urinary%20tract%20infection%20(pediatric)
URINARY TRACT INFECTION (PEDIATRIC)
Nonspecific urinary tract infection symptoms in infants <3 months are fever, feeding difficulties, vomiting, lethargy, irritability and failure to thrive.
Toddlers and preschoolers have unusual odor of urine, abdominal or flank pain, frequency, dysuria, and urgency.
School-age children have the classical symptoms of fever, frequency, urgency and dysuria.
Consider UTI in all seriously ill children even when there is evidence of infection outside the urinary tract.

Diagnosis

Presumed Urinary Tract Infection (UTI)

  • Diagnosed while urine culture results are pending in a patient w/ abnormal lab exams & clinical findings consistent w/ urinary tract infection (UTI)

Definite Urinary Tract Infection (UTI)

  • Diagnosis requires both positive results from urinalysis & culture obtained through catheterization or suprapubic bladder aspiration (SPA)
    • Culture results should have presence of >50,000 cfu/mL
  • Acute pyelonephritis is suggested in a patient who presents w/ dysuria & urinary frequency associated w/ flank pain, high-grade fever (temp >38.5oC) & chills
  • An immunocompromised patient or patient <2 months is assumed to have acute pyelonephritis or complicated urinary tract infection (UTI)

Atypical Urinary Tract Infection (UTI)

  •  Serious illness
  •  Poor urine flow
  •  Abdominal or bladder mass
  •  Elevated creatinine
  •  Septicemia
  •  Failure to respond w/in 48 hours to appropriate antibiotic therapy
  •  Infection w/ non-E coli organisms

Recurrent Urinary Tract Infection (UTI)

  •  ≥2 episodes of urinary tract infection (UTI) w/ acute pyelonephritis/upper urinary tract infection (UTI) or
  •  1 episode of urinary tract infection (UTI) w/ acute pyelonephritis/upper urinary tract infection (UTI) plus ≥1 episodes of cystitis/lower urinary tract infection (UTI) or
  •  ≥3 episodes of urinary tract infection (UTI) w/ cystitis/lower urinary tract infection (UTI)

Assessment

Signs & symptoms consistent w/ urinary tract infection (UTI) based on patient’s age

Infants <3 months

  • Nonspecific: Fever, feeding difficulties, vomiting, lethargy, irritability, failure to thrive
  • Less common: Abdominal pain, jaundice, hematuria, strong-smelling urine, sepsis syndrome, shock

Toddlers & preschoolers

  • Unusual odor of urine
  • Abdominal or flank pain
  • Frequency, dysuria, urgency
  • Nonspecific signs may be present

School age

  • Classical symptoms more common: Fever, frequency, urgency, dysuria
  • Strong-smelling urine, new onset urinary incontinence, changed behavior
  • Abdominal or flank pain

Consider urinary tract infection (UTI) in all seriously ill children even when there is evidence of infection outside the urinary tract

Signs & symptoms consistent w/ urinary tract infection (UTI) based on severity

Simple urinary tract infection (UTI)

  • Mild pyrexia, good fluid intake, mild dehydration, good treatment compliance

Severe urinary tract infection (UTI)

  • Fever ≥39°C, persistent vomiting, severe dehydration, poor treatment compliance

Urine Specimen Collection

  • It is difficult to obtain an uncontaminated urine specimen

Bag

  • Least traumatic method
  • Useful in infants
  • A plastic bag is taped at the perineal area & urine is collected after the child voids
  • Because of high risk of contamination, a bagged specimen is not useful in accurately documenting urinary tract infection (UTI)
  • Useful in ruling out urinary tract infection (UTI) when result is negative
  • Not ideal for urine culture: 88% false positive result, 63% specificity; 95% false positive rate for febrile boys, 99% false positive rate for circumcised boys

Clean-catch midstream urine specimen

  • May be obtained from toilet trained patients w/ no apparent infection or abnormality of the external genitalia
  • Cleansing before specimen collection is not needed
  • Likely to be contaminated by periurethral & preputial organisms, esp in young girls & uncircumcised boys
  • Useful in ruling out urinary tract infection (UTI) when result is negative

Urethral catheterization

  • Traumatic & invasive procedure that may introduce periurethral organisms into an otherwise sterile urinary tract
  • 95% sensitivity, 99% specificity of urine sample when used for culture
  • Requires cleansing & strict aseptic technique
  • Initial portion of urine should be discarded because it may be contaminated by periurethral organisms

Suprapubic aspiration (SPA)

  • Gold standard for identifying bacteria w/in the bladder
  • Traumatic, difficult to perform
  • Recommended for the following:
    • Diapered, uncircumcised boys whose urethral openings are difficult to see
    • Patients w/ urgent indications for treatment who cannot produce a clean-catch midstream urine specimen & cannot be catheterized
  • It is difficult to obtain an uncontaminated urine specimen

Laboratory Tests

Urine dipstick test

  • May reduce the need for culture especailly in patients w/ a low likelihood of urinary tract infection (UTI) (eg vague urinary complaints, w/ an alternative cause of fever)
  • Urine dipstick may have lower sensitivity in infants

Leukocyte esterase

  • Produced by activated white blood cells (WBC)
  • May be falsely negative if white blood cells (WBC) are not present during a urinary tract infection (UTI)
  • Sensitivity of 48-86% & specificity of 17-93%

Nitrite

  • Gram negative bacteria reduce dietary nitrates to nitrites
  • May be falsely negative if pathogen is Gram positive or bacterial metabolism has not yet produced nitrites
  • Sensitivity of 45-60% & specificity of 85-98%

Urine microscopy

  • Findings supportive of urinary tract infection (UTI)
    • ≥5-10 white blood cells (WBC)/high power field
    • Any bacteria seen on Gram stain of unspun urine, w/ sensitivity of 93% & specificity of 95%
  • Urine specimen should have been collected <1 hour after voiding or <4 hours after voiding when refrigerated
  • White blood cells (WBC) casts are almost pathognomonic of pyelonephritis

Urine culture

  • Gold standard for urinary tract infection (UTI) diagnosis
  • Results may take 24-48 hours
  • Indicated in the following patients:
    • Diagnosed w/ acute pyelonephritis or upper urinary tract infection (UTI)
    • Have a high to intermediate risk of serious illness
    • <3 years of age
    • W/ a high likelihood of urinary tract infection (UTI) (eg classic urinary symptoms)
    • Have cloudy urine or single positive results for leukocyte esterase or nitrite activity
    • W/ recurrent symptoms
  • Diagnostic thresholds for urine culture based on method of specimen collection:
Collection method Diagnostic threshold
Clean-catch voiding 105 colony forming units (cfu)/mL Repeat testing if 104-105 cfu/mL
Urethral catheterization 105 cfu/mL
Suprapubic bladder aspiration (SPA) Any number of cfu/mL (>10 identical colonies)

Additional lab exams

Blood culture

  • Unnecessary in most children w/ urinary tract infection (UTI)
  • Must be done in children w/ septic syndrome or septic shock & febrile infants

Complete septic work up

  • Must be done in neonates to avoid missing a diagnosis of meningitis & in children w/ septic syndrome or septic shock

Imaging

  • In the acute setting, diagnostic urinary tract imaging is generally not necessary unless the diagnosis of urinary tract infection (UTI) is equivocal
  • Imaging studies can most often be done after the resolution of the acute infection because management during this time is based on patient’s clinical profile
  • Routine imaging for patients w/ a first urinary tract infection (UTI) is not recommended because imaging has not been shown to alter outcomes; also, it is not cost-effective

Indications for early imaging during urinary tract infection (UTI)

  • Persistence of signs & symptoms of urinary tract infection (UTI) after 48 hours of appropriate antibiotic therapy
    • To identify conditions that require invasive therapy (eg renal abscess, anatomic abnormalities) that may be corrected surgically
  • Possible urinary tract obstruction (eg abdominal mass, elevated creatinine, poor urine flow, sepsis)
  • In rare cases when localization is clinically important
  • Atypical urinary tract infection (UTI) in all patients
  • Recurrent urinary tract infection (UTI) in patients <6 months

Indications for delayed imaging

  • Atypical urinary tract infection (UTI) in patients <3 years
  • Recurrent urinary tract infection (UTI) in all patients

Types of Imaging Studies

Ultrasound (US)

  • Identify abnormalities in renal size & shape, scars, duplication anomalies, ureteric dilatation
  • May reveal bladder diverticula or ureteroceles
  • Doppler ultrasonography can detect small areas of inflammation in the kidneys
  • Recommended early imaging test in infants & children w/ atypical urinary tract infection (UTI) to identify structural urinary tract abnormalities
  • Recommended for febrile infants if evaluation of the renal parenchyma & size are needed
  • Advantages: Noninvasive & radiation-free
  • Disadvantage: Results are operator-dependent

Voiding cystourethrogram (VCUG)

  • Invasive procedure requiring urethral catheterization; should only be done when hydronephrosis, scarring, findings suggestive of high-grade vesicoureteral reflux (VUR)/obstructive uropathy, atypical/complicated disease are seen w/ renal & bladder ultrasound (RBUS)
  • Detects & grades vesicoureteral reflux (VUR)  accurately & can show bladder & urethral anatomy, periureteral diverticula, spinal abnormalities
  • Disadvantages: Radiation exposure, possibility of introducing infection into the urinary tract, retrograde filling of the bladder may be necessary
  • In a patient for voiding cystourethrogram (VCUG) prophylactic antibiotics should be given for 3 days, w/ the procedure taking place on the 2nd day

Radionuclide cystography

  • May be considered for patients w/ reflux
  • Advantages: Less radiation exposure
  • Disadvantages: Poor image resolution, low sensitivity for lower urinary tract infection (UTI) & other abnormalities

Tc 99m dimercaptosuccinic acid renal scintigraphy (DMSA)

  • Gold standard for localizing infection to the renal parenchyma
  • More sensitive in detecting cortical scarring than ultrasound (US) & intravenous pyelogram (IV) pyelogram
  • Radiolabeled Tc 99m dimercaptosuccinic acid renal scintigraphy (DMSA) is injected intravenously & binds to renal proximal tubular cells, after which renal cortical images are taken
    • An area of decreased uptake delineates an area of focal defect in the renal parenchyma
    • Star-shaped defect in the renal parenchyma may indicate acute pyelonephritis
    • A focal defect in the renal cortex may signify chronic lesion or renal scar
  • Renal scarring may indicate that vesicoureteral reflux (VUR) is likely to persist in patients w/ reflux
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