Urinary Tract Infections in Children

Diagnostic Imaging based on Clinical Practice Guidelines

Emily D. Kucera, M.D.Assistant Professor,

UMKC

Learning Objectives

• State prevalence, associations, and consequences of febrile UTI’s in children

• Discuss imaging options and timing of procedures

• Discuss classification systems used in radiologic reports

• Review variations of Clinical Practice Guidelines from reputable institutions- will discuss CMH guidelines and include others in handout.

Febrile UTI’s

Most common serious bacterial infection occurring in infancy and childhoodAffects at least 3.6% of boys, 11% of girls10-30% of children with febrile UTI’s will develop renal scarring

Diagnosis of UTICombination of clinical features and presence of bacteria in urine > 10⁵ cfu/mlAcute pyelonephritis = UTI + fever •> 38℃ (100.4℉) - most common in

infantsCystitis = symptoms of dysuria, frequency, suprapubic pain in toilet-trained child

Urinary Tract Infections in Children

Prevalence of positive culture in children 0-21 years 8.8 - 14.8%Males < 1 year (3%); males > 1 year (2%)Females < 1 year (7%); females > 1 year (8%)50-91% of children with febrile UTI’s are found to have acute pyelonephritisAll infants < 8 weeks of age with fever should be suspected of having an upper tract infection/pyelonephritis

Organisms Associated with UTI’s in Children

• Escherichia coli - Most common organism; causative agent in > 80% of 1st UTI

• Klebsiella species - 2nd most common organism. Seen more in young infants

• Proteus species - May be more common in males

• Enterobacter species - cause < 2% of UTI’s

• Pseudomonas species - cause < 2% or UTI’s

• Enterococci species- Uncommon > 30 days of age

• Coagulase-negative staphylococcus - Uncommon in childhood

• Staphylococcus aureus - Uncommon > 30 days of age

• Group B streptococci - Uncommon in childhood

_

+

Risk Factors for UTI’sMale

Uncircumcised < 1 yr (5-20 x higher risk than circumcised males)All < 6 months

Female< 1 yrnon-African American racefever > 39℃ (102.2℉)

Atypical UTI’s• Seriously ill• Poor urine flow• Abdominal or bladder mass• Raised creatinine• Septicemia• Failure to respond to treatment

within 48 hrs• Infection with non- E. coli organisms

“Seriously Ill”

Recurrent UTI’s• 2 or more episodes of acute

pyelonephritis / upper urinary tract infection

• or

• 1 episode of acute pyelonephritis + > 1 episode of cystitis

• or

• > 3 episodes of cystitis/lower urinary tract infection

Recurrent UTI’sGirls are more prone to recurrences with ageChildren who present early in life with UTI are more prone to recurrences

¾ of children presenting < 1 year will have recurrences> 1 year of age ~ 40% of girls, 30% of boys Overall incidence of UTI recurrences after pyelonephritis is 20.1%

Asymptomatic Bacteriuria

Most common in boys in early infancy1.6% boys < 2 monthsaffects 0.2% in school age boys

Girls have lower rates until 8-14 months1.5 - 2% in school age girls; peak prevalence 7-11 years of age

Dysfunctional Elimination Syndromes (DES)

Constipation- seen in 50 % of DES and VUR• May induce uninhibited bladder

contractions• Rectal distention causes bladder distortion

causing detrusor dyssynergism and ureteral valve incompetence

Bladder instabilityInfrequent voiding (< 4 times/day)Contributes to UTI’s and slower resolution of reflux

Associations with UTI’s

Dysfunctional Elimination Syndromes (DES)

67% of girls with DES develop UTI’s40% of girls with UTI’s have DES20% of girls with DES have reflux

A 6 month old female has had 3 UTI’s. Which of the

following is the best approach?

A. B. C. D.

63%

0%

13%

25%

A. No imaging needed

B. US + VCUGC. MRID. DMSA scan

Imaging Procedures• Ultrasound - detect renal anomalies,

dilatation, renal sizes, bladder abnormalities, ureteral dilatation

• VCUG - Voiding Cystourethrogram- assess for vesicoureteral reflux, bladder volumes, bladder abnormalities, urethral anatomy

• DMSA Scintigraphy- assess for pyelonephritis and renal scarring

• Radionuclide Cystogram - assess for VUR; used infrequently at CMH

Abnormal Ultrasound Findings

Dilatation of at least 1 calyxAnteroposterior (AP) diameter of the renal pelvis > 7 mm; ureteral diameter > 5 mmFocal scarringDifference of > 10% of length between kidneys or renal length > 2 standard deviations above mean Bladder abnormality

Normal Hydronephrotic MCDK

Society of Fetal Urology Classification of Prenatal and Postnatal Hydronephrosis

1 2

4 3

Duplicated Collecting Systems

• Duplication of renal pelvis and ureter is one of the most common anomalies of the urinary tract• Partial - range from bifid renal pelvis to 2 ureters

joining anywhere proximal to uterovesical junction

• Complete - 2 separate ureters with the upper pole ureter draining more caudal and medial than the lower pole ureter = ectopia (Weigert-Meyer rule)

• Ureteral duplication is of no clinical significance unless it is complicated with ectopia, VUR, UTI, or obstruction

Duplicated Collecting Systems

Non-dilated Dilated

Voiding Cystourethrogram

• Requires bladder catheterization: • 8 Fr feeding tube (No balloon)• Lidocaine gel used on majority of patients

•Local analgesia•Dilates meatal opening

• Radiation: • Decreased dose with pulse and digital

techniques• 1-3% risk of UTI

Need for Sedation• Sedation not needed in the vast majority

of the cases• CMH Guidelines for sedation follow the

AAP and ASA (Anesthesia) Guidelines• If need for anxiolysis, please directly

communicate with the Radiologist who will be performing the exam at the time of scheduling

• Child Life personnel available at the Main and the South Campuses.

Vesicoureteral Reflux

International Reflux Grading System of VUR

Bilateral Grade 2

Grade 1 Grade 3

Vesicoureteral Reflux

Incidence 20-40 % of children presenting with UTI

Girls 17-34% Boys 18-45%

Increased incidence if family history of VUR•Parent to Child: up to 66%•Siblings: up to 34%

Overall prevalence in general population 1-3%

Prevalence of VUR by Age• Prevalence in 54 studies of UTI in Children

Prevalence of VUR

Girls: 0 - 18 yrsGrade I - 7%

Grade II - 22%

Grade III - 6 %

Grade IV - 1%

Grade V - < 1%

DMSA ScintigraphyIntravenous injection of a radiopharmaceutical labelled with TC-99m DMSA is concentrated in the proximal renal tubules. Identifies functioning renal tissueImages obtained between 2-6 hours after injectionUsually requires sedation in children < 3 years of age

Timing of DMSA• Acute imaging: Within 5-7 days of

acute infection • 90% sensitivity for pyelonephritis• Cannot differentiate pyelonephritis

from renal scarring

• Delayed imaging ~ 6-12 months after UTI• Assess for renal damage• Gold standard for detection of

parenchymal defects

DMSA

Normal Renal Scarring

Risk of Renal Parenchymal Defects

In the presence of VUR, more frequent in boys and children > 1 year of age~ 5% of children presenting with 1st febrile UTI will have parenchymal defectsPyelonephritis and renal scarring occur as frequently in children without VUR as with VURIn the general population: 0.5 - 0.13% girls versus 0.17 - 0.11% boys will develop reflux nephropathy

Renal Parenchymal Defects

Boys more susceptible to developing dysplasia or parenchymal defects in uteroGirls tend to acquire their parenchymal defects at a later ageInfants have a higher risk of renal damageRecurrent UTI’s a significant risk factor for girls, not boysThe only effective way to reduce renal scarring associated with UTI’s is early diagnosis and prompt, effective treatment

Renal DamageOf children with acute pyelonephritis diagnosed by DMSA, 38-57% will develop permanent renal scarring Seen in 78% of infants with dilating reflux(grades III-V), obstruction, clinically relevant anomalies (renal aplasia, ectopic kidney, complete duplication)Seen in 15% of infants without the above diagnoses

Risk of Renal ScarringRisk of Renal Scarring versus # of

UTI’s

A 5 year old female has recurrent febrile UTI’s. What imaging study would be useful to detect renal

scarring?

A. B. C. D.

38% 38%

13%13%

A. VCUG

B. US

C. CT abdomen

D. DMSA scan

Recommendations and Guidelines

No universally accepted work-up for children with UTI’sLack of consensus among different guidelinesComplex approaches; Regional variations

Multiple tables dividing children into different age groupsClassifying UTI’s into different variantsDetermine nature and timing of imaging studies

Utility of Diagnostic Imaging Procedures

Identifying pathologic malformations and risk factorsChanging management approachesAffecting follow-up monitoring

Outside of Guidelines

Infants and children:known pre-existent uropathy or underlying renal diseasehydronephrosis or obstructionneurogenic bladderwith urinary catheters in situimmunosuppressed

Clinical Practice Guidelines

• Children’s Mercy Hospitals (last edited 2007)

• Included in Handout• American Academy of Pediatrics (last edited

1999)

• Cincinnati Children’s (last edited 2006)

• NICE (National Institute for Health & Clinical Excellence) (2007)

• Royal College of Physicians (1991)

CMH Guidelines

• Boys- All• Girls < 36 months• Girls 3-7 years of

age with fever > 38.5℃ ( 101.3 ℉)

Ultrasound ⇓VCUG ⇓If identification of pyelonephritis or renal scarring ⇓DMSA

CMH Guidelines

• Girls > 3 years with fever < 38.5℃ (101.3℉)

• All Girls > 7 years

Observation without imaging ⇓If subsequent UTI ⇓ Ultrasound ⇓VCUG ⇓If pyelonephritis or renal scarring ⇓DMSA

Children’s Mercy Guidelines

Children who should have RUS + VCUG after 1st febrile UTI

Failure of good response after 48-72 hrs of effective antibioticsInfection with an unusual organismLack of assurance of close follow upAbnormal urine stream, abdominal massRecurrence of febrile UTI

Timing of VCUG during Acute Illness

•VCUG during first 10 days of treatment IF•The patient has good response to Tx;

afebrile > 24 hours•The infecting bacteria is susceptible to

antibiotic administered•Voiding pattern has normalized to pre-

infection•Younger infant should have no dysuria

and normal behavior

An uncircumcized 2 month old male was admitted with a febrile UTI that has not responded to antibiotic therapy after 48

hours. When is the best time to perform a

VCUG?

A. B. C. D.

13%

25%

50%

13%

A. On the day of admission

B. After 24 hours

C. After 24 hours without a fever

D. No need to do VCUG

Vesicoureteral RefluxClassification per CMH Clinical Practice Guidelines

Mild: grade I and II, unilateral grade III in a child < 2 years oldModerate-Severe: all other grade III’s, IV, V

Referral to Pediatric Urologist or Nephrologist

Any child with evidence of urinary tract obstruction: Refer to Pediatric UrologistVUR > Grade III or evidence of renal damage VUR > Grade III with break through infectionAny child with Grade V VUR should be referred immediately. The presence of Grade IV and lower grades of VUR + the presence of renal damage frequently reflects intrauterine VUR and damage rather than acquired damage.

Recommendations for Follow-up VCUG’sCMH Clinical Practice Guidelines:

In children maintained on prophylactic Antibiotics:

every 2 years with grades I and II, and for those < 2 years with unilateral grade IIIevery 3 years for all others with grade III and IV

Conclusions• Better understanding of the impact of

febrile UTI’s on children• Better understanding of some of the

radiologic procedures and findings• Understanding of CMH Clinical Practice

Guidelines and ability to compare with other Clinical Practice Guidelines from reputable institutions

• Effects on diagnostic imaging and timing of imaging procedures

AAP GuidelinesEvery febrile infant or young child, 2 months-2 years of age, should be imaged with ultrasound and a study to detect for VURThose who do not demonstrate the expected clinical response within 2 days of antibiotics, should have ultrasound promptly and reflux study at earliest convenience

Cincinnati Children’s Guidelines

Children with 1st UTI, need Ultrasound and Voiding Cystogram:

all boysgirls age < 36 months (dependent on ability to verbalize dysuria girls 3-7 years with fever > 38.5 ℃ (101.3℉)

Observation without Imaging per Cincinnati Children’s

Girls > 3 years with fever (< 38.5℃)All girls > 7 yearsFollow up with dipstick of routine urinalysis if symptoms of UTI

NICE Guidelines• Not recommend antibiotic

prophylaxis following 1st UTI, even in child with VUR•Not routinely evaluate for VUR with

imaging• Infants < 6 months with 1st UTI that

responds to treatment - US within 4-6 weeks of UTI

• Infants > 6 months- US not recommended unless atypical UTI

NICE Guidelines Infants < 6 months

Responds to Tx within 48 hours

Atypical UTI Recurrent UTI

Ultrasound during acute infection

No Yes* Yes

Ultrasound within 6 weeks

Yesª No No

DMSA within 4-6 months following infection

No Yes Yes

VCUG No Yes Yes

ª If Ultrasound abnormal, consider VCUG

*In a child with non-E. coli UTI, responding well to antibiotics and no other features of atypical infection, ultrasound can be requested on a non-urgent basis

NICE GuidelinesChildren 6 months - < 3 yrs

Responds well to Tx within 48 hours

Atypical UTI Recurrent UTI

Ultrasound during infection

No Yes* No

Ultrasound within 6 weeks

No No Yes

DMSA 4-6 months following acute infection

No Yes Yes

VCUG No Noª Noª

ªConsider VCUG if dilatation on ultrasound, poor urine flow, non-E. coli infection, family history of VUR

*In a child with non-E. coli UTI, responding well to antibiotics and no other features of atypical infection, ultrasound can be requested on a non-urgent basis

NICE GuidelinesChildren > 3 yrs Responds well to

Tx within 48 hours

Atypical UTI Recurrent UTI

Ultrasound during acute infection

No Yes* No

Ultrasound within 6 weeks

No No Yes

DMSA 4-6 months following acute infection

No No Yes

VCUG No No No

*In a child with non-E. coli UTI, responding well to antibiotics and no other features of atypical infection, ultrasound can be requested on a non-urgent basis

Royal College of Physicians in 1991

Infants: Ultrasound, VCUG, and DMSA Children 1-7 yrs: Ultrasound and DMSA> 7 yrs: Ultrasound and potential additional exams dependent on ultrasound findings

Guidelines of the Royal College of Physicians

Ultrasound should be considered in all cases of children with 1st UTI.Late DMSA scintigraphy in children up to 7 yearsVCUG in children < 1 year