Utility of non-enhanced magnetic resonance imaging to detect acute pyelonephritis.

It has been established that enhanced computed tomography (CT) and (99m) Tc-dimercaptosuccinic acid renal scintigraphy ((99m) Tc-DMSA scintigraphy) used in conjunction with single-photon emission CT is a useful tool for the diagnosis of acute pyelonephritis (APN). The utility of non-enhanced magnetic resonance imaging (MRI), however, has not been investigated extensively for the diagnosis of APN or renal abscess in children. We describe the case of a 23-month-old boy with suspected APN who received non-enhanced MRI. Whole body diffusion-weighted imaging (DWI) was used, and a background body-signal suppression sequence was applied. High-intensity focal lesions were identified on DWI and low-intensity lesions on the apparent diffusion coefficient map in the acute phase. This case suggested that non-enhanced MRI could be a useful tool for the diagnosis of APN in children, because it can avoid the risks of not only radiation exposure but also nephrogenic systemic fibrosis associated with gadolinium-based contrast agents, especially in infants.