At the initial bpMRI, focal nephritic areas in all patients appeared striated, band-like, or triangular in morphology and were inhomogeneous, moderately-markedly hypointense or homogeneously markedly hypointense on the ADC map. Focal nephritic areas were unilateral in 19 patients of whom 17 with multiple unilateral lesions. Bilateral and multiple nephritic areas were observed in 12 patients. The mean ADC value of all lesions was lower than the grayscale mean ADC value, with a percentage difference ranging from 29% to 53% (mean 41.78%, SD 6.56% ± 1.55%) (Fig. 2–4).

At follow-up bpMRI, 8 out of 31 patients were re-evaluated. Two patients showed complete resolution of the nephritis areas after antibiotic therapy, as confirmed by clinical and laboratory findings, as well as by bpMRI (Fig. 5). In the remaining five patients, including three with transplanted kidneys, focal nephritic areas with moderately restricted diffusion on DWI/ADC were still present 3 to 6 months after antibiotic therapy. The mean ADC value of the lesions increased but remained lower than the mean grayscale ADC value. (Fig. 6).