Acute Kidney Injury From Contrast CT Scans: Is There an Association?

One common concern emergency medicine professionals face is the risk for acute kidney injury (AKI) secondary to the use of intravenous (IV) contrast for CT studies. Currently, emergency medicine professionals typically avoid the use of CT scans with IV contrast before checking renal function, and the use of IV contrast is discouraged for patients who have abnormal renal function. There have been studies in the literature recently that have evaluated this circumstance and have suggested that perhaps AKI related to IV contrast may not be as much of an issue as we have all thought.

In a meta-analysis published in Annals of Emergency Medicine ,^[1] researchers scrutinized 28 articles including 107,335 patients to ascertain the risk for AKI secondary to IV contrast exposure, the possible need for renal replacement therapy, and total mortality comparing noncontrast CT and contrast CT. All reviewed studies were observational, and most were retrospective chart reviews. Only five were prospective observational studies. Six studies evaluated only emergency department patients, while seven evaluated only intensive care unit patients. Most studies included low or iso-osmolar contrast material, and only one study used high osmolar contrast.

The primary outcome of the study was the development of AKI in patients exposed to contrast CT. The secondary outcomes included the need for renal replacement therapy (RRT) and all-cause mortally. Researchers obtained data from the studies such as which body part was scanned, setting of the study, type of contrast, comorbidities, timing of follow-up creatinine checks after exposure to contrast, and definition of post-contrast-induced nephropathy.

This meta-analysis found that there was no significant association with contrast CT and AKI, need for RRT, or all-cause mortality. Although the researchers admitted that there are multiple important limitations of their study, the results are in line with recent studies suggesting that the fears of IV contrast-induced nephropathy may be less warranted than we all have been led to believe. Subgroup analysis did not find significant differences with respect to study setting or the timing of follow-up creatinine levels.

Where Does That Leave Us on the Use of IV Contrast CT?

Researchers identified multiple significant limitations of the study. First, all evidence was observational, which we know limits the conclusions we can draw. Second, there was significant variation in how the included studies defined post-contrast-induced nephropathy. Third, there was wide variation in study design and confounding variables, including setting, how sick or not sick the patients were, the definition used for post-contrast-induced nephropathy, comorbid conditions that may have affected renal function such as sepsis or trauma, and even the use of nephrotoxic medications or treatments apart from the studied IV contrast.

Like any emergency medicine professional, I personally rely on CT imaging on a frequent basis during my clinical work. Many of the studies we order are indicated with IV contrast for a variety of reasons. We all have found ourselves in a situation where we believe a patient would benefit from CT imaging with IV contrast, but we are concerned about the possibility of harm to the patient. In some cases, the patient may already have renal impairment or other comorbidities that factor in our decision-making. Although we do not yet have enough evidence to contradict decades old dogma regarding the renal side effects of IV contrast, this is more evidence to the contrary that seems to indicate that maybe we are blowing the concern out of proportion.

Additional research definitely needs to be done on this matter. We will likely never get the randomized controlled trial data we yearn for because of the ethical implications of administering IV contrast to some patients and not others, given literature suggesting harm already, but creative efforts by researchers such as those who conducted this study may continue to add to the evidence against the dogma. Until then, the best we can do for our patients is to remain cautious and judicious in our use of IV contrast CT, reflecting on possible harm to our patients, and to follow institutional and local policies and guidelines about the use of IV contrast.