|
Clinical presentation:
The
incidence of urinary tract infection (UTI) is sex and
age related, except in the newborn, it was found to be
more common in girls than boys and the incidence is 1%
in boys and 3% in girls, about 11 % of girls are found
to have at least one attack of UTI by the age of 11
years. The usual signs and symptoms of lower UTI in
adults like dysuria and frequency may not be obvious in
children. Because younger children and infants often
have non-localizing symptoms, the physician must have a
high index of suspicion.
Because UTIs in neonates often occur as a consequence
of bacteremia and do not result from ascending UTI, as
common in older patients, neonates may show signs and
symptoms most consistent with sepsis and appear gravely
ill. Additional signs of UTI in neonates include
abdominal distension, diarrhea and jaundice. In any
infant in whom sepsis is considered in the clinical
diagnosis, urine culture must be part of the laboratory
evaluation!
Symptoms
of UTI in children may include dysuria, frequency and
urgency, but vague complaints of abdominal pain,
vomiting, decreased appetite and malodorous urine also
occur .2.3 Fever is less common than in the younger age
group and if present may signify renal parenchymal
infection or infection in an obstructed urinary tract.
Symptoms of dysuria may be related to problems other
than UTI, including, vaginitis and local perineal
irritation. Urinary tract infection during adolescence
is much more common in girls, and generally present with
dysuria.3 Again fever is unusual and usually signifies
upper UTI .Sexual activity may exacerbate symptomatic
UTI, in this age group other causes of dysuria must be
considered (e.g. sexually transmitted hypercalciuria,
and urolithiasis).
History:
Urinary tract infections can be caused by a number of
predisposing factors operating either alone or in
combination, which eventually leads to bacterial
inoculation of the urinary tract. A careful history,
looking for possible causes are important; namely urine
and fecal elimination habits. It is usually quite easy
to get a detailed voiding history as the patient often
presents with a wetting problem, which can be associated
with frequency, urgency or infrequent voiding, but the
topic of fecal elimination is considered a private
matter. Even the parents may not be aware of the
frequency, size, and shape consistency of their child's
stool. Involving the child in the interview, time should
be taken at this point, avoid any embarrassment, and to
facilitate answers, asking specific qualitative and
quantitative questions that will generate a yes or no
answer.
Constipation is more of a degree of fecal retention,
infrequent passage of stools, passage of small compact
stools, palpable stool in the sigmoid fossa, residual
stool after defecation by rectal examination, or
encopresis.4 A normal child should void to completion
about 6 times daily. Infrequent voiding or lazy bladder
syndrome; more common in girls who usually delay and
void about only 3 times daily, their first void more
than 2 hours after getting up of bed5.
Observant mothers may describe malodorous cloudy urine.
Feeding intolerance or poor weight gain may be a
historical clue to UTI in the very young. Older children
may also complain of back pain. Vague abdominal
complaints in school- girls are not rare and are often
described by other physical as behavioral problems
though UT I commonly responsible for such presentation.
Physical examination.
Although the prognosis UTI in childhood is generally
favorable,6 significant number of patients will have
anatomical abnormalities of their urinary tracts that
predispose them to renal parenchymal damage,
hypertension and even renal failure7. Therefore careful
evaluation is essential to identify those who may
develop these serious consequences. Fever and abnormal
vital signs (hypertension) may be signs of upper UTI;
Growth failure may be evident in patients who already
have renal insufficiency or who have had recurrent
infections in an abnormal urinary tract. Close attention
should be paid to abdominal examination, palpating
carefully for masses that suggest genito-urinary tract
pathology.
Gentle
examination of the external genitalia is very important,
in boys; phimosis and banalities may mimic the signs of
UTI. Urethral metal stenosis, more common in circumcised
boys, may predispose to voiding difficulties; narrow,
weak urinary stream and UTI. Other major associated
abnormalities signal structural problems in the urinary
tract, including cardiac defects, abdominal muscular
defects, cryptorchidism, hypospadias and skeletal
deformities.
Examination of the back looking for any signs spina
bifida, testing the cremastric and anal reflexes may
help in the diagnosis of neurological causes responsible
for neurogenic bladder, that are commonly associated
with UTI.
Diagnosis:
A definitive diagnosis of UTI requires documentation of
significant bacteriuria. Definition of 'significant' is
not simple and depends on the method of urine
collection, prompt handling of the collected specimen
and the pattern organism(s) recovered. Physicians are
generally aware that bacterial colony counts of greater,
100,000 /ml of urine obtained by mid stream clear catch
represent infection.8 Many bacteria colonize the skin
around the urethra, and fecal reservoir is in close
proximity. Because of this, contamination of urine
specimen obtained by clean-catch method is common. Signs
of contamination include low colony counts, multiple
organisms, different organisms obtained in serial
samples, or isolation of organisms not commonly
associated with UTI. Certainly the clean-catch method is
the easiest to use in the older child and generally
reliable .Antiseptic cleansing prior to the collection
is usually not necessary and may even mask significant
bacterial growth. One cannot expect an infant to provide
a clean-catch specimen so other methods have been
devised. The most convenient method of obtaining a urine
sample in an infant is by applying a sterile collection
bag that is adherent to the genitalia. Unfortunately, it
is also the most prone to contamination –negative
cultures obtained by this technique are of value, but,
positive culture should be confirmed by culture of
catheter specimen or suprapubic aspirate whenever,
possible.2.9 Urethral catheterization may provide, quick
access to urine but is not without problems, trauma to
the urethra is possible, discomfort of the patient and
contamination can occur.
The
finding of pyuria has strong supportive evidence of UTI,
but approximately 30% to 50% patients with bacteriuria
and UTI will not demonstrate a significant number of
white cells (>5 white blood cells / high power field) in
centrifuged urinary sediment. Because of this screening
test that relies on the detection of white blood cell
products (leukocyte esterase) are not the appropriate
for the diagnosis of UTI. Likewise, nitrite dipstick is
a sensitive screening procedure for gram-negative
organism, but it should not be used in symptomatic
children.5 However the accuracy is affected by the
probability of the patient being infected based on
clinical findings. Accordingly, urine culture may be
omitted when the dip stick test is negative only when
there is limited suspicion of UTI based on clinical
symptoms. Conversely, urine culture should be obtained
in any patient suspected of having a UTI or in whom the
dipstick test is positive.5
As
Pediatric Urologists, we think that the diagnosis and
treatment of UTI by ntimicrobials in a child is not
enough and usually more evaluation and diagnostic
imaging are needed to detect the presence of any
predisposing factors. Infants and young children with
UTI warrant specific attention because of the
opportunity to prevent kidney damage. Urinary tract
infections may bring attention to a child with an
obstructive anomaly or severe vesico-ureteral reflux.
Pathophysiology:
Pathophysiology of UTI appears to be related to both
characteristics of the invading bacteria and those of
the host's urinary tract.
Bacterial factors.
A large proportion of Escherichia coli (E. coli) types
are isolated from patients with UTI without detectable
structural genito-urinary abnormality. The most
important virulent factor of these bacteria is the
presence of pili or fimbria with an affinity for
receptors (glycosphingolipids) present on the mucosal
epithelial cells. Adherence of E. Coli to transitional
epithelial cells precipitates decreased peristalsis and
urethral dilation.l0 Conversely, pyelonephritis in the
absence of such uropathogenic E.Coli may be a marker for
urinary tract abnormalities.11 Some clones of E. Coli
marked by specific antigen type appear to be
particularly virulent in producing renal parenchymal
inflammation and scarring 3, and these strains (P-Fimbriated
E.Coli) demonstrate the ability to attach to globosides
on human red cells and to some uroepithelial cells.
Escherichia coli is responsible for at least 80% of UTI
in children. Other organisms include Proteus,
Pseudomonas Klebsiella. Multiple organisms in urine
culture may signal an underlying structural problem
(e.g. vesico-ureteral reflux, posterior urethral valve
etc.) requiring surgical intervention.
Host defense and risk factors.
These can be classified into perineal factors, lower
urinary tract factors and upper urinary tract factors 5.
Perineal factors;
perineal colonization by intestinal flora is the most
common source of primary and recurrent UTI, an infants
initial exposure to uro-pathogenic bacteria occurs at
the time of birth especially if born to bacilluric
mother. Ultimately, the infants' own uropathgenic
bacteria that colonize the intestinal tract. Most UTIs
are ascending infections, which begin with perimeatal
colonization. Uncircumcised male infants have a higher
incidence of UTI because of the preputile
colonization.13 In girls the short urethra, and the
location of the external urethral meatus deep into the
vulva, appears to be the most obvious explanation for
increased relative incidence of UTIs.In this regard we
recommend that girls should void while in abduction
position with the legs widely separated in order to
obtain a clear and well identified urinary-stream to
avoid retrograde urinary vaginal reflux which can
increase the incidence of UTIs.
Lower urinary tract factors.
Common voiding disorders in children prone to UTI
range from small capacity , unstable bladder
characterized by frequency, urgency, posturing, and
wetting to the infrequent voider 'lazy bladder'
characterized by very infrequent voiding, large capacity
bladder, and constipation. Constipation in general can
predispose to bladder insensibility by the stimulation
of stretch receptors in bladder mucosa. In children
with. recurrent UTIs associated with abnormal voiding"
patterns, normalization of voiding pattern generally
results in the resolution of UTI, host defense factors
and bacterial virulence factors, however, do affect the
susceptibility to UTI, since many children do not
develop UTI despit abnormal voiding habits .
Infrequent emptying of an over distended bladder may
result in significant post void residual urine which act
as a reservoir for invading organisms.
Upper urinary tract factors.
Although the presence of vesico-ureteral reflux (VUR),
Significantly enhances the likelihood that even the less
virulent organism will get access to the kidney, still
at least one third of cases of acute pyelonephritis in
children, documented by dimercaptosuccinic acid (DMSA)
renal scan are not associated with VUR.
Diagnostic
imaging. In pediatric patients all initial UTIs
should be considered complicated and requiring
appropriate radiological evaluation because nearly 50%
of children with UTI are found to have associated
congenital urological abnormalities.
The
vast majority of renal scarring occurs within the first
3-5 years of life 7. Many will not have had documented
UTIs but may have had. Unexplained fever. So it is
reasonable to identify patients who are likely to have
renal damage associated with structural abnormalities
(primary vesicoureteric reflux or obstruction) as early
as possible. However, it may not be particularly
cost-effective to image adolescent girls with cystitis
because it is a common occurrence and scarring, if
present, is already established. Though the incidence of
UTIs is lower in boys, they are much more likely to have
structural abnormalities. Recommendation for the imaging
of children with UTIs varies geographically,
institutionally and from one individual to another.
However we recommend the policy to perform an evaluation
after the first culture- documented UTI in all boys and
girls younger than 5 years of age, further more, all
patients with physical findings of genitourinary
abnormalities, and older children with recurrent
symptomatic UTIs particularly those with dysfunctional
voiding.5 Renal and bladder ultrasonography alone as the
initial urologic evaluation is probably sufficient in
older boys with their first episode of cystitis, girls
with recurrent cystitis in the absence of voiding
dysfunction and adolescent girls.5 Infants and young
children with UTI who do not demonstrate the expected
clinical response within 2 days of antimicrobial therapy
should undergo ultrasonography promptly, and voiding
cystourethrogram (VCUG) should be perfumed at the
earliest convenient time after control of the acute UTI
episode. A normal ultrasound does not exclude VUR. The
rate of VUR among children younger than 1 year with UTI
exceeds 50%.5 Dimercaptosuccinin acid renal scan can be
used to diagnose acute pyelonephritis as well as renal
scarring, information that is important for the
longitudinal assessment of children with VUR because the
detection of new or progressive renal scaring are
considered indications for ureteral reimplantaion 14 .
Renal scars however may not show. On DMSA until a few
month or even years after the pyelonephritis episode.
(It is Important also to realize that scars appear only
if pyelonpehritis is not treated or if there was a delay
in treatment).
Treatment.
Therapy of UTI depends on the clinical
circumstances,knowledge of pre-existing structural
abnormality, the type of offending microorganism and
its documented or suspected sensitivity, the presence of
recurrent bacteriuria and the age of the child 2-9 .Intial
treatment should ideally be based on urine culture
both for documentation of UTI and to provide bacterial
antibiotic sensitivity.
In
general, children who appear ill or who are at a
significant risk of becoming seriously ill because of
their age (infants)or the presence of urinary tract
abnormalities should be admitted to hospital and treated
with intravenous antibiotics avoiding aminoglycosids in
those with renal impairment.
Patient with first time UTI who require imaging should
be maintained on low dose antibiotic prophylaxis until
their workup is completed. Resolution can be anticipated
when urinary and bowel habits normalized.Long-term
antibiotic prophylaxis is indicated for children with
frequent symptomatic recurrences of UTI and for those
with known VUR.Diagnosis and treatment of underlying
voiding dysfunction and constipation is
essentialcomponent for the successful management of UTIs
in children 15 .Unstable bladder may be helped with
behavioral modification approach involving
self-motivation, frequent voiding,anticholinergic
agents,such as oxybutinin which may be added very
selectively .
Clean intermittent catheterization
( CIC )or surgical bladder drainage procedure may be
needed to protect the kidneys in specific cases such as
neurogenic bladder and in children with complicated
urological procedures like patients with bladder
augmentation. Infrequent voiders are to be encouraged to
void every 2 to 3 hours while awake until their voiding
pattern is reset. Infrequent bowel movement should be
attended to with appropriate use of diet -high fiber
with plenty of fluids, vegetables and fruits. Stool
softeners and laxatives may be needed in severely
constipated children, e.g. those with spinal dysraphism.
Primary vesicoureteral reflux resolves spontaneously in
about 80% of patients by the age of 4 years by using the
usual conserative management, which involves keeping the
urine sterile by prophylaxis antibiotics, surgical
intervention should be perfomed if indicated. |
