Background. Contrast-induced nephropathy (CIN) is a recognised complication of intravascular administration of iodinated contrast media (ICM). Previous studies suggest a higher incidence in the elderly, but no large study has assessed this to date. We set out to assess changes in creatinine in elderly inpatients following computed tomography (CT) examination and compare those who received intravenous contrast to those who did not. Methods. Using the Radiology Information System in two teaching hospitals, inpatients over the age of seventy who had a CT examination and a baseline creatinine were identified and their follow-up creatinine levels were analysed. Elderly inpatients who underwent a noncontrast CT over the same period were used as controls. Results. 677 elderly inpatients who received ICM were compared with 487 controls. 9.2% of patients who received ICM developed acute kidney injury (AKI) compared to 3.5% of inpatient controls ( ). Patients with higher baseline eGFR had a higher incidence of post-CT AKI. Conclusions. The incidence of post-CT AKI is higher in patients who received IV ICM compared to those who did not; the difference may be partly attributable to contrast-induced nephropathy. This suggests that the incidence of CIN in the elderly may not be as high as previously thought. 1. Background Intravascular administration of iodinated contrast media (ICM) is used in a variety of diagnostic and therapeutic procedures. While ICM are generally safe, only resulting in minor side effects, they can result acute renal impairment known as contrast induced nephropathy (CIN) [1]. The majority of cases of CIN are self-limiting, although occasionally chronic renal failure ensues necessitating long-term renal replacement. Even when transient, CIN is associated with increased length of hospital stay and significant morbidity [1, 2]. Diabetes mellitus, preexisting renal failure, congestive heart failure, and hypotension, dehydration as well as the use of ACE inhibitors, diuretics, and nonsteroidal anti-inflammatory drugs have all been identified as important risk factors for developing CIN [3, 4]. Hydration in high-risk patients remains the most important preventative measure [5, 6]. Many attempts at defining CIN exist, but the most widely accepted definition is a 25% rise in serum creatinine concentration from baseline or an absolute increase by 44？μmol/L over the 48 to 72 hours following ICM administration, once other causes of renal impairment have been excluded [2, 4]. The use of CT in clinical medicine has exponentially increased over the past two
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