Focal renal masses: magnetic resonance imaging.

Abstract

Patients (30) with focal renal masses were evaluated on a .12-Tesla resistive magnetic resonance unit using partial saturation and spin echo pulse sequences. A short repetition time (TR = 143 ms) was employed for partial saturation images and a spin echo was present in each case (TE = 10 ms). Additional pulse sequences through regions of interest were also obtained. Patients (15) had cystic lesions, 9 patients had renal cell carcinoma, 2 had metastatic lesions, 1 had an angiomyolipoma and 3 had focal bacterial infection. Cystic lesions were well circumscribed and demonstrated a range of signal intensities. Small intraparenchymal cysts were difficult to identify. Renal cell carcinomas demonstrated areas of increased signal using a partial saturation sequence (TR = 143-415 ms, TE = 10 ms). Magnetic resonance imaging accurately detected perinephric extension and vascular invasion in all patients. Metastatic disease to the kidney was uniformly low in signal, in contrast to primary renal cell carcinoma; an angiomyolipoma demonstrated very high signal intensity. Two masses resulting from acute focal bacterial nephritis were uniformly low in signal. One additional case of a more indolent pyelonephritis demonstrated high signal in regions of replacement lipomatosis and low signal in sites of active infection. Magnetic resonance imaging appears to be an accurate way of detecting, identifying and staging focal renal masses.