Use of the contrast volume to estimated creatinine clearance ratio to predict renal failure after angiography

Little data exists regarding the relationship between the volume of radiographic contrast infused and the risk of contrast nephropathy for individual patients based on specific patient characteristics. Because the likelihood of renal failure is increased when there is preexisting azotemia or when larger volumes of contrast are used, it was hypothesized that the contrast volume:estimated creatinine clearance ratio would serve as a predictor of nephropathy following cardiac angiography. A retrospective analysis was performed of 152 high risk patients whose baseline serum creatinine concentration was greater than or equal to 2.0 mg/dL or who received greater than or equal to 300 cc of contrast. Nephropathy, defined as in increase in serum creatinine of greater than or equal to 1.0 mg/dL within 48 hours, occurred in 11 patients (7%). The contrast volume:creatinine clearance ratio was >6.0 in 64% of patients who developed nephropathy and 31% of patients who did not (P < 0.05). The contrast volume:creatinine clearance ratio was then studied prospectively in 250 consecutive patients. The risk of nephropathy was 61% for patients with a ratio >6.0, but only 1% otherwise (P < 0.01). This ratio can be used to calculate an upper limit for contrast volume and might reduce the chance of renal failure.