Imaging Male Neonates after a Urinary Tract Infection
Abstract & Commentary
Synopsis: Workup of male infants younger than two months of age with a urinary tract infection is most efficiently performed with an ultrasound and voiding cystourethrogram. Renal scan is reserved for infants with ultrasound evidence of renal parenchymal damage or grade 3 or above vesicoureteral reflux.
Source: Goldman M, et al. Imaging male neonates after a urinary tract infection. Pediatrics 2000;105:1232-1241.
Urinary tract infection (uti) is one of the most frequent causes of unexplained fever in neonates, with males more commonly affected. Review of the literature has suggested that recommendations concerning imaging evaluation of infants with UTI are not well established for neonates younger than 2 months old. This study assesses the frequency of UTI in males younger than 8 weeks old and suggests an imaging approach after the initial infection.
Over four and one-half years, all male infants younger than 8 weeks old presenting with UTI were investigated prospectively. Urine culture was obtained by suprapubic aspiration and sepsis was defined when blood and urine were positive for identical bacteria. All patients had voiding cystourethrogram (VCUG) and an ultrasound (US) and a DMSA scan was recommended to all patients but was performed in 30 out of 45. Results of VCUG, DMSA, and US were analyzed separately. Data concerning intrauterine US were collected from the neonatal department medical charts.
Urinary tract abnormalities were observed in 22 neonates. The most common finding was vesicoureteral reflux (VUR). Other findings were double collecting system, posterior urethral valve, renal atrophy, or focal scars. One infant had pelviureteric junction stricture diagnosed by diuretic diethylenetriamine penta-acetic acid renal scan and IV urography.
The American Academy of Pediatrics recommended performing an US and VCUG in infants 2-24 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. In the present study, 49% of the boys had urinary tract abnormalities, mostly VUR, an incidence similar to that observed by others.
The most common pathogen was Escherichia coli (62%). Bacteremia occurred in 20% of patients. Others have observed sepsis in the range of 6-36.4%. 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 simple, readily available, and noninvasive. It rapidly detects obstruction or perinephric abscess. It is not so accurate in detecting renal parenchymal pathology. In this study, an US alone would have failed to diagnose VUR in two neonates with grade 2 and 3 neonates with grade 3 reflux.
Renal parenchymal lesions were detected on DMSA in 20% (6/30)—all but one with VUR grade 3 or above. The single neonate with VUR grade 1 and renal scar on scintigraphy had an abnormal US. In the neonates with normal US without VUR or with VUR grade 1-3, DMSA was performed in 20 of 33, and was normal in all infants. The data suggest that the likelihood of detecting renal scars in this group is probably low. Performing a DMSA scan only in neonates with suspected renal damage on US, or in males with VUR grades 3 and above will reduce the number of scans without missing significant information.
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. It seems that DMSA findings may contribute in defining prognosis and affect decisions concerning prophylactic treatment.
Comment by Beverly P. Wood, MD
This study indicates that US and VCUG should be performed routinely after an initial UTI in male neonates. DMSA scan does not need to be included in the schema for workup but can be reserved for infants with US evidence of renal parenchymal damage or those with VUR grade 3 and above. The savings from doing a scan are significant in terms of finance and also in the outcomes of infant management.
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