Risk of intravenous contrast material-mediated acute kidney injury: a propensity score-matched study stratified by baseline-estimated glomerular filtration rate

Perioperative intravenous contrast administration and the incidence of acute kidney injury after major gastrointestinal surgery: prospective, multicentre cohort study

BACKGROUND

This study aimed to determine the impact of preoperative exposure to intravenous contrast for CT and the risk of developing postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery.

METHODS

This prospective, multicentre cohort study included adults undergoing gastrointestinal resection, stoma reversal or liver resection. Both elective and emergency procedures were included. Preoperative exposure to intravenous contrast was defined as exposure to contrast administered for the purposes of CT up to 7 days before surgery. The primary endpoint was the rate of AKI within 7 days. Propensity score-matched models were adjusted for patient, disease and operative variables. In a sensitivity analysis, a propensity score-matched model explored the association between preoperative exposure to contrast and AKI in the first 48 h after surgery.

RESULTS

A total of 5378 patients were included across 173 centres. Overall, 1249 patients (23·2 per cent) received intravenous contrast. The overall rate of AKI within 7 days of surgery was 13·4 per cent (718 of 5378). In the propensity score-matched model, preoperative exposure to contrast was not associated with AKI within 7 days (odds ratio (OR) 0·95, 95 per cent c.i. 0·73 to 1·21; P = 0·669). The sensitivity analysis showed no association between preoperative contrast administration and AKI within 48 h after operation (OR 1·09, 0·84 to 1·41; P = 0·498).

CONCLUSION

There was no association between preoperative intravenous contrast administered for CT up to 7 days before surgery and postoperative AKI. Risk of contrast-induced nephropathy should not be used as a reason to avoid contrast-enhanced CT.

Acute kidney injury following percutaneous mechanical thrombectomy of subclavian artery stent graft thrombosis: a case report

BACKGROUND

Percutaneous mechanical thrombectomy (PMT) is a well-established technique for treatment of acute arterial and venous thrombosis which inevitably leads to intravascular erythrocyte hemolysis, resulting in hemoglobinuria.

CASE PRESENTATION

We present a case of 66-year-old Caucasian female with subclavian artery aneurysm causing distal embolization and hand ischemia. The aneurysm was treated with stent graft, but with a subsequent graft thrombosis 3 months later. After graft recanalisation, AngioJet PMT was performed which resulted in dialysis-requiring acute kidney injury.

CONSLUSION

Only several cases of acute kidney injury following AngioJet PMT have been published in literature. To our knowledge, this is the first reported case of dialysis-requiring AKI after PMT for peripheral arterial thrombosis. Until there is sufficient evidence and recommendation on preventing AKI in this setting, we believe that by being aware of the risk and by monitoring of patient, one might minimize the damage in case it occurs.

Safety of a rapid outpatient hydration protocol for patients with renal impairment requiring intravenous iodinated contrast media for CT

INTRODUCTION

Patients receiving intravenous iodinated contrast media (IOCM) for CT are predisposed to contrast-induced nephropathy. Chronic kidney disease is an important risk factor, and hydration is the mainstay of prevention. While inpatients can undergo intravenous hydration, there is a knowledge deficit regarding regimens for outpatients. We employed a rapid outpatient hydration protocol to reduce postponement of scan appointments for patients with suboptimal estimated glomerular filtration rate (eGFR).

METHODS

From June 2015, we amended our CT preparation protocol to mandate rapid hydration (oral, intravenous or both) for patients with an eGFR of 30-60 mL/min/1.73 m2. Patients receiving this hydration protocol from June to November 2015 were followed up for one month to monitor any admissions for fluid overload, and up to one year to determine the long-term effect on eGFR.

RESULTS

226 outpatients received the hydration protocol, which correlated with a 95% reduction in postponement of imaging appointments. No complications of fluid overload from hydration were encountered. There was a significant association between age and decrease in eGFR, but this was not significant when stratified by drop in eGFR category. No statistical significance was found between decrease in eGFR and gender or race. Higher baseline eGFR was less likely to be associated with decrease in eGFR after imaging. Type of hydration was not related to a drop in eGFR category for patients with eGFR of 45-59 mL/min/1.73 m2.

CONCLUSION

We defined a shorter hydration regimen that is safe to use in the outpatient setting.

Acute Kidney Injury after Endovascular Treatment in Patients with Acute Ischemic Stroke

Acute kidney injury (AKI) is often associated with the use of contrast agents. We evaluated the frequency of AKI, factors associated with AKI after endovascular treatment (EVT), and associations with AKI and clinical outcomes. We retrospectively analyzed consecutively enrolled patients with acute ischemic stroke who underwent EVT at three stroke centers in Korea. We compared the characteristics of patients with and without AKI and independent factors associated with AKI after EVT. We also investigated the effects of AKI on functional outcomes and mortality at 3 months. Of the 601 patients analyzed, 59 patients (9.8%) developed AKI and five patients (0.8%) started renal replacement therapy after EVT. In the multivariate analysis, diabetes mellitus (odds ratio (OR), 2.341; 95% CI, 1.283–4.269; p = 0.005), the contrast agent dose (OR, 1.107 per 10 mL; 95% CI, 1.032–1.187; p = 0.004), and unsuccessful reperfusion (OR, 1.909; 95% CI, 1.019–3.520; p = 0.040) were independently associated with AKI. The presence of AKI was associated with a poor functional outcome (OR, 5.145; 95% CI, 2.177–13.850; p < 0.001) and mortality (OR, 8.164; 95% CI, 4.046–16.709; p < 0.001) at 3 months. AKI may also affect the outcomes of ischemic stroke patients undergoing EVT. When implementing EVT, practitioners should be aware of these risk factors.

Retrospectively ECG-gated helical vs. non-ECG-synchronized high-pitch CTA of the aortic root for TAVI planning

Background

Multidetector computed tomography (MDCT) plays a key role in patient assessment prior to transcatheter aortic valve implantation (TAVI). However, to date no consensus has been established on what is the optimal pre-procedural imaging protocol. Variability in pre-TAVI acquisition protocols may lead to discrepancies in aortic annulus measurements and may potentially influence prosthesis size selection.

Purpose

The current study evaluates the magnitude of differences in aortic annulus measurements using max-systolic, end-diastolic, and non-ECG-synchronized imaging, as well as the impact of method on prosthesis size selection.

Material and methods

Fifty consecutive TAVI-candidates, who underwent retrospectively-ECG-gated CT angiography (CTA) of the aortic root, directly followed by non-ECG-synchronized high-pitch CT of the entire aorta, were retrospectively included. Aortic root dimensions were assessed at each 10% increment of the R-R interval (0–100%) and on the non-ECG-synchronized scan. Dimensional changes within the cardiac cycle were evaluated using a 1-way repeated ANOVA. Agreement in measurements between max-systole, end-diastole and non-ECG-synchronized scans was assessed with Bland-Altman analysis.

Results

Maximal dimensions of the aortic root structures and minimum annulus-coronary ostia distances were measured during systole. Max-systolic measurements were significantly and substantially larger than end-diastolic (p<0.001) and non-ECG-synchronized measurements (p<0.001). Due to these discrepancies, the three methods resulted in the same prosthesis size selection in only 48–62% of patients.

Conclusions

The systematic differences between max-systolic, end-diastolic and non-ECG-synchronized measurements for relevant aortic annular dimensions are both statistically significant and clinically relevant. Imaging strategy impacts prosthesis size selection in nearly half the TAVI-candidates. End-diastolic and non-ECG-synchronized imaging does not provide optimal information for prosthesis size selection. Systolic image acquisition is necessary for assessment of maximal annular dimensions and minimum annulus-coronary ostia distances.

Contrast-Induced Acute Kidney Injury-Definitions, Epidemiology, and Implications

Contrast-induced acute kidney injury (CI-AKI) is the acute onset of renal injury following exposure to iodinated contrast media. Several definitions have been used, which complicates the estimation of the epidemiological relevance of this condition and comparisons in outcome research. The incidence of CI-AKI increases as a function of patient and procedure complexity in coronary, endovascular, and structural interventions. CI-AKI is associated with a high burden of short- and long-term adverse events, and leads to increased healthcare costs. This review will provide an overview of the definitions, epidemiology, and implications of CI-AKI in patients undergoing coronary, endovascular, and structural catheter-based procedures.

Intermodality feature fusion combining unenhanced computed tomography and ferumoxytol-enhanced magnetic resonance angiography for patient-specific vascular mapping in renal impairment

OBJECTIVE

The purpose of this study was to establish the feasibility of fusing complementary, high-contrast features from unenhanced computed tomography (CT) and ferumoxytol-enhanced magnetic resonance angiography (FE-MRA) for preprocedural vascular mapping in patients with renal impairment.

METHODS

In this Institutional Review Board-approved and Health Insurance Portability and Accountability Act-compliant study, 15 consecutive patients underwent both FE-MRA and unenhanced CT scanning, and the complementary high-contrast features from both modalities were fused to form an integrated, multifeature image. Source images from CT and MRA were segmented and registered. To validate the accuracy, precision, and concordance of fused images to source images, unambiguous landmarks, such as wires from implantable medical devices or indwelling catheters, were marked on three-dimensional (3D) models of the respective modalities, followed by rigid co-registration, interactive fusion, and fine adjustment. We then compared the positional offsets using pacing wires or catheters in the source FE-MRA (defined as points of interest [POIs]) and fused images (n = 5 patients, n = 247 points). Points within 3D image space were referenced to the respective modalities: x (right-left), y (anterior-posterior), and z (cranial-caudal). The respective 3D orthogonal reference axes from both image sets were aligned, such that with perfect registration, a given point would have the same (x, y, z) component values in both sets. The 3D offsets (Δx mm, Δy mm, Δz mm) for each of the corresponding POIs represent nonconcordance between the source FE-MRA and fused images. The offsets were compared using concordance correlation coefficients. Interobserver agreement was assessed using intraclass correlation coefficients and Bland-Altman analyses.

RESULTS

Thirteen patients (aged 76 ± 12 years; seven female) with aortic valve stenosis and chronic kidney disease and two patients with thoracoabdominal vascular aneurysms and chronic kidney disease underwent FE-MRA for preprocedural vascular assessment, and unenhanced CT examinations were available in all patients. No ferumoxytol-related adverse events occurred. There were 247 matched POIs evaluated on the source FE-MRA and fused images. In patients with implantable medical devices, the mean offsets in spatial position were 0.31 ± 0.51 mm (ρ = 0.99; Cb = 1; 95% confidence interval [CI], 0.99-0.99) for Δx, 0.27 ± 0.69 mm (ρ = 0.99; Cb = 0.99; 95% CI, 0.99-0.99) for Δy, and 0.20 ± 0.59 mm (ρ = 1; Cb = 1; 95% CI, 0.99-1.00) for Δz. Interobserver agreement was excellent (intraclass correlation coefficient, >0.99). The mean difference in offset between readers was 1.5 mm.

CONCLUSIONS

Accurate 3D feature fusion is feasible, combining luminal information from FE-MRA with vessel wall information on unenhanced CT. This framework holds promise for combining the complementary strengths of magnetic resonance imaging and CT to generate information-rich, multifeature composite vascular images while avoiding the respective risks and limitations of both modalities.

Use of Contrast Medium Volume to Guide Prophylactic Hydration to Prevent Acute Kidney Injury After Contrast Administration: A Meta-Analysis

OBJECTIVE. The purpose of this study was to determine whether contrast medium volume and method of administration and baseline estimated glomerular filtration rate influence the efficacy of prophylactic hydration for prevention of acute kidney injury after contrast administration. MATERIALS AND METHODS. An online search of PubMed conducted on August 25, 2017, produced a total of 697 studies. After the reports were reviewed, nine were included in this study. The extracted data on all patients in these studies were separated into a group that received prophylactic hydration and a group that did not. The following three parameters were used for subgroup analysis: contrast medium volume, contrast administration method, and baseline estimated glomerular filtration rate. The t test was performed, and study-level odds ratios with 95% CIs and p values were calculated. Tests of heterogeneity were conducted. RESULTS. When the volume of contrast agent administered exceeded 100 mL, hydration was beneficial in the prevention of contrast-induced acute kidney injury (odds ratio, 0.546). If the volume was less than 100 mL, hydration had no efficacy in preventing contrast-induced acute kidney injury (odds ratio, 0.917). Administration route and baseline estimated glomerular filtration rate exerted no effect on the efficacy of prophylactic hydration. CONCLUSION. For patients who receive less than 100 mL of contrast medium, the prevalent practice for contrast-enhanced CT studies, prophylactic hydration may not be necessary, regardless of the estimated glomerular filtration rate or route of contrast administration. For patients undergoing procedures requiring administration of large volumes of contrast medium, however, hydration is recommended to prevent contrast-induced acute kidney injury.

The conundrum of contrast-induced acute kidney injury

More than sixty years have elapsed since contrast induced nephropathy (CIN) was first described in the medical literature. This term has since been extensively explored, with a variety of studies conducted to investigate its incidence and various mechanisms examined to explain its pathophysiology. However, the topic of CIN remains one of controversy with a widely variable and often questionable incidence derived from various studies. The past two decades have seen a surge in reports questioning the existing of CIN altogether and if more harm is actually being caused to patients out of fear of this potential complication. We have attempted to review relevant studies regarding CIN and highlight the key points of its surmised understanding. The review has a higher focus on more recent literature and updates, in order to determine if an accurate estimate can be made on the incidence of CIN. While there was certainly no lack of material available, practically all the studies reviewed were limited by one or more significant drawbacks that limited the reliability of their conclusions regarding CIN. Based on the information reviewed, the strengths and the flaws encountered in other studies can be used to design a randomized control trial that may help in concluding the longstanding debate on this topic. However due to time, financial, and perhaps even ethical constraints such a trial will be difficult to arrange, and so a definitive answer on CI-AKI, and whether it really exist, may continue to elude clinicians.

Metformin treatment for patients with diabetes and chronic kidney disease: A Korean Diabetes Association and Korean Society of Nephrology consensus statement

The safety of metformin use for patients with type 2 diabetes mellitus (T2DM) and advanced kidney disease is controversial, and more recent guidelines have suggested that metformin be used cautiously in this group until more definitive evidence concerning its safety is available. The Korean Diabetes Association and the Korean Society of Nephrology have agreed on consensus statements concerning metformin use for patients with T2DM and renal dysfunction, particularly when these patients undergo imaging studies using iodinated contrast media (ICM). Metformin can be used safely when the estimated glomerular filtration rate (eGFR) is ≥ 45 mL/min/1.73 m². If the eGFR is between 30 and 44 mL/min/1.73 m², metformin treatment should not be started. If metformin is already in use, a daily dose of ≤ 1,000 mg is recommended. Metformin is contraindicated when the eGFR is < 30 mL/min/1.73 m². Renal function should be evaluated prior to any ICM-related procedures. During procedures involving intravenous administration of ICM, metformin should be discontinued starting the day of the procedures and up to 48 hours post-procedures if the eGFR is < 60 mL/min/1.73 m².

A Randomized Trial of Recombinant Human C1-Esterase-Inhibitor in the Prevention of Contrast-Induced Kidney Injury

OBJECTIVES

This study sought to determine the efficacy profile and safety of recombinant human C1 esterase inhibitor (rhC1INH) in the prevention of contrast-associated acute kidney injury after elective coronary angiography.

BACKGROUND

Contrast-associated acute kidney injury is caused by tubular cytotoxicity and ischemia/reperfusion injury. rhC1INH is effective in reducing renal ischemia/reperfusion injury in experimental models.

METHODS

In this placebo-controlled, double-blind, single-center trial 77 patients with chronic kidney disease were randomized to receive 50 IU/kg rhC1INH before and 4 h after elective coronary angiography or placebo. The primary outcome was the peak change of urinary neutrophil gelatinase-associated lipocalin within 48 h, a surrogate marker of kidney injury.

RESULTS

Median peak change of urinary neutrophil gelatinase-associated lipocalin was lower in the rhC1INH group (4.7 ng/ml vs. 22.5 ng/ml; p = 0.038) in the per-protocol population but not in the modified intention-to-treat analysis, and in patients with percutaneous coronary interventions (median, 1.8 ng/ml vs. 26.2 ng/ml; p = 0.039 corresponding to a median proportion peak change of 11% vs. 205%; p = 0.002). The incidence of a cystatin C increase ≥10% within 24 h was lower in the rhC1INH group (16% vs. 33%; p = 0.045), whereas the frequency of contrast-associated acute kidney injury was comparable. Adverse events during a 3-month follow-up were similarly distributed.

CONCLUSIONS

Administration of rhC1INH before coronary angiography may attenuate renal injury as reflected by urinary neutrophil gelatinase-associated lipocalin and cystatin C. The safety profile of rhC1INH was favorable in a patient population with multiple comorbidities. (Recombinant Human C1 Esterase Inhibitor in the Prevention of Contrast-induced Nephropathy in High-risk Subjects [PROTECT]; NCT02869347).

The optimal monoenergetic spectral image level of coronary computed tomography (CT) angiography on a dual-layer spectral detector CT with half-dose contrast media

Background

To investigate the optimal monoenergetic level of spectral reconstructions in coronary computed tomography angiography (coronary CTA) on a dual-layer spectral detector computed tomography (SDCT) with half-dose contrast media.

Methods

Two hundred patients with suspected coronary artery disease (CAD) were enrolled in this prospective coronary CTA study and randomly divided into a routine-dose contrast media group and a half-dose contrast media group (each n=100). Coronary CTA was performed using SDCT with prospective electrocardiogram (ECG)-gated mode. A tube voltage of 120 kVp was used, along with an automated tube current modulation. A dose of iodixanol 270 mgI/mL of 0.8 and 0.4 mL/kg was administered to the routine and half-dose groups, respectively. For the routine-dose group, 120 kVp polychromatic images with a model-based iterative reconstruction (IMR) (Group A) were reconstructed. For the half-dose group, three monoenergetic levels of images were reconstructed (Group B, 45 keV; Group C, 50 keV; and Group D, 55 keV). Objective indicators [mean CT values; noise; signal-to-noise ratio (SNR); and contrast-to-noise ratio (CNR)] and subjective indicators (contrast, sharpness, subjective noise, and acceptability) in each group were compared.

Results

There were no significant differences in demographics or radiation dose (1.83±0.51 vs. 1.80±0.53 mSv, P=0.78) between the routine- and half-dose groups. The average iodine loads were 15.33±2.26 and 7.48±1.14 g, respectively. Mean CT values, SNR, CNR, and subjective contrast in Group C were higher than those in Group A (P<0.05), and there were no significant differences in other indicators between Group C and Group A (P>0.05). The objective and subjective noise in Group B were worse than those in Group A (P<0.05). The contrast, sharpness, and acceptability of Group D were all worse than those of Group A (P<0.05).

Conclusions

Compared to routine polychromatic images, 50 keV monoenergetic images can provide equivalent or improved coronary image quality in coronary CTA performed on SDCT with half the amount of contrast media.

Use of Intravenous Iodinated Contrast Media in Patients with Kidney Disease: Consensus Statements from the American College of Radiology and the National Kidney Foundation

Intravenous iodinated contrast media are commonly used with CT to evaluate disease and to determine treatment response. The risk of acute kidney injury (AKI) developing in patients with reduced kidney function following exposure to intravenous iodinated contrast media has been overstated. This is due primarily to historic lack of control groups sufficient to separate contrast-induced AKI (CI-AKI; ie, AKI caused by contrast media administration) from contrast-associated AKI (CA-AKI; ie, AKI coincident to contrast media administration). Although the true risk of CI-AKI remains uncertain for patients with severe kidney disease, prophylaxis with intravenous normal saline is indicated for patients who have AKI or an estimated glomerular filtration rate less than 30 mL/min/1.73 m² who are not undergoing maintenance dialysis. In individual high-risk circumstances, prophylaxis may be considered in patients with an estimated glomerular filtration rate of 30-44 mL/min/1.73 m² at the discretion of the ordering clinician. This article is a simultaneous joint publication in Radiology and Kidney Medicine. The articles are identical except for stylistic changes in keeping with each journal's style. Either version may be used in citing this article.

Metformin Treatment for Patients with Diabetes and Chronic Kidney Disease: A Korean Diabetes Association and Korean Society of Nephrology Consensus Statement

The safety of metformin use for patients with type 2 diabetes mellitus (T2DM) and advanced kidney disease is controversial, and more recent guidelines have suggested that metformin be used cautiously in this group until more definitive evidence concerning its safety is available. The Korean Diabetes Association and the Korean Society of Nephrology have agreed on consensus statements concerning metformin use for patients with T2DM and renal dysfunction, particularly when these patients undergo imaging studies using iodinated contrast media (ICM). Metformin can be used safely when the estimated glomerular filtration rate (eGFR) is ≥45 mL/min/1.73 m². If the eGFR is between 30 and 44 mL/min/1.73 m², metformin treatment should not be started. If metformin is already in use, a daily dose of ≤1,000 mg is recommended. Metformin is contraindicated when the eGFR is <30 mL/min/1.73 m². Renal function should be evaluated prior to any ICM-related procedures. During procedures involving intravenous administration of ICM, metformin should be discontinued starting the day of the procedures and up to 48 hours post-procedures if the eGFR is <60 mL/min/1.73 m².

Use of Intravenous Iodinated Contrast Media in Patients With Kidney Disease: Consensus Statements from the American College of Radiology and the National Kidney Foundation

Intravenous iodinated contrast media are commonly used with CT to evaluate disease and to determine treatment response. The risk of acute kidney injury (AKI) developing in patients with reduced kidney function following exposure to intravenous iodinated contrast media has been overstated. This is due primarily to historic lack of control groups sufficient to separate contrast-induced AKI (CI-AKI; ie, AKI caused by contrast media administration) from contrast-associated AKI (CA-AKI; ie, AKI coincident to contrast media administration). Although the true risk of CI-AKI remains uncertain for patients with severe kidney disease, prophylaxis with intravenous normal saline is indicated for patients who have AKI or an estimated glomerular filtration rate less than 30 mL/min/1.73 m² who are not undergoing maintenance dialysis. In individual high-risk circumstances, prophylaxis may be considered in patients with an estimated glomerular filtration rate of 30-44 mL/min/1.73 m² at the discretion of the ordering clinician.

Risk of Acute Kidney Injury Following Contrast-enhanced CT in Hospitalized Pediatric Patients: A Propensity Score Analysis

Background Acute kidney injury (AKI) remains a concern in hospitalized children undergoing CT with intravenous iodinated contrast material (ICM). Adult studies have shown frequencies of AKI after CT with intravenous ICM to be similar to propensity score-matched ICM-unexposed patient groups; similar data in pediatric patients are lacking. Purpose To evaluate the association between intravenous ICM exposure and AKI in hospitalized pediatric patients with stable kidney function undergoing contrast material-enhanced CT by comparing with a propensity score-matched ICM-unexposed patient sample undergoing abdominal US. Materials and Methods In this retrospective observational study, hospitalized patients aged 18 years or younger with stable kidney function and available serum creatinine (SCr) measurement before and after imaging who underwent CT with intravenous ICM or abdominal US (control group) between January 2009 and November 2018 were identified. The 1:1 propensity score matching was performed by using 23 covariates, stratified by estimated glomerular filtration rate (eGFR) before imaging (≥60 mL/min/1.73 m² or <60 mL/min/1.73 m²). AKI was defined by using Acute Kidney Injury Network SCr-related criteria. Multivariable logistic regression was performed to identify risk factors for AKI after imaging, including the effects of eGFR and intravenous ICM exposure before imaging. Results A total of 1850 unique patients were included in the propensity score-matched sample (925 exposed to ICM [mean age ± standard deviation, 8 years ± 6; 484 female patients]; 925 unexposed to ICM [mean age, 7 years ± 6; 484 female patients]). Frequency of AKI with eGFR greater than or equal to 60 mL/min/1.73 m² was 2.2% (20 of 889) for CT and US (odds ratio [OR]: 0.98; 95% confidence interval [CI]: 0.52, 1.86; adjusted P = .95) and with eGFR less than 60 mL/min/1.73 m² was 5.6% (two of 36) and 11.1% (four of 36) for CT and US, respectively (OR: 0.75; 95% CI: 0.11, 5.00; adjusted P = .76). Significant multivariable predictors of AKI included eGFR before imaging (OR: 0.99; 95% CI: 0.98, 0.995; P = .001), body mass index (OR: 1.06; 95% CI: 1.02, 1.10; P = .003), acquired kidney disease (OR: 1.95; 95% CI: 1.004, 3.78; P = .049), and nephrotoxic antibiotic exposure (OR: 2.86; 95% CI: 1.55, 5.25; P < .001). Intravenous ICM exposure was not predictive (OR: 0.91; 95% CI: 0.51, 1.64; P > .05). Conclusion Hospitalized children with stable kidney function who underwent CT with intravenous iodinated contrast material (ICM) had a similar frequency of acute kidney injury (AKI) compared with a propensity score-matched ICM-unexposed patient group. In pediatric inpatients with estimated glomerular filtration rate greater than or equal to 60 mL/min/1.73 m², ICM was not independently associated with AKI. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Paltiel in this issue.

Updated guidelines for intravenous contrast use for CT and MRI

Intravenous (IV) contrast material is used extensively for CT and MRI scans done in emergency departments (ED). Its use is essential to make many critical diagnoses in ED patients. While adverse reactions can occur, newer research has added to our knowledge of IV contrast media tolerance and safety leading to improved and more liberal guidelines for intravenous contrast use. The updated information described in this review article indicates how intravenous contrast can be used safely in more patients, more expeditiously and with fewer precautions than with prior guidelines. This review article explains the basis for the new recommendations for intravenous contrast material use and describes indicated precautions and preparations to avoid adverse reactions for iodinated agents used for CT and gadolinium agents for MRI.

tert-Butylhydroquinone Treatment Alleviates Contrast-Induced Nephropathy in Rats by Activating the Nrf2/Sirt3/SOD2 Signaling Pathway

Oxidative stress plays a critical role in the pathophysiology of contrast-induced nephropathy (CIN). Since the specific treatment of CIN remains an unmet medical need, it is imperative to find an effective strategy against the clinical management of CIN. The transcription factor Nrf2 is known to regulate antioxidative stress response. The aim of the present study was to assess the effects of tert-butylhydroquinone (t-BHQ), an activator of Nrf2, in the prevention of CIN and elucidate the underlying mechanism of its action in vitro and in vivo. We established a rat model of CIN and treated the animals with t-BHQ (25 mg/kg). The effects of t-BHQ treatment on CIN rats were elucidated by assessing renal function, HE staining, immunohistochemistry, and western blotting. We also studied the activity of oxidative stress-related markers, such as intracellular ROS level, MDA level, SOD2 activity, and GSH/GSSG ratio. We validated our results by siRNA-mediated silencing of Nrf2 in HK-2 cells exposed to the radiocontrast agent. Treatment with t-BHQ significantly ameliorated the renal function and the histopathological lesions in CIN rats. Further, pretreatment with t-BHQ significantly increased the SOD2 activity and GSH/GSSG ratio and decreased the levels of ROS and MDA in animals subjected to ioversol exposure. In addition, t-BHQ treatment increased the expression of Nrf2, Sirt3, and SOD2 and concomitantly decreased the expression of acetylated-SOD2. When Nrf2-silenced HK-2 cells were exposed to radiocontrast agent, they suffered severe cell oxidative stress, exhibited lower expression of Sirt3 and SOD2, and expressed higher levels of acetylated-SOD2; however, t-BHQ treatment did not affect the protein expression of these indicators in si-Nrf2 HK-2 cells. Our findings suggested that Nrf2 plays an important role in the regulation of the Sirt3/SOD2 antioxidative pathway, and t-BHQ may be a potential agent to ameliorate radiocontrast-induced nephropathy via activating the Nrf2/Sirt3/SOD2 signaling pathway in vitro and in vivo.

Venous-phase chest CT with reduced contrast medium dose: Utilization of spectral low keV monoenergetic images improves image quality

PURPOSE

Intravenous contrast administration is crucial in many CT examinations but also poses a potential risk to the patient. Monoenergetic images (MonoE) of dual-energy CT systems can virtually increase iodine attenuation and might improve image quality (IQ) if contrast dose is reduced. In this study, we investigated the influence of MonoE on lymph node (LN) delineation and IQ in chest CT examinations with significantly reduced contrast dose (50 %) of a novel dual-layer CT (DLCT).

METHOD

30 patients with clinically indicated reduced contrast dose underwent venous-phase chest DLCT scans. Conventional polyenergetic (PolyE) and MonoE images at 40 keV were calculated. The contrast difference of hilar lymph nodes (LN-CD) to the adjacent right pulmonary artery, their signal-to-noise (SNR) and contrast-to-noise-ratio (CNR) were determined. Subjective IQ was evaluated by 2 readers with respect to LN delineation and overall contrast enhancement (CE) using a 5-point-Likert-scale.

RESULTS

LN-CD, SNR and CNR were significantly higher in MonoE than in PolyE images (LN-CD 92.3 ± 37.9 vs. 33.1 ± 14.5 HU, SNR 8.4 ± 3.4 vs. 4.0 ± 1.2, CNR 9.2 ± 6.3 vs. 2.6 ± 1.5; all p < 0.01). The LN delineation (3.7 ± 0.9 vs.1.8 ± 0.7; p < 0.01) and the CE (3.9 ± 0.7 vs. 2.3 ± 0.7; p < 0.01) were rated significantly better for MonoE than for PolyE images. There was no MonoE examination classified as non-diagnostic.

CONCLUSIONS

Subjective and objective IQ parameters can be significantly improved for venous-phase chest CT examinations with reduced contrast doses by utilization of low-keV MonoE reconstructions. All MonoE images provided sufficient overall CE and therefore reduced contrast doses might be considered in a wider range of DLCT examinations and patients.

Effect of a Contrast Modulation System on Contrast Media Use and the Rate of Acute Kidney Injury After Coronary Angiography

OBJECTIVES

The aim of the AVERT (AVERT Clinical Trial for Contrast Media Volume Reduction and Incidence of CIN) trial was to test the efficacy of the AVERT system to reduce the contrast media volume (CMV) used during coronary angiographic procedures without impairing image quality and to prevent contrast-induced acute kidney injury (CI-AKI) in patients at risk for CI-AKI.

BACKGROUND

CI-AKI is a common complication of percutaneous coronary procedures, associated with increased morbidity and mortality. The AVERT system alters the coronary injection pressure profile by diverting contrast away from the patient during coronary injection.

METHODS

The AVERT trial was a prospective, multicenter, 1:1 randomized clinical trial in 578 subjects with either baseline estimated glomerular filtration rate 20 to 30 ml/min/1.73 m² or estimated glomerular filtration rate 30 to 60 ml/min/1.73 m² and at least 2 additional risk factors for CI-AKI. Patients undergoing coronary angiography with planned or possible percutaneous coronary intervention (PCI) were randomized to hydration plus the AVERT system (n = 292) or hydration only (n = 286). The primary effectiveness endpoints were: 1) the total CMV used; and 2) the incidence of CI-AKI, defined as a ≥0.3 mg/dl increase in serum creatinine within 5 days post-procedure.

RESULTS

Patient demographics were well balanced between the groups, with mean baseline serum creatinine of 1.6 ± 0.4 mg/dl and 64.9% patients with diabetes mellitus. PCI was performed in 42.2% of procedures, with coronary angiography in the remainder. Use of AVERT resulted in a 15.5% relative reduction in CMV overall (85.6 ± 50.5 ml vs. 101.3 ± 71.1 ml; p = 0.02) and a 22.8% relative reduction in CMV among PCI patients (114 ± 55 ml vs. 147 ± 81 ml; p = 0.001). The maximum relative reduction in CMV was 46% (124 ± 48 ml vs. 232 ± 97 ml; p = 0.01) when ≥3 lesions were treated. There were no differences in the rates of CI-AKI (27.0% vs. 26.6%; p = 0.70) between the study groups.

CONCLUSIONS

Use of the AVERT system was feasible and safe, with acceptable image quality during coronary angiography and PCI. AVERT significantly reduced CMV, with the extent of CMV reduction correlating with procedural complexity. No significant differences in CI-AKI were observed with AVERT in this trial. (AVERT Clinical Trial for Contrast Media Volume Reduction and Incidence of CIN [AVERT]; NCT01976299).

Contrast Induced Acute Kidney Injury and its Impact on Mid-Term Kidney Function, Cardiovascular Events and Mortality

The existence and clinical relevance of contrast induced acute kidney injury (CI-AKI) is still heavily debated and angiographic procedures are often withheld in fear of CI-AKI, especially in CKD-patients. We investigated the incidence of CI-AKI in cardiovascular high risk patients undergoing intra-arterial angiography and its impact on mid-term kidney function, cardiovascular events and mortality. We conducted a prospective observational trial on patients undergoing planned intra-arterial angiographic procedures. All subjects received standardized intravenous hydration prior to contrast application. CI-AKI was defined according to a ≥25% increase of creatinine from baseline to either 24hrs or 48hrs after angiography. Plasma creatinine and eGFR were recorded from the institutional medical record system one and three months after hospital discharge. Patients were followed up for two years to investigate the long term effects of CI-AKI on cardiovascular events and mortality. We studied 706 (317 female) patients with a mean eGFR of 52.0 ± 15 ml·min⁻¹·1.73 m⁻². The incidence of CI-AKI was 10.2% (72 patients). In 94 (13.3%) patients serum creatinine decreased ≥25% either 24 or 48 hours after angiography. Patients with CI-AKI had a lower creatinine and a higher eGFR at baseline, but no other independent predictors of CI-AKI could be identified. Kidney function was not different between both groups one and three months after discharge. After a two year follow up the overall incidence of cardiovascular events was 56.5% in the CI-AKI group and 58.8% in the Non CI-AKI group (p = 0.8), the incidence of myocardial infarctions, however, was higher in CI-AKI-patients. Overall survival was also not different between patients with CI-AKI (88.6%) and without CI-AKI (84.7%, p = 0.48). The occurrence of CI-AKI did not have any negative impact on mid-term kidney function, the incidence of cardiovascular events and mortality. Considerable fluctuations of serum creatinine interfere with the presumed diagnosis of CI-AKI. Necessary angiographic procedures should not be withheld in fear of CI-AKI.

EANM guideline for ventilation/perfusion single-photon emission computed tomography (SPECT) for diagnosis of pulmonary embolism and beyond

These guidelines update the previous EANM 2009 guidelines on the diagnosis of pulmonary embolism (PE). Relevant new aspects are related to (a) quantification of PE and other ventilation/perfusion defects; (b) follow-up of patients with PE; (c) chronic PE; and (d) description of additional pulmonary physiological changes leading to diagnoses of left ventricular heart failure (HF), chronic obstructive pulmonary disease (COPD) and pneumonia. The diagnosis of PE should be reported when a mismatch of one segment or two subsegments is found. For ventilation, Technegas or krypton gas is preferred over diethylene triamine pentaacetic acid (DTPA) in patients with COPD. Tomographic imaging with V/PSPECT has higher sensitivity and specificity for PE compared with planar imaging. Absence of contraindications makes V/PSPECT an essential method for the diagnosis of PE. When V/PSPECT is combined with a low-dose CT, the specificity of the test can be further improved, especially in patients with other lung diseases. Pitfalls in V/PSPECT interpretation are discussed. In conclusion, V/PSPECT is strongly recommended as it accurately establishes the diagnosis of PE even in the presence of diseases like COPD, HF and pneumonia and has no contraindications.

CT angiography for pulmonary embolism in the emergency department: investigation of a protocol by 20 ml of high-concentration contrast medium

OBJECTIVES

To retrospectively compare semi-qualitative and quantitative CT pulmonary angiography (CTPAs) image metrics testing diagnostic performance between protocols performed by 20 or 40 ml of contrast medium (CM) in patients with suspected pulmonary embolism (PE).

METHODS

A total of 102 CTPAs performed by 20 ml (ultra-low volume: ULV) and 74 CTPAs performed by 40 ml (low volume: LV) protocol for the diagnosis of clinically suspected PE performed between October 2012 and September 2013 were retrieved. High-concentration CM (Iomeprol 400 mgI/ml) was injected at 3 ml/s (iodine delivery rate 1.2 mgI/s). Two radiologists (blinded and independent) semi-qualitatively scored vascular enhancement and image noise according to a five-point visual scoring system. Quantitative analysis was performed by regions of interest quantifying densitometric parameters, such as central and peripheral pulmonary arteries vascular contrast enhancement (CE, threshold for diagnostic CE ≥ 250 HU), and metrics for image noise. Continuous variables were compared by the Student's t test between groups if normally distributed while categorical variables were analyzed with the Chi-squared test. Interobserver agreement was calculated by the weighted kappa test; correlation coefficients were calculated using Pearson's correlation tests.

RESULTS

The semi-qualitative scores for central and peripheral pulmonary arteries vascular CE were sufficient by ULV, yet inferior than LV (p < 0.001). Semi-qualitative image noise was comparable between ULV and LV, and the interobserver agreement was only fair for quality of peripheral vessels. Agreement on nondiagnostic semi-qualitative parameters was seen in 9/102 (8.8%) ULV CTPAs, in particular associated with massive PE (2/9), pleuro-pulmonary abnormalities (5/9) or without major abnormalities (2/9). Quantitative analysis showed that mean CE was lower in ULV group (p < 0.001), though greater than the diagnostic threshold of 250 HU in both groups.

CONCLUSIONS

Diagnostic vascular CE (> 250 HU) was obtained in both 20 ml and 40 ml CTPAs. CTPA by 20 ml of CM rendered diagnostic CE for the assessment of pulmonary arteries in patients with clinical suspicion of acute PE. Decreased image quality was mostly associated with massive PE or concomitant pleuro-parenchymal abnormalities.

Exposure to contrast media in the perioperative period confers no additional risk of acute kidney injury in surgical patients

Background

Iodinated contrast media (CM) used in angiography and computed tomography (CT) scans is an important cause of acute kidney injury (AKI) in hospitalized patients undergoing surgery. Contrast-induced nephropathy leads to AKI soon after CM administration. The aim of the study was to determine whether the timing of contrast media exposure related to diagnostic imaging during the immediate perioperative period influences the risk of post-operative AKI.

Methods

All patients aged 18 years or above who underwent diagnostic imaging within 7 days of non-cardiac surgery between 1 January 2003 and 31 December 2013 in the Tayside region of Scotland, UK were included in the analysis. The primary outcome of AKI was defined using the Kidney Disease: Improving Global Outcomes creatinine-based criteria. Multiple logistic regressions were performed to identify predictors for AKI.

Results

Of 9300 patients, 6224 were exposed to CM in the immediate perioperative period and 3076 were not. Post-operative AKI occurred in 678 (10.9%) of the 6224 patients who were exposed to CM. On multiple logistic regression, independent predictors of post-operative AKI were increasing age, male gender, lower baseline renal function and treatment with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers. Timing of CM exposure did not affect risk of developing AKI, odds ratio 0.972 (95% confidence interval 0.935-1.010), P = 0.146.

Conclusions

For patients who have either just had or are soon to undergo general surgical procedures there appears to be no need to limit CT scan quality by avoiding the administration of CM. These patients may benefit from the increased diagnostic utility of contrast-enhanced CT scans without increasing their risk of perioperative AKI.

Contrast-Enhanced Ultrasound in Renal Imaging and Intervention

PURPOSE OF REVIEW

In recent years, there has been renewed interest in the use of contrast-enhanced ultrasound (CEUS) in abdominal imaging and intervention. The goal of this article is to review the practical applications of CEUS in the kidney, including renal mass characterization, treatment monitoring during and after percutaneous ablation, and biopsy guidance.

RECENT FINDINGS

Current evidence suggests that CEUS allows accurate differentiation of solid and cystic renal masses and is an acceptable alternative to either computed tomography (CT) or magnetic resonance imaging (MRI) for characterization of indeterminate renal masses. CEUS is sensitive and specific for diagnosing residual or recurrent renal cell carcinoma (RCC) following percutaneous ablation. Furthermore, given its excellent spatial and temporal resolution, CEUS is well suited to demonstrate tumoral microvascularity associated with malignant renal masses and is an effective complement to conventional grayscale ultrasound (US) for percutaneous biopsy guidance. Currently underutilized, CEUS is an important problem-solving tool in renal imaging and intervention whose role will continue to expand in coming years.

Intravascular Iodinated Contrast Is an Independent Cause of Acute Kidney Injury Following Coronary Angiography

OBJECTIVES

Recent studies have questioned whether intravascular iodinated contrast remains an independent cause of acute kidney injury (AKI). We sought to assess whether iodinated contrast administered during coronary angiography is an independent cause of AKI.

METHODS

We identified all of the patients who underwent coronary angiography between July 1, 2015 and June 30, 2017 with a discharge diagnosis of AKI that developed within 7 days following angiography. Using chart review, we categorized patients as having multifactorial AKI if ≥1 insults other than intravascular contrast potentially contributed to kidney injury or contrast-induced AKI (CI-AKI) if the only insult was contrast administration. We compared the severity of AKI and renal function upon discharge between patients with CI-AKI and multifactorial AKI.

RESULTS

We identified 78 patients who experienced AKI within 7 days following angiography, 10 (13%) of whom had CI-AKI and 68 of whom (87%) experienced multifactorial AKI. Nine (90%) patients with CI-AKI manifested stage 1 disease, 1 (10%) had stage 2 disease, and 9 (90%) experienced full recovery of kidney function. More patients with multifactorial AKI developed stage 2 or 3 disease (42% vs 10%, χ² = 3.73, P = 0.05) and experienced either partial recovery of kidney function or persistent kidney impairment compared with patients with CI-AKI (25% vs 10%, χ² = 1.9, P = 0.17), although the latter comparison was not statistically significant.

CONCLUSIONS

The intravascular administration of iodinated contrast remains an independent cause of AKI. Compared with those with multifactorial AKI, patients with CI-AKI appear to be more likely to experience mild decrements in kidney function that recover completely.

Radiological iodinated contrast-induced nephropathy

The use of iodinated contrast media can cause renal toxicity. Whether contrast media are exclusively responsible for kidney damage is currently the subject of debate, given that in most cases, other potential causes of the renal failure are present. With current low-osmolar and iso-osmolar contrast media, the incidence rate of contrast-induced nephropathy is estimated to be <1% in the low-risk population but can increase to 37% in patients who are administered contrast by an intra-arterial administration and/or who have renal failure with an estimated glomerular filtration rate (eGFR) <30mL/min/1.73m². To minimize the risk of renal toxicity, the recommendation is to administer the least amount of contrast possible and ensure appropriate volume expansion by infusing 0.9% saline solution.

Global epidemiology and outcomes of acute kidney injury

Acute kidney injury (AKI) is a commonly encountered syndrome associated with various aetiologies and pathophysiological processes leading to decreased kidney function. In addition to retention of waste products, impaired electrolyte homeostasis and altered drug concentrations, AKI induces a generalized inflammatory response that affects distant organs. Full recovery of kidney function is uncommon, which leaves these patients at risk of long-term morbidity and death. Estimates of AKI prevalence range from <1% to 66%. These variations can be explained by not only population differences but also inconsistent use of standardized AKI classification criteria. The aetiology and incidence of AKI also differ between high-income and low-to-middle-income countries. High-income countries show a lower incidence of AKI than do low-to-middle-income countries, where contaminated water and endemic diseases such as malaria contribute to a high burden of AKI. Outcomes of AKI are similar to or more severe than those of patients in high-income countries. In all resource settings, suboptimal early recognition and care of patients with AKI impede their recovery and lead to high mortality, which highlights unmet needs for improved detection and diagnosis of AKI and for efforts to improve care for these patients.

New Insights Into Mechanisms of Acute Kidney Injury in Heart Disease

Acute kidney injury is a frequent occurrence in patients with heart disease, and is associated with higher risk of adverse outcomes, including mortality. In the setting of decompensated heart failure, acute kidney injury can occur from hemodynamic and neurohormonal activation, venous congestion, and nephrotoxic medications. Certain medications, such as loop diuretics, renin angiotensin system blockers, and mineralocorticoid antagonists can seemingly cause acute kidney injury. However, this increase in creatinine level is not always associated with adverse outcomes and should be carefully differentiated so as to allow deliberate continuation of these cardio- and nephroprotective agents. In other settings such as cardiac surgery, acute kidney injury can occur from factors related to the cardiopulmonary bypass, renal hypoperfusion, or other perioperative factors. Last, patients with heart disease commonly undergo imaging procedures that require contrast administration. Contrast can indeed cause acute kidney injury, but these interventional procedures also can result in kidney injury from atheroembolic phenomena. This is well documented by the recent data reporting a higher risk of acute kidney injury from femoral compared with radial access. The advent of biomarkers of kidney injury present an opportunity for early detection, accurate differential diagnosis, as well as potentially designing innovative biomarker-enriched adaptive clinical trials.

Influence of Clinical Factors on Risk of Contrast-Induced Nephrotoxicity From IV Iodinated Low-Osmolality Contrast Material in Patients With a Low Estimated Glomerular Filtration Rate

OBJECTIVE. The objective of our study was to explore whether clinical factors historically associated with contrast material-causative kidney injury (contrast-induced nephrotoxicity [CIN]) increase risk after use of IV iodinated low-osmolality contrast material (LOCM) in patients with stage IIIb-V chronic kidney disease. MATERIALS AND METHODS. In this retrospective hypothesis-generating study, 1:1 propensity score matching was used to assess post-CT acute kidney injury (AKI) after unenhanced or contrast-enhanced CT in patients with stable estimated glomerular filtration rate (eGFR; 1112 patients with an eGFR = 30-44 mL/min/1.73 m² and 86 patients with an eGFR < 30 mL/min/1.73 m² and no dialysis). Historical risk factors including diabetes mellitus, age more than 60 years, hypertension, loop diuretic use, hydrochlorothiazide use, and cardiovascular disease were evaluated for modulation of CIN risk. Stepwise multivariable logistic regression was performed. RESULTS. Overall IV LOCM was an independent risk factor for post-CT AKI in patients with an eGFR of less than 30 mL/min/1.73 m² (odds ratio, 3.96 [95% CI, 1.29-12.21]; p = 0.016) but not in those with an eGFR of 30-44 mL/min/1.73 m² (p = 0.24). In patients with an eGFR of less than 30 mL/min/1.73 m², the tested covariates did not significantly modify the risk of CIN (p = 0.096-0.832). In patients with an eGFR of 30-44 mL/min/1.73 m², risk of CIN emerged in those with cardiovascular disease (p = 0.015; number needed to harm from LOCM = 11 patients); the other tested cofactors had no significant effect (p = 0.108-0.822). CONCLUSION. CIN was observed when eGFR was less than 30 mL/min/1.73 m². In those with an eGFR of 30-44 mL/min/1.73 m², CIN was not observed with LOCM alone but was observed in the presence of cardiovascular disease. Other cofactors historically thought to increase CIN risk (e.g., diabetes mellitus) did not increase risk of CIN. Further study is needed to determine whether these exploratory results are true associations.

Are patients with mild to moderate renal impairment on metformin or other oral anti-hyperglycaemic agents at increased risk of contrast-induced nephropathy and metabolic acidosis after radiocontrast exposure?

AIM

To investigate whether the use of metformin during computed tomography (CT) with radiocontrast agents increases the risk of contrast-induced nephropathy (CIN) and metabolic acidosis after CT in type 2 diabetes patients with mild to moderate renal failure.

MATERIALS AND METHODS

Patient records from January 2015 to December 2017 were reviewed retrospectively. A total of 374 patients were included in the final analysis. Of them, 157 patients received metformin, and 217 patients were taking other oral hypoglycaemic agents (OHAs) during radiocontrast administration.

RESULTS

No significant difference in CIN incidence was observed between the metformin use group and the other OHAs group (p=0.085). Metabolic acidosis after CT was seen in 91 (58%) patients who used metformin and 141 (65%) patients who were taking other OHAs. There was no relationship between metabolic acidosis after CT and the use of metformin (p=0.195). Metabolic acidosis after radiocontrast agent exposure was associated with malignant disease, low serum albumin level, and low serum total CO₂ level at baseline.

CONCLUSION

These data show that other factors, but not metformin use, are associated with metabolic acidosis after radiocontrast agent exposure in patients with reduced renal function. These data support current recommendations that there is no need to discontinue metformin before CT using radiocontrast agents in patients with mild to moderate renal failure.