Urinary Tract Infection in Infants and Children




(1)
Pediatric Surgery, AlSadik Hospital, Qatif, Saudi Arabia

 




12.1 Introduction






  • Urinary tract infection (UTI) is one of the most common infections in infants and children.


  • The occurrences of symptomatic UTI for the first time in boys and girls is highest during the first year of life and decreases markedly after that.


  • The workup of infants who present with fever should include evaluation for urinary tract infection.


  • Urinary tract infection (UTI) in infants and children is divided into two categories:



    • Upper urinary tract infection (Pyelonephritis)


    • Lower urinary tract infection (Cystitis)


  • Most episodes of UTI during the first year of life are pyelonephritis.


  • It is not uncommon for infants younger than 3 months to present with fever without a localizing source and these patients should be evaluated for UTI.


  • After age 2 years, UTI in the form of cystitis is common among girls.


  • Rarely, UTI maybe the first presentation of an important underlying structural or neurogenic abnormality of the urinary tract.


  • The most common causative organisms are bowel flora, typically gram-negative rods.



    • Escherichia coli is the most common organism.


    • The most common pathogen is Escherichia coli, accounting for approximately 85 % of urinary tract infections in children.


    • Klebsiella, Proteus, Enterobacter, Citrobacter, Staphylococcus saprophyticus, and Enterococcus.


    • Other organisms that can cause urinary tract infection include fungi (Candida species) and viruses.


  • The incidence of UTIs varies based on age, sex, and gender.


  • The exact incidence of UTIs is not known but in the United States UTIs are estimated to affect 2.4–2.8 % of children.


  • The overall prevalence of UTI in infants presenting with fever was 7.0 %.


  • Approximately 7 % of children 2–24 months of age presenting with fever without a source were diagnosed with a UTI.


  • 8 % of children 2–19 years of age presenting with possible urinary symptoms were diagnosed with a UTI.


  • The frequency of UTIs is also variable according to age and sex. The rates of UTIs in girls according to age as follows:



    • 0–3 months (7.5 %)


    • 3–6 months (5.7 %)


    • 6–12 months (8.3 %)


    • >12 months (2.1 %)


  • In boys, the incidence of UTIs is also influenced by whether the child is circumcised or not.



    • The rate in uncircumcised febrile boys <3 months of age was 20.7 %


    • The rate in circumcised febrile boys <3 months of age was 2.4 %


    • The rate in uncircumcised febrile boys 6–12 months of age was 7.3 %


    • The rate in circumcised febrile boys 6–12 months of age was 0.3 %


    • However, contamination is very common in obtaining a urine sample from a male when the foreskin cannot be retracted and the rates in uncircumcised males are, undoubtedly, overestimates.


  • During the first few months of life, the incidence of UTI in boys exceeds that in girls.


  • By the end of the first year and thereafter, first-time and recurrent UTIs are most common in girls.


  • The incidence of UTI in children aged 1–2 years is 8.1 % in girls and 1.9 % in boys.


  • In a study of infants presenting to pediatric emergency departments, the prevalence of UTI in infants younger than 60 days with a temperature greater than 100.4 °F (38 °C) was 9 %.


  • Guidelines from the American Academy of Pediatrics recommend considering the diagnosis of UTI in patients aged 2 months to 2 years who present with unexplained fever.


  • Acute urinary tract infections are relatively common in children, with 8 % of girls and 2 % of boys having at least one episode of UTIs by 7 years of age.


  • Renal parenchymal defects are present in 3–15 % of children within 1–2 years of their first diagnosed urinary tract infection.


  • Clinical signs and symptoms of a urinary tract infection depend on the age of the child, but all febrile children 2–24 months of age with no obvious cause of infection should be evaluated for urinary tract infection.


  • Prophylactic antibiotics do not reduce the risk of subsequent urinary tract infections, even in children with mild to moderate vesicoureteral reflux.


  • Constipation should be avoided to help prevent urinary tract infections.


  • The reference standard for the diagnosis of UTI is a single organism cultured from a specimen obtained at the following concentrations:



    • Suprapubic aspiration urine specimen, greater than 1,000 colony-forming units per mL


    • Catheter urine specimen, greater than 10,000 colony-forming units per mL


    • Clean-catch, midstream urine specimen, 100,000 colony-forming units per mL or greater.


  • Urological abnormalities known to be associated with URIs:



    • Baseline abnormalities of the urogenital tract have been reported in up to 3.2 % of healthy, screened infants.


    • Obstructive anomalies are found in up to 4 %


    • Vesicoureteral reflux in 8–40 % of children being evaluated for their first UTI.


    • Children younger than 2 years may be at greater risk of parenchymal defects than older children.


12.2 Etiology






  • Bacterial infections are the most common cause of UTI in infants and children.


  • E coli is the most frequent organism causing UTI responsible for 75–90 % of UTIs.


  • Other bacterial organisms that cause UTI include:



    • Klebsiella species


    • Proteus species


    • Enterococcus species


    • Staphylococcus saprophyticus


    • Streptococcus group B, especially among neonates


    • Pseudomonas aeruginosa


  • Other relatively rare organisms responsible for UTIs include Fungi (Candida species) and viruses (Adenovirus)


  • Adenovirus is a rare cause of hemorrhagic cystitis.


  • Genes that are possibly responsible for increased susceptibility to recurrent UTIs include HSPA1B, CXCR1, CXCR2, TLR2, TLR4, and TGFβ1.


  • Susceptibility to UTI may be increased by any of the following factors:



    • Alteration of the periurethral flora by antibiotic therapy


    • Anatomic anomalies of the renal system leading to urinary stasis


    • Bowel and bladder dysfunction


    • Constipation


  • The use of antibiotics for other infections increases the risk for UTIs.


  • The use of antibiotics alter the gastrointestinal and periurethral flora, disturbing the urinary tract’s natural defense against colonization by pathogenic bacteria.


  • Neurogenic or anatomic abnormalities of the urinary bladder may also cause voiding dysfunction.


  • Anatomic abnormalities of the renal system are known to predispose to UTIs.


  • Constipation, with the rectum chronically dilated by feces, is an important cause of voiding dysfunction and UTIs.


  • For male infants, neonatal circumcision substantially decreases the risk of UTI.



    • The Risk is particularly high during the first 3 months of life.


    • It was shown that during the first year of life, the rate of UTI was 2.15 % in uncircumcised boys, versus 0.22 % in circumcised boys.


    • In another study, it was shown that in febrile boys younger than 3 months, UTI was present in 2.4 % of circumcised boys and in 20.1 % of uncircumcised boys.


12.3 Pathophysiology






  • UTIs result when colonized organisms in the periurethral area ascend into the bladder via the urethra to cause cystitis.


  • From the bladder, organisms can spread up the urinary tract to the kidneys and cause pyelonephritis.


  • Sometimes, the organisms can spread to the bloodstream and cause bacteremia or septicemia.


  • Normally, urine in the proximal urethra and urinary bladder is sterile.


  • Access of microorganisms to the urethra and urinary bladder can result from several factors including:



    • Stasis and turbulent urine flow during normal voiding


    • Voiding dysfunction


    • Urethral catheterization


    • Colonization of organisms during episodes of sepsis


    • Direct spread from the perineum


  • The short female urethra and its proximity to fecal flora may, in part, explain the predominance of UTI in girls after the neonatal period.


  • Mortality related to UTI is exceedingly rare in otherwise healthy children.


  • Cystitis may cause voiding symptoms but it is not associated with long-term kidney damage.


  • Approximately 10–30 % of children with UTI develop some renal scarring.


  • Long-term complications of pyelonephritis are:



    • Renal parenchymal scarring


    • Hypertension


    • Impaired renal function


    • End-stage renal disease


12.4 Clinical Features






  • A urinary tract infection (UTI), is divided into two types depending on the level of infection.


  • Acute cystitis or bladder infection, is an infection that affects the lower urinary tract.


  • Acute pyelonephritis (infection of the kidney), is an infection that affects the upper urinary tract.


  • All febrile children between 2 and 24 months of age with no obvious cause of infection should be evaluated for UTI, with the exception of circumcised boys older than 12 months.


  • Older children who present with fever should be evaluated for UTI if the clinical presentation points toward a urinary source.


  • The clinical features of patients with UTIs are variable and differ according to the patient’s age.


  • Neonates and infants up to age 2 months who have pyelonephritis usually do not have symptoms localized to the urinary tract and UTI is discovered as part of an evaluation for neonatal sepsis.


  • Boys are at increased risk of UTI if younger than 6 months, or if younger than 12 months and uncircumcised.


  • Girls are generally at an increased risk of UTI, particularly if younger than 1 year.


  • Infants from 2 to 36 months of age with a fever of >39 °C and no other source for fever on history or physical examination could have a UTI, and should have urine collected for urinalysis. Unless this test is completely normal, they should then have urine collected by catheter or suprapubic aspirate and sent for culture.


  • When UTI is suspected in toilet-trained children, a midstream urine sample rather than a catheter or suprapubic aspiration specimen should be submitted for urinalysis and culture.


  • Children with possible UTI who require antibiotic treatment immediately for other indications, such as suspected bacteremia, should have urine collected for urinalysis, microscopy and culture. The test sample should be midstream urine if the child is toilet trained, and a catheter or suprapubic aspiration or clean-catch specimen if not, and obtained before starting antibiotics.


  • Over diagnosis of UTI is a common problem, leading to overuse of antibiotics and unnecessary imaging.


  • Urines collected by bag should never be used for diagnosis of UTI. Urines with low colony counts, mixed growth or no pyuria are usually contaminated.


  • Children <2 years of age should be investigated after their first febrile UTI with a renal and bladder ultrasound to identify significant renal abnormalities and grade IV or V VUR.


  • A voiding cystourethrogram (VCUG) is not indicated with a first febrile UTI when the renal and bladder ultrasound is normal.


  • VCUG may detect vesicoureteric reflux (VUR). Low-grade VUR (grade 1–2) usually resolves without permanent damage, but high-grade (grade 4–5) VUR may require surgical correction.


  • Physical examination findings can be nonspecific but may include suprapubic tenderness or costovertebral angle tenderness.


  • Neonates with UTI may present with the following symptoms:



    • Jaundice


    • Fever


    • Failure to thrive


    • Poor feeding


    • Vomiting


    • Irritability


  • Infants and children aged 2 months to 2 years lack symptoms localized to the urinary tract but may present with the following symptoms:



    • Poor feeding


    • Fever


    • Loss of appetite, poor oral intake and vomiting


    • Strong and foul smelling urine


    • Abdominal pain or suprapubic pain


    • Irritability


    • Voiding symptoms suggestive of cystitis, with crying on urination


  • Children aged 2–6 years may present with the following symptoms:



    • Vomiting


    • Abdominal, flank, back pain or suprapubic pain


    • Loss of appetite


    • Irritability


    • Fever


    • Strong and foul smelling urine


    • Enuresis


    • Dysuria, urgency, frequency


  • Children older than 6 years may present with the following symptoms:



    • Fever


    • Vomiting


    • Abdominal pain


    • Flank/back pain


    • Strong and foul smelling urine


    • Dysuria, urgency, frequency


    • Enuresis


    • Incontinence


  • Older children with pyelonephritis often have tenderness of the flank or costovertebral angle.


  • Those with cystitis may have suprapubic tenderness with or without a palpable bladder.


  • The finding of hypertension should raise suspicion of hydronephrosis or renal parenchyma disease.


12.5 Investigations and Diagnosis






  • Complete blood count (CBC)


  • Blood cultures (in patients with suspected bacteremia or urosepsis)


  • Serum creatinine and blood urea nitrogen


  • Serum electrolyte levels


  • The diagnosis of a urinary tract infection in children depends on a positive urinary culture.


  • Contamination poses a frequent challenge depending on the method of urine collection used.


  • A blood culture in febrile infants and older patients who are clinically ill, toxic, or severely febrile.


  • Urine analysis:



    • Urinalysis alone is not sufficient for diagnosing UTI.


    • However, urinalysis can help in identifying febrile children who should receive antibacterial treatment while culture results from a properly collected urine specimen are pending.


    • Rapid urine tests (also known as dipsticks or macroscopic urinalysis) remain useful for the diagnosis of UTI.


    • Urine dipstick test:



      • Urine dipstick testing alone may provide an adequate initial UTI screen.


      • Urine dipstick tests for UTI include leukocyte esterase, nitrite, blood, and protein.


      • Positive dipstick readings for nitrite, leukocyte esterase, or blood may suggest a UTI.


      • Dipstick tests have sensitivities of approximately 85–94 %.


      • Dipstick tests for blood and protein have poor sensitivity and specificity in the detection of UTI and may be misleading.


      • Automated microscopy has better specificity and likelihood ratios than dipstick testing, but it had slightly lower sensitivity.


    • The nitrite test:



      • This measures the conversion of dietary nitrate to nitrite by Gram-negative bacteria.


      • A positive nitrite test makes UTI very likely.


      • The test may be falsely negative if the bladder is emptied frequently or if an organism that does not metabolize nitrate (including all Gram-positive organisms) is the cause of infection.


      • The test for nitrite is more specific but less sensitive.


    • The leukocyte esterase test:

Jul 10, 2017 | Posted by in UROLOGY | Comments Off on Urinary Tract Infection in Infants and Children
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