Contrast-medium nephropathy is defined as acute renal impairment that occurs after exposure to contrast media and for which other causes have been eliminated. 1 , 2 It is a diagnosis of exclusion. On CT it may be diagnosed by the finding of persistent cortical and corticomedullary attenuation differences 24 h after the administration of the contrast agent (Fig. 10.1). On conventional radiographs a ‘white’ kidney is present bilaterally. However, a persistent bilateral nephrogram may also be seen in bilateral obstruction and in hypotension. If the parenchymal accumulation is unilateral, it is usually due to obstruction (e.g. renal colic), and accumulation of contrast material will also occur in the renal pelvis. Other 151processes (vascular impairment or infection) should be considered in the differential diagnosis. Contrast-induced nephrotoxicity: persistent nephrogram. CT scan performed 24 h after arterial administration of a contrast medium in a patient with diabetic nephropathy. There is bilateral parenchymal accumulation, especially in the cortex, but no contrast evident in the renal pelvis. https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9780203741320/5c378b34-64e4-4eba-90e8-b294769edb5f/content/fig10_1_OB.tif"/>