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What is urinary
tract infection?
Urinary tract infection (UTI) is
defined as the presence of multiplying
micro-organisms (bugs) in the tract through which
urine flows from the kidneys via the bladder to
the outside world. UTI is 50 times more common in
women, with about 5 per cent per year developing
symptoms. UTI is uncommon in men below 60 years of
age, but the frequency is similar in men and women
in older age groups. The condition ranges from
cystitis (a mild but distressing inflammation that
is limited to the bladder) to severe infections of
the kidney such as pyelonephritis (when the
infection has reached the kidney tissue itself).
Treatment depends on how and why the infection
shows itself. Most patients respond rapidly to
antibiotic therapy and are unlikely to have any
other urinary tract abnormality.
Good advice
UTIs are rare in men, so all cases
require investigation. Prostatitis, the infection
or inflammation of the prostate (a gland beneath
the bladder that produces some components of
semen), causes symptoms that can be mistaken for
UTI in men.
What causes UTI?
In healthy men, urine is sterile
(contains no micro-organisms). The most important
factor in maintaining the sterility of the urinary
tract is emptying the bladder completely and
frequently. The cause of most UTIs is bacteria
that initially settle (colonise) around the
urethra (urine tube), and then ascend into the
rest of the urinary tract. Several factors can
make this process more likely to occur.
Obstruction:
-
enlarged prostate
-
gland urethral stricture (narrowing).
Neurological
conditions:
-
spina bifida
-
multiple sclerosis
-
spinal cord injury.
Structural
bladder disease:
-
diverticula (small sacs or bulges) in the
bladder wall
-
tumour.
Abnormal
urine drainage:
-
horseshoe kidney
-
obstruction by kidney or bladder stones
-
polycystic kidney
-
bladder reflux disease (usually due to leaky
valves between the bladder and ureter tubes
that connect to the kidneys).
Foreign body:
-
instrumentation (ie during a procedure)
-
catheters and stents.
Underlying
disease:
-
diabetes
-
steroid therapy.
UTIs are
classified as either community acquired or
hospital acquired. 70 per cent of infections are
community acquired, usually caused by the bacteria
Escherichia coli (E coli) from the
patient's own bowels.
Hospital acquired infections are
usually E. Coli but Pseudomonas and
Staphlococci are important causes,
particularly when a surgical instrument such as a
catheter is used, instrumentation is the
predisposing factor. Hospital infections can often
be due to multiple organisms, and antibiotic
resistance is a common problem.
What are the
symptoms of UTI?
Symptoms differ, depending on
whether the infection affects the lower (bladder
and urethra) or upper (kidneys and ureters) parts
of the urinary tract. The symptoms of lower
urinary tract infectoin are dysuria (burning on
passing urine), frequency (frequent need to pass
urine) and urgency (compelling need to urinate).
The urine can be cloudy with an offensive odour.
In older men, generalised symptoms such as
confusion and incontinence can be present. Urine
infections are much commoner in the elderly, due
to poor bladder emptying, an enlarged prostate, or
incontinence associated with stroke or dementia.
The symptoms of upper urinary tract
infection are the same as lower tract symptoms
plus loin (flank) pain, fever and chills. The
patient is likely to be ill and might require
hospital admission.
How is the
diagnosis made?
Test strips dipped into a urine
sample can detect indirect signs of infection such
as blood, protein, white blood cells and nitrites
(most common bacteria convert nitrate, which is a
chemical normally present in urine into nitrites,
which are not usually present).
A clean midstream urine sample
should be sent to the laboratory for a microscopy
examination. A level of 100,000 bacteria per
millilitre of urine is regarded as a significant
infection, especially if found together with pus
or white blood cells (leucocytes) on microscopy.
Any infecting bacteria are cultured in the
laboratory to assess their sensitivity to common
antibiotics.
How is UTI treated?
General measures
A high fluid intake is essential.
Alkaline substances, such as citrates, taken in
water might improve symptoms. By making the urine
more alkaline, they make the environment more
hostile to bacterial growth and improve the
results of antibiotic therapy.
Antibiotic therapy
This is the mainstay of treatment.
Trimethoprim is currently the first choice for
lower UTI in the UK, because it is cost-effective,
well tolerated and works in 80 per cent of
infections. Cephalosporins, nitrofurantoin, and
norfloxacin are reserved as second line drugs in
patients with lower UTI, but are first choices in
patients with signs of upper UTI or kidney
infection.
Antibiotics such as amoxycillin now
have resistance levels of 50 per cent in the
community, because of widespread use over many
years. Based on such experiences, many specialists
are concerned about the possible overuse of the
more powerful antibiotics as first line therapy in
the general community.
Recurrent UTI
If UTIs keep occurring,
identification and treatment of the underlying
cause is essential. Patients who have the same
infection coming back can be managed successfully
by attending to 'bladder toilet' (drinking 2-3
litres of fluid daily and always passing urine at
bedtime and after sex). Drinking 250-500ml of
cranberry juice daily and avoidance of bubble
baths may also help. If these measures fail, six
months of continuous therapy with low dose
antibiotics is usually required. |
