1. In a retrospective review of over 240 patients with solitary kidneys and over 600 patients with bilateral kidneys, there were no significant differences in the rate of acute kidney injury following contrast-enhanced computed tomography (CT).
2. There were no significant differences in rates of 30-day post-CT dialysis or death attributed to contrast-enhanced CT between the two groups.
Evidence Rating Level: 3 (Average)
Study Rundown: Patients with a solitary kidney are considered to be at a high risk for contrast-induced nephropathy (CIN), creating a dilemma in which clinicians must balance the risk of acute kidney injury against the potentially superior imaging characteristics of a contrast-enhanced examination. However, there has been a paucity of large trials analyzing the likelihood of CIN in this unique population post-contrast CT. The purpose of this retrospective trial was to compare the rates of CIN/AKI between patients with solitary kidneys and native, bilateral kidneys.
This study retrospectively reviewed the results of over 240 adult patients with a solitary kidney from unilateral nephrectomy and over 600 propensity-matched controls who received an IV contrast-enhanced CT scan of the chest, abdomen, or pelvis. The presence of CIN was measured by serum creatinine per the standard Acute Kidney Injury Network definition 24-72 hours after the scan. At the conclusion of the trial, the solitary kidney cohort did not demonstrate a significantly higher rate of CIN compared to the propensity-matched controls. Furthermore, there were no significant differences in the rates of emergent dialysis use or death secondary to CIN between the two groups. The results of this study support the hypothesis that patients with normal-functioning solitary kidneys are not at higher risk for CIN compared to patients with native, bilateral kidneys. Furthermore, all patients in the study received a standard dose of contrast, opposing previous hypothesis that CIN in patients with solitary kidneys may be due to a dose-dependent mechanism. The study is limited by the retrospective design and the relatively small sample size, which in particular may have limited its ability to evaluate for differences between the groups for rare outcomes, such as 30-day post-CT dialysis. Additional larger trials are needed to increase the power to detect potential differences between these two groups.
Click to read the study in Radiology
Relevant Reading: Frequency of acute kidney injury following intravenous contrast medium administration: a systematic review and meta-analysis
In-Depth [retrospective cohort]: This study was a retrospective analysis on the rate of CIN in patients with solitary kidneys compared to patients with native, bilateral kidneys from 2004 to 2013 in a single institution in the United States. Patients were included if they had a solitary kidney from a unilateral nephrectomy with a CT scan with IV contrast of the chest, abdomen, or pelvis. Patients were excluded if they received contrast 14 days prior to the CT scan or were previously on dialysis. The presence of CIN/AKI was defined as the increase in maximum measured serum creatinine (SCr) of either >44.2 umol/L (0.5 mg/dL) or 50% over baseline in the 24-72 hours post-CT scan. All patients were propensity-matched to patients with bilateral kidneys in a 3:1 ratio. The outcomes of interest were the rate of CIN/AKI, emergent-dialysis use, and death attributed to CIN. Overall, 247 patients with solitary kidneys and 691 patients with bilateral kidneys were included in the review. At the conclusion of the study, the rate of CIN (OR: 1.11; 95%CI: 0.41-2.07; p = 0.99) and emergent dialysis (OR: 1.70; 95%CI: 1.06-2.71; p = 0.61) was similar between the two groups. There was a statistically significant increase in the rate of mortality in the solitary kidney group as opposed to those with bilateral kidneys, however, no deaths were attributed to CIN.
Image: PD
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