Iso-osmolar contrast media vs. low-osmolar: the debate continues
CHICAGO—Iso-osmolar contrast media is not the solution to solve the major problem of renal failure after injection, according to a retrospective study presented at the 94th annual meeting of the Radiological Society of North America (RSNA). But more studies need to be conducted to definitively clarify the issue.

Per Liss, MD, PhD, from the department of radiology at Uppsala University in Uppsala, Sweden, said that the beneficial effect of using iso-osmolar iodinated contrast media compared with a low-osmolar agent to reduce contrast-induced nephropathy (CIN) has been under debate due to conflicting results.

In 2003, a NEPHRIC study on contrast nephropathy, published by Aspelin et al, compared outcomes in 129 renally-impaired angiography patients with diabetes randomized to the iso-osmolar iodixanol or to the low-osmolar iohexol. In this study, the rate of CIN was 26 percent with the iohexal and 3 percent with iodixanol. In addition, six patients in the iohexol group developed acute renal failure, while none did in the iodixanol group.  

Liss and colleagues previously published a study in Kidney International in 2006, which suggested no beneficial effect for iso-osmolar agents, but rather the opposite.

To further evaluate the incidence of CIN in clinical practice, the researchers analyzed retrospective data of more than 23,000 patients in 18 Swedish hospitals who underwent percutaneous coronary interventions (PCI) and coronary angiography during the years 2005-2006. Iso-osmolar iodixanol was used in 18,517 patients, low-osmolar ioxaglate in 4,707 subjects.

Liss and colleagues found that the incidence of renal failure within 12 months after PCI/angiography was greatest for patients receiving iodixanol (1.4 percent) compared to ioxaglate (0.9 percent).

When adjusted for gender, age, diabetes, injected volume, previous PCI and previous renal insufficiency, and the hazard ratio for iodixanol, Liss said that CIN remained significantly higher in patients treated with iodixanol than for ioxaglate.

The average volume of injected contrast medium was significantly higher in the patients receiving ioxaglate (202.4 ml) compared to those receiving iodixanol (188.1 ml).

He noted that the calculated creatinine clearance before the injection was similar in the two groups.

Liss concluded that within one year after injection, renal failure was found more often in the iso-osmolar iodixanol group than in the low-osmolar ioxaglate group.

However, he said that further clinical studies are needed, adding that he and his colleagues have begun another study to assess the conflicting outcomes.