Nephrotoxicity of high-dose gadolinium compared with iodinated contrast

Signal quality of single dose gadobenate dimeglumine pulmonary MRA examinations exceeds quality of MRA performed with double dose gadopentetate dimeglumine

During a recent multi-center trial assessing gadolinium (Gd)-enhanced magnetic resonance angiography (MRA) for diagnosis of acute pulmonary embolism (PE), the Food and Drug Administration announced a risk of nephrogenic sclerosing fibrosis in patients with renal insufficiency who had received intravenous Gd-based MR contrast agents. Although no patients in this trial had renal insufficiency, in cautious response to this announcement, the trial protocol was changed from an intravenous administration of 0.2 mmol/Kg of a conventional Gd-based MR contrast agent to 0.1 mmol/Kg of gadobenate dimeglumine. The study described herein compares the signal quality of pulmonary MRA performed with double dose conventional agent to single dose gadobenate dimeglumine. This study is a retrospective analysis of data from a prospective, multicenter study in men and women ≥18 years with documented presence or absence of PE. The study was approved by the Institutional Review Board at all participating centers, and all patients provided written indication of informed consent. We performed both objective and subjective analysis of pulmonary artery image quality. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in the main pulmonary artery were assessed in single and double dose protocols and compared. SNR and CNR of the main PA were correlated with subjective quality assessment of main/lobar, segmental and subsegmental pulmonary arteries. Although there were individual outliers, both SNR (P = 0.01) and CNR (P = 0.008) were higher in all quartiles for examinations using gadobenate dimeglumine than with gadopentetate dimeglumine. Subjective quality of vascular signal intensity at each vessel order was significantly better for gadobenate dimeglumine (P < 0.0001), and correlated well with SNR and CNR at each order (<0.001). Because of agent high relaxivity, a single dose of gadobenate dimeglumine provides better pulmonary MRA signal quality than double dose of a conventional Gd-based MR contrast agent.

The use of gadolinium for arterial interventions

BACKGROUND

Gadolinium (Gd) has been traditionally used as a non-nephrotoxic alternative to iodinated contrast for digital subtraction angiography (DSA) in patients with chronic renal insufficiency. However, its use has been questioned on the basis of reports of nephrotoxicity and its recent association with nephrogenic systemic fibrosis (NSF), a potentially lethal complication. Recently available data are conflicting with respect to the true safety profile of intra-arterial Gd. The purpose of this study was to examine the risk of contrast nephropathy and NSF after Gd exposure in a large population of azotemic patients undergoing DSA.

METHODS

A comprehensive database encompassing data on all patients who underwent DSA between June 2003 and December 2007 at the New York Presbyterian Hospital was retrospectively reviewed. Patients receiving Gd either alone or in combination with iodinated contrast during DSA were identified and further analyzed. Acute renal failure (ARF) was defined as an elevation in serum creatinine (Cr) by >0.5 mg/dL within 48 hours of exposure. Clinical follow-up was conducted through chart reviewing as well as telephonic interviews with patients and their primary care physicians.

RESULTS

A total of 153 patients underwent 179 exposures to Gd either alone (33%) or in combination (67%) with iodinated contrast. Mean follow-up duration was 27.1 months. The mean Cr level was 1.94 ± 0.78 mg/dL and 1.96 ± 1.1 mg/dL before and after DSA, respectively. There were 20 (11.2%) instances of ARF. The mean Cr level before DSA was higher in patients who developed ARF versus those in the non-ARF group (2.7 ± 1.1 mg/dL vs. 1.9 ± 0.7 mg/dL, p = 0.004). In the ARF group, 12 patients had a return to baseline renal function, four experienced irreversible renal deterioration, and four needed dialysis (4.5% incidence of irreversible renal failure). There were 19 deaths at the time of this study (12.4%). The highest risk for the development of ARF after Gd exposure occurred in patients with Cr levels of >3.0 mg/dL before DSA and in those receiving >0.4 mmol/kg of Gd. For patients who received iodinated contrast in combination with Gd, there was a trend toward a higher risk for developing ARF as compared with those receiving only Gd. Finally, there were no instances of NSF identified in any of the patients who received intra-arterial Gd.

CONCLUSIONS

Although Gd has the potential to cause kidney injury similar to iodinated contrast, the risk of irreversible renal failure and the requirement for dialysis is low. Life- or limb-threatening interventions should not be avoided in this patient cohort because of preexisting elevations in Cr. These data should help guide the use of Gd in patients with chronic renal insufficiency.

Magnetic resonance angiography and Doppler scanning for detecting atherosclerotic renal artery stenosis

BACKGROUND

Atherosclerotic renal artery stenosis (ARAS) is a progressive but potentially reversible chronic kidney disease. Although the high sensitivity and specificity of renal Doppler scanning (RDS) for ARAS has been reported in western countries, ARAS has not been detected by RDS. This study used magnetic resonance angiography (MRA) to evaluate the sensitivity and specificity of RDS for detecting ARAS among outpatients at a nephrology clinic, and to calculate the degree of underestimation of ARAS by RDS.

METHODS

A total of 257 outpatients, aged > 50 years were examined for ARAS by RDS and MRA.

RESULTS

Thirty-seven (14.4%) and 139 (54.1%) of 257 patients had stenosis detected by RDS and MRA, respectively. Among the 220 patients whose RDS results were negative, MRA detected stenosis in 111 (50.45%). Multivariate logistic regression analysis showed that age > 65 years, duration of smoking, coronary artery disease, and serum creatinine levels > 354 mmol/L (4 mg/dL) were significant and independent factors that influenced ARAS in patients with negative results by RDS.

CONCLUSION

RDS might still be the diagnostic procedure of choice for screening outpatients for ARAS because it is inexpensive, convenient, able to detect severity, and avoids the use of contrast media. When RDS is negative in aged people who have smoked longer than 20 years, with coronary artery disease or serum creatinine > 4 mg/dL, MRA is recommended for further evaluation of ARAS.

The current state of endovascular therapy in the evaluation and management of renovascular disease

Hypertension is the most common reason for physician office visits among nonpregnant adults in the United States; up to one-third of Americans over the age of 18 have been diagnosed with hypertension. Patients with physiologically significant renal artery stenosis often go unnoticed because hypertension can often be well controlled with antihypertensive medications. As a result, screening for renovascular causes of hypertension is rarely done. However, the likelihood of renovascular disease increases in patients with acute, severe, or refractory hypertension and should be explored in patients who fall into these categories. Renovascular disease is a crucial consideration in the management of hypertension due to its increasing incidence and its potential for reversibility. Although renovascular disease accounts for less than 1% of patients with mild hypertension, it is estimated that between 10 and 45% of white patients with severe or malignant hypertension have renal artery stenosis (RAS). In this population, diagnosing and treating RAS can have a profound and long-lasting effect on the treatment of hypertension.

Nephrogenic systemic fibrosis and its impact on abdominal imaging

The objective of this article is to review the current knowledge about nephrogenic systemic fibrosis (NSF) and how to prevent it. More than 300 cases of NSF in patients with severe chronic renal insufficiency or acute renal failure or in patients undergoing dialysis have been reported in the peer-reviewed literature, with an overwhelming majority occurring within weeks to months after injection of a gadolinium-based contrast agent (GBCA). Because administration of a high dose of a GBCA is a primary risk factor and because most high-dose magnetic resonance (MR) imaging applications involve abdominal imaging (eg, liver and abdominal MR angiography), NSF cases have been associated with abdominal MR imaging. Additional major risk factors for developing NSF include proinflammatory conditions, failure to perform dialysis promptly after GBCA administration, use of nonionic linear contrast agents, hyperphosphatemia, and younger age. Recent recommendations to use GBCAs with caution in patients with acute renal failure, patients receiving dialysis, or patients with an estimated glomerular filtration rate of less than 30 mL/min have resulted in virtually no new NSF cases being reported with onset in 2008 or 2009 in spite of a high level of awareness about this entity. In conclusion, NSF has been virtually eliminated by using caution in administering GBCAs to patients known to have severe or acute renal failure. In these patients, avoid high doses; and for patients undergoing dialysis, schedule MR imaging to occur just before a dialysis session to ensure rapid elimination of gadolinium.

Clinical Practice Guideline: Hoarseness (Dysphonia)

Objective:

This guideline provides evidence-based recommendations on managing hoarseness (dysphonia), defined as a disorder characterized by altered vocal quality, pitch, loudness, or vocal effort that impairs communication or reduces voice-related quality of life (QOL). Hoarseness affects nearly one-third of the population at some point in their lives. This guideline applies to all age groups evaluated in a setting where hoarseness would be identified or managed. It is intended for all clinicians who are likely to diagnose and manage patients with hoarseness.

Purpose:

The primary purpose of this guideline is to improve diagnostic accuracy for hoarseness (dysphonia), reduce inappropriate antibiotic use, reduce inappropriate steroid use, reduce inappropriate use of anti-reflux medications, reduce inappropriate use of radiographic imaging, and promote appropriate use of laryngoscopy, voice therapy, and surgery. In creating this guideline the American Academy of Otolaryngology—Head and Neck Surgery Foundation selected a panel representing the fields of neurology, speech-language pathology, professional voice teaching, family medicine, pulmonology, geriatric medicine, nursing, internal medicine, otolaryngology–head and neck surgery, pediatrics, and consumers.

Results

The panel made strong recommendations that 1) the clinician should not routinely prescribe antibiotics to treat hoarseness and 2) the clinician should advocate voice therapy for patients diagnosed with hoarseness that reduces voice-related QOL. The panel made recommendations that 1) the clinician should diagnose hoarseness (dysphonia) in a patient with altered voice quality, pitch, loudness, or vocal effort that impairs communication or reduces voice-related QOL; 2) the clinician should assess the patient with hoarseness by history and/or physical examination for factors that modify management, such as one or more of the following: recent surgical procedures involving the neck or affecting the recurrent laryngeal nerve, recent endotracheal intubation, radiation treatment to the neck, a history of tobacco abuse, and occupation as a singer or vocal performer; 3) the clinician should visualize the patient's larynx, or refer the patient to a clinician who can visualize the larynx, when hoarseness fails to resolve by a maximum of three months after onset, or irrespective of duration if a serious underlying cause is suspected; 4) the clinician should not obtain computed tomography or magnetic resonance imaging of the patient with a primary complaint of hoarseness prior to visualizing the larynx; 5) the clinician should not prescribe anti-reflux medications for patients with hoarseness without signs or symptoms of gastroesophageal reflux disease; 6) the clinician should not routinely prescribe oral corticosteroids to treat hoarseness; 7) the clinician should visualize the larynx before prescribing voice therapy and document/communicate the results to the speech-language pathologist; and 8) the clinician should prescribe, or refer the patient to a clinician who can prescribe, botulinum toxin injections for the treatment of hoarseness caused by adductor spasmodic dysphonia. The panel offered as options that 1) the clinician may perform laryngoscopy at any time in a patient with hoarseness, or may refer the patient to a clinician who can visualize the larynx; 2) the clinician may prescribe anti-reflux medication for patients with hoarseness and signs of chronic laryngitis; and 3) the clinician may educate/counsel patients with hoarseness about control/preventive measures.

Disclaimer:

This clinical practice guideline is not intended as a sole source of guidance in managing hoarseness (dysphonia). Rather, it is designed to assist clinicians by providing an evidence-based framework for decision-making strategies. The guideline is not intended to replace clinical judgment or establish a protocol for all individuals with this condition, and may not provide the only appropriate approach to diagnosing and managing this problem.

[Gadolinium-enhanced thoracic CTA: retrospective analysis of image quality and tolerability in 45 patients evaluated prior to the description of nephrogenic systemic fibrosis]

PURPOSE

To assess the accuracy and torerability of gadolinium-enhanced thoracic CTA using a 64 MDCT compared to a 16 MDCT. Because this study was started prior to the description of NSF, particular attention was paid to long-term follow-up of the patient population.

MATERIALS AND METHODS

The study protocol was approved by the ethics committee of our institution and informed consent was obtained from all patients. Fourteen patients (Group 1) (9 males and 5 females; mean age: 64.3 years) with contraindication to the administration of iodinated contrast material underwent thoracic CTA (collimation: 32 x 2 x 0.6 mm; pitch: 1.2) with gadolinium administration (0.5 mml/ml) at 0.4 mmol/kg injected at 6 ml/sec with evaluation of clinical and biological tolerability of the gadolinium based contrast agent. Results from this patient population were compared to results from a population of 31 patients (21 males; 10 females; mean age: 63.2 years) (Group 2) imaged on a 16 MDCT. All patients were folloowed-up for a mean time of 22.6 months.

RESULTS

Using a mean contrast volume (standard deviation) that was not significantly different (Group 1: 54.8+/-11 ml; Group 2: 53.4+/-6.9 ml) (p=0.94), patients in Group 1 underwent complete thoracic CTA whereas patients in Group 2 underwent CTA of only the middle third of the thoracic region. All CTA examinations were diagnostic for Group 1 and Group 2 patients; however, evaluation of subsegmental vessels was possible in a significantly larger proportion of patients in Group 1 (10/14; 72%) compared to Group 2 (6/31; 19%) (p=0.003). Mean attenuation values within pulmonary arterial branches were similar for Groups 1 and 2 (central arteries: 194.5+/-51.3 HU vs 180.6+/-53.8 HU; p=0.38) (lobar arteries: 208.5+/-52.5 HU vs 189.9+/-60.1 HU; p=0.33) (segmental arteries: 220.4+/-50.4 HU vs 201.5+/-54.7 HU; p=0.42). Transient alteration of renal function was recorded in one patient from Group 1 with severe pre-existing chronic renal failure. No change in renal function was observed for Group 2 patients. No case of NSF was reported in patients with pre-existing renal failure at the time of enrollment.

CONCLUSION

The use of gadolinium-based contrast agent for thoracic CTA using a 64 MDCT provides diagnostic quality examinations in all patients with improved image quality compared to a 16 MDCT. No complication other than transient alteration of renal function was observed. Because the likelihood of developing NSF may vary with the type of gadolinium-based contrast agent used, the least toxic agent should be used.

Current status of gadolinium toxicity in patients with kidney disease

Gadolinium-based contrast (GBC) agents have recently been the subject of intense interest for physicians across numerous specialties. These agents are widely used as contrast for magnetic resonance imaging and have been generally considered safe. Early on, phase III trials and small studies in low-risk patients suggested a benign renal profile; however, more recent studies raised the possibility of nephrotoxicity, although it is not clear whether it approaches the incidence of nephropathy associated with iodinated radiocontrast. In 2006, reports of a rare systemic fibrosing condition called nephrogenic systemic fibrosis (NSF) were recently linked to exposure of patients with advanced kidney disease to GBC agents. Analysis of the data suggests that certain GBC agents are more likely to be associated with NSF. Also, not all patients with kidney disease are at risk for developing NSF, only those with advanced acute or chronic kidney disease. Avoidance of GBC exposure is the best approach for high-risk patients. When GBC is required to obtain optimal images, use of low dosages of more stable macrocyclic agents is safer and preferred. This article reviews the current status of GBC agents as nephrotoxins and causes of NSF and provides opinions on how to use these agents in patients with underlying kidney disease.

Does gadolinium-based angiography protect against contrast-induced nephropathy?: a systematic review of the literature

We evaluated the incidence of contrast-induced nephropathy (CIN) in patients exposed to gadolinium for diagnostic or therapeutic procedures.

BACKGROUND

CIN with iodinated contrast agents is a leading cause of acute renal failure. Gadolinium is often used as an alternative to iodinated contrast in patients at increased risk of CIN. The safety of gadolinium in patients at increased risk of CIN has not been established.

METHODS AND RESULTS

The authors performed a systematic review by searching MEDLINE, ISI Web of Knowledge, Current Contents, Embase, and the Cochrane Central Register of Controlled Trials to identify relevant studies evaluating gadolinium and its associated incidence of CIN. They identified 17 studies that reported both favorable and negative results with regard to the association of gadolinium and CIN. The differences in the results appeared to be dose related. When gadolinium was used in doses of 0.4 mmol/kg or higher, there appeared to be an increased incidence of ARF particularly in patients with preexisting renal insufficiency.

CONCLUSIONS

Although the evidence base is limited, gadolinium does not appear to be safer than iodinated contrast in patients at risk of CIN. Given the lack of randomized data to support its safety, gadolinium in lieu of iso-osmolar iodinated contrast cannot be advocated in patients at high risk of contrast nephropathy.

Clinical and economic impact of falsely decreased calcium values caused by gadoversetamide interference

OBJECTIVE

Gadolinium is administered as a contrast agent in MRI procedures. Two gadolinium-based contrast agents, gadodiamide and gadoversetamide, interfere with colorimetric total serum calcium methods. The purpose of this prospective observational study was to examine the incidence of calcium interference after gadoversetamide procedures, associated clinical outcomes, and costs 20 months after implementation of quality assurance and physician education programs.

MATERIALS AND METHODS

Records of patients who received gadoversetamide from June 24, 2006, to October 7, 2006, were reviewed to determine if a routine calcium test had been performed after the injection. Calcium values were repeated with an alternate method that is less susceptible to gadoversetamide interference. If the difference was > or = 2.0 mg/dL or if the initial test value was < or = 7.0 mg/dL, patient charts were reviewed for any related treatment. Costs associated with this algorithm were tracked.

RESULTS

The initial calcium test was performed after gadoversetamide in 766 of 3,439 instances. The alternate test was performed in 633 of 766. One hundred twenty-five of 633 (20%) showed a difference in calcium values that was > or = 0.7 mg/dL, with 16 showing differences of > or = 1.6 mg/dL. Chart review for 56 instances revealed that calcium supplements were administered in 22 of 56 around the time of gadoversetamide injection. However, none appeared to be related to the spurious hypocalcemia. The total additional cost (reagent and technologist) for following this algorithm for just over 3 months was $6,807.

CONCLUSION

Approximately 20% of patients receiving gadoversetamide exhibited spurious hypocalcemia. No patients were identified who received inappropriate calcium because of this interference. This may be attributable to the quality assurance and physician education programs.

Role of contrast-enhanced 3D magnetic resonance portography in evaluating portal venous system compared with color Doppler ultrasonography

AIM

The purpose of this study was to evaluate the capability of contrast-enhanced three-dimensional (3D) MR portography in detecting abnormal findings associated with the portal venous system compared with the results of color Doppler ultrasonography (CDUS).

MATERIALS AND METHODS

MR portography findings were retrospectively compared with the results of CDUS examinations in 161 patients, who were suspected of having portal venous system abnormalities. Portal venous vessels were divided into main 5 groups including the main portal vein, its left and right intrahepatic branches, splenic vein and superior mesenteric vein. Imaging findings were classified as normal, occluded, or partially thrombosed. Results of clinical and imaging follow-up examinations including CDUS, MR portography or angiography, if available, were used as a proof of final diagnosis. The potential sites of varicose veins and collateral vessels were also examined by both imaging methods.

RESULTS

Vascular abnormalities were identified in 79 of 161 patients. There was a statistically significant agreement between the results of MR portography and CDUS in evaluating portal venous system (kappa = 0.871, P < 0.05). The sensitivity of MR portography was slightly superior to CDUS in detecting partially thrombosis and occlusion in the main portal venous vessels. In addition, MR portograms were superior to CDUS in the management of patients with portal hypertension by identifying portosystemic collaterals more adequately, and clearly demonstrated portal venous vessels that cannot be visualized at CDUS.

CONCLUSION

Results of present study indicates that contrast-enhanced 3D MR portography is well suited and superior to CDUS in the management of patients with portal hypertension.

Biochemical safety profiles of gadolinium-based extracellular contrast agents and nephrogenic systemic fibrosis

Gadolinium (Gd)-based paramagnetic contrast agents are relatively safe when used in clinically recommended doses. However, with the rapidly expanding body of literature linking Gd-based paramagnetic contrast agents and nephrogenic systemic fibrosis (NSF), awareness of the potential side effects and adverse reactions from Gd is now an important requirement for practicing radiologists. In addition to the ongoing accumulation and analyses of clinical NSF data, it is also essential for the practicing radiologist to understand the biochemical characteristics of the extracellular Gd-chelates. The purpose of this review is to consolidate and update the available information on known side effects, adverse reactions, and toxicity of the Gd chelates, with particular emphasis on the potential mechanisms of NSF.

Imaging of deep vein thrombosis

Background

Deep vein thrombosis of the leg affects 1–2 per cent of the population with an annual incidence of 0·5–1 per 1000. It presents with non-specific symptoms and signs making clinical diagnosis difficult. Techniques to image and diagnose this condition are advancing rapidly.

Methods and results

A literature review from 1980 to 2007 was undertaken using PubMed, The Cochrane Library, Medline and Embase. The most frequently used diagnostic test is duplex ultrasonography which is accurate above the knee and has a low cost, but is limited by inaccuracy when assessing the pelvic and distal veins and in diagnosing a new thrombosis in the post-thrombotic limb. Magnetic resonance imaging (MRI) and sonographic elasticity imaging are more recent techniques that have shown promise in overcoming these limitations. However, their availability is currently restricted because they are expensive. Computed tomography (CT) is sensitive, specific and provides good imaging of the pelvis. It has the advantage that it can be performed at the same time as CT pulmonary angiography.

Conclusion

MRI has some specific advantages over duplex ultrasonography, but requires refinement before it can be used clinically. Venography or CT venography should be considered when duplex scanning is inadequate.

What nephrologists need to know about gadolinium

Gadolinium chelates are commonly used to improve tissue contrast in MRI. Until recently the use of gadolinium was thought to be risk-free compared with alternative contrast agents. Recent studies, however, have raised serious concerns regarding the safety of gadolinium chelates. Although safe in patients with normal kidney function, administration of these agents in people with renal dysfunction can result in up to three clinical problems that the nephrologist should be familiar with. The first is nephrogenic systemic fibrosis (NSF), which was initially observed in 1997. Although manifesting primarily in skin, NSF can also cause systemic fibrosis, leading to disabling contractures and even death. Gadodiamide is the agent that has been most frequently associated with NSF, but other chelates might also pose a risk. The second clinical problem is that gadolinium chelates cause acute kidney injury, especially at high doses required for angiography. The third problem is that several laboratory artifacts are associated with gadolinium administration, with pseudohypocalcemia being the most important. The risk of a patient experiencing all three of these complications increases as renal function declines. In light of these problems, nephrologists need to re-evaluate the risks and benefits of gadolinium administration in patients with chronic kidney disease stage 3 or greater, as well as in those with acute kidney injury.

Perspectives for preventive screening with total body MRI

Radiology has started to increasingly recognise its potential for screening with the advent of "whole-body" imaging techniques. This article briefly reviews prerequisites for successful screening, presents a quick summary of single-organ screening with magnetic resonance (MR) imaging, and introduces how this knowledge can be integrated into whole-body MR (wb-MR) screening. MR colonography has demonstrated its potential for screening. Wb-MR in the form of wb-MR angiography has already entered both clinical and screening settings; also, the search for metastases with wb-MR has been evaluated and has performed well when compared with other imaging modalities. But screening a group of healthy subjects requires more than feasibility and high accuracy of the screening test; thus, technical and ethical considerations are also presented. Wb-MR is only at its beginning and will in the near future certainly inspire many new research activities as well as transform the radiological market.

Current techniques for assessment of upper extremity vasculature prior to hemodialysis vascular access creation

Vascular access problems lead to increased patient morbidity and mortality and place a large burden on care facilities, manpower and costs. Autogenous arteriovenous fistulas (AVF) are preferred over arteriovenous grafts (AVG) because of a lower incidence of vascular access related complications. An aggressive increase in the utilization of AVF, however, results in an increased incidence of AVF early failure and non-maturation. Increasing evidence suggests that routine preoperative assessment results in an increased utilization of functioning AVF by better selection of adequate vessels. To date, the reproducibility and standardization of assessment protocols are lacking and assessment of a single morphological parameter has not enabled adequate prediction of postoperative AVF function for individual patients. In this paper, we provide an overview of available diagnostic modalities and parameters that potentially enable better selection of adequate vessels for successful AVF creation.

Whole-body contrast-enhanced magnetic resonance angiography: new advances at 3.0 T

During the past decade, technical improvements and numerous advances in scanner hardware and software have significantly improved image quality, speed, and reliability of 3-dimensional (3-D) contrast-enhanced magnetic resonance angiography (CE-MRA). The accuracy of CE-MRA is now comparable with that of computed tomography angiography or even conventional catheter angiography. Peripheral vascular disease (PVD) accounts for 50,000 to 60,000 cases of percutaneous transluminal angioplasty and for about 100,000 cases of amputation annually in the United States. Proper treatment of the arterial disease requires a comprehensive assessment of the underlying vascular morphology because it is crucial to localize and gauge the severity of arterial lesions for further therapeutic decision making.Contrast-enhanced magnetic resonance angiography has been widely implemented in noninvasive evaluation of PVD with high diagnostic accuracy. The lack of ionizing radiation and the use of contrast agent with relatively small potential nephrotoxicity in population of PVD with high prevalence of renal impairment are the appealing features for broad acceptance of CE-MRA in initial diagnosis and repeated follow-up studies of patients with PVD. The minimum anatomical coverage for evaluation of PVD comprises the aortic bifurcation to the ankles; however, because of the systemic nature of atherosclerosis hypertension, renal or cerebrovascular disease frequently coexist. Thus, many clinicians regard evaluation of the whole-body arterial vasculature as desirable.

Comparison of the usefulness of gadodiamide and iodine mixture versus iodinated contrast alone for prevention of contrast-induced nephropathy in patients with chronic kidney disease undergoing coronary angiography

Contrast-induced nephropathy (CIN) is a common cause of hospital-acquired renal failure. Gadolinium-based contrast agents have been proposed as alternatives to iodinated contrast in patients at high risk for CIN. The use of high-dose intraarterial gadolinium chelates in the catheterization laboratory has been investigated in only a small number of patients. We compared patients with a creatinine clearance <60 ml/min/1.73 m2 who received intravenous hydration (> or =1,500 ml) and oral n-acetylcysteine prophylaxis with those who received a gadodiamide-iodine mixture (n = 90) or iodinated contrast alone (n = 79) in the cardiac catheterization laboratory. CIN was defined as an increase of 0.5 mg/dl in serum creatine from baseline. The 2 groups were similar with respect to demographics and risk factors. Although less iodinated contrast was used in the gadolinium mixture group, there was no difference in the incidence of CIN between the 2 groups. However, the initiation of dialysis (n = 7) and death (n = 8) only occurred in the diluted gadolinium contrast group. A stepdown multivariate analysis found diabetes mellitus to be the only independent predictor of CIN (p = 0.02, odds ratio 3.35, 95% confidence interval 1.21 to 9.29, c-statistic 0.66). In conclusion, the incidence of CIN was not decreased in high-risk patients receiving a gadolinium-iodinated contrast mixture versus iodinated contrast alone.

Contrast medium-induced nephropathy. Aspects on incidence, consequences, risk factors and prevention

Contrast media-induced nephropathy (CIN) is a well-known complication of radiological examinations employing iodine contrast media (I-CM). The rapid development and frequent use of coronary interventions and multi-channel detector computed tomography with concomitant administration of relatively large doses of I-CM has contributed to an increasing number of CIN cases during the last few years. Reduced renal function, especially when caused by diabetic nephropathy or renal arteriosclerosis, in combination with dehydration, congestive heart failure, hypotension, and administration of nephrotoxic drugs are risk factors for the development of CIN. When CM-based examinations cannot be replaced by other techniques in patients at risk of CIN, focus should be directed towards analysis of number and type of risk factors, adequate estimation of GFR, institution of proper preventive measures including hydration and post-procedural observation combined with surveillance of serum creatinine for 1-3 days. For the radiologist, there are several steps to consider in order to minimise the risk for CIN: use of "low-" or "iso-osmolar" I-CM and dosing the I-CM in relation to GFR and body weight being the most important as well as utilizing radiographic techniques to keep the I-CM dose in gram iodine as low as possible below the numerical value of estimated GFR. There is as yet no pharmacological prevention that has been proven to be effective.

Usefulness of magnetic resonance angiography in the evaluation of complex congenital heart disease in newborns and infants

This study evaluated the quality of the visualization of extracardiac thoracic vessels by magnetic resonance angiography (MRA) in young infants with congenital heart disease. Echocardiography is often sufficient in evaluating CHD in young infants. Cardiac catheterization is needed in some instances to evaluate extracardiac thoracic vessels. Extracardiac thoracic vessels can be accurately evaluated using MRA in adults and older children, but image quality in small infants may be limited. Twenty-nine magnetic resonance angiographic scans were performed at a single institution on 28 infants aged <3 months (median 6 days, range 1 to 90 days) with complex CHD in whom imaging was inconclusive by echocardiography. A blinded observer at a different institution graded (from 0 to 3) the quality of the visualization of the main, branch, lobar, and second-generation pulmonary arteries; lobar pulmonary veins; aortopulmonary collaterals; vena cavae; thoracic aorta and its branches; patent ductus arteriosus; and visceral sidedness. The results of MRA were compared with those of x-ray angiography and surgical inspection, when available. The mean image quality grade was >2 for all structures except the second-generation pulmonary arterial branches, for which it was 2. The median total scan duration was 9 minutes (range 3 to 46). Findings were concordant with surgical inspection (n = 25) and cardiac catheterization (n = 8) in all subjects. There were no complications. In conclusion, MRA is excellent for the visualization of extracardiac thoracic vessels in young infants with CHD and can be used as an alternative to cardiac catheterization when echocardiography is inconclusive.

MR colonography

Combining the advantages of unsurpassed soft tissue contrast and lack of ionizing radiation, MR imaging of the gastrointestinal tract has become increasingly used clinically. Both bowel inflammation and tumor disease of the large bowel can be well visualized by means of MR colonography (MRC). This article describes current techniques of MRC and gives an overview of its clinical outcome. Special focus is directed toward the evaluation of patients' acceptance of MRC.

Feasibility of gadolinium-diethylene triamine pentaacetic acid enhanced multidetector computed tomography for the evaluation of coronary artery disease

BACKGROUND

Multidetector computed tomography (MDCT) has been proposed as a noninvasive method for the diagnosis of obstructive coronary artery disease (CAD). In patients with high risk of iodinated contrast adverse effects such as acute allergic-type reactions, the use of gadolinium could be an alternative.

OBJECTIVE

We sought to evaluate the feasibility of gadolinium-enhanced MDCT for the diagnosis of obstructive CAD.

METHODS

Twenty patients (mean age, 61 years; range, 50-73 years) referred for X-ray coronary angiography were studied by both gadolinium and iodine-enhanced 16-row MDCT coronary angiography. The degree of enhancement and the accuracy for detection of obstructive CAD (>50% diameter reduction) were evaluated with X-ray coronary angiography as the standard. Renal nephrotoxicity was strictly monitored.

RESULTS

Gadolinium- and iodine-enhanced MDCT showed adequate visualization of the coronary arteries in 310 of the 312 coronary artery segments that were available by X-ray angiography, respectively. The average density of the coronary arteries in both iodine and gadolinium CT scans was 253.65 Hounsfield unit (HU) and 135.20 HU, respectively. In a per-coronary segment analysis, gadolinium- and iodine-enhanced MDCT showed sensitivities of 89% vs 84%, specificities of 96% vs 95%, and negative predictive values of 97% vs 96%, respectively. In a per-patient analysis, both gadolinium- and iodine-enhanced MDCT showed sensitivities of 92.85% vs specificities of 83.33%. Intermethod agreement between gadolinium- and iodine-enhanced MDCT (kappa) was 0.95 (P < 0.0001).

CONCLUSION

Our preliminary results indicate lower attenuation with gadolinium but similar diagnostic accuracy for the detection of obstructive CAD when compared with iodine-enhanced MDCT. Therefore, gadolinium is a feasible alternative contrast agent for patients with iodine contrast allergy referred for MDCT coronary angiography.

MR colonography with fecal tagging: do individual patient characteristics influence image quality?

PURPOSE

To evaluate if different patient characteristics influence performance of fecal tagging (a new MR colonography (MRC) technique to label stool to avoid bowel cleansing) and, consecutively, MR image quality.

MATERIALS AND METHODS

A total of 333 patients (mean age = 61 years) underwent MRC with fecal tagging. Four segments of the large bowel (ascending, transverse, descending, and sigmoid colon) were assessed as for the presence of nontagged stool particles, which can impede an assessment of the colonic wall. Ratings were correlated with patients' characteristics including patient age (<55 vs. > or =55 years), body mass index (BMI) (<25 vs. > or =25), gender, and acceptance levels for fecal tagging. Statistical analysis was performed using a Mann-Whitney U-test.

RESULTS

A total of 1332 colonic segments were evaluated. Among them, 327 segments (25%) did not contain any visible stool particles. Considerably reduced image quality was found in 61 segments (5%). Best image quality was found in the sigmoid colon (mean value = 1.9), while image quality of the ascending colon turned out to be worst (mean value = 2.6). Fecal tagging effectiveness showed a reverse correlation with patient age. However, all other characteristics did not have a statistically significant influence on fecal tagging outcome.

CONCLUSION

MRC in conjunction with barium-based fecal tagging led to diagnostic image quality in 95% of all colonic segments. Since tagging results were significantly decreased in patients > or =55 years, tagging protocols should to be modified in this group, i.e., by increasing the time interval of tagging administration.

Effectiveness and renal tolerance of multidetector helical CT with gadobutrol: results of a comparative porcine study

PURPOSE

To prospectively evaluate the safety and effectiveness of high doses of 1 mol/L gadobutrol as a contrast agent for computed tomography (CT).

MATERIALS AND METHODS

Experiments were performed according to guidelines for care of laboratory animals. The local animal care committee approved the study protocol. Unenhanced and contrast material-enhanced CT images of the chest and abdomen were obtained randomly in nine domestic pigs. Gadobutrol was injected (1, 2, or 3 mL per kilogram of body weight; three pigs for each dose). Attenuation was measured in different vascular and parenchymal structures. Changes in blood chemistry and hematologic parameters were monitored before and 1, 2, 3, and 7 days after gadobutrol administration. Urine samples were evaluated before and 7 days after gadobutrol administration. Technetium 99m mertiatide renal scintigraphy was performed before and 7 days after contrast medium injection. Animals were sacrificed 7 days after contrast medium administration, and one kidney was removed from each animal for examination with light microscopy. No serious adverse events occurred. A mixed-model nested analysis of variance was used for statistical evaluation.

RESULTS

Mean attenuations for the 1, 2, and 3 mL/kg gadobutrol doses, respectively, were 148 HU +/- 20 (standard deviation), 282 HU +/- 18, and 289 HU +/- 20 in the thoracic aorta; 99 HU +/- 11, 166 HU +/- 9, and 153 HU +/- 18 in the kidneys; and 106 HU +/- 7, 186 HU +/- 18, and 224 HU +/- 24 in the inferior vena cava. No clinically relevant changes in hematologic, blood chemistry, or urine analysis results were detected. Markers for glomerular filtration and tubular function were unaffected in all groups. Scintigraphy revealed no differences between unenhanced and contrast-enhanced results. No morphologic changes of the renal parenchyma were found at histologic analysis.

CONCLUSION

Contrast-enhanced CT with a 2 or 3 mmol/kg dose of 1 mol/L gadobutrol resulted in excellent vascular and parenchymal enhancement. A gadobutrol dose of up to 3 mL/kg did not affect renal function.

Dialyzability of gadodiamide in hemodialysis patients

PURPOSE

The aim of this study was to evaluate the contrast enhancement, pharmacokinetics, dialyzability, and safety of gadodiamide in patients on hemodialysis.

MATERIALS AND METHODS

Thirteen hemodialysis patients with abdominal disease were examined after receiving intravenous gadodiamide (0.1 mmol/kg body weight) by magnetic resonance imaging (MRI) and were dialyzed at l, 3, 5, and 8 days. Blood samples were obtained immediately before, during, and at the end of the first hemodialysis session and immediately before and at the end of the next three sessions. The complete blood count, blood biochemistry, beta2-microglobulin, and gadolinium were measured. Dialysis of urea, creatinine, and gadolinium during the first hemodialysis session was assessed. Precontrast and postcontrast MRI and Gd-enhanced MR angiography (MRA) images were reviewed and visually evaluated by two radiologists; their evaluation was based on consensus.

RESULTS

Gadodiamide did not cause any changes in renal function. An average of 73.8%, 92.4%, and 98.9% of the gadodiamide dose was eliminated by the end of the first, second, and third hemodialysis sessions, respectively. The average half-time of gadodiamide was 1.93 h (SD 0.55). The mean clearance of gadodiamide during hemodialysis was 63.5 ml/min (SD 21.9). There were no side effects related to the injection of gadodiamide. In all cases, diagnosable MRI and MRA images were obtained after gadodiamide injection in the hemodialysis patients.

CONCLUSION

In hemodialysis patients, gadodiamide achieves diagnosable images. It is dialyzable and can be used safely without measures to increase excretion.

Editorial: Gadolinium Use in Patients with Kidney Disease: A Cause for Concern

Gadolinium is widely used as a magnetic resonance imaging contrast agent and is considered to have a good overall safety profile. Recently, both renal and extra-renal toxicities have been reported following exposure to gadolinium in patients with underlying kidney disease. Gadolinium-related contrast-induced nephropathy appears to be a risk in patients with advanced kidney disease and especially those with diabetic nephropathy. Even more concerning is the strong association of gadolinium with nephrogenic systemic fibrosis (NSF), a devastating fibrosing disorder of the skin and other systemic organs. Although cause and effect have not been proven for the NSF-gadolinium link, the impaired renal elimination of gadolinium in patients with kidney disease and the instability of gadolinium-chelate binding may expose tissues to toxic free Gd(3+) and promote this fibrosing disorder. Caution should be exercised when utilizing gadolinium as a contrast agent in patients with advanced CKD or ESRD.

Imaging in the time of NFD/NSF: do we have to change our routines concerning renal insufficiency?

To date there are potential chronology-based but not conclusive reasons to believe that at least some of the gadolinium complexes play a causative role in the pathophysiology of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). Still, the exact pathogenesis and the risk for patients is unclear beside the obvious connection to moderate to severe renal insufficiency. So far, MR imaging with Gd-enhancement was regarded as the safest imaging modality in these patients--the recent development creates tremendous uncertainty in the MR-community. Nevertheless, one should remember that, despite the over 200 cases of NSF and about 100 with proven involvement of Gd(3+), the vast majority of over 200 million patients exposed to gadolinium since the 1980s have tolerated these agents well. Importantly, NSF is a rare disease and does not appear to occur in patients without renal impairment. Many patients and researchers have undergone MR investigations with Gd exposure in the past. For those, it is essential to know about the safety of the agents at normal renal function. We can hope that pharmacoepidemiological and preclinical studies will allow us to better understand the pathophysiology and role of the various MR contrast agents in the near future.

One-molar gadolinium chelate (gadobutrol) as a contrast agent for CT angiography of the thoracic and abdominal aorta

The aim of our study was to evaluate the use of a 1-molar gadolinium chelate (gadobutrol) as an alternative contrast medium for computed tomography angiography (CTA) exams of the aorta. CTA exams of the thoracic and/or abdominal aorta were performed on 15 patients with contraindications for the use of iodine who were not suitable for magnetic resonance examinations. The exams were performed with a 16-detector row scanner, injecting a mean dose of 0.37 mmol Gd/kg of body weight at a flow rate of 4 ml/s. Creatinine levels were obtained prior to the exam in patients with impaired renal function, and 24 and 48 h afterwards. The mean attenuation values obtained in the middle ascending and middle descending thoracic aorta were 202.3 and 216.8, respectively. The mean HU values of the abdominal aorta were 210.4 at the level of the renal arteries and 186.8 in the aortic bifurcation. All the exams were considered diagnostically adequate. No significant increase in serum creatinine was observed 24 and 48 h after the exam. We believe that gadobutrol could be an alternative contrast medium for CTA exams with 16-detector row scanners in patients with contraindications for iodinated contrast medium.