Ultrasound is an effective and noninvasive method of evaluating renal swelling in infants with their first urinary tract infection.

AIM: This study evaluated renal swelling in infants with a first urinary tract infection (UTI) by correlating renal length and volume with C-reactive protein (CRP) and body temperature.

METHODS: Ultrasounds were carried out on 104 infants at The Queen Silvia Children's Hospital, Gothenburg, Sweden - 58 boys (mean age 3.3 months) and 46 girls (mean age 4.8 months) - during the acute phase of their UTI. A second scan was performed on 94 of them 4 weeks later. Renal length and volume were computed to standard deviation scores (SDS).

RESULTS: The mean renal length and volume at the first ultrasound were 1.90 SDS (±1.54) and 1.67 SDS (±1.13) for the larger kidney and 0.86 SDS (±1.01) and 0.84 SDS (±0.90) for the smaller kidney. There was a significant decrease in renal length and volume between the two ultrasounds, with a mean difference of 0.96 SDS (±1.24) and 1.07 SDS (±1.10) for the larger kidney (p < 0.0001). The length and volume of the larger kidney correlated with CRP (p < 0.001), but only the renal length correlated with fever (p < 0.001).

CONCLUSION: Early ultrasound determined renal swelling in infants with a UTI and may be a valuable noninvasive way of identifying infants with renal parenchymal involvement.