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 Urinary tract infection in childhood

A practical approach and Pediatric Urologists

point of view

ABSTRACT:

Urinary tract infection is a common problem in infants and children; it is the 2nd most common infection in children; moreover, morbidity is not limited to the acute period of illness. Urinary tract infection may also result in renal scarring which has the potential for diminished renal function and hypertension.

The significant morbidity from urinary tract infection in early childhood has led to our current recognition of the importance of early diagnosis, prompt antibiotic treatment, and thorough evaluation of urinary tract infections in young children with documented urinary tract infection.

Especially important are the differences in urinary tract infection between adults and children that emphasize that children are not 'little adults' and they need different management. The risk of renal scarring is greatest in infants and may be progressive if there is a delay in diagnosis and management of urinary tract infections in children.

Normal anatomy and physiology of the urinary tract with unidirectional urinary flow and complete emptying at regular reasonable intervals should protect children from urinary tract infections.

A normal child should not have urinary tract infection. The obvious goals of urinary tract infection management are to provide symptomatic relief and to prevent renal damage.

In the meantime to be able to prevent the recurrences of urinary tract infection, we have to evaluate the patient more ,looking for any structural or functional predisposing factors. Treatment of underlying voiding dysfunction and constipation is an essential component of successful management of urinary tract infections in children.

We will elaborate on urinary tract infection in children and concentrate mainly on the pediatric urologists' point of view and our practical approach to this problem.

Keywords: Urinary tract infection, Escherichia coli, renal scarring, vesico-ureteral reflux.


Clinical presentation
:

The incidence of urinary tract infection (UTI) is sex and age related, except in the newborn, it was found to be more common in girls than boys and the incidence is 1% in boys and 3% in girls, about 11 % of girls are found to have at least one attack of UTI by the age of 11 years. The usual signs and symptoms of lower UTI in adults like dysuria and frequency may not be obvious in children. Because younger children and infants often have non-localizing symptoms, the physician must have a high index of suspicion.

 Because UTIs in neonates often occur as a consequence of bacteremia and do not result from ascending UTI, as common in older patients, neonates may show signs and symptoms most consistent with sepsis and appear gravely ill. Additional signs of UTI in neonates include abdominal distension, diarrhea and jaundice. In any infant in whom sepsis is considered in the clinical diagnosis, urine culture must be part of the laboratory evaluation!

Symptoms of UTI in children may include dysuria, frequency and urgency, but vague complaints of abdominal pain, vomiting, decreased appetite and malodorous urine also occur .2.3 Fever is less common than in the younger age group and if present may signify renal parenchymal infection or infection in an obstructed urinary tract. Symptoms of dysuria may be related to problems other than UTI, including, vaginitis and local perineal irritation. Urinary tract infection during adolescence is much more common in girls, and generally present with dysuria.3 Again fever is unusual and usually signifies upper UTI .Sexual activity may exacerbate symptomatic UTI, in this age group other causes of dysuria must be considered (e.g. sexually transmitted hypercalciuria, and urolithiasis).

History: Urinary tract infections can be caused by a number of predisposing factors operating either alone or in combination, which eventually leads to bacterial inoculation of the urinary tract. A careful history, looking for possible causes are important; namely urine and fecal elimination habits. It is usually quite easy to get a detailed voiding history as the patient often presents with a wetting problem, which can be associated with frequency, urgency or infrequent voiding, but the topic of fecal elimination is considered a private matter. Even the parents may not be aware of the frequency, size, and shape consistency of their child's stool. Involving the child in the interview, time should be taken at this point, avoid any embarrassment, and to facilitate answers, asking specific qualitative and quantitative questions that will generate a yes or no answer.

   Constipation is more of a degree of fecal retention, infrequent passage of stools, passage of small compact stools, palpable stool in the sigmoid fossa, residual stool after defecation by rectal examination, or encopresis.4 A normal child should void to completion about 6 times daily. Infrequent voiding or lazy bladder syndrome; more common in girls who usually delay and void about only 3 times daily, their first void more than 2 hours after getting up of bed5.

 Observant mothers may describe malodorous cloudy urine. Feeding intolerance or poor weight gain may be a historical clue to UTI in the very young. Older children may also complain of back pain. Vague abdominal complaints in school- girls are not rare and are often described by other physical as behavioral problems though UT I commonly responsible for such presentation.

Physical examination. Although the prognosis UTI in childhood is generally favorable,6 significant number of patients will have anatomical abnormalities of their urinary tracts that predispose them to renal parenchymal damage, hypertension and even renal failure7. Therefore careful evaluation is essential to identify those who may develop these serious consequences. Fever and abnormal vital signs (hypertension) may be signs of upper UTI; Growth failure may be evident in patients who already have renal insufficiency or who have had recurrent infections in an abnormal urinary tract. Close attention should be paid to abdominal examination, palpating carefully for masses that suggest genito-urinary tract pathology.

Gentle examination of the external genitalia is very important, in boys; phimosis and banalities may mimic the signs of UTI. Urethral metal stenosis, more common in circumcised boys, may predispose to voiding difficulties; narrow, weak urinary stream and UTI. Other major associated abnormalities signal structural problems in the urinary tract, including cardiac defects, abdominal muscular defects, cryptorchidism, hypospadias and skeletal deformities.

Examination of the back looking for any signs spina bifida, testing the cremastric and anal reflexes may help in the diagnosis of neurological causes responsible for neurogenic bladder, that are commonly associated with UTI.

Diagnosis: A definitive diagnosis of UTI requires documentation of significant bacteriuria. Definition of 'significant' is not simple and depends on the method of urine collection, prompt handling of the collected specimen and the pattern organism(s) recovered. Physicians are generally aware that bacterial colony counts of greater, 100,000 /ml of urine obtained by mid stream clear  catch represent infection.8 Many bacteria colonize the skin around the urethra, and fecal reservoir is in close proximity. Because of this, contamination of urine specimen obtained by clean-catch method is common. Signs of contamination include low colony counts, multiple organisms, different organisms obtained in serial samples, or isolation of organisms not commonly associated with UTI. Certainly the clean-catch method is the easiest to use in the older child and generally reliable .Antiseptic cleansing prior to the collection is usually not necessary and may even mask significant bacterial growth. One cannot expect an infant to provide a clean-catch specimen so other methods have been devised. The most convenient method of obtaining a urine sample in an infant is by applying a sterile collection bag that is adherent to the genitalia. Unfortunately, it is also the most prone to contamination ľnegative cultures obtained by this technique are of value, but, positive culture should be confirmed by culture of catheter specimen or suprapubic aspirate whenever, possible.2.9 Urethral catheterization may provide, quick access to urine but is not without problems, trauma to the urethra is possible, discomfort of the patient and contamination can occur.

 The finding of pyuria has strong supportive evidence of UTI, but approximately 30% to 50% patients with bacteriuria and UTI will not demonstrate a significant number of white cells (>5 white blood cells / high power field) in centrifuged urinary sediment. Because of this screening test that relies on the detection of white blood cell products (leukocyte esterase) are not the appropriate for the diagnosis of UTI. Likewise, nitrite dipstick is a sensitive screening procedure for gram-negative organism, but it should not be used in symptomatic children.5  However the accuracy is affected by the probability of the patient being infected based on clinical findings. Accordingly, urine culture may be omitted when the dip stick test is negative only when there is limited suspicion of UTI based on clinical symptoms. Conversely, urine culture should be obtained in any patient suspected of having a UTI or in whom the dipstick test is positive.5

As Pediatric Urologists, we think that the diagnosis and treatment of UTI by ntimicrobials in a child is not enough and usually more evaluation and diagnostic imaging are needed to detect the presence of any predisposing factors. Infants and young children with UTI warrant specific attention because of the opportunity to prevent kidney damage. Urinary tract infections may bring attention to a child with an obstructive anomaly or severe vesico-ureteral reflux.

  Pathophysiology: Pathophysiology of UTI appears to be related to both characteristics of the invading bacteria and those of the host's urinary tract.

  Bacterial factors. A large proportion of Escherichia coli (E. coli) types are isolated from patients with UTI without detectable structural genito-urinary abnormality. The most important virulent factor of these bacteria is the presence of pili or fimbria with an affinity for receptors (glycosphingolipids) present on the mucosal epithelial cells. Adherence of E. Coli to transitional epithelial cells precipitates decreased peristalsis and urethral dilation.l0 Conversely, pyelonephritis in the absence of such uropathogenic E.Coli may be a marker for urinary tract abnormalities.11 Some clones of E. Coli marked by specific antigen type appear to be particularly virulent in producing renal parenchymal inflammation and scarring 3, and these strains (P-Fimbriated E.Coli) demonstrate the ability to attach to globosides on human red cells and to some uroepithelial cells.

Escherichia coli is responsible for at least 80% of UTI in children. Other organisms include Proteus, Pseudomonas Klebsiella. Multiple organisms in urine culture may signal an underlying structural problem (e.g. vesico-ureteral reflux, posterior urethral valve etc.) requiring surgical intervention.

 Host defense and risk factors. These can be classified into perineal factors, lower urinary tract factors and upper urinary tract factors 5.

Perineal factors; perineal colonization by intestinal flora is the most common source of primary and recurrent UTI, an infants initial exposure to uro-pathogenic bacteria occurs at the time of birth especially if born to bacilluric mother. Ultimately, the infants' own uropathgenic bacteria that colonize the intestinal tract. Most UTIs are ascending infections, which begin with perimeatal colonization. Uncircumcised male infants have a higher incidence of UTI because of the preputile colonization.13 In girls the short urethra, and the location of the external urethral meatus deep into the vulva, appears to be the most obvious explanation for increased relative incidence of UTIs.In this regard we recommend that girls should void while in abduction position with the legs widely separated in order to obtain a clear and well identified urinary-stream to avoid retrograde urinary vaginal reflux which can increase the incidence of UTIs.

 Lower urinary tract factors. Common voiding  disorders in children prone to UTI  range from small capacity , unstable bladder characterized by frequency, urgency, posturing, and wetting to the infrequent voider 'lazy bladder' characterized by very infrequent voiding, large capacity bladder, and constipation. Constipation in general can predispose to bladder insensibility by the stimulation of stretch receptors in bladder mucosa. In children with. recurrent UTIs associated with abnormal voiding" patterns, normalization of voiding pattern generally results in the resolution of UTI, host defense factors and bacterial virulence factors, however, do affect the susceptibility to UTI, since many children do not develop UTI  despit abnormal voiding habits .

Infrequent emptying of an over distended bladder may result in significant post void residual urine which act as a reservoir for invading organisms.

Upper urinary tract factors. Although the presence of vesico-ureteral reflux (VUR),

Significantly enhances the likelihood that even the less virulent organism will get access to the kidney, still at least one third of cases of acute pyelonephritis in children, documented by dimercaptosuccinic acid (DMSA) renal scan are not associated with VUR.

 Diagnostic imaging. In pediatric patients all initial UTIs should be considered complicated and requiring appropriate radiological evaluation because nearly 50% of children with UTI are found to have associated congenital urological abnormalities.

The vast majority of renal scarring occurs within the first 3-5 years of life 7. Many will not have had documented UTIs but may have had. Unexplained fever. So it is reasonable to identify patients who are likely to have renal damage associated with structural abnormalities (primary vesicoureteric reflux or obstruction) as early as possible. However, it may not be particularly cost-effective to image adolescent girls with cystitis because it is a common occurrence and scarring, if present, is already established. Though the incidence of UTIs is lower in boys, they are much more likely to have structural abnormalities. Recommendation for the imaging of children with UTIs varies geographically, institutionally and from one individual to another.

However we recommend the policy to perform an evaluation after the first culture- documented UTI in all boys and girls younger than 5 years of age, further more, all patients with physical findings of genitourinary abnormalities, and older children with recurrent symptomatic UTIs particularly those with dysfunctional voiding.5 Renal and bladder ultrasonography alone as the initial urologic evaluation is probably sufficient in older boys with their first episode of cystitis, girls with recurrent cystitis in the absence of voiding dysfunction and adolescent girls.5 Infants and young children with UTI who do not demonstrate the expected clinical response within 2 days of antimicrobial therapy should undergo ultrasonography promptly, and voiding cystourethrogram (VCUG) should be perfumed at the earliest convenient time after control of the acute UTI episode. A normal ultrasound does not exclude VUR. The rate of VUR among children younger than 1 year with UTI exceeds 50%.5  Dimercaptosuccinin acid renal scan can be used to diagnose acute pyelonephritis as well as renal scarring, information that is important for the longitudinal assessment of children with VUR because the detection of new or progressive renal scaring are considered indications for ureteral reimplantaion 14 . Renal scars however may not show. On DMSA until a few month or even years after the pyelonephritis episode. (It is Important also to realize that scars appear only if pyelonpehritis is not treated or if there was a delay in treatment).

 Treatment. Therapy of UTI depends on the clinical circumstances,knowledge of pre-existing  structural abnormality, the type of offending  microorganism and its documented or suspected sensitivity, the presence of recurrent bacteriuria and the age of the child 2-9 .Intial  treatment should ideally be based  on urine culture  both for documentation of UTI and to provide bacterial antibiotic sensitivity.

 In general, children who appear ill  or who are at a significant risk of becoming seriously ill because of their age (infants)or the presence of  urinary tract abnormalities should be admitted to hospital and treated with intravenous antibiotics avoiding aminoglycosids in those with renal impairment.

Patient with first time UTI who require imaging should be maintained on low dose antibiotic prophylaxis until their workup is completed. Resolution can be anticipated when urinary and bowel habits normalized.Long-term antibiotic prophylaxis is indicated for children with frequent symptomatic recurrences of UTI and for those with known VUR.Diagnosis and treatment of underlying voiding dysfunction and constipation is essentialcomponent for the successful management of UTIs in children 15 .Unstable bladder may be helped with behavioral modification approach involving self-motivation, frequent voiding,anticholinergic agents,such as oxybutinin which may be added very selectively .

Clean intermittent catheterization ( CIC )or surgical bladder drainage procedure may be needed to protect the kidneys in specific cases such as neurogenic bladder and in children with complicated urological procedures like patients with bladder augmentation. Infrequent voiders are to be encouraged to void every 2 to 3 hours while awake until their voiding pattern is reset. Infrequent bowel movement should be attended to with appropriate use of diet -high fiber with plenty of fluids, vegetables and fruits. Stool softeners and laxatives may be needed in severely constipated children, e.g. those with spinal dysraphism. Primary vesicoureteral reflux resolves spontaneously in about 80% of patients by the age of 4 years by using the usual conserative management, which involves keeping the urine sterile by prophylaxis antibiotics, surgical intervention should be perfomed if indicated.


References:

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  2. McCracken GH. Diagnosis and management of acute urinary tract infections in infants and children. Pediatr Infect Dis J 1987; 6: 107-122.

  3. Milner LS, Kaplan BS. Urinary tract infection and reflux in the child. Medicine 1985; 27:3680-3685.

  4. Homsy YL. Constipation and UTI. In: Dialogues in Pediatric Urology Volume 12. Number 12. William J. Miller; 1998.P.5-7.

  5. Pohl HG, Rushton HG. The diagnosis and management of urinary tract infection in children. AUA Update Series. Lesson 13, Volume XXVII. Houston, Texas: AUA Office of Education; 1998.P.242-248.

  6. Kunin CM. Epidemiology and natural history of urinary tract infection in school age children .  Pediatr Clin North Am 1971; 18: 509-528.

  7. Winberg J , Bollgren I, Kallenius G, Mollby R, Svenson SB. Clinical yelonephritis and focal renal  scarring . Padiater clin North Am 1971; 29: 801-814.

  8. Kass EH. Bacteriuria and the diagnosis of infections of the urinary tract. Arch Intern Med 1957; 100:709-712.

  9. Hellerstein S. Recurrent urinary tract infections in children. Pediatr Infect Dis 1982; 1:271-275.

  10. Marild S, Hellstrom M, Jacobsson  B, Jodal U, Svanborg Eden C. Influence of bacterial  adhesions on ureteral width in children with acute pyelonephritis . J pediatr 1989; 115: 265-270.

  11. De Man P, Claeson I, Johanson IM, Jodal U, Svenborg Eden  C. Bacterial attachment as a predictor of renal abnormalities  in boys with urinary tract infection. Jpediatr 1989; 115: 915-922.

  12. Marlid S, Jodal U, Orskov I, Orskov F, Svanborg Eden C. Special Virulence of the Escherichia Coli O1:K1:H7 clone in acute pyelonephritis. J pediatr 1989; 115: 40-45.

  13.  Lohr JA. The foreskin and urinary tract infections. J pediatr 1989; 114: 502-504

 

 

  وزارة الصحة - مركز المعلومات - قسم النشر الالكتروني - 2005