A. Ultrasound – Explanation

UTI presents atypically in neonates and may be associated with life-threatening sepsis.

If the child is less than 6 months old like in this case and responds well to treatment
within 48 hours, an ultrasound can be arranged to be done within 6 weeks.

Micturating cystourethrogram (MCUG) is considered only if ultrasound is abnormal or if
the child fails to respond to antibiotics within 48 hours. MCUG can also be performed if
there is a history of recurrent UTI.

Dimercaptosuccinic acid (DMSA) scan is usually performed 4 to 6 months after the
acute infection. It is not needed if the child responds well to antibiotics.

REMEMBERING PAEDIATRIC UROLOGY SCANS
The key to remember paediatric urology scans are to remember the number 6!
If younger than 6 months:

• Ultrasound during acute infection – If does NOT respond well to antibiotics within 48
  hours
• Ultrasound within 6 weeks – If responds well to antibiotics
• MCUG – If did NOT respond well to antibiotics during acute infection
• DMSA scan 4-6 months – If did NOT respond well to antibiotics during acute
  infection

IMAGING CHILDREN WITH URINARY TRACT INFECTIONS

The different test

Ultrasound

• First line test
• Non-invasive
• No radiation exposure
• Good at determining anatomy, renal size, presence of most congenital anormalies
• Not effective at detetecting mild to moderate vesicoureteric reflux

Micturating cystourethrography (MCUG)

• Gold standard test for detecting vesicoureteric reflux which affects between 25% and
  40% of children with confirmed urinary tract infectin
• Requires catheterisation
• Radiation exposure

DMSA (dimercaptosuccinic acid) scan

• Gold standard test for detecting renal scarring or damage to renal parenchyma
  occuring in about 5% of children after proven urinary tract infection
• Uses intravenous radioactive isotope which concentrates in renal tissue
• Should not be done at time of infection as may get false positive results
• Usually done 4 to 6 months after infection

Recommended Imaging
Three definitions are important in deciding on imaging and when it should be done.

Straightforward UTI

• Responds well to treatment within 48 hours

Atypical UTI (Any of the following)

• Failure to respond to treatment within 48 hours
• Septicaemia
• Raised creatinine
• Infection with non E. coli species

Recurrent UTI (Any of the following)

• Two or more episodes of UTI with acute pyelonephritis/infection of the UTI
• Three or more episodes of UTI with cystitis/lower UTI

If the table above is too complicated to remember, at least remember these golden rules
and you will likely get the answer:

• Below 6 months – ultrasound within 6 weeks if straightforward UTI
• Above 6 months – do NOT ultrasound if straightforward UTI
• If atypical, always ultrasound during acute infection no matter the age
• Always perform DMSA 4 to 6 months after any atypical or recurrent infection
• DMSA during an acute infection is always the WRONG answer
• MCUG after 3 years old is always the WRONG answer