[Diagnostic efficiency of renal ultrasound after the first urine infection in infants].

INTRODUCTION: Several authors question the performance of systematic renal ultrasound after first urinary tract infection (UTI) in young children, given the high sensitivity of prenatal ultrasounds to detect major malformations and the low prevalence of clinical relevant findings. The aims of this study are to evaluate the yield of renal ultrasound performed after the first UTI in patients aged less than 2 years and to analyse potential risk factors (RF) of altered renal ultrasound.

PATIENTS AND METHODS: Retrospective study, including patients aged less than 2 years diagnosed with UTI in the Emergency Department between July 2013 and December 2014. Patients with an underlying nephro-urological pathology, previous UTIs and those without prenatal or post-infection renal ultrasound were excluded. Altered renal ultrasound was defined as the presence of dilated urinary tract or structural abnormalities. Potential RF analysed were: male, age less than 3 months, presence of fever and microorganism other than Escherichia coli. Univariate and multivariate logistic regression were performed.

RESULTS: A total of 306 patients were included. Altered renal ultrasound was found in 35 cases (11.4%; 95% CI 8.3-15.5): 24 (68.6%) urinary tract dilation, and 11 (31%) structural abnormalities. Among the cases with altered ultrasound, 68.6% were male, 51.4% were younger than 3 months, 74.3% were febrile, and 31.4% were caused by microorganisms other than E. coli, compared to 45% (P=.009), 31.7% (P=.021), 78.2% (P=.597) and 10% (P=.001) of cases with normal ultrasound. In the multivariate analysis, age less than 3 months (OR 2.1; 95% CI 1.0-4.3, P=.05) and microorganism other than E. coli (OR 3.8; 95% CI 1.7-8.7, P=.002) remained as RF.

CONCLUSIONS: The yield of renal ultrasound after the first UTI is low. Its indication should be individualised according to the presence of RF: age less than 3 months and microorganism other than E. coli.