almost always the result of a bacterial
infection. Urethritis is often due to a
sexually transmitted infection, such as
gonorrhoea, but may have other causes.
Urethral infections are more common
in men. Infections further up the urinary
tract are more common in women. In
men, there is often a predisposing fac-
tor, such as an enlarged prostate gland
(see prostate, enlarged). In women, preg-
nancy is a risk factor.
In both sexes, causes of urinary tract
infections include stones (see calculus,
urinary tract), bladder tumours, congeni-
talabnormalities of the urinary tract, or
defective bladder emptying as a result
of spina bifidaor a spinal injury. The
risks of developing a urinary tract infec-
tion can be reduced by strict personal
hygiene, drinking lots of fluids, and reg-
ularly emptying the bladder.
Urethritis can lead to the formation of
a urethral stricture. Cystitis usually only
causes complications if the infection
spreads to the kidneys. Pyelonephritis,
if it is left untreated, can lead to perm-
anent kidney damage, septicaemia, and
septic shock.
The infection is diagnosed by the
examination of a urine culture. Further
investigations using urographyor ultra-
sound scanning may be necessary. Most
infections of the urinary tract are treated
with antibiotic drugs.
urination, excessiveThe production of
more than 2.5 litres of urineper day.
The medical term is polyuria.
Causes include psychiatric problems,
which may cause a person to drink com-
pulsively; diabetes mellitus; disorders of
the kidney known as salt-losing states;
and central diabetes insipidus. Any per-
son who passes large quantities of
urine should consult a doctor.
urination, frequentAlso known as uri-
nary “frequency”, the passing of urine
more often than the average of 4–6
times daily. Causes of frequent urina-
tion include excessive production of
urine (see urination, excessive), cystitis,
anxiety, stones in the bladder (see cal-
culus, urinary tract), enlargement of the
prostate gland (see prostate, enlarged)
in men, and, rarely, a bladder tumour.
Some people who are suffering fromkidney failurepass urine more frequent-
ly, especially during the night. Treatment
of frequent urination is always of the
underlying cause.
urination, painfulPain or discomfort
that occurs when urine is being passed.
Painful urination is known medically as
dysuria. The pain is often described
as burning; sometimes it is preceded by
difficulty in starting urine flow. Pain
after the flow has ceased, with a strong
desire to continue, is called strangury.
The most common cause, especially in
women, is cystitis. Other causes include
a bladder tumour, bladder stone (see cal-
culus, urinary tract), urethritis, balanitis,
prostatitis, vaginal candidiasis(thrush),
or allergy to vaginal deodorants. Strang-
ury is usually caused by spasm of an
inflamed bladder wall, but it may be
due to bladder stones. Mild discomfort
when passing urine may be caused by
highly concentrated urine.
Dysuria may be investigated by phys-
ical examination, urinalysis, urography,
or cystoscopy. (See also urethral syn-
drome, acute.)
urineThe pale yellow fluid produced by
the kidneysand excreted from the body
via the ureters, bladder, and urethra.
Urine is produced when blood is filtered
through the kidneysto remove waste
products and excess water or chemical
substances. The main component is urea.
A healthy adult produces between 0.5
and 2 litres of urine per day. The mini-
mum volume of urine needed to remove
all waste products is about 0.5 litres. A
high fluid intake increases the amount
of urine produced; high fluid loss from
sweating, vomiting, or diarrhoea leads
to reduced production.
urine, abnormalUrinemay be pro-
duced in abnormal amounts or have an
abnormal appearance or composition.
Conditions of abnormal production of
urine include excessive production (see
urination, excessive), oliguria, and anuria.
Abnormal appearances of urine include
cloudiness (which may be caused by a
urinary tract infection, a calculus, or the
presence of salts); haematuria; discol-
oration from certain foods or drugs; and
frothiness (which may be caused by an
excess of protein).URINATION, EXCESSIVE URINE, ABNORMALU