Diffusion-weighted MRI in the identification of renal parenchymal involvement in children with a first episode of febrile urinary tract infection

Abstract

Aims: This study aims to assess the diagnostic accuracy of diffusion-weighted Magnetic Resonance Imaging (DW-MRI) and determine the inter-reader agreement between two expert radiologists in detecting pyelonephritic foci during the initial episode of febrile urinary tract infection (fUTI) in children aged 0-5 years. Also, we aim to establish the correlation between clinical data and DW-MRI findings.

Methods: Children aged 0-5 years presenting with their first episode of fUTI were included in the study and underwent DW-MRI and Ultrasound (US) examinations within 72 h of admission. Inter-observer agreement between the two expert radiologists in assessing DW-MRI scans was evaluated using Cohen's kappa statistic. Clinical and laboratory data were subjected to statistical analysis.

Results: 84 children (40 male, 44 female) with a mean age of 7.3 (SD 6.2) months were enrolled. DW-MRI detected pyelonephritis in 78 out of 84 cases (92.9%), with multiple foci observed in 73 out of 78 cases (93.6%). There was a "substantial" level of agreement between the two expert radiologists (κ = 0.725; observed agreement 95.2%). Renal US revealed pyelonephritis in 36 out of 78 cases (46.2%). White blood cell (WBC) count (p = 0.04) and lymphocyte count (p = 0.01) were significantly higher in patients with positive DW-MRI. Although not statistically significant, patients with positive DW-MRI had higher mean values of C-Reactive Protein, Procalcitonin, and neutrophil WBC count (7.72 mg/dl, 4.25 ng/dl, and 9,271 /μl, respectively).

Conclusions: DW-MRI exhibited excellent diagnostic performance in detecting pyelonephritic foci, with substantial inter-reader agreement among expert radiologists, indicating the reliability of the technique. However, a weak correlation was observed between laboratory parameters and DW-MRI results, potentially because of the low rate of negative DW-MRI findings.

Keywords: DWI (diffusion weighted imaging); MRI; UTI (urinary tract infection); pediatric; pyelonephritis.

Figure 1

A 6-month-old child with fUTI; DW-MRI showed no focal renal areas of restricted diffusion. Right adrenal hemorrhage (arrow).

Figure 2

2-year-old girl with fUTI (A&B): DW-MRI (b = 1,000) (A) shows a significant focal area of restricted diffusion at left lower pole (arrow) with corresponding T2 signal alteration (arrow) (B); other smaller foci are pointed by arrowhead (A) 35-month-old boy with fUTI (A&B): DW-MRI (b = 1,000) shows multiple focal areas of restricted diffusion (arrows) (C) with corresponding hypointensities in the ADC map (arrows) (D).

Figure 3

A 3-month-old boy with fUTI (A,B); US shows no focal areas suggestive of APN, pelvic dilatation with thickened pelvic walls, and some echoic debris within the pelvis.