['Suprapubic bladder aspiration (SBA) is a widely accepted technique used to collect uncontaminated urine samples from infants with suspected urinary tract infection (UTI). Ultrasound-based guidance improves the success rates. The standard measurements for a successful procedure, however, have been scarcely evaluated.', 'To assess the efficacy of ultrasound-guided SBA versus blind SBA, and to establish the bladder measurements associated with optimal results.', 'Ultrasound-guided SBA was performed in 50 infants≤4 months of age with suspected UTI, and the anteroposterior (APD) and transverse diameter of the bladder were determined using ultrasound equipment (Esaote MyLab® 25 Gold, and Hewlett Packard Sonos® 5500) with a 3.5MHz convex probe. The success rates and the total volumes of collected urine were compared to a control group of 50 patients of similar age and clinical characteristics, to whom conventional blind SBA was performed.', 'The rate of successful ultrasound-guided SBA was 92.3% compared to 30.8% in the blind SBA group (P<.05). The collected urine volumes were 7.65±1.85ml and 6.1±2.13ml, respectively (P<.001). An APD≥2cm was associated with an optimal performance of the technique (97.8% success). No major complications were observed in either group.'] Does [ Ultrasound-guided suprapubic bladder aspiration increase the success of the technique in infants less than 4 months-old ]?