IMAGING

Frequency of serum creatinine changes in the absence of iodinated contrast material: implications for studies of contrast nephrotoxicity
Newhouse JH, Kho D, Rao QA, Starren J
Department of Radiology, Columbia University Medical Center, New York, NY, USA
AJR Am J Roentgenol. 2008; 191: 376-82

• Objective: Most studies of contrast-induced nephropathy lack controls to distinguish it from nephropathy from other causes. We assessed the frequency and magnitude of serum creatinine changes in patients not receiving iodinated contrast material to compare with creatinine changes in publications regarding contrast nephropathy.
• Materials and Methods: From the electronic medical records of an academic medical center, adults with creatinine determinations on five consecutive days who had not received contrast material during the previous 10 days were identified. The first creatinine level was compared with those on subsequent days. We calculated the frequency with which these levels exceeded thresholds used to identify contrast nephropathy in previous publications.
• Results: Among 32,161 patients, more than half showed a change of at least 25% and more than two fifths, a change of at least 0.4 mg/dL. Among patients with baseline creatinine levels of 0.6-1.2 mg/dL, increases of at least 25%, 33%, and 50% occurred in 27%, 19%, and 11% of patients, respectively. Increases of 0.4, 0.6, and 1.0 mg/dL occurred in 13%, 7%, and 3% of patients. Among patients with baseline creatinine levels greater than 2.0 mg/dL, increases of at least 25%, 33%, and 50% occurred in 16%, 12%, and 7%. Increases of 0.4, 0.6, and 1.0 mg/dL occurred in 33%, 26%, and 18%. These increases were not different from the incidences of contrast nephropathy previously published.
• Conclusion: The creatinine level increases in patients who are not receiving contrast material as often as it does in published series of patients who are receiving contrast material. The role of contrast material in nephropathy may have been overestimated.
  
  
• Editorial Comment
  Contrast agent-induced nephropathy (CIN) is the occurrence of renal failure, characterized by an increase in serum creatinine level or a fall in creatinine clearance, after the administration of an iodinated contrast agent. This entity occurs only in patients who have abnormal renal function before contrast agent injection. Unfortunately, the parameters used clinically (creatinine levels) for the estimative of the risk of CIN are imprecise. For this reason, one should calculate the creatinine clearance. Although contrast agents have been considered as one of the most frequent causes of in-hospital renal failure, many other concomitant risk factors exists such as dehydration, diabetes, previous extensive surgery and the use of nephrotoxic medications (e.g., gentamycin, nonsteroidal anti-inflammatory drugs, and certain chemotherapeutic drugs). Adequate hydration and the use N-acetyl cysteine or both can prevent CIN.
  This report raises several questions, and the most important are: what if there is no such entity as CIN?, b) what if there is no real increase in serum creatinine level in the general population that can be attributed to the intravascular administration of contrast media? (1). It is obvious that until more rigorous studies including an appropriate control group address the issue of CIN, our understanding of the actual risk of CIN when administering IV contrast media is limited. We should also considerer that most studies have been shown that N-acetyl cysteine is useful for intra-arterial / intracardiac contrast but we do not know if the patient that receives intravenous contrast injection has the same risk of these patients. For this reason, we should not avoid doing a necessary iodinated contrast-enhanced radiological examination in a patient at risk of CIN. Obviously, the risk-benefit should be always balanced but in such situation, hyper-hydration should be immediately initiated and N-acetyl cysteine and non-ionic contrast material should be used.

Reference
1. Baumgarten DA, Ellis JH: Contrast-induced nephropathy: contrast material not required? AJR Am J Roentgenol. 2008; 191: 383-6.

Dr. Adilson Prando
Chief, Department of Radiology and
Diagnostic Imaging, Vera Cruz Hospital
Campinas, São Paulo, Brazil
E-mail: adilson.prando@gmail.com