Urinary Tract Infections

Key Features

Essentials of Diagnosis

• Signs in newborns and infants are nonspecific

• Abdominal or flank pain, vomiting, fever, urinary frequency, dysuria, urgency, or enuresis in preschool children

• Classic signs of cystitis or pyelonephritis in school-aged children

General Considerations

• An estimated that 8% of girls and 2% of boys acquire urinary tract infections (UTIs) in childhood

• Girls older than age 6 months have UTIs far more commonly than boys, whereas uncircumcised boys younger than 3 months have more UTIs than girls

• Circumcision reduces the risk of UTI

• The organisms most commonly responsible for UTI are

  • Escherichia coli (> 85%)

  • Klebsiella

  • Proteus

  • Other gram-negative bacteria

  • Enterococcus or coagulase-negative staphylococci (less commonly)

• Vesicoureteral reflux (VUR)

  • A congenital abnormality present in about 1% of the population beyond infancy

  • Detected in 30–50% of children who have a UTI at 1 year of age or younger

  • Graded using the international scale

    • I—reflux into ureter

    • II—reflux to the kidneys

    • III—reflux to kidneys with dilation of ureter only

    • IV—reflux with dilation of ureter and mild blunting of renal calyces

    • V—reflux with dilation of ureter and blunting of renal calyces

  • The natural history of reflux is to improve, and 80% of reflux of grades I, II, or III resolve or significantly improve within 3 years of detection

Clinical Findings

Symptoms and Signs

• Newborns and infants have nonspecific signs, including

  • Fever

  • Hypothermia

  • Jaundice

  • Poor feeding, vomiting, failure to thrive

  • Irritability

  • Sepsis

  • Strong, foul-smelling, or cloudy urine may be noted

• Preschool children may have

  • Abdominal or flank pain

  • Vomiting

  • Fever

  • Urinary frequency, urgency

  • Dysuria

  • Enuresis

• School-aged children commonly have

  • Frequency, dysuria, and urgency (classic signs of cystitis)

  • Fever, vomiting, and flank pain (classic signs of pyelonephritis)

  • Costovertebral tenderness

• Urethritis, poor perineal hygiene, herpes simplex virus, or other genitourinary infections may be apparent on examination

Diagnosis

Laboratory Findings

• Screening urinalysis

  • Indicates pyuria (> 5 WBCs/hpf) in most children

  • However, some children can have sterile pyuria without UTI

• Nitrite tests

  • Detection of urinary nitrite by dipstick is highly correlated with enteric organisms being cultured from urine

  • However, most young children (70%) with UTI have negative nitrite tests

• Urine culture

  • Gold standard for diagnosis

  • Proper collection of specimen is difficult in children due to frequent contamination of sample

  • Quantitative recovery of 10⁵ cfu/mL or greater is considered significant from clean-catch specimens, and 10⁴–10⁵ is considered significant from catheterized specimens

  • Usually the recovery of multiple organisms indicates contamination

• Asymptomatic bacteriuria

  • Seen commonly in children requiring chronic bladder catheterization

  • Represents colonization of the urinary tract with nonuropathogenic bacteria

  • Treatment in such cases may increase the risk of symptomatic UTI by eliminating nonpathogenic colonization

  • Screening urine cultures in asymptomatic children are, therefore, generally discouraged

Imaging

• Renal ultrasound

  • Recommended because it ...