulmonary
arteries (which carry blood from the
right side of the heart to the lungs for
oxygenation). The shunt may be used
as a temporary treatment for congenital
in which oxygen-depleted blood
is diverted back to the heart before it
reaches the lungs. The shunt redirects the
DISORDERS OFTHE BLADDER
The most important causes of bladder
problems are infection, tumours,
calculi (stones), and impairment of
the bladder’s nerve supply.
Bacterial infection of the bladder, which
causes inflammation of the bladder wall
is particularly common in
women. The short female urethra makes
it relatively easy for bacteria to enter from
outside the body. In men, infection is
usually associated with obstruction of
urine flow from the bladder by, for
example an enlarged prostate gland (see
or bladder tumours.
may be cancerous or
noncancerous and are more common in
men than in women. They are usually
painless in the early stages, the first
symptoms being blood in the urine (see
the bladder cannot be emptied. All
bladder tumours need careful follow-up
because, left untreated, noncancerous
bladder tumours may become cancerous.
Bladder stones (see
are mostly caused by the crystallization
of substances, such as calcium, in the
urine. They mainly affect men and
usually result from a longstanding
urinary tract infection and/or
incomplete emptying of the bladder.
Damage to the nerves controlling the
bladder can prevent normal bladder
function and lead either to incontinence
) or to urinary
retention. The most common cause is
spinal-cord injury or tumours. Bladder
control can be affected by nerve degen-
eration in conditions such as
An unstable or
common condition, particularly in
women, in whom the bladder wall is
especially sensitive to being stretched.
Weakness of the muscles at the bladder
, is also
common in women, particularly after
childbirth. Tension or anxiety can cause
In children, delayed bladder control
) is most often
due to delayed maturation of the
nervous system. Injury to the bladder
is rare but may occur if the pelvis is
fractured when the bladder is full.
Various methods are used to investigate
bladder disorders. Urinary tract
infection is diagnosed by tests on a
sample of urine. The bladder can be
viewed directly by
of a viewing tube).
is often performed, particularly if
stones are suspected. X-ray procedures
which normally shows only the
bladder and urethra, and intravenous
, which shows the whole
urinary tract except the urethra.
which may involve
X-rays, are studies carried out to
investigate bladder control problems.
measures bladder capacity
in relation to pressure.