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PEDIATRICS Vol. 105 No. 6 June 2000, pp. 1232-1235
,, §,
From the Departments of * Pediatrics and Radiology, Assaf
Harofeh Medical Center, and § Sackler School of Medicine, Tel Aviv
University, Tel Aviv, Israel.
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ABSTRACT |
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Discussion
Conclusion
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Objective. To assess the frequency of urinary tract anomalies in male neonates <8 weeks old who presented with urinary tract infection (UTI), and to evaluate a suitable imaging approach after the initial infection.
Design. During a period of 4.5 years, from July 1994 through December 1998, 45 male neonates <8 weeks old (range: 5-56 days; mean: 23.77 days) with UTI were hospitalized. All patients had an ultrasound (US) and a voiding cystourethrogram (VCUG), except 1 neonate in whom VCUG was unsuccessful because of technical problems. A dimercaptosuccinic acid (DMSA) scan was recommended to all patients but was performed only in 30 of 45, most of them with an abnormal VCUG. The renal scan was performed at least 4 months after the UTI.
Results. Urinary tract abnormalities were observed in 22 of 45 male neonates. Nineteen had vesicoureteral reflux (VUR), 1 had VUR and a double collecting system, 1 had VUR and a posterior urethral valve, and 1 had an ureteropelvic junction stricture. Renal atrophy or scars, as demonstrated by DMSA scan, were detected almost exclusively in neonates with VUR grade 3 and above. Only 1 neonate with VUR grade 1 had a pathologic DMSA, and the US of this male also demonstrated renal atrophy. Escherichia coli was the pathogen in 62% (28 of 45), and 9 boys had bacteremia.
Conclusion. We suggest that US and VCUG should be performed routinely after the initial UTI in male neonates. Renal scan should be reserved for those cases in which the US suggests renal parenchymal damage or when VCUG detects VUR grade 3 and above. Key words: urinary tract infection, neonate, male, imaging.
Urinary tract infection (UTI) is one of the most
common causes of unexplained fever in neonates. During the first 2 months of life, males are more commonly affected1 possibly
because of an increased incidence of structural
abnormalities.2,3 The recommended diagnostic imaging in
the evaluation of the first UTI in male neonates includes an ultrasound
(US) during the acute phase, a voiding cystourethrogram (VCUG) several
weeks after the infection, and a renal scan with dimercaptosuccinic
acid (DMSA) or glucoheptonate several months after the
UTI.3-5 The renal scan can be performed during the acute
phase when the diagnosis is uncertain. Based on a survey of the
literature, it seems that current recommendations concerning the
imaging evaluation in patients with UTI are not
well-established.6
Recently, the American Academy of Pediatrics published recommendations
for diagnosis, treatment, and evaluation of the initial UTI in febrile
infants and young children. No recommendations for neonates <2 months
old have been suggested.7
The aim of the present study was to assess the frequency of urinary
tract anomalies in males <8 weeks old presenting with UTI, and to
evaluate a suitable imaging approach after the initial infection.
During a period of 4.5 years, from July 1994 through December
1998, all male infants <8 weeks old presenting with UTI were investigated prospectively. The study comprised 45 males aged 5 to 56 days, (mean: 23.77 days). All neonates were followed in the outpatient
clinic. Urine culture was obtained by suprapubic aspiration. Sepsis was
defined when blood and urine were positive for identical bacteria. All
patients had US and VCUG (except 1 neonate in whom VCUG was
unsuccessful because of technical problems).
A DMSA scan was recommended to all patients, but was performed in only
30 of 45, most of them with an abnormal VCUG (Fig
1). All neonates were treated with
intravenous (IV) antibiotics continued at least 48 hours after fever
had subsided. Thereafter, full treatment was continued with oral
antibiotics for 10 to 14 days. Subsequently, prophylaxis was initiated
until VCUG was performed, and continued when reflux was present.
PATIENTS AND METHODS
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Fig. 1.
Results of imaging studies. Numbers in brackets signify number of
patients studied. RPD, renal parenchymal damage.
US was performed during the acute phase. Hydronephrosis was graded as mild, moderate, or severe.8 VCUG was performed within 6 weeks after the infection, and vesicoureteral reflux (VUR) was classified according to the international VUR classification.9 When not specifically mentioned, infants with bilateral reflux were graded according to the higher VUR score.
DMSA scan was used for the identification of residual parenchymal damage, and not as a diagnostic tool during the acute phase. It was, therefore, performed at least 4 months after the UTI, renal scintigraphy was performed 2 to 3 hours after the IV injection of 99mTechnetium-DMSA (Kit Tecnescan DRN 4341 DMSA, Mallinckrodt Diagnostica, Petten, The Netherlands) using a dose of 50 µCi (1.85 MBq)/kg (minimal dose: 300 µCi). Six views (1 posterior, 2 posterior oblique, 2 lateral, and 1 anterior) were obtained with a 1-head gamma camera filtered with a high-resolution parallel whole collimator (Elscint SP-4 Haifa, Israel). All images were stored in an Elscint computer with a matrix size of 256 × 256. The relative uptake between left and right kidneys was calculated from the posterior view. Renal pathology was defined as focal or multifocal perfusion defects or as split renal uptake of <45%.
Results of US, VCUG, and DMSA were analyzed separately. Informed consent was obtained from 1 or both parents.
Data concerning intrauterine US were collected from the neonatal department medical charts.
Results were compared by Student's t test. All P values <.05 were considered significant.
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RESULTS |
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Discussion
Conclusion
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Urinary tract abnormalities were observed in 22 of 45 neonates. The most common finding was VUR (Table 1). Additional findings were double collecting system, posterior urethral valve, renal atrophy, or focal scars. One neonate had an isolated pelviureteric junction stricture diagnosed by diuretic diethylenetriamine pentaacetic acid renal scan and IV urography. This infant was operated successfully at the age of 1 year.
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Ultrasonography, performed in all neonates, was normal in 33 (Fig 1). Thirty-two of those had a VCUG. In 19, the VCUG was normal. In 1 neonate with an unsuccessful VCUG, the DMSA scan was normal. Prophylactic antibiotic treatment was discontinued without any evidence of further infections. In 13 neonates, the VCUG demonstrated VUR grades 1 to 3. DMSA scan performed in 20 infants in this group was normal in all (Fig 1).
Abnormal US was observed in 12 neonates (Fig 1). Eleven had hydronephrosis, and 3 of them also had evidence of renal parenchymal damage. One neonate had isolated renal atrophy. The infant with the posterior urethral valve had severe hydronephrosis without evidence of parenchymal damage. VCUG was performed in all neonates with abnormal US, and found to be normal in 4. Of those, 1 had pelviureteric junction stricture, and 3 had mild hydronephrosis that resolved on follow-up. VUR was observed in 8 neonates. The neonate with the posterior urethral valve had VUR grade 1. Renal parenchymal changes were observed almost exclusively in boys with VUR grade 3 or above (Table 2). Only 1 neonate with VUR grade 1 had a pathologic DMSA. The US in this boy demonstrated renal atrophy.
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Forty-four of 45 neonates had intrauterine US. All 33 with normal US postinfection also had a normal intrauterine US. Of the 12 with an abnormal US, 8 had a normal intrauterine US (including the infant with posterior urethral valve, 4 with VUR grade 3 to 5, and 3 with mild hydronephrosis that resolved later on). Three neonates had an abnormal US, including 1 child with pelviureteric junction stricture, 1 with VUR grade 1 and renal atrophy, and 1 with VUR grade 4. One neonate with VUR grade 4 and renal atrophy did not have an intrauterine US.
Escherichia coli was found in 62% (28 of 45) of the neonates with UTI. Nine had bacteremia as well. No correlation between the presence of sepsis and urinary tract pathology or its severity was observed.
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DISCUSSION |
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Discussion
Conclusion
References
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UTI is a common clinical problem in neonates. At this age, the infection is more common in males, possibly attributable to a higher incidence of structural abnormalities.1-3 It is common practice, especially in male neonates, to perform routine imaging by US, VCUG, and renal scan.3,4 In 1991, the Royal College of Physicians recommended the performance of US, VCUG, and DMSA studies in infants <1 year old, and US and DMSA for those between 1 and 7 years.5 Those recommendations are not based on firm evidence.6 The American Academy of Pediatrics recently recommended performing an US and VCUG in infants 2 to 24 months old with UTI. The diagnostic approach in younger infants and neonates was not addressed. The clinical contribution of the DMSA scan has been questioned.7 In the present study, 49% of the boys had urinary tract abnormalities, mostly VUR, an incidence similar to that observed by others.3,10
The most common pathogen observed was Escherichia coli (62%). Bacteremia occurred in 20% (9 of 45) of our patients. Others have observed sepsis in the range of 6% to 36.4%.11,12 In the present study, neonates with sepsis did not differ from those with UTI alone in the incidence of renal abnormalities such as reflux, its severity, or the presence of renal scars.
US is a simple, readily available, and noninvasive mode of urinary tract investigation. It is performed routinely in any child with UTI because it rapidly detects obstruction or perinephric abscess. Its main drawback is lack of accuracy in detecting renal parenchymal pathology. Thirteen boys in our study, who had a normal US, had VUR. Therefore, if we would have performed only an US, we would have failed to diagnose VUR in 2 neonates with grade 1, 8 neonates with grade 2, and 3 neonates with grade 3.
One might consider performing an US and a renal scan, and reserving VCUG only in those with pathologic findings. However, 13 neonates with normal US, had VUR, although DMSA scan was normal in 11(in the remaining 2, the scintigraphy was not performed). Adopting this approach would have resulted in failing to diagnose an appreciable number of infants with VUR, a finding that may affect further management.
Renal parenchymal lesions were detected on DMSA in 20% (6 of 30), all but 1 with VUR grade 3 or above. The single neonate with VUR grade 1 and renal scar on scintigraphy had an abnormal US also suggestive of renal atrophy. In the neonates with normal US without VUR or with VUR grade 1 to 3, DMSA was performed in 20 of 33, and was normal in all. Although speculative, our data suggest that the likelihood of detecting renal scars in this group is probably low. Our data suggest that performing a DMSA scan only in neonates with suspected renal damage on US, or in males with VUR grades 3 and above, will significantly reduce the number of scans without missing significant information. Several authors have reported the presence of renal scars in children with normal US and with mild or no VUR.13-15 Because the populations studied were older than the one reported by us, it may well be that the presence of scars is either the consequence of recurrent UTIs or an improvement or resolution of VUR over time.
Because the decision for prophylactic treatment is keyed to the presence or absence of VUR, the clinical relevance of the DMSA scan may be questioned. However, it seems to us that DMSA findings may contribute in defining prognosis and affect decisions concerning prophylactic treatment.
In our hands, intrauterine US correlated poorly with ultrasonographic findings detected after birth. Eight of the 11 neonates with pathologic US had a normal intrauterine study, including 1 infant with posterior urethral valve and 4 neonates with VUR.
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CONCLUSION |
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Abstract
Results
Discussion
Conclusion
References
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In summary, US and VCUG should be performed routinely after the initial UTI in male neonates. We suggest that a renal nuclear scan should be performed only when US exhibits renal parenchymal damage or when VCUG detects VUR grade 3 and above (Fig 2).
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We are aware that adopting this approach may result in occasionally failing to diagnose mild parenchymal damage that could have been detected by DMSA scan, but it seems to us that these findings will probably have an insignificant impact on patient management.
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FOOTNOTES |
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Received for publication Nov 16, 1999; accepted Nov 16, 1999.
Reprint requests to (M.A.) Department of Pediatrics "B", Assaf Harofeh Medical Center, 70300 Zerifin, Israel.
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ABBREVIATIONS |
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UTI, urinary tract infection; US, ultrasound; VCUG, voiding cystourethrogram; DMSA, dimercaptosuccinic acid; IV, intravenous; VUR, vesicoureteral reflux.
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REFERENCES |
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This article has been cited by other articles:
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  G Zamir, W Sakran, Y Horowitz, A Koren, and D Miron Urinary tract infection: is there a need for routine renal ultrasonography? Arch. Dis. Child., May 1, 2004; 89(5): 466 - 468. [Abstract] [Full Text] [PDF]
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 M. J. Maisels, T. B. Newman, F. J. Garcia, and A. L. Nager Neonatal Jaundice and Urinary Tract Infections Pediatrics, November 1, 2003; 112(5): 1213 - 1214. [Full Text] [PDF]
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F. J. Garcia and A. L. Nager Jaundice as an Early Diagnostic Sign of Urinary Tract Infection in Infancy Pediatrics, May 1, 2002; 109(5): 846 - 851. [Abstract] [Full Text] [PDF]
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 UTIs and Imaging in Male Neonates Journal Watch (General), June 16, 2000; 2000(616): 6 - 6. [Full Text]
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