Sami Al Kasab, MD

Brinjikji W, Demchuk AM, Murad MH, Rabinstein AA, McDonald RJ, McDonald JS, et al. Neurons Over Nephrons: Systematic Review and Meta-Analysis of Contrast-Induced Nephropathy in Patients With Acute Stroke. Stroke. 2017

In the era of mechanical thrombectomy, the use of advanced imaging, such as computed tomographic angiography (CTA) and CT perfusion, has become an essential component in the evaluation of patients presenting with acute stroke symptoms. Due to the concern of acute kidney injury (AKI) that might result from the use of iodine contrast, many stroke centers require having a baseline serum creatinine prior to performing the CTA/CTP imaging; this, however, might lead to delay in obtaining the imaging, which could delay time to treatment.

Previous studies have evaluated the risk of AKI in stroke patients undergoing CTA/CTP; however, the risk remains unclear, with no major impact on the current clinical practice.

In this study, Drs. Brinjikji et al perform a systematic review and meta-analysis of the literature to determine whether acute ischemic stroke (AIS) patients receiving CTA/CTP are at higher risk for AKI than those receiving only non-contrast head CT (NCCT). The authors aim to determine the overall rate of AKI among patients with AIS undergoing CTA/CTP, and whether having chronic kidney disease is a risk factor for AKI after receiving CTA/CTP.

The authors performed a comprehensive literature search of Ovid MEDLINE, Ovid EMBASE, and the Web of Science from their inception through December 2016. Identified studies were then further evaluated for the inclusion of this meta-analysis. Both case-control and single-arm studies were included. Only studies that included patients that underwent CTA/CTP were included in this analysis. A minimum number of 50 patients (if single arm and 50 in each arm if case-control) was required for a study to be included in this analysis. Collected data included: definition of AKI, mean age for each group, mean baseline creatinine for each group, number of patients with CKD in each group, whether a pre- or post-contrast administration intervention was taken, contrast load, and number of patients receiving CTA/CTP who required hemodialysis.

A 2 x 2 table was extracted from each case-control study for binary outcome and group sample size. A random-effects model was used to perform the meta-analysis. A study level meta-regression was performed due to concern of lack of similarity between the 2 study groups.

The authors’ search yielded 431 articles; of those, 401 were excluded following abstract and titles review. A total of 32 articles were included for full text evaluation, of which 14 met the inclusion criteria. Of the 14 studies, 6 were case-control studies in which both groups consisted of patients with stroke. Eight were single-arm studies that examined the rates of AKI among patients receiving CTA/CTP. Six studies evaluated the rates of AKI among patients receiving CTA/CTP with and without CKD.

A total of 6708 were included in this analysis; of those, 5727 received CTA or CTP, and 981 received NCCT alone.

AKI was most commonly defined as a > 25% increase in baseline Creatinine. Mean baseline creatinine in the CTA/CTP group ranged from 0.9-1.2 and 1.0-1.4 in the NCCT group.

In the case-control studies, meta-regression adjusting for baseline creatinine demonstrated no difference in AKI rates between groups ((OR=0.34; 95% CI=0.10–1.21). The authors also evaluated the possibility of publication bias and noticed an asymmetry in the funnel plot, raising the possibility of publication bias; however, due to the small number of studies included in the analysis, no conclusion could be made.

In the uncontrolled group, of the 5727 in the CTA/CTP group, 128 (2.2%) developed AKI. Among patients with CKD, the overall rate of AKI following CTA/CTP was 2.3% compared to 3.7% in the non-CKD group. On unadjusted meta-analysis, patients with CKD had similar odds of developing AKI as patients without CKD (OR=0.63; 95% CI=0.35–1.12; P>0.05).

In summary, this systematic review shows that the rate of AKI among patients receiving CTA/CTP for evaluation of AIS is close to 3%. Hemodialysis in this group of patients was very low at 0.07%. Patients receiving NCCT had similar odds of developing AKI when compared with patients receiving CTA/CTP. Importantly, there was no increased risk of AKI following CTA/CTP in patients with CKD compared to patients with normal baseline kidney function.

The findings of this analysis are very important and of clinical significance given that many stroke centers have a protocol that requires a baseline creatinine level prior to administering contrast for CTA/CTP; given the low risk of AKI in this group of patients, this might not be necessary and could delay the time to treatment.

The study has few limitations. The main limitation is the fact that none of the included studies is a randomized controlled trial, raising the possibility of selection bias, though this didn’t seem to be the case on further analysis performed in this study.

In conclusion, in this systematic review and meta-analysis, there was no associated risk of AKI among patients receiving CTA/CTP for the evaluation of AIS. Patients with CKD were not at a higher risk for AKI when compared to patients without CKD receiving CTA/CTP.