Urinary tract infection

Aim

This guideline provides an evidence-based framework for the investigation and follow up of children following the diagnosis of a Urinary Tract Infection (UTI).

Background 

• UTIs in children and young people are common.
• Upper UTIs (i.e. pyelonephritis) may result in kidney scarring. In most cases this is not clinically meaningful. A small proportion of children develop long term complications including hypertension and chronic kidney disease. However, these are rare in children and young people with a structurally normal urinary tract.¹
• The rationale for imaging following a UTI is to identify children with anatomic or functional abnormalities of the urinary tract that will predispose them to recurrent UTI’s. Management strategies to mitigate this risk can then be considered. Antimicrobial prophylaxis does not have a role in first UTI in children with a normal urinary tract² but may benefit children with underlying structural abnormalities or frequent infections. The most common risk factor for recurrent UTIs is bowel and bladder dysfunction³, for which there is a limited role for imaging.
• Advances in antenatal imaging have significantly reduced the likelihood of detecting a new significant urinary tract abnormality postnatally.⁴ This, together with better postnatal ultrasound quality, has diminished the need for further radiological investigations. There is also increasing evidence that many cases of chronic kidney disease historically thought to be caused by reflux nephropathy are actually due to congenital renal dysplasia.⁵

Risk

Children with urinary tract infections may undergo unnecessary investigations or not receive the appropriate investigations and follow up.

Initial management

• Febrile infants less than 3 months of age should be managed according to the Febrile Child (PIC).
• Children aged greater than 3 months presenting to PCH with a UTI should be initially managed in accordance with the Urinary Tract Infection (PIC) guideline.
• Antibiotic therapy should be commenced in accordance with the ChAMP antimicrobial guideline – Urinary Tract Infection – Paediatric – ChAMP guideline.

Investigations 

Refer to flowchart in Appendix 1: UTI investigation flowchart.

Renal Tract Ultrasound (USS)

• Used to assess urinary tract anatomy
• A 2023 Meta-analysis found that of children with a first febrile UTI 22% will have an abnormality on renal USS but only 3% of these were clinically important.⁴
• Recommended during hospital admission or acute infection for:
  • Children with an atypical UTI
    • seriously unwell
    • poor urine flow
    • abdominal or bladder mass
    • renal impairment
    • failure to respond to appropriate treatment within 48 hours
    • infection with non E. coli organism** can be done as an outpatient if responds well to appropriate treatment
  • Boys less than 3 months old
• Recommended within 6 weeks of acute infection for:
  • First febrile UTI under 6 months of age
  • Recurrent UTI
    • ≥ 2 episodes of pyelonephritis
    • 1 episode of pyelonephritis plus ≥ 1 episode of cystitis
    • ≥ 3 episodes of cystitis
• Children over the age of 6 months with their first typical UTI that responds to appropriate treatment do not need a routine ultrasound⁶.

Micturating Cystourethrogram (MCUG)

• Provides an assessment of renal tract anatomy during voiding. Its purpose is to detect urethral and bladder anomalies, including vesicoureteral reflux (VUR) and posterior urethral valves. It involves radiation and is invasive (requires urethral catheterisation).
• An audit performed within our institution found that a renal tract US performed by the PCH radiology service effectively excluded high grade (4 or 5) VUR and posterior urethral valves (n=220).⁷
• Lower grade VUR may be missed on USS but is generally managed conservatively, thus the utility of performing an invasive test to achieve this diagnosis is questionable.⁸
• Consider only in discussion with nephrology/urology. Refer to Appendix 2: Indications for MCUG or Urogenitogram (PCH).

Dimercaptosuccinic Acid Scan (DMSA scan) 

• Nuclear medicine scan; indicates degree of renal parenchymal involvement. An abnormal result during acute infection may indicate pyelonephritis whereas an abnormal result > 4 months after acute infection indicates renal scarring. The clinical importance of this is uncertain.⁹
• An audit performed within our institution found that a normal renal tract USS performed by the PCH radiology service excluded significant abnormalities on DMSA with a negative predictive value of 90% (n = 143). Of those children who had a normal ultrasound and abnormal DMSA scan, 4/9 had a small single renal scar with normal differential function and 5/9 had no scar but borderline differential function (4/5 were 44% vs 56% and 1/5 was 43% vs 57%).¹⁰
• Only consider in discussion with nephrologist or urologist.

Other imaging

• Other nuclear medicine scans e.g. DTPA or MAG3 can be used to assess differential and excretory renal function
• Generally used to differentiate between obstructive and nonobstructive hydronephrosis
• Only consider in discussion with nephrologist or urologist.

References and related external legislation, policies, and guidelines

1. Hughes K, Cannings-John R, Jones H, Lugg-Widger F, Lau TMM, Paranjothy S, et al. Long-term consequences of urinary tract infection in childhood: an electronic population-based cohort study in Welsh primary and secondary care. Br J Gen Pract. 2024;74(743):e371-e8.
2. Investigators RT, Hoberman A, Greenfield SP, Mattoo TK, Keren R, Mathews R, et al. Antimicrobial prophylaxis for children with vesicoureteral reflux. N Engl J Med. 2014;370(25):2367-76.
3. Larkins N, Hewitt I. Urinary Tract Infection in Children. Current Pediatrics Reports. 2018;6:259-268
4. Yang S, Gill PJ, Anwar MR, Nurse K, Mahood Q, Borkhoff CM, et al. Kidney Ultrasonography After First Febrile Urinary Tract Infection in Children: A Systematic Review and Meta-analysis. JAMA Pediatr. 2023;177(8):764-73.
5. Hewitt IK, Roebuck DJ, Montini G. Conflicting views of physicians and surgeons concerning pediatric urinary tract infection: a comparative review. Pediatr Radiol. 2023;53(13):2651-61.
6. National Institute for Health and Care Excellence (NICE). Urinary tract infection in under 16s: diagnosis and management. National Institute for Health and Care Excellence: Guidelines [NG224]. London 2022. Available from: http://www.nice.org.uk/guidance/ng224
7. Leung M, Ozanne R, Smith L, Martin AC. Utility of Screening Ultrasound After First Febrile UTI Among Patients With Clinically Significant Vesico-ureteral Reflux. Urology 2014. 83(3) pp680-681. 
8. Williams G, Hodson EM, Craig JC. Interventions for primary vesicoureteric reflux. Cochrane Database Syst Rev. 2019;2(2):CD001532.
9. Mattoo TK, Shaikh N, Nelson CP. Contemporary Management of Urinary Tract Infection in Children. Pediatrics. 2021;147(2).
10. Tan A, Troedson R, Martin AC. A normal Renal Ultrasound Scan reliably excludes major abnormalities on DMSA in children with UTIs. J Paed Child Health. 2014. 50(12) pp1033-1034. 

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