The persistent computed tomography nephrogram: its significance in the diagnosis of contrast-associated nephrotoxicity.

A study was undertaken to find out if there is a quantitative relationship between the development of contrast-associated nephrotoxicity (CAN) and the mean renal cortical attenuation (RCA) as seen on computed tomography (CT) examination of the kidneys 24 hours after injection of contrast medium. 96 patients undergoing aortography were selected, who were considered "high risk" either because of the presence of a baseline serum creatinine (Cr) of 123.76 mumol l-1 (1.4 mg dl-1) or higher, or who were 73 or older with or without elevated creatinine levels. A CT study of the kidneys at approximately 24 h was correlated with baseline serum creatinine as well as 24 h Cr (48-72 h Cr when available). Medical history and medications were recorded. Eight of 96 patients had RCA of 108-236 HU at 24 h CT and all developed significant CAN of varying degree; 3/96 had RCA ranging from 48 to 67 HU and had transient CAN; two other patients with RCA of 67-90 HU developed CAN; and there was increased incidence of CAN in patients: (a) with pre-existing renal insufficiency; (b) with diabetes with renal insufficiency; (c) on diuretics; (d) who were older; and (e) had a unilateral atrophic kidney. It was concluded that a 24 h CT study evaluating the RCA had better predictive value for the development of CAN than a 24 h creatinine level.