Download Imaging Tests in localizating the site of UTI

Approach to the Children with
Urinary Tract Infection
By
Seyed Taher Esfahani,MD
Professor of Pediatrics
Tehran University Of Medical Sciences
Definition of UTI
UTI is defined by the presence of bacteria
in bladder urine
DEFINITION OF URINARY TRACT
INFECTION
The reference standard for urinary tract infection
(UTI) is the isolation of a pure growth of bacteria
in an uncontaminated sample of urine using
semiquantitative culture methods
The Importance of Pediatric UTIS
UTIS are common in children
UTIS may have nonspecific sign and symptoms
UTIS have tendency to recur
UTIS can lead to renal damage
Prevalence
• UTIs are relatively common in infants and
young children.
• The risk before puberty is 3–5% in girls
and 1–2% in boys .
• In young febrile infants aged less
than 24 months the prevalence is 3–5%.
• Prevalence is different depending on age and
gender.
Pathogenesis of UTI
UTI is most often an ascending process
except:
 During first 8-12 weeks of life
 Immunocompromised children
 Bacteriemia from an extra urinary site:
skin ,heart , gastrointestinal, skeleton
E.Coli
E.Coli
BLADDER CONTMINATION
BLADDER INFECTION
( Vesicoureteral reflux )
( Vesicoureteral reflux )
PELVICALYCEAL CONTAMINATION
( Intrarenal reflux)
RENALMEDULIARY CONTAMINATION
RENALINFECTION
REFLUX NERPHROPATHY
Bacterial inoculation of renal parenchyma
Complement activation
Immune response
Chemo taxis - opsonization
Phagocytosis…….........…….
Intravascular
Granulocyte
aggregation
Super oxide release
Lysozyme
Release
Bacterial killing
Tubular cell death
Focal
Interstitial invasion
RENAL SCAR
ischemia
Classification of UTI
1- symptomatic:
acute pyelonephritis
acute cystitis
unspecified UTI
2- Asymptomatic bacteriuria
Approach to the children with
UTI
1-Diagnosis of UTI
2-Determination of the site of infection
3-Search for the cause of UTI
4-Treatment
•False positive diagnosis of UTI may lead to
unnecessary treatment ,invasive and
expensive clinical and radiological
examinations
•False negative diagnosis of UTI increases risk
of scarring, hypertension, complications of
pregnancy and end stage renal disease
Methods to Obtain Urine
Specimens
• The gold standard for obtaining urine in an infant
is by suprapubic aspiration. Complications are rare
with the use of ultrasound guidance.
• Urinary catheterization is also a very
reliable method for obtaining urine
without contamination,
• Clean-catch mid-stream urine specimens
can be collected in toilet-trained children.
• The collection of urine in ‘‘collection bags’’
adhesively attached to the the perineal area
The American Academy of Pediatrics
The collection of urine in‘‘collection bags’’ adhesively
attached to the the perineal area has no role in the
diagnosis of childhood UTIs. The high contamination
rate, with ‘‘false positive’’ rates as high as 86% may lead
to unnecessary hospitalizations, and/or inappropriate
clinical and radiological testing.
the American Academy of Pediatrics
Suprapubic aspiration
Suprapubic aspiration
Bacteria that Cause UTI in Children
• E.Coli 60-80%
• The other common
bacteria are:
Proteus, Klebsiella,
Staphylococcus
saprophyticus,
Enterococcus, and
Enterobacter
Urinalysis for Immediate Diagnostic
Information
Dipstick testing: nitrite, leucocytes
protein and blood
Microscopic examination: WBC, RBC,
Bacteria, Cast
Localization of the UTI(1)
• The differentiation between upper(pyelonephritis)
and lower (cystitis) UTI is very important.
• It particularly has major clinical implications in
young children. The risk of renal scarring is
significant with pyelonephritis, and not a
concern with cystitis.
Localization of the UTI(2)
Clinical signs
Pyelonephritis:
high fever, chills, back or flank pain,
renal tenderness, varied gastrointestinal
symptoms: diarrhea, vomiting, and
nausea, In addition, neurological
symptoms such as irritability, and
seizures (particularly with high fever)
may exist.
Localization of the UTI(3)
Clinical signs
Bacterial cystitis:
There is rarely fever >38
Common findings include low grade
abdominal pain and bladder/voiding symptoms
such as frequency, pain with micturation,
suprapublic discomfort, difficulty in voiding
(retention) or hesitancy, urgency, and enuresis.
Specific Clinical Signs of UTIs in
Neonates and Infants
The symptoms are nonspecific and require a
high degree of clinical suspicion. They include
fever, poor feeding, failure to thrive,
abdominal pain, haematuria, and malodorous
urine. Jaundice may be an early diagnostic
sign of UTI in infancy
• unexplained fever
Localization of the UTI(4)
Biological Tests
• decreased renal concentrating capacity in pyelonephritis
• Specific antibodies to the infecting bacteria
• An elevated erythrocyte sedimentation rate, a positive Creactive protein,
• An elevated peripheral WBC count with an increased
absolute neutrophil counts
• Recently a high procalcitonin concentration was
described as a validated predictor of acute pyelonephritis
Serum procalcitonin
• Procalcitonin is an acute inflammatory
marker with a sensitivity of 70-95% and a
specificity that approaches 90% for renal
involvement compared with results of DMSA
scan in infants and children with febrile UTI.
Although less sensitive than CRP,
procalcitonin is more specific for the
diagnosis of acute pyelonephritis.
Procalcitonin values are better correlated
with long-term renal scarring than CRP.
Serum procalcitonin
• Procalcitonin levels near 0.5 ng/mL
may not consistently correlate with
acute pyelonephritis. As procalcitonin
levels increase, the severity of renal
lesions on DMSA increases.
• Higher levels of procalcitonin
predict VUR in infants and children at
the onset of pyelonephritis
Serum and urinary interleukin (IL)-6 and IL8
Serum and urinary interleukin (IL)-6 and
IL-8 are correlated with renal
involvement in infants and children
with UTI with high sensitivity (81-88%)
and acceptable specificity (7883%). These markers are not reliable in
neonates with suspected acute
pyelonephritis.
Imaging Tests in Localizing the Site of
Infection
1-Renal cortical scintigraphy
2-Renal ultrasound
3- Computed Tomography
4-Magnetic resonance Imaging
Imaging of pyelonephritis
RUS and IVU are relatively insensitive for
detection of pyelonephritis
Radionuclide cortical scan, Computed tomography,
magnetic resonance imaging are
more sensitive
Application of
•
99mT -DMSA
c
99mT -DMSA
c
is the gold standard for the identification of
pyelonephritis and renal scars
• Determining split renal function
• To identify and character renal infarcts
horseshoe kidney
pelvic kidney
crossed fused ectopia
National institute of Health and Clinical Excellence
(NICE): Clinical Guideline, August 2007
The use of DMSA scintigraphy scanning is only
recommended by the NICE clinical guidelines in
situations when it is clinically important to confirm
or exclude acute pyelonephritis, and when the
power Doppler ultrasound is not available or the
diagnosis still cannot be performed
guidance.nice.org
National institute of Health and Clinical Excellence
(NICE): Clinical Guideline, August 2007
Despite a large body of published literature,
the role of radionuclide renal scans in the clinical
management of the child with UTI still is unclear.
Most of the time such imaging has no role in the
specific management of childhood UTIs.
guidance.nice.org
Factors that may complicate interpretation
of 99mTc-DMSA
• Fetal lobulation
• The splenic impression
• The relatively decreased uptake of the
poles of normal kidney
Causes of defects in DMSA
•
•
•
•
•
•
•
•
Acute pyelonephritis
Renal scars
Cysts
Hydronephrosis
Infarcts
Masses
Dysplastic half of a duplex kidney
Proximal tubulopathies
DMSA
• Planar scintigraphy
• Single photon emission computed
tomography (SPECT)
SPECT Cortical Scintigraphy
• Superior sensitivity for detecting renal scars
• Higher rates of false positive results
• The increased imaging time with SPECT may
necessitate sedation
Split renal function in DMSA
scintigraphy
Normal split function = 50% ± 6%
Renal Ultrasound
Most of the time, conventional renal ultrasound is
insensitive for the diagnosis of pyelonephritis.
Signs of pyelonephritis include focal or diffuse
renal enlargement, an abnormal cortical
echogenicity mostly areas of increased
echogenicity which may mimic a renal mass
Renal Ultrasound
•Power Doppler ultrasound is more sensitive
than gray scale ultrasound:
“Pyelonephritis is associated with renal
ischemia. It is seen as a hypovascular
zone in renal cortex”.
Normal Kidney
Gray-scale ultrasound shows diffuse enlargement
of the left kidney, which measures 10.3 cm, and a
loss of corticomedullary differentiation
Pyelonephritis. Transverse gray-scale sonography of
the right kidney demonstrate two wedge-shape areas of
decreased echogenicity (arrow)
Renal abscess
Renal abscess Longitudinal gray-scale ultrasound
of the right kidney reveal presence
of a well-defined hypoechoic lesion
Renal abscess. transverse (B) gray-scale
ultrasound of the right kidney reveal presence
of a well-defined hypoechoic lesion (A) near the
superior pole
Fungal Ball
Power Doppler interrogation shows
decreased perfusion to the lower pole of
the left kidney
Pyelonephritis. Transverse gray-scale (A) and
color flow Doppler (B) sonography of the right
kidney demonstrate absence of color
flow, consistent with multifocal pyelonephritis.
Renal abscess power Doppler image (C)
demonstrates an increased peripheral vascularity
Power Doppler ultrasound. Triangular area of
cortical ischemia which is well correlated with the
results of DMSA Scintigraphy
Computed Tomography
The features of pyelonephritis by CT have
been well described:
After intravenous contrast, areas of infected renal
parenchyma have decreased contrast
enhancement due to the renal ischemia,
whereas normal renal parenchyma becomes
brighter
CT:Right kidney is markedly enlarged and
has a wedge-shaped area of low attenuation
Enhanced CT at the level of the kidneys demonstrates an
area in the posteromedial aspect of the right kidney with
diminished enhancement(arrow), consistent with the clinical
suspicion of pyelonephritis.
Magnetic resonance imaging
After IV gadolinium contrast the lesions of pyelonephritis
remain bright and the normal renal parenchyma is dark.
MRI / Acute pyelonephritis
Note clumps of small focal lesions irregularly
distributed about kidney. Some elevated.
.Acute pyelonephritis
Acute Pyelonephritis
Acute Pyelonephritis
Diagrammatic representation of
features of renal scars seen in IVU
Search for the Cause of UTI
• Anatomical abnormalities:
urinary tract obstruction, nephrolithiasis,
vesico-ureteral reflux
• Functional disturbances:
Voiding dysfunction
Traditional goals of performing
imaging in a child with UTI
to detect urologic abnormalities:
VUR, obstructive uropathy,
bladder dysfunction
to detect renal parenchymal damage
Imaging studies in children with UTI
Renal ultrasonography (RUS)
Voiding cystourethrography (VCUG)
Radionuclide cystography ( RNC)
Scintigraphic rénal imaging
(DTPA,DMSA)
Advantages and disadvantages of
RUS
1- RUS primarily provides an anatomic evaluation
and is used to seen renal anomalies and
hydronephrosis, renal parenchymal
abnormalities, urethral dilatation bladder wall
thickening ,ureterocells or calculi
2-RUS is not sensitive for focal or general
scarring
3- Normal RUS dose not exclude VUR.
RNG:
VCUG or RNG?
1- lower radiation dose
2- Continuous monitoring during study
for reflux
3- Dose not provide any anatomic evaulation
of bladder or urethra
4- Reflux grading is not accurate
Grading of reflux
International classification of
vesicoureteral reflux
Grades of Reflux
VUR is benign(1)
•
•
Natural tendency of VUR to resolve spontaneously
The historical studies showing that VUR is much more common,
even among healthy children,
•
Evidence supporting the role VUR leading to
pyelonephritis is controversial
The unanimous conclusion of recent meta-analyses on the
treatment of VUR has been that surgical abolishment of VUR,
compared with microbial UTI prophylaxis and
spontaneous resolution of VUR, has the same risk of new
renal parenchymal injury or recurrent non-febrile UTI.
•
VUR is benign(12)
• The antimicrobial prophylaxis of recurrent UTI is
controversial too, and it may have unpleasant
short-term side effects and increase the
antimicrobial resistance of bacteria
• In one randomised prospective study comparing
continuous, intermittent or no treatment with
antimicrobials in children with VUR, there was
no difference between the groups studied in the
risk of recurrent UTI or renal parenchymal injury.
Conclusions:
Vesicoureteral reflux is a fairly common
phenomenon that can be associated with
congenital renal dysplasia.Vesicoureteral
reflux does not markedly increase the risk
of recurring UTI or new acquired renal
scars. The surgical correction of VUR does
not prevent recurrences of nonfebrile UTI or
new renal scars. In some children VUR is a
symptom of developmental maturation
defect of the “uretero-vesical valve.
VUR is not benign
• VUR predisposes to UTI and renal scars
• There is not an age limit for renal scarring
• Scarring can be prevented
VUR is not benign
Conclusion
I believe it may be possible to reduce the
rate and extent of renal scarring in future
by altering our approach to infant and
childhood UTIs, with more prompt
diagnosis and treatment and an
awareness of the potential hazard that
having VUR may cause in this setting.
The hope is, that by doing this, we will
reduce the numbers of adults with
hypertension and renal failure in the next
generation of adults.
Treatment of UTI
• First: empiric treatment
• Then: according to the result of culture
Treatment of Pyelonephritis
• Completely intravenous treatment
• Initial 3-4 days IV treatment followed by oral treatment
• Completely oral treatment (except high risk children)
Indications for hospitalization
•
•
•
•
•
Age <2 months
Clinical urosepsis or potential bacteremia
Immunocompromised patient
Vomiting or inability to tolerate oral medication
Lack of adequate outpatient follow-up (eg, no
telephone, live far from hospital, etc.)
• Failure to respond to outpatient therapy