This will be a randomized controlled trial performed in a tertiary paediatric emergency department. Participants will include all infants younger than 6 months of age who need a urinary culture and/or analysis requested by the attending physician. The intervention will consist of the use of emergency point-of-care ultrasound by a trained research assistant. The primary outcome will be the rate of success of the procedure. Secondary objectives will be to evaluate time to collect urine samples and to determine which transversal bladder diameter correlates with more than a 90% success rate for the procedure. Independent variables will be sex and age. In both groups, trained research nurses will collect clean-catch urine samples using bladder stimulation techniques. The success rate of the CCU procedure in both groups will be calculated. The time required to collect urine samples will be analysed. In group 1, the investigators will determine the transversal bladder diameter corresponding to a success rate for the procedure of > 80%. It is estimated that, in the worse-case scenario, the evaluation of 200 participants will provide a 95% confidence interval smaller than 10% for proportions. In addition, 20 participants with a successful CCU sample would allow to evaluate 2 risk factors using univariate and multivariate analysis.