Dynamic magnetic resonance imaging in acute pyelonephritis

PURPOSE: This study was conducted to evaluate the role and clinical impact of dynamic magnetic resonance imaging (MRI) in the diagnosis and follow-up of acute pyelonephritis (APN). MATERIALS AND METHODS: We retrospectively reviewed 442 consecutive renal MRI examinations (279 diagnostic and 163 follow-up) performed in 285 patients (mean age 42.17 years), 35 of whom were kidney transplant recipients with a clinical suspicion of APN. RESULTS: MRI showed signal abnormalities suggestive of APN in 125/244 (51.2%) patients with native kidneys. Except for two examinations performed without paramagnetic contrast material, the inflammatory foci appeared as areas of nonenhancement: single in 39/123 cases, multiple in 84/123, unilateral in 60/84 and bilateral in 24/84. Abscesses were present in 40/123 (32.5%) positive cases. During follow-up, we observed complete normalisation of MRI signs in 86/103 patients; 17/103 (16.5%) cases evolved into fibrosis and scarring. In 15/35 (42.8%) patients with transplanted kidney, MRI was positive for APN. CONCLUSIONS: Renal MRI is an effective tool for the diagnosis and follow-up of APN both in patients not at risk and those at higher risk, such as those with a transplanted kidney. The high costs of the examination are offset by better treatment planning and early complication detection.