Pediatric urinary tract infection

Pediatric urinary tract infections are common and are a source of significant imaging in young children.

Epidemiology

Pediatric urinary tract infections affect up to 2.8% of all children every year, with approximately 2% of boys and 8% or more of girls developing a urinary tract infection at some stage during childhood.

More frequent in boys until three months of age, after that it mainly affects girls.

Clinical presentation

It is important to realize that in children symptoms may be nonspecific.

Clinical features suggestive of UTI in a child under five years include:

• vomiting
• poor feeding
• lethargy
• irritability
• abdominal pain or tenderness
• urinary frequency or dysuria
• offensive urine or hematuria

In patients under two years look out for:

• pyrexia of unknown origin
• feeding disorder
• diarrhea
• slow weight gain
• failure to thrive
• sepsis

Pathology

Urinary tract infection is usually defined as a pure growth of at least 100,000 organisms/ml of a single strain of bacterial pathogen.

For urinary infection to be called 'recurrent',  it needs to be a symptomatic and proven UTI, which is adequately treated and then recurs.

Radiographic features

Ultrasound

Ultrasound is the first line investigation:

• assess renal morphology, echogenicity and position of kidneys
• observe congenital abnormalities: horseshoe, pancake, dysplasia, etc.
• greater than 10% size difference indicative of renal scarring
• assess bladder morphology

Voiding cystography is performed >6/52 after the acute phase.

DMSA is carried out after 6/12 (to allow for resolution of acute inflammatory changes). This represents the gold standard in assessing for renal scarring.

If there is a clinical concern of vesicoureteric reflux, micturating cystography can be performed.

There are four types performing micturating cystography:

1. micturating (voiding) cystourethrography (MCUG): requires fluoroscopy
2. direct isotope cystography (DIC): isotope Tc99 is introduced into the bladder via the urethra and the kidneys are imaged with a gamma camera
3. indirect isotope cystography: may be done as part of a MAG 3 study
4. voiding ultrasonography (echo-enhanced cystosonography): no ionizing radiation