Genitourinary MR: Kidneys and adrenal glands

Due to its high tissue contrast and multiplanar imaging capabilites, MRI provides a detailed display of renal and adrenal anatomy. Recent technical developments overcoming the problem of respiration induced motion artifacts and the use of paramagnetic contrast agents have further improved the performance of MRI which has now evolved as an alternative or complementary imaging modality to ultrasound, excretory urography and computed tomography. Dynamic contrast-enhanced studies will usually allow to detect even small enhancing solid areas within the cyst wall. Use of a fast (turbo) spoiled gradient echo sequence allows for assessment of contrast enhancement dynamics in renal and adrenal masses. For tumor staging, the multiplanar imaging capabilities of MRI are advantageous. Perinephric extent is best detected using opposed-phase GRE images resulting in an artifical accentuation of renal contours. Extension into venous structures is best diagnosed by using a GRE sequence allowing for distinction between flowing blood and tumor thrombus. Noninvasive differentiation of adrenal lesions can be performed with an unprecedented accuracy using chemical-shift imaging. (orig.)