MR imaging in patients at risk for developing nephrogenic systemic fibrosis: protocols, practices, and imaging techniques to maximize patient safety

Nephrogenic systemic fibrosis (NSF) is a rare but potentially debilitating or even fatal fibrosing condition that most often affects the skin but is now also recognized to involve multiple organs. The first report on NSF was published in 1997, and there is mounting evidence that this condition is associated with renal failure and the administration of large amounts of gadolinium. Although gadolinium-enhanced magnetic resonance (MR) imaging was once considered one of the safer imaging procedures, concerns over NSF have led the radiology community to rethink its imaging practices. Several noncontrast angiographic techniques based on fast spin-echo, gradient-echo, phase-contrast, and inversion-recovery principles are currently available. These techniques allow MR angiography to be performed safely, even in patients at risk for developing NSF. When use of gadolinium-based contrast material is necessary for diagnosis, it is possible to reduce total gadolinium administration through the use of agents with higher relaxivity, time-resolved imaging, high-field-strength magnets, and body compression devices. Management of NSF also requires an understanding of the risk factors of this disease and developing an institutional policy for identifying and testing at-risk patients.

Magnetic resonance urography in pediatric urology

PURPOSE OF REVIEW

Magnetic resonance urography (MRU) has emerged as a powerful diagnostic tool in the evaluation of the pediatric genitourinary tract. The purpose of this review is to familiarize the reader with the basic techniques, strengths and limitations, as well as the current and potential future applications of MRU in pediatric urology.

RECENT FINDINGS

MRU can provide detailed anatomical information and assess renal function and drainage in a single study. MRU does not employ ionizing radiation and may be utilized in patients with iodine-based contrast allergy or impaired renal function. MRU has been most often applied to the evaluation of hydronephrosis and provides valuable insight into a wide range of obstructive uropathies. MRU was shown to be superior to renal scintigraphy for the diagnosis of pyelonephritis and renal scarring. The use of MRU for the assessment of urolithiasis and vesicoureteral reflux is limited and technical refinements are required. Potential future applications include fetal MRU, virtual endoscopy, and MRU-guided procedures. The development of new contrast agents and new image-processing software will further enhance the diagnostic potential of MRU in pediatric urology.

SUMMARY

MRU is currently thought of as a problem-solving tool to define anatomy and function when conventional methods fall short. This technique is likely to emerge as the imaging modality of choice for children with complex genitourinary pathology.

Dialytic therapies to prevent NSF following gadolinium exposure in high-risk patients

Prolonged exposure to gadolinium-based contrast (GBC) appears to be the core pathophysiologic factor in the development of nephrogenic systemic fibrosis (NSF). As the GBC is renally excreted, this condition is predominantly seen only following exposure in patients with severe reductions in renal function. Fortunately, GBC is easily hemodialyzed with 95% of an administered dose removed after two hemodialysis sessions. Peritoneal dialysis, on the other hand, is not an efficient means of GBC removal. This has led to recommendations to hemodialyze a high-risk patient immediately following GBC administration and to repeat the treatment the following day. Although this approach seems logical and is more aggressive than the usual thrice-weekly hemodialysis schedule that most patients were receiving when they developed this devastating condition, there are no data to support the supposition that this approach will reduce the risk of NSF. Therefore, although an aggressive hemodialysis strategy postexposure is not unreasonable, it is probably best at this point to try to avoid GBC administration altogether in these high-risk patients.

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.

Assessment of Utilization and Pharmacovigilance Based on Spontaneous Adverse Event Reporting of Gadopentetate Dimeglumine as a Magnetic Resonance Contrast Agent After 45 Million Administrations and 15 Years of Clinical Use

PURPOSE

Although contrast agents have become indispensable tools in magnetic resonance and their safe and effective use the foundation of many essential diagnostic procedures, only limited summary information on their utilization and pharmacovigilance is available to the community. After voluntary access to the manufacturer spontaneous adverse event database, we assessed the available data for gadopentetate dimeglumine.

MATERIAL AND METHODS

Gadopentetate dimeglumine (Gd-DTPA, Magnevist; Berlex/Schering AG, Berlin, Germany) became commercially available in 1988 and is currently marketed in 101 countries. Using the manufacturer's continuous and cumulative database on product distribution and spontaneous adverse event (AE) reporting, we categorized AEs and assessed their cumulative occurrence after 10, 20, and 45 million applications that occurred in 1993, 1997, and 2002, respectively. Furthermore, we reviewed publications in Medline to assess prevalence of the 4 most common MR contrast agents in the indexed literature.

RESULTS

Gd-DTPA has been used in more than 45 million magnetic resonance imaging procedures since 1988 and is currently used globally in more than 5 million applications annually. The broadest category of spontaneously reported AEs, subjective symptoms, occurs in less than 0.01% of procedures. Within the total AEs reported, the distribution of serious and nonserious reports was 9.3% and 90.7%, respectively. The rates of AE reporting have changed over time, with increased rates in the second reporting period (1993 to 1997), followed by substantially lower rates in subsequent years. AE reporting rates are the most comprehensive data available; however, there will always be some underestimation of the true event rates. Although no substantial differences were noted among major age groups, substantial differences in reporting frequency were found among regions, with the United States reporting nearly twice as many AEs as Europe in the postmarketing phase.

CONCLUSION

The postmarketing utilization and pharmacovigilance analysis of Gd-DTPA has revealed temporal changes and regional differences, overall with an excellent safety profile. Its extensive utilization and safety information have firmly established it as highly used and safe magnetic resonance imaging agent.

MR peritoneography in complications of continuous ambulatory peritoneal dialysis

BACKGROUND

We evaluated the usefulness of magnetic resonance (MR) peritoneography for the examination of complications from continuous ambulatory peritoneal dialysis (CAPD).

METHODS

MR peritoneography was performed in 20 patients who had suspected CAPD-related complications. Patients who had active peritonitis were not included in the study. Before MR imaging, a mixture of 2000 mL of peritoneal dialysis solution and 20 mL of gadopentetate dimeglumine was instilled into the peritoneal cavity. MR imaging was performed on a 1.0-Tesla system using a body coil. Axial, coronal, and sagittal fat-saturated fast spoiled gradient echo (repetition/echo times, 100/6.3 ms; flip angle, 90 degrees), axial fat-saturated T2-weighted fast spin echo (repetition/echo times, 6000/107 ms), and coronal fat-saturated T2-weighted fast spin echo (repetition/echo times, 3000/96.2 ms) images of the abdomen and the pelvis were obtained. After drain-age, triplanar fat-saturated fast spoiled gradient echo images were repeated with the same parameters.

RESULTS

Homogeneous distribution of the dialysate in the peritoneal cavity was detected in 18 patients (90%). In 12 patients (60%), fluid leaks were discovered peripheral to the exit site, tunnel, and site of peritoneal entrance of the catheter. Fluid leaks through the abdominal wall in five patients (25%), retroperitoneum in one patient (5%), and a previous operation site in one patient (5%) were demonstrated. No abnormal finding was detected in three patients (15%) who had clinically suspected complications, whereas a dialysate leak was found in two patients (10%) who had no significant finding at physical examination.

CONCLUSIONS

MR peritoneography provides detailed information about the anatomic distribution of dialysate leaks in patients treated with CAPD and poses no risks associated with ionizing radiation and nephrotoxic contrast medium.

Iron-mobilizing properties of the gadolinium-DTPA complex: clinical and experimental observations

BACKGROUND

Gadolinium (Gd) magnetic resonance imaging (MRI) contrast agents are considered to be safe in patients with impaired renal function. Our study investigates a mechanism of severe iron intoxication with life-threatening serum iron levels in a haemodialysis patient following MRI with Gd-diethylenetriaminepentaacetic acid (Gd-DTPA) administration. His previous history was remarkable for multiple blood transfusions and biochemical evidence of iron overload. We hypothesized that Gd-DTPA may have an iron-mobilizing effect in specific conditions of iron overload combined with prolonged exposure to the agent.

METHODS

For the in vitro study, Gd-DTPA was added to mice liver homogenate and iron metabolism parameters were measured after incubation in comparison with the same samples incubated with saline only. For the in vivo study, an experimental model of acute renal failure in iron-overloaded rats was designed. Previously iron-overloaded and normally fed rats underwent bilateral nephrectomy by renal pedicle ligation, followed by Gd-DTPA or saline injection. Iron and iron saturation levels were checked before and 24 h after Gd-DTPA or vehicle administration.

RESULTS

Significant mobilization of iron from mice liver tissue homogenate in mixtures with Gd in vitro was seen in the control (saline) and in the experimental (Gd) groups (513+/-99.1 vs 1117.8+/-360.8 microg/dl, respectively; P<0.05). Administration of Gd-DTPA to iron-overloaded rats after renal pedicle ligation caused marked elevation of serum iron from baseline 143+/-3.4 to 570+/-8 microg/dl (P<0.0001). There were no changes of the named parameter, either in iron-overloaded anuric rats after saline injection or in normal diet uraemic animals, following Gd-DTPA administration.

CONCLUSIONS

The combination of iron overload and lack of adequate clearance of Gd chelates may cause massive liberation of iron with dangerous elevation of free serum iron. It is highly recommended that after Gd contrast study, end-stage renal disease patients with probable iron overload should undergo prompt and intensive haemodialysis for prevention of this serious complication.

Contrast agents in patients on dialysis

Contrast media are used to enhance the structural and functional information that is provided by imaging methods. They are used particularly in conventional radiographic (X-ray) investigations, but are also used in magnetic resonance imaging (MRI) and increasingly in ultrasound (US). The water-soluble, iodinated, intravascular radiographic agents are commonly used, and in large doses. They are excreted almost exclusively by the kidney and may have nephrotoxic effects. The use of these agents in patients with renal impairment may potentially be problematic. In this article the chemical composition and pharmacokinetics of these contrast agents are reviewed, as are their potentially toxic effects on the heart, neural tissues, kidney, and endothelium. Their safety for use in the patient with end-stage renal disease (ESRD) and those on dialysis is discussed. This aspect is also addressed briefly for the contrast agents used to augment MRI and US.

Gadolinium chelates in angiography and interventional radiology: a useful alternative to iodinated contrast media for angiography

Gadolinium has physical properties that are well suited for radiographic imaging. Digital subtraction angiography with a gadolinium chelate as contrast medium can provide images of suitable quality for diagnosis and intervention. The overall safety profile of gadolinium-based contrast media is excellent. In particular, these contrast media are well tolerated in patients with renal insufficiency when administered intraarterially in doses of less than 0.3-0.4 mmol per kilogram body weight, with a decreased incidence of contrast medium-induced nephropathy, as compared with similar volumes of iodinated contrast material. The currently available formulations of gadolinium chelates can be injected safely into every arterial and venous structure. However, substantial data are lacking on the intraarterial use of gadolinium in patients with renal insufficiency, particularly at doses that exceed those routinely used in magnetic resonance angiography. Gadolinium chelates in appropriate volumes are useful alternative contrast media in selected high-risk patients undergoing angiographic studies.

Using highly concentrated gadobutrol as an MR contrast agent in patients also requiring hemodialysis: safety and dialysability

OBJECTIVE

The purpose of our study was to assess the safety and dialysability of gadobutrol, a new, electrically neutral, and highly concentrated MR contrast agent, in patients who require hemodialysis.

SUBJECTS AND METHODS

Eleven patients with end-stage renal failure who required ongoing hemodialysis were enrolled in our prospective study. Gadobutrol (1 mol/L) was injected IV at randomly assigned doses of either 0.1 or 0.3 mmol of gadolinium per kilogram of body weight for contrast-enhanced MR imaging. Hematology, clinical chemistry, and vital signs were closely monitored at baseline and during an observation period of 120 hr after the IV injection of gadobutrol. To calculate the dialysability, blood samples were drawn before and after each of three hemodialysis sessions. Additional arterial and venous blood sampling was performed during the first hemodialysis session after 30 and 90 min.

RESULTS

No gadobutrol-related changes in hematology, clinical chemistry, or vital signs were detected at either dose level during the observation period. The mean and the standard deviation for the eliminated fraction of gadobutrol was 68.2% +/- 12.7% after a 3-hr hemodialysis session using a 1.2 m(2) low-flux polysulfone membrane. After three consecutive hemodialysis sessions, the total amount of gadobutrol eliminated increased to 98.0% +/- 1.8%. The mean clearance rates of gadobutrol were 126.1 +/- 17.8 mL/min and 126.6 +/- 24.5 mL/min at 30 and 90 min, respectively.

CONCLUSION

Gadobutrol is effectively removed by three hemodialysis sessions using a low-flux polysulfone membrane. Our study documents initial evidence that gadobutrol can be used safely in hemodialysis patients.

Safety of approved MR contrast media for intravenous injection

In the last 10 years, the use of intravenous contrast media in magnetic resonance (MR) has become well-established clinical practice. Contrast media provide critical additional diagnostic information in many instances. The gadolinium chelates constitute the largest group of MR contrast media and are considered to be very safe. These agents are thought to be safer than nonionic iodinated contrast agents. Unlike x-ray agents, the gadolinium chelates are not nephrotoxic. Minor adverse reactions, including nausea (1%-2% for all agents) and hives (<1% for all agents), occur in a very low percent of cases. Health care personnel should be aware of the (extremely uncommon) potential for severe anaphylactoid reactions in association with the use of MR contrast media and be prepared should complications arise. The four gadolinium chelates currently available worldwide, gadopentetate dimeglumine, gadoteridol, gadodiamide, and gadoterate meglumine, cannot be differentiated on the basis of adverse reactions. Far fewer patients have been examined to date with the two other agents that have widespread approval, mangafodipir trisodium and ferumoxides. These latter two agents are considered to be very safe but have a higher percentage of associated adverse reactions (7%-17% with mangafodipir trisodium and 15% with ferumoxides). This review discusses the safety issues involved with administration of intravenous contrast media in MR imaging, focusing on the six agents (four gadolinium chelates, one manganese chelate, and the last a large iron particle) with widespread use world-wide.

Complications of continuous ambulatory peritoneal dialysis: findings on MR peritoneography

OBJECTIVE

The purpose of this study was to assess the diagnostic value of MR peritoneography in complications of continuous ambulatory peritoneal dialysis.

SUBJECTS AND METHODS

Twenty consecutive patients treated with continuous ambulatory peritoneal dialysis who were clinically suspected of dialysis-related complications were prospectively studied with MR peritoneography. For MR peritoneography, 20 ml of gadodiamide was added to 2000-ml dialysate solution (1.36% glucose) that was instilled into the peritoneal cavity. MR peritoneography was performed with the peritoneal cavity filled (n = 12) and after complete drainage of the contrast material-dialysate mixture (n = 20) on a 1.5-T MR unit with a phased array coil. Imaging included axial T1-weighted fast low-angle shot (TR/TE, 174/4.2) with and without fat saturation and axial and coronal T2-weighted fat-saturated turbo spin-echo (3000/138) sequences. All studies were performed without IV contrast material. Images were reviewed for evidence of peritoneal leaks, hernias, loculated fluid collections, and adhesions.

RESULTS

Abnormal findings were detected in 13 (65%) of 20 patients and included retroperitoneal leaks (n = 6), diaphragmatic leaks (n = 2), catheter exit-site leaks (n = 2), inguinal hernias (n = 2), and peritoneal adhesions (n = 1).

CONCLUSION

MR peritoneography is useful for the evaluation of complications related to continuous ambulatory peritoneal dialysis, and it offers excellent tissue contrast and multiplanar imaging for assessment of complications.

Pharmacokinetics of gadodiamide injection in patients with severe renal insufficiency and patients undergoing hemodialysis or continuous ambulatory peritoneal dialysis

RATIONALE AND OBJECTIVES

The authors performed this study to evaluate the pharmacokinetics, dialysability, and safety of gadodiamide injection in patients with severely reduced renal function not treated with renal replacement therapy and patients undergoing hemodialysis or continuous ambulatory peritoneal dialysis.

MATERIALS AND METHODS

Twenty-seven patients--nine with severely reduced renal function (glomerular filtration rate, 2-10 mL/min), nine undergoing hemodialysis, and nine undergoing continuous ambulatory peritoneal dialysis--were followed up for 5, 8, and 22 days, respectively, after receiving gadodiamide injection (0.1 mmol per kilogram body weight).

RESULTS

Gadodiamide injection caused no changes in renal function. In patients with severely reduced renal function, the elimination half-life of gadodiamide injection was prolonged (34.3 hours +/- 22.9) compared with data in healthy volunteers (1.3 hours +/- 0.25). An average of 65% of the gadodiamide injected was eliminated during a hemodialysis session. After 22 days of continuous ambulatory peritoneal dialysis, 69% of the total amount of gadodiamide was excreted; this reflects the low peritoneal clearance. In all patients, no metabolism or transmetallation of gadodiamide was found. There were no contrast material-related adverse events.

CONCLUSION

Gadodiamide is dialysable and can safely be used in patients with severely impaired renal function or those undergoing hemodialysis or continuous ambulatory peritoneal dialysis. No precautions to increase the elimination are necessary.