Prevalence of bacteriuria in infants and preschool children

Prevalence of Asymptomatic Bacteriuria in Children: A Meta-Analysis

OBJECTIVE

To determine the point prevalence of bacteriuria and bacteriuria without pyuria in asymptomatic children by a systematic review of the literature.

STUDY DESIGN

We searched MEDLINE and EMBASE for English-, French-, German-, Italian-, and Spanish-language articles. We included articles reporting data on bacteriuria in asymptomatic children up to 19 years of age who had urine collected by suprapubic bladder aspiration, bladder catheterization, or by 3 consecutive clean catch samples. Two independent reviewers assessed studies for inclusion and abstracted data.

RESULTS

Fourteen studies (49 806 children) were included. The prevalence of asymptomatic bacteriuria was 0.37% (95% CI, 0.09-0.82) in boys and 0.47% (95% CI, 0.36-0.59) in girls. The corresponding values for asymptomatic bacteriuria without pyuria were 0.18% (95% CI, 0.02-0.51) and 0.38% (95% CI, 0.22-0.58), respectively. The subgroups with the highest prevalence of asymptomatic bacteriuria were uncircumcised males <1 year of age and females >2 years of age. In males, the prevalence of asymptomatic bacteriuria after infancy was 0.08% (95% CI, 0.01-0.37). The median duration of asymptomatic bacteriuria in untreated boys and girls, from the one study reporting this outcome, was 1.5 and 2 months, respectively.

CONCLUSIONS

Some clinicians are concerned that when a preverbal child with asymptomatic bacteriuria develops a nonlocalizing febrile illness and presents for evaluation, they may be mistakenly diagnosed as having a urinary tract infection (UTI). Given that the prevalence of asymptomatic bacteriuria is considerably lower than the prevalence of UTI in most subgroups examined, this will occur extremely rarely. These data suggest that the current definition of UTI should be revisited.

The Diagnosis of Urinary Tract infection in Young children (DUTY): a diagnostic prospective observational study to derive and validate a clinical algorithm for the diagnosis of urinary tract infection in children presenting to primary care with an acute illness

BACKGROUND

It is not clear which young children presenting acutely unwell to primary care should be investigated for urinary tract infection (UTI) and whether or not dipstick testing should be used to inform antibiotic treatment.

OBJECTIVES

To develop algorithms to accurately identify pre-school children in whom urine should be obtained; assess whether or not dipstick urinalysis provides additional diagnostic information; and model algorithm cost-effectiveness.

DESIGN

Multicentre, prospective diagnostic cohort study.

SETTING AND PARTICIPANTS

Children < 5 years old presenting to primary care with an acute illness and/or new urinary symptoms.

METHODS

One hundred and seven clinical characteristics (index tests) were recorded from the child's past medical history, symptoms, physical examination signs and urine dipstick test. Prior to dipstick results clinician opinion of UTI likelihood ('clinical diagnosis') and urine sampling and treatment intentions ('clinical judgement') were recorded. All index tests were measured blind to the reference standard, defined as a pure or predominant uropathogen cultured at ≥ 10(5) colony-forming units (CFU)/ml in a single research laboratory. Urine was collected by clean catch (preferred) or nappy pad. Index tests were sequentially evaluated in two groups, stratified by urine collection method: parent-reported symptoms with clinician-reported signs, and urine dipstick results. Diagnostic accuracy was quantified using area under receiver operating characteristic curve (AUROC) with 95% confidence interval (CI) and bootstrap-validated AUROC, and compared with the 'clinician diagnosis' AUROC. Decision-analytic models were used to identify optimal urine sampling strategy compared with 'clinical judgement'.

RESULTS

A total of 7163 children were recruited, of whom 50% were female and 49% were < 2 years old. Culture results were available for 5017 (70%); 2740 children provided clean-catch samples, 94% of whom were ≥ 2 years old, with 2.2% meeting the UTI definition. Among these, 'clinical diagnosis' correctly identified 46.6% of positive cultures, with 94.7% specificity and an AUROC of 0.77 (95% CI 0.71 to 0.83). Four symptoms, three signs and three dipstick results were independently associated with UTI with an AUROC (95% CI; bootstrap-validated AUROC) of 0.89 (0.85 to 0.95; validated 0.88) for symptoms and signs, increasing to 0.93 (0.90 to 0.97; validated 0.90) with dipstick results. Nappy pad samples were provided from the other 2277 children, of whom 82% were < 2 years old and 1.3% met the UTI definition. 'Clinical diagnosis' correctly identified 13.3% positive cultures, with 98.5% specificity and an AUROC of 0.63 (95% CI 0.53 to 0.72). Four symptoms and two dipstick results were independently associated with UTI, with an AUROC of 0.81 (0.72 to 0.90; validated 0.78) for symptoms, increasing to 0.87 (0.80 to 0.94; validated 0.82) with the dipstick findings. A high specificity threshold for the clean-catch model was more accurate and less costly than, and as effective as, clinical judgement. The additional diagnostic utility of dipstick testing was offset by its costs. The cost-effectiveness of the nappy pad model was not clear-cut.

CONCLUSIONS

Clinicians should prioritise the use of clean-catch sampling as symptoms and signs can cost-effectively improve the identification of UTI in young children where clean catch is possible. Dipstick testing can improve targeting of antibiotic treatment, but at a higher cost than waiting for a laboratory result. Future research is needed to distinguish pathogens from contaminants, assess the impact of the clean-catch algorithm on patient outcomes, and the cost-effectiveness of presumptive versus dipstick versus laboratory-guided antibiotic treatment.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Effect of confounding in the association between circumcision status and urinary tract infection

OBJECTIVES

To estimate the impact of confounding in the association between circumcision status and urinary tract infection from epidemiological factors, sample collection, and health-seeking behaviors in the first year of life.

METHODS

Beginning with the assumption that true urinary tract infection occurred equally regardless of circumcision status, a Markov model incorporating the differences in the rates of prematurity, of urine collection, of false positive urine specimens, and of health-seeking behaviors in infant boys based on circumcision status was developed. Using this model, the rates of false-positive urine cultures, asymptomatic bacteriuria, and true urinary tract infection detected in the first year of life were estimated and contrasted. Error of the model was estimated using Monte Carlo simulations.

RESULTS

Keeping the incidence of true urinary tract infection constant between groups, the factors included in the model could account for urinary tract infection being diagnosed 4.27 times more frequently in non-circumcised males under a year of age.

CONCLUSIONS

Previously reported differences in the rate of urinary tract infection by circumcision status could be entirely due to sampling and selection bias. Until clinical studies adequately control for sources of bias, circumcision should not be recommended as a preventive for urinary tract infection.

Labial fusion and asymptomatic bacteriuria

Thirty-three female children with labial fusion were screened for bacteriuria which was defined as the growth of a single micro-organism with < or = 100,000 colony-forming units/ml (> or = 100 x 10(6) colonies/l) in a properly collected urine specimen. Six girls were found to have bacteriuria. In contrast, none of the 33 girls in a control group had bacteriuria. We recommend that a urine culture be performed in girls with labial fusion and that all girls with bacteriuria should be checked for labial fusion.

Asymptomatic urinary tract infection in childhood

In this study 2,591 apparently healthy children aged 1 day-16 years were examined to determine the existence of asymptomatic urinary tract infection. A prevalence of 4% in newborns, 5.2% in infants, 5.8% in preschool children, 4.5% in elementary school children, and of 4.8% in high-school children was found.

Six year follow up of infants with bacteriuria on screening

OBJECTIVE

To determine the value of screening for bacteriuria in infants with special emphasis on the natural course of untreated asymptomatic bacteriuria, renal growth, and renal damage.

DESIGN

Prospective six year follow up of infants with bacteriuria on screening in an unselected infant population.

SETTING

Paediatric outpatient clinic.

PATIENTS

50 Infants (14 girls, 36 boys) with bacteriuria on screening verified by suprapubic aspiration from an unselected population of 3581 infants in a defined area of Gothenburg.

INTERVENTIONS

Children with asymptomatic bacteriuria and normal findings on initial urography were untreated, although other infections were treated.

MAIN OUTCOME MEASURES

Culture of urine and determination of C reactive protein concentration every six weeks for the first six months after diagnosis, every three months from six months to two years, and every six months between two and three years; thereafter yearly urine culture. Evaluation of renal concentrating capacity with a desmopressin test; radiological examination, including first and follow up urography and micturition cystourethrography without antibiotic cover; and measurement of renal parenchymal thickness and renal surface area.

RESULTS

Of the original 50 infants, 37 (12 girls, 25 boys) were followed up for at least six years. Two infants developed pyelonephritis within two weeks after bacteriuria was diagnosed; the others remained free of symptoms. 45 Infants were untreated; the bacteriuria cleared spontaneously in 36 and in response to antibiotics given for infections in the respiratory tract in eight. Recurrences of bacteriuria were observed in 10 of the 50 children, of whom one had pyelonephritis. No child had more than one recurrence. At follow up urography in 36 of the 50 children (9 girls, 27 boys) after a median of 32 months no child had developed renal damage. First samples tested for renal concentrating capacity showed significantly higher values than those from a reference population (mean SD score 0.50, 95% confidence interval 0.21 to 0.79; p less than 0.001), but the last samples showed no significant difference (mean SD score 0.08, -0.24 to 0.40; p greater than 0.05).

CONCLUSIONS

Mass screening for bacteriuria in infancy results primarily in detection of innocent bacteriuric episodes and is not recommended.

Spontaneous clearance of asymptomatic bacteriuria in infants

In an unselected population of 3,581 infants, 14 girls and 36 boys were found to have bacteriuria verified by suprapubic aspiration. Among the bacteriuric infants, one girl and one boy developed symptoms of pyelonephritis close to the time of detection; the others remained asymptomatic. Eleven girls and 34 boys were left untreated. One of these girls and 7 of the boys became abacteriuric after treatment for respiratory tract infections. Ten girls and 26 boys became spontaneously abacteriuric, with a median persistence of bacteriuria of 2 months in girls and 1.5 months in boys. Recurrences were observed among boys only in those who had been treated with antibiotics.

Unsuspected bacterial infections in febrile convulsions

In a 12-month prospective study in 1984, blood and urinary cultures were obtained as a routine from 307 children who presented with fever and convulsions to the Mater Misericordiae Children's Hospital, Brisbane, and the results were compared with data from 1981-1983 when cultures were not taken as a routine. In the prospective study, bacteraemia was found in 12 (4.3%) of 282 patients but was not suspected clinically in half of these; urinary-tract infection was found in seven (2.6%) of 272 patients and in six of these it was not suspected clinically. All 12 patients with unsuspected bacteraemia or urinary-tract infection had persistent fever; of these, nine patients suffered simple convulsions and all cases of urinary-tract infection occurred in female patients. Bacteraemia was significantly more common in patients of less than two years of age, in children who were selected for lumbar puncture and in the study period compared with the retrospective period, 1981-1983. Leukocytosis (white-cell count, more than 15.0 X 10(9)/L) was a sensitive (75%) diagnostic aid but was poorly specific (59%) for bacteraemia. Bacterial meningitis was not diagnosed initially in four of the nine cases which occurred among children who presented with fever and convulsions between 1981 and 1984; in all four children, the cerebrospinal fluid appeared normal at hospital admission. We conclude that bacteraemia and urinary-tract infections are detected more frequently in children who are admitted to hospital with febrile convulsions when cultures are performed as a routine. In the at-risk group (children of less than two years of age), the prevalence of urinary-tract infection is increased in female patients and the prevalence of bacteraemia is increased in those patients who are selected for lumbar puncture. The use of leukocytosis as a criterion to determine the need for blood cultures improves the diagnostic yield but would result in increased costs and additional venepuncture. Bacterial meningitis was rare in our case series and the performance of a lumbar puncture as a routine at admission to hospital would not have led to its earlier diagnosis.

Epidemiology of bacteriuria during the first year of life

Bacteriuria was studied in an unselected population of 3,581 infants. Screening was performed at three time intervals during the infants' first year of life. The public Child Health Centers cooperated in the screening and bag samples were obtained from the infants with the parents help. Bacteriuria was verified by suprapubic aspiration. 94% of the infants took part in the screening and bacteriuria was confirmed in 14 girls (0.9%) and 36 boys (2.5%). An additional 20 girls (1.1%) and 20 boys (1.2%) in the study population presented with symptomatic urinary tract infection before 12 months of age. Bacteriuria in boys was predominantly found early in infancy both with screening techniques and through symptomatic urinary tract infections.

Urinary tract infection in infants with unexplained fever: a collaborative study

Nine centers collaborated to determine the rate of urinary tract infection in infants with unexplained fever, to determine whether the rate is higher in febrile infants than in asymptomatic infants, and whether the yield justifies urine cultures in febrile infants. Urine cultures were done in 501 infants 0 to 2 years of age. The rate of confirmed urinary tract infections in the 193 febrile infants was 4.1%. All infections were in girls, with a rate of 7.4%. The rate of confirmed urinary tract infections in the 312 asymptomatic infants was 0.3%; again, all infections were in girls, with a rate of 0.7%. The rate in febrile girls was significantly higher than the rate in asymptomatic girls (P less than 0.01). The data support the advisability of culturing the urine of infant girls with unexplained fever.

Asymptomatic bacteriuria in healthy preterm babies

Urine was cultured from 51 healthy preterm babies. If the initial bag specimen grew more than 50 000 organisms/ml, a second bag specimen was cultured. After two positive bag specimens a suprapubic urine was cultured. Significant bacteriuria was excluded on the basis of one or two bag specimens in 90% of the babies. Suprapubic urine was sterile in a further 11 babies. Four babies with positive bag specimens were unfortunately not completely investigated: 2 had mixed growths and 2 had pure growths of 100 000 organisms/ml. As we and others consider that bacteriuria can only be diagnosed on a suprapubic sample of urine the incidence of proved infection in our series was zero. If both the babies with a pure growth of 100 000 organisms/ml had true bacteriuria, the incidence would rise to 1.3%. In view of the difficulties in obtaining clean urine samples in preterm babies and as the incidence of bacteriuria is so low, we do not recommend that healthy preterm babies be screened for bacteriuria.

Renal scarring and vesicoureteric reflux

A review of 105 children with urinary tract infection showed an increasing prevalence of grades II-III vesicoureteric reflux with diminishing age. During infancy reflux was almost always severe, and affected boys as often as girls. Radiologically scarred kidneys were drained by refluxing ureters in 98% of cases. The prevalence of scars also rose significantly with increasinglyly severe reflux. Deterioration of existing scars or new scar formation was seen in 15 children; 18 out of 20 affected kidneys (90%) were associated with grade III vesicoureteric reflux. 2 out of 5 children who developed new scars did so after 5 years of age. Because severe reflux may occasionally be seen in the presence of a normal intravenous urogram, and since the finding of grades II-III vesicoureteric reflux is an indication for chemoprophylaxis, we consider cystourethrography essential in children of all ages with recurrent urinary tract infection. In children under 5 years the increased prevalence of both severe reflux and renal scarring are arguments for regarding cystourethrography as a necessary initial investigation.

External sphincter activity and recurrent urinary tract infection in girls

Urodynamic investigations, including pressure studies, anal sphincter electromyography, and cystourethrography, done in young girls having symptomatic urinary infection show hyperreflexive activity of both striated sphincter and detrusor muscles, due to increased afferent input. In our series, this activity ranged froma a pattern similar to "uninhibited" bladder contractions, with normal voiding, to hyperactivity causing frequency, with voiding interrupted by frank sphincter spasms. The wide range and epidemiology of urinary infection in girls suggest that urethral dilatation (or urethrotomy) with long-term chemoprophylaxis is indicated only at one extreme--where the hyperactivity persists in the absence of infection. The role of persistent hyperactivity of detrusor and sphincter in recurrent urinary infection of childhood needs to be defined by a long-term longitudinal study; the high over-all recurrence rates of both covert bacteriuria and overt infection in girls still constitute a major medical problem.

Value of cystography in urinary tract infections

Fifty-one children with a bacteriologically proven urinary tract infection had both an intravenous urogram (IVU) and a micturating cystogram. The IVU was normal in 35. Only 6 of these children showed reflux in the cystogram, affecting 7 of the 70 ureters at risk. Since reflux on its own does not cause renal damage, which occurs only with super-added infection, detection of reflux is not important providing the urine is kept sterile. We suggest that cystography be deferred providing the IVU is normal until recurrent infections occur while under hospital care, and, with this policy this unpleasant and sometimes hazardous investigation could be avoided in many children with a single urinary tract infection.

Urinary tract in schoolgirls with covert bacteriuria

During screening of 16,800 primary schoolgirls, aged 4-12 years, in Cardiff and Oxford, significant bacteriuria was found in 294 (1-7%). Intravenous urography and micturating cystography were performed in 246 of these girls. The urinary tract was abnormal in 47%. Pyelonephritis with or without vesicoureteric reflux was present in 26% and reflux without renal abnormality in a further 16%. The prevalence of pyelonephritis and reflux was independent of age. With few exeptions kidneys without pyelonephritic scars appeared to be normal in size, even when ureteric reflux was present.