Diffusion-weighted magnetic resonance imaging is more sensitive than dimercaptosuccinic acid scintigraphy in detecting parenchymal lesions in children with acute pyelonephritis: A prospective study.

INTRODUCTION: Static renal scintigraphy is the gold standard for detection of inflammatory changes in the renal parenchyma in acute pyelonephritis. Our aim was to determine whether diffusion-weighted magnetic resonance imaging (DW-MRI) was comparable with static renal scintigraphy (DMSA-SRS) to demonstrate acute renal parenchymal lesions.

OBJECTIVE: To compare 99m Tc-dimercaptosuccinic acid static renal scintigraphy (DMSA-SRS) with diffusion-weighted magnetic resonance imaging (DW-MRI) for detecting acute inflammatory changes in the renal parenchyma in children with febrile urinary tract infection.

METHODS: Thirty-one children (30 girls) aged 3-18 years with a first episode of febrile UTI without a previously detected congenital malformation of the urinary tract, were prospectively included. DMSA-SRS and DW-MRI were performed within 5 days of diagnosis to detect renal inflammatory lesions. The DW-MRI examination was performed without contrast agent and without general anesthesia. Late examinations were performed after 6 months using both methods to detect late lesions.

RESULTS: DW-MRI confirmed acute inflammatory changes of the renal parenchyma in all 31 patients (100%), mostly unilateral. DMSA-SRS detected inflammatory lesions in 22 children (71%; p = 0.002). The lesions were multiple in 26/31 children (84%) on DW-MRI and in 9/22 (40%) on DMSA-SRS. At the control examination, scarring of the renal parenchyma was found equally by DW-MRI and DMSA-SRS in five patients (16%), three of whom were the same patients. The overall concordance of positive and negative late findings occurred in 87% of patients. There was correspondence in the anatomical location of acute and late lesions.

DISCUSSION: The clinical significance of acute and late parenchymal findings on DWI-MR is yet to be determined. A limitation of our study is the age of the patients (older than 3 years) who are less sensitive to scar development; therefore, a smaller number of patients with scars could be analyzed during control examination. Further studies using the DW-MRI should confirm its reliability to detect acute and late lesions in younger children and infants and determine the clinical consequences.

CONCLUSION: DW-MRI has higher sensitivity for detecting acute renal inflammatory lesions and multifocal lesions than DMSA-SRS. The incidence of scars was low and corresponded with the anatomical location of acute and late lesions.