Urinary Tract Infection by Dr. Elizabeth Pingree.
Introduction.
Not only are urinary tract infections,
or UTIs, common in children, but they
can have significant health implications.
For example, young infants are at risk for bacteremia
from a UTI.
In children of all ages, without prompt treatment,
UTIs can lead to renal scarring, hypertension,
and chronic kidney disease.
By the end of this video, you should
be able to list risk factors for UTI in children,
describe the pathophysiology of UTIs in children,
discuss the common presentations of UTIs
in children of different ages, diagnose a UTI based
on clinical presentation and laboratory data,
choose empiric therapy for an infant with a febrile UTI,
and describe the approach to imaging after first febrile
UTI in infants.
Epidemiology and risk factors.
When we consider infants less than two years
of age presenting with fever, the prevalence of UTI
is approximately 7%.
The prevalence is also about 7% in older children presenting
with urinary symptoms.
There are many risk factors to consider
when deciding which children are most likely to have a UTI.
In children less than two years of age,
risk factors include female sex, and lack of circumcision in males.
Infants with higher fever and longer duration of fever
are also much more likely to have a UTI.
Since infants cannot describe their symptoms,
we rely on risk factors to determine which infants
to test.
For example, uncircumcised boys less than three months of age
presenting with a fever are at the highest risk for UTI,
with an infection rate of approximately 20%.
Circumcision appears to matter less as infants grow,
and UTI quickly becomes more common in girls
compared to boys.
The increased incidence of UTI in girls as compared to boys
is hypothesized to be due to a shorter urethra.
There are also anatomic and functional factors that
predispose children to UTIs.
The basic principle is that any abnormality that
alters or slows the flow of urine from the kidney
to the bladder, or voiding through the urethra,
increases the risk of UTI.
The most common anatomic predisposition to UTI
is vesicoureteral reflux, or VUR.
Typically, the uretero vesical junction
where the ureters meet the bladder
closes off when the bladder contracts and does not
allow urine to travel back from the bladder
into the ureters and kidneys.
VUR occurs when this connection is not tight enough
and allows urine to reflux from the bladder
into the upper urinary tract.
VUR is graded based on the severity.
Grade 1, or mild VUR, occurs when the reflux only
fills the ureter.
Grade 5, or severe VUR, occurs when the reflux is so severe
that it causes dilation of the ureters and renal collecting
system.
This retrograde flow allows bacteria to grow and cause
infection in the upper urinary tract.
The risk of UTI and renal scarring
increases with increased severity of VUR.
There are many other anatomic anomalies that
may predispose children to UTI.
If there is an obstruction or narrowing anywhere
along the urinary tract, urine will pool before the narrowing,
and the child is at increased risk for UTI.
Some common obstructions include ureteropelvic junction
obstruction and posterior urethral valves.
These conditions will often be diagnosed with ultrasound.
In the absence of an anatomic obstruction,
children are also at increased risk of UTI
if they do not empty their bladders normally.
Neurogenic bladder refers to abnormal innervation,
such that the muscles of the bladder and the urinary
sphincter do not coordinate properly,
and the bladder cannot empty normally.
Children with this condition will often retain urine
or do not empty their bladders fully when voiding.
Neurogenic bladder may be secondary to conditions
affecting the lower spinal cord, such as myelomeningocele
or spinal cord injury.
Incomplete bladder emptying can also
be secondary to constipation.
As a result, constipation is a common cause
of UTI in children.
Pathophysiology.
Urinary tract infections are typically ascending infections,
meaning that bacteria colonizing the urogenital skin
enter through the urethra and travel to the bladder,
where they cause infection.
If the infection ascends to the kidney,
it is called pyelonephritis.
Most UTIs are caused by Escherichia coli, or E-coli.
It has a variety of virulence factors
that make it a powerful uropathogen, including
fimbriae, or finger-like projections, that
allow it to adhere to the wall of the urinary tract.
Many other bacteria are washed away
by the normal flow of urine.
But uropathogenic E-coli remains, grows, and ascends.
Because E-coli has very effective mechanisms
to cause infection in the urinary tract,
it is often the cause of UTI in children with normal anatomy.
Children with abnormal urinary tract anatomy,
such as VUR or ureteropelvic junction obstruction,
are much more likely to have UTIs caused by less virulent
uropathogens, like citrobacter or enterococcus species.
If a patient has UTI caused by an atypical organism,
one must consider whether there is
an abnormality in the patient's urinary tract
and perform imaging tests to further evaluate.
Clinical presentation.
The symptoms of urinary tract infection in older children
are similar to adults.
In addition to fever, the child may
complain of dysuria, abdominal pain, increased urinary
frequency, or hematuria.
Infants often present with fever only
and it is difficult to distinguish UTI
from other causes of fever in these young patients.
Less common presentations of UTI in young infants
include failure to thrive, or prolonged neonatal jaundice.
Symptoms of pyelonephritis in older children
include fever, vomiting, and flank or abdominal pain.
Younger children cannot describe their symptoms and evidence
shows that most infants less than two years old with
a febrile UTI have renal inflammation.
Therefore, we consider infants less than 24 months
with a febrile UTI to have pyelonephritis.
Diagnosis.
Diagnosis is made by obtaining a urine specimen
and performing urinalysis and urine culture.
On urinalysis, one looks for pyuria and bacteriuria.
Pyuria refers to the presence of white blood cells in the urine.
This is shown on your analysis either by positive leukocyte
esterase, an enzyme that is released by white blood cells,
or by visualizing white blood cells on microscopy.
Bacteriuria refers to evidence of bacteria in the urine.
This is typically seen by the presence
of nitrites on urinalysis, or bacteria
visualized on microscopy.
Nitrites are produced by an enzyme in many gram
negative bacteria, which reduces the nitrate naturally
present in urine to nitrite.
The nitrite test will be negative
if the infection is caused by a gram positive organism,
like enterococcus.
This test is also commonly negative in young infants
because they void too frequently to allow time
for this conversion.
Diagnosis relies on culturing a sterile specimen
to ensure that the bacteria growing are not
a contaminant from the skin.
In a toilet-trained child, a clean catch specimen
may be obtained by cleaning the perineum prior to the child
voiding into a sterile specimen cup.
In infants who are still in diapers,
only a urethral or superpubic catheterized specimen
should be sent for a urine culture
due to the high risk of contamination
with organisms on the skin or from the GI tract.
In many cases, catheterization can
be avoided if there is no evidence
of a UTI on the urinalysis.
Urinalysis is first performed on urine
that is collected from a bag placed around the urethra.
If the urinalysis is negative, without bacteriuria or pyuria,
there is no need to send a culture.
If there are any concerning findings on the urinalysis,
a second step of sending a catheterized specimen
for urinalysis and urine culture is necessary.
Diagnosis is confirmed when urine culture
grows a significant number of colonies of uropathogen.
Management.
Typically, empiric antibiotics are
started if urinalysis is suggestive of UTI
because delayed treatment increases
the risk of renal scarring and other complications.
Empiric oral antibiotics, such as amoxicillin-clavulanate,
trimethoprim-sulfamethoxazole, cephalexin, and cefixime
are targeted at E-coli.
Intravenous antibiotics are often
started in young infants, patients
who are toxic appearing, or those
who have nausea and vomiting, limiting their ability
to take oral antibiotics.
Ceftriaxone is a typical IV antibiotic
for empiric treatment of UTI.
Treatment can be tailored based on susceptibility results when
culture data is available.
The treatment course for pyelonephritis is 7 to 14 days.
The treatment course for simple cystitis can often be shorter.
Imaging.
As previously discussed, UTI in young infants
raises concern for an anatomic abnormality
predisposing the child to UTIs.
American Academy of Pediatrics' guidelines
recommend renal ultrasound for all infants
who present with a febrile UTI.
If there are any abnormalities on ultrasound to suggest VUR,
a voiding cystourethrogram, or VCUG, should be performed.
During a VCUG, the bladder is filled with radio opaque
dye, via urethral catheterization
under fluoroscopy.
VUR will be diagnosed if the dye refluxes
into the ureters as the bladder muscles contract.
A similar approach is also used for children
presenting with recurrent UTIs.
Renal ultrasound is also performed
to evaluate for abscess formation
if a child is not responding as expected
to appropriate antibiotic therapy.
Summary.
One.
UTIs are common in children and can
have significant long-term consequences.
Two.
Young infants with UTIs often present with fever alone.
Three.
Children are at higher risk for UTI,
including recurrent UTIs, if they
have an anatomic abnormality, or if they do not
empty their bladders normally.
Four.
UTI is diagnosed based on pyuria and/or bacteriuria
on urinalysis and urine culture growing a uropathogen.
Five.
Young children with first febrile UTI
should be evaluated for an anatomic abnormality
with imaging.
Thank you for watching this video
on urinary tract infection.