MRI and suspected acute pyelonephritis in children: comparison of diffusion-weighted imaging with gadolinium-enhanced T1-weighted imaging

Objectives To evaluate the performance of diffusion-weighted imaging (DWI) against the reference standard of gadolinium-enhanced T1-weighted imaging (Gd-T1-WI) in children. Methods Thirty-nine consecutive patients (mean age 5.7 years) with suspected acute pyelonephritis underwent magnetic resonance imaging (MRI) including DWI and (the reference standard) Gd-T1-WI. Each study was read in double-blinded fashion by two radiologists. Each kidney was graded as normal or abnormal. Sensitivity and specificity of DWI were computed. Agreement between sequences and interobserver reproducibility were calculated (Cohen kappa statistic and the McNemar tests). Results Thirty-two kidneys (41 %) had hypo-enhancing areas on Gd-T1-W images. The sensitivity and specificity of DWI were 100 % (32/32) and 93.5 % (43/46). DWI demonstrated excellent agreement (kappa=0.92,) with Gd-T1-W, with no significant difference (P=0.25) in detection of abnormal lesions. Interobserver reproducibility was excellent with DWI (kappa=0.79). Conclusion DWI enabled similar detection of abnormal areas to Gd-T1-WI and may provide an injection-free means of evaluation of acute pyelonephritis. Key points Diffusion weighted magnetic resonance imaging (DWI) can confirm acute pyelonepritis. DWI provided comparable results to gadolinium enhanced T1-W MRI in acute pyelonepritis. Contrast medium injection could be avoided for diagnosing acute pyelonephritis by MRI. MRI with T2-WI and DWI provide a fast and comprehensive diagnostic tool.