Journal of Perinatology (2010) 30, 281–285 r 2010 Nature Publishing Group All rights reserved. 0743-8346/10 $32 www.nature.com/jp ORIGINAL ARTICLE Prevalence of renal anomalies after urinary tract infections in hospitalized infants less than 2 months of age L Nowell1, C Moran2, PB Smith2,3, P Seed2, BD Alexander3,4, CM Cotten2, JS Wiener2,5 and DK Benjamin Jr2,3 1Duke University School of Medicine, Durham, NC, USA; 2Department of Pediatrics, Duke University Medical Center, Durham, NC, USA; 3Duke University Clinical Research Institute, Durham, NC, USA; 4Department of Medicine and Pathology, Duke University Medical Center, Durham, NC, USA and 5Department of Surgery, Duke University Medical Center, Durham, NC, USA to 24 months of age.7 However, recent data suggest that VUR may Objective: Our aim was to determine the incidence of anatomical not be an independent predictor of recurrent UTIs or new renal abnormalities after a urinary tract infection (UTI) in infants <2 months of scarring.8 A recent randomized controlled trial showed that age hospitalized in the neonatal intensive care unit (NICU). mild–moderate reflux did not increase the incidence of recurrent 6 Study Design: This was a retrospective, single-center cohort study of UTIs and scarring in children. infants <2 months of age in the NICU with a UTI and documented renal Although there are no current recommendations for infants <2 imaging. months of age, the current practice at the Duke University Medical Center, like many medical centers, has been to extend the Result: We identified 141 infants with UTIs. The mean gestational age radiographic recommendations to infants <2 months of age and and birth weight were 28 weeks and 1254 g, respectively. The most to screen infants with both an RUS and a VCUG after a UTI. commonly identified pathogen was coagulase-negative Staphylococcus However, there are concerns about unnecessarily exposing infants (28%, 44 of 156). A major abnormality was found on at least one imaging to invasive procedures and to the radiation involved with a study for 4% (5 of 118) of infants. Major abnormalities were noted on 4% VCUG.9–11 Furthermore, the lack of consensus regarding the utility (5 of 114) of renal ultrasounds and 2% (2 of 82) of voiding of VCUG to prevent renal scarring and end-stage renal disease cystourethrography examinations. makes this concern even more relevant. Conclusion: Among infants in the NICU <2 months of age at the time We sought to identify the prevalence of reflux and other of a UTI, the prevalence of major anatomical abnormalities is <5%. functional and structural abnormalities identified on urinary tract Journal of Perinatology (2010) 30, 281–285; doi:10.1038/jp.2009.147; imaging after UTIs in infants hospitalized in the Duke University published online 8 October 2009 Medical Center neonatal intensive care unit (NICU). Owing to the increased length of hospitalization and immature immune status Keywords: renal abnormalities; renal ultrasound; voiding cystoure- thrography predisposing these infants to UTIs, we hypothesized that the incidence of major structural abnormalities would be uncommon in hospitalized infants compared with estimates in older infants Introduction and children. Urinary tract infections (UTIs) are common in children, occurring in up to 1% of all infants and 8% of infants <1500 g birth weight.1–5 Recurrent UTIs of the upper tract (pyelonephritis) are Methods associated with renal scarring, defined by perfusion defects and loss We identified all infants <2 months of age in the Duke University of kidney contours or cortical thinning with volume loss.6 Such Medical Center NICU with a positive urine culture for a single scarring may lead to end-stage renal disease. To prevent these organism from January 1996 to August 2006 from the Clinical sequelae, the American Academy of Pediatrics recommends a renal Microbiology Laboratory database. RUS and VCUG results were bladder ultrasound (RUS) and either a voiding cystourethrography obtained from the patients’ medical records. (VCUG) or radionuclide cystography to detect the presence of Urine cultures were obtained as part of sepsis evaluations. This vesicoureteral reflux (VUR) after an initial febrile UTI in children 2 cohort contained all the UTI cases in the NICU during this time period. We defined a UTI as isolation of X1000 colony forming Correspondence: Dr PB Smith, Department of Pediatrics, Duke University Medical Center, PO units of a single organism from a specimen obtained by either Box 17969, Durham, NC 27715, USA. E-mail: [email protected] Received 12 March 2009; revised 14 August 2009; accepted 25 August 2009; published online suprapubic aspiration or in and out catheterization. If mixed 8 October 2009 organisms were isolated from a urine culture or the infant’s Prevalence of renal anomalies in infants L Nowell et al 282 antibiotic treatment was stopped when culture results were Table 1 Demographics reported, the episode was not considered a UTI. UTIs were classified Demographics Total (%) as separate infections for the same infant if: (i) >14 days had elapsed between cultures and there was at least one negative urine Gender culture between two positive cultures; (ii) >30 days had elapsed Male 91 (64) between two urine cultures with the same organism; or (iii) a Female 50 (35) different organism was isolated. Demographic information (age, birth weight, gender and race) Ethnicity was collected for each infant. Method of urine collection African-American 75 (53) Caucasian 53 (38) (suprapubic aspiration or catheterization) and organism cultured Hispanic 11 (8) were recorded. In cases in which the collection method was Indian 2 (1) unknown, the samples were treated as bag collections and not included in the analysis. Results from cerebrospinal fluid (CSF) Gestational age (weeks) and blood cultures obtained within 72 h of the positive urine <28 76 (54) culture were recorded. We reviewed the most recent RUS and VCUG 28–33 43 (31) for each infant. The NICU practice was typically to obtain the RUS >33 21 (15) at least 1 week after completing UTI treatment and a VCUG when the patient attained a weight X1500 g and was deemed to be Birth weight (grams) clinically stable. <1000 65 (46) The degree of hydronephrosis and/or VUR was recorded. The 1000–1499 43 (31) X classification systems used to describe the degrees of severity by 1500 33 (23) VCUG and RUS were (i) the International system of radiographic Day of life of UTI (days) grading of vesicoureteric reflux: International Reflux Study in 0–3 1 (0.7) Children and (ii) Ultrasound grading of hydronephrosis: 4–7 3 (2) introduction to the system used by the Society for Fetal Urology, 8–30 76 (54) 12,13 respectively. If VUR was bilateral, the higher grade was 31–60 61 (43) recorded. If any radiographic study had abnormalities other than hydronephrosis or VUR, a pediatric urologist was consulted to Outcome determine which abnormalities were significant. Renal agenesis, Lived/transferred 128 (91) posterior urethral valves, horseshoe kidneys, dysplastic kidneys, Died 13 (9) VUR X3 and hydronephrosis X3 were considered major abnormalities. Infection status Our NICU practice is to obtain repeat urine cultures after an Single UTI 128/141 (91) Multiple UTIs 13/141 (9)a initial positive urine culture until negative. A RUS and VCUG are Total 141 obtained for all infants with a documented UTI. Although a RUS is Abbreviation: UTI, urinary tract infection. performed at any point, the VCUG is generally delayed until after a the UTI treatment is complete and the infant’s birth weight is Eleven infants had two UTIs and two infants had three UTIs. >1500 g. Indications to begin UTI prophylaxis for infants are as follows: (i) two UTIs, (ii) UTI and any abnormality on RUS and confidence interval 24, 38), 1254 g (610, 2670) and 29 days (iii) any infant regardless of UTI status with Xgrade 3 (8, 56), respectively. Males represented 65% (91 of 141) of the hydronephrosis on RUS, until a VCUG is performed. infants with a UTI. We used STATA 10 (College Station, TX, USA) to analyze the The organisms most commonly isolated were coagulase- data. Fisher’s exact tests were used where appropriate. The Duke negative Staphylococcus (CoNS) (28%, 44 of 156), Escherichia coli University Medical Center Institutional Review Board approved this (17%, 27 of 156), Enterococcus sp. (12%, 18 of 156) and Klebsiella study. species (11%, 17 of 156) (Table 2). Mortality after Gram-positive UTIs was 6% (4 of 72) compared with 9% (6 of 70) after Gram- negative UTIs (P ¼ 0.49). Mortality after Candida UTIs was 21% Results (3 of 14) compared with bacterial UTIs, 7% (10 of 142) We identified 141 infants with at least one UTI. Of the 141 infants, (P ¼ 0.06). 9% (13 of 141) had multiple UTIs (Table 1). The mean gestational There were 134 blood cultures obtained within 72 h of the initial age, birth weight and day of life of first UTI were 28 weeks (95% diagnostic urine culture, and 92% (123 of 134) were negative Journal of Perinatology Prevalence of renal anomalies in infants L Nowell et al 283 Table 2 Organisms identified by urine culture Table 4 Results of renal ultrasound (n ¼ 114) and VCUG (n ¼ 82) after UTI Organism Total (%) Total (%) Gram-positive Renal ultrasound study results 114 CoNS 44 (28) Hydronephrosis Enterococcus sp. 18 (12) Hydronephrosis grade 1 27 (24) Staphylococcus aureus 10 (6) Hydronephrosis grade 2 5 (4) Hydronephrosis grade 3 2 (2)a Gram-negative Escherichia coli 27 (17) Other findings Klebsiella sp. 17 (11) Echogenic foci/stones 9 (8) Enterobacter sp. 14 (9) Duplication 0 (0) Citrobacter sp. 5 (3) Unilateral agenesis 1 (1)a Proteus sp. 4 (3) Dysplastic 1 (1)a Pseudomonas sp. 2 (1) Horseshoe 1 (1)a Gram-negative rods unspeciated 1 (0.6) VCUG study results 82 Candida sp.