Iodixanol and Chronic Kidney Disease

Dear Editor, I read with great interest the Tadros, et al. article¹ entitled Iso-osmolar Radiocontrast Iodixanol in Patients with Chronic Kidney Disease (J Invasive Cardiol 2005;17:211–215). They concluded that the volume of iso-osmolar radio contrast does not affect the incidence of contrast-induced nephropathy (CIN) in diabetic patients with chronic kidney disease. They also compared the incidence of CIN with the use of iso-osmolar contrast iodixanol compared to a similar historical control, and found a lower incidence of CIN with the former (57% versus 24%). Although the Tadros article suggests interesting perspectives, major questions have yet to be answered: 1. Is iodixanol less nephrotoxic than LOCM? Although one study has suggested so,² we are still waiting for the VALOR trial results. This study has now been stopped for several months. All results and reasons why the study was interrupted should be published as soon as possible. We clearly need additional evidence as to the comparative renal tolerance of LOCM and iodixanol. As stated by Carl Sander³ in his editorial published simultaneously with Aspelin's paper, “Yet, since previous clinical studies have yielded conflicting results, there is reason to believe that future studies of iodixanol may provide conflicting data as well”. Obviously Tadros’s results cannot provide any firm conclusion as to the respective renal tolerance of nonionic dimmers and LOCM considering the retrospective design of the study Therefore, one should not conclude that iodixanol is the answer to contrast agent-induced renal dysfunction. 2. Several studies have shown that the risk of CIN increases with increasing dose of contrast media.^4,5 Consequently, current guidelines for preventing CIN indicate that “the minimum dose of contrast consistent with diagnostic angiographic quality should be used and rapid re-exposure avoided where possible”.^6,7 On this also very practical issue, Tadros’s retrospective study design does not allow any serious conclusion as to the relationship between contrast volume and CIN. It seems, therefore, unwise to suggest that iodixanol may be considered safer than LOCM, regardless of the volume injected, especially in the high-risk patients. Gilbert Deray, MD

1. Tadros GM, Malik JA, Manske CL, et al. Iso-osmolar radio contrast iodixanol in patients with chronic kidney disease. J Invasive Cardiol 2005;17:211–215. 2. Aspelin P, Aubry P, Fransson SG, et al. Nephrotoxic effects in high-risk patients undergoing angiography. N Engl J Med 2003;348:491–499. 3. Sandler CM, Contrast-agent-induced acute renal dysfunction – Is Iodixanol the answer? N Engl J Med 2003;348:551–553. 4. Manske CL, Sprafka JM, Strony JT, Wang Y. Contrast nephropathy in azotemic diabetic patients undergoing coronary angiography. Am J Med 1990;89:615–620. 5. Rudnick MR, Berns JS, Cohen RM, Goldfarb S. Nephrotoxic risks of renal angiography: Contrast media-associated nephrotoxicity and atheroembolism – A critical review. Am J Kidney Dis 1994;24:713–727. 6. Thomsen HS. Guidelines for contrast media from the European Society of Urogenital radiology. Am J Radiol 2003;181:1463–1471. 7. Maeder M, Klein M, Fehr T, Rickli H. Contrast nephropathy: Review focusing on prevention. J Am Coll Cardiol 2004;44:1763–1771.