The diagnostic value of renal cortex-to-medulla contrast on magnetic resonance images.

The diagnostic value of magnetic resonance contrast between the renal cortex and renal medulla as an indicator of renal disease was retrospectively studied in 38 patients (ten patients with a variety of diseases affecting the renal parenchyma, nine with renal obstruction, four with diffusely infiltrating renal-cell carcinoma, one with renal hematoma, nine with normally functioning renal allograft, and five with renal allograft failure). Twelve normal volunteers served as controls. On spin-echo (SE) images (TR 0.5 sec, TE 28 msec), the cortex-to-medulla contrast was present in the kidneys of all the normal volunteers (19% contrast +/- 2% S.D.) and in all the normally functioning allografts (17% contrast +/- 2% S.D.). Decrease or absence of cortex-to-medulla contrast (SE image with TR 0.5 sec and TE 28 msec) was found to be a sensitive but nonspecific sign of renal disease. It occurred in renal diseases of various causes and was produced by different pathophysiologic mechanisms such as edema, scarring, and tissue replacement by neoplasm or hematoma. Of the calculated T1 and T2 relaxation times and spin density of the cortex and the medulla, the T1 changes most consistently reflected renal disease.