Urinary tract infection

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Chapter 46 URINARY TRACT INFECTION

Theodore X. O’Connell

General Discussion

Urinary tract infection (UTI) in the pediatric population is well recognized as a cause of acute morbidity. Children with vesicoureteral reflux (VUR) are believed to be at risk for ongoing renal damage with subsequent infections, resulting in hypertension and renal insufficiency in adulthood. Infants and young children are at higher risk than are older children for incurring acute renal injury with UTI. The incidence of VUR is higher in this age group than in older children, and the severity of VUR is greater. The risk of renal damage increases as the number of recurrences increases.

The American Academy of Pediatrics 1999 Practice Parameter focuses on the diagnosis, treatment, and evaluation of febrile infants and young children 2 months to 2 years of age. Children older than 2 years were excluded because they are more likely than younger children to have symptoms referable to the urinary tract, are less likely to have factors predisposing them to renal damage, and are at lower risk of developing renal damage.

During the first year of life, boys have a higher incidence of UTI; in all other age groups, girls are more prone to developing UTI. Up to 7% of girls and 2% of boys will have a symptomatic, culture-confirmed UTI by 6 years of age. Most UTIs in children result from ascending infections, although hematogenous spread may be more common in the first 12 weeks of life. Escherichia coli (E. coli) is the most frequent documented uropathogen. Among neonates, UTI attributable to group B streptococcus is more common than in older populations.

Children who have UTI often do not show the characteristic signs and symptoms seen in the adult population. Older children with UTI may have dysuria, urgency, frequency, or lower abdominal pain. Infants with UTI more commonly present with nonspecific symptoms such as fever, irritability, vomiting, failure to thrive (FTT), or jaundice. The presence of UTI should be considered in infants and young children 2 months to 2 years of age with unexplained fever. The prevalence of UTI in children of this age who have no fever source evident from the history or physical examination is about 5%.

Diagnosis of UTI requires a culture of the urine, which must be properly collected. Urinalysis can only suggest the diagnosis. In infants and young children 2 months to 2 years of age, the urine specimen should be obtained by suprapubic aspiration or transurethral bladder catheterization. The diagnosis of UTI cannot be established by a culture of urine collected in a bag. Older children can provide a clean-catch midstream urine specimen.

Imaging of the urinary tract is recommended in every febrile infant or young child with a first UTI to identify those with abnormalities that predispose to renal damage. Imaging consists of urinary tract ultrasonography to identify hydronephrosis, dilatation of the distal ureters, hypertrophy of the bladder wall, and the presence of ureteroceles. In addition, either voiding cystourethrography (VCUG) or radionuclide cystography (RNC) is recommended for detecting reflux.

Initial antimicrobial therapy should be administered parenterally, and hospitalization should be considered for the infant or child with suspected UTI who is assessed as toxic, dehydrated, or unable to retain oral intake. For the infant or child who does not appear ill but who has a culture confirming the presence of UTI, antimicrobial therapy should be initiated either parenterally or orally. Seven to 14 days of oral antimicrobial therapy should be completed. Children 2 months to 2 years of age with UTI should receive antimicrobials in therapeutic or prophylactic dosages until the imaging studies are completed to prevent recurrent infection.

If a child does not have the expected clinical response within 2 days of antimicrobial therapy, the child should be reevaluated and another urine specimen should be cultured. Children who do not respond clinically should undergo ultrasonography promptly. In addition, either VCUG or RNC should be performed at the earliest convenient time.

Key Physical Findings

General assessment of well-being

Back examination for costovertebral angle tenderness

Abdominal examination for suprapubic tenderness

Sacral examination for the presence of dimples, pits, or a sacral fat pad

Scrotal examination to evaluate for epididymitis or epididymo-orchitis

Table 46-1 Criteria for the Diagnosis of Urinary Tract Infection

Method of Collection	Diagnostic Threshold
Suprapubic aspirate	Gram-negative bacilli: any number
	Gram-positive cocci: more than a few thousand
Transurethral catheterization	10,000 CFU/mL
	Repeat testing if 1000-10,000 CFU/mL
Clean-catch void in boys	10,000 CFU/mL
Clean-catch void in girls	100,000 CFU/mL
	Repeat testing if 10,000-100,000 CFU/mL

CFU, colony-forming units.

Suggested Work-up

Urine culture	In infants and young children 2 months to 2 years of age, the urine specimen should be obtained by suprapubic aspiration or transurethral bladder catheterization. The diagnosis of UTI cannot be established by a culture of urine collected in a bag. Older children can provide a clean-catch midstream urine specimen. Criteria for the diagnosis of UTI are presented in Table 46-1.
Urinary tract ultrasonography	Should be performed on all infants and young children 2 months to 2 years of age with fever and their first documented UTI
	May be considered for older children, although the yield is lower
VCUG or RNC	VCUG or RNC is recommended for all infants and young children 2 months to 2 years of age with fever and their first documented UTI to detect reflux.
	May be considered for older children, although the yield is lower

Additional Work-up

Urine dipstick analysis	Urine dipstick analysis can rule out UTI if the result is negative, but a positive result on dipstick testing is insufficient to diagnose UTI
Complete blood cell count (CBC), C-reactive protein, and sedimentation rate	Not routinely indicated but may help to determine the presence of a UTI if the clinical picture and urinalysis are equivocal
Blood cultures	Indicated for infants younger than 60 days of age

1. Alper B.S., Curry S.H. Urinary tract infection in children. Am Fam Physician. 2005;72:2483–2488.

2. American Academy of Pediatrics. Practice parameter: the diagnosis, treatment, and evaluation of the initial urinary tract infection in febrile infants and young children. Pediatrics. 1999;103:843–852.

3. Chang S.L., Shortliffe L.D. Pediatric urinary tract infections. Pediatr Clin North Am. 2006;53:379–400.

4. Chon C., Lai F., Shortliffe L.M.. Pediatric urinary tract infections. Pediatr Clin North Am. 2001;;48:1445.

5. Lin D.S., et al. Urinary tract infection in febrile infants younger than eight weeks of age. Pediatrics. 2000;105:e20.

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