[Nephrogenic systemic fibrosis]

Dynamic CTA in Native Kidneys Using a Multiphase CT Protocol-Potential of Significant Reduction of Contrast Medium

RATIONALE AND OBJECTIVE

The objective of this study was to assess an optimized renal multiphase computed tomography angiography (MP-CTA) protocol regarding reduction of contrast volume.

MATERIALS AND METHODS

Thirty patients underwent MP-CTA (12 phases, every 3.5 seconds, 80 kV/120 mAs) using 30 mL of contrast medium. The quality of MP-CTA was assessed quantitatively measuring vessel attenuation, image noise, and contrast-to-noise ratio. MP-CTA was evaluated qualitatively regarding depiction of vessels, cortex differentiation, and motion artifacts (grades 1-4, 1 = best). Mean effective radiation dose was registered. Results were compared to standard renal computed tomography angiography (CTA) (80 mL). Student t test was applied, if variables followed normal distribution. For other variables, nonparametric Mann-Whitney U test was used.

RESULTS

All acquisitions were successfully performed, and no patient had to be excluded from the study. MP-CTA enabled high attenuation (aorta: 503 ± 91 HU, renal arteries: 450 ± 73 HU/456 ± 72 HU) at adequate image noise (13.7 ± 1.5) and good contrast-to-noise ratio (34.2 ± 10.2). Good attenuation of renal veins was observed (286 ± 43 HU/282 ± 42 HU). Arterial enhancement was significantly higher compared to renal CTA (aorta: 396 ± 90 HU, renal arteries: 331 ± 74 HU/333 ± 80 HU; P < .001). MP-CTA protocol enabled good image quality of renal arteries (1.5 ± 0.6) and veins (1.7 ± 0.6). Cortex differentiation and motion artifacts were ranked 1.8 ± 0.8 and 1.6 ± 0.8. The mean effective radiation dose was 9 mSv (MP-CTA).

CONCLUSIONS

Compared to standard renal CTA, the renal MP-CTA enabled the significant reduction of contrast volume and simultaneously provided a significantly higher arterial attenuation.

Radiological Central Vein Treatment in Vascular Access

In the last decades, the percutaneous interventional approach for the treatment of central venous obstructions (CVO) has become increasingly popular as the treatment of first choice because of its minimal invasiveness and reported success rates. CVOs are caused by a diverse spectrum of diseases which can be broadly categorized into two principal eliciting genera, either benign or malignant obstructions. The large group of benign venous obstructions includes the increasing number of end-stage renal disease patients with vascular access related complications. Due to the invasiveness and complexity of thoracic surgery for benign CVOs, the less invasive percutaneous interventional therapy can generally be considered the preferred treatment option. Initially, the radiological intervention consisted of balloon angioplasty alone, subsequently additional stent placement was applied. This was advocated as either primary placement or secondary in cases of elastic recoil or residual stenosis after percutaneous transluminal angioplasty (PTA). The efficacy of angioplasty of CVO in patients with vascular accesses, either with or without stenting, has been addressed by various studies. Overall, reports indicate an initial technical and clinical success rate above 95% and satisfactory patency rates. However, systematic follow-up and frequent re-interventions are necessary to maintain vascular patency to achieve long-term success.

Minimizing risk of nephrogenic systemic fibrosis in cardiovascular magnetic resonance

Nephrogenic Systemic Fibrosis is a rare condition appearing only in patients with severe renal impairment or failure and presents with dermal lesions and involvement of internal organs. Although many cases are mild, an estimated 5% have a progressive debilitating course. To date, there is no known effective treatment thus stressing the necessity of ample prevention measures. An association with the use of Gadolinium based contrast agents (GBCA) makes Nephrogenic Systemic Fibrosis a potential side effect of contrast enhanced magnetic resonance imaging and offers the opportunity for prevention by limiting use of gadolinium based contrast agents in renal failure patients. In itself toxic, Gadolinium is embedded into chelates that allow its safe use as a contrast agent. One NSF theory is that Gadolinium chelates distribute into the extracellular fluid compartment and set Gadolinium ions free, depending on multiple factors among which the duration of chelates exposure is directly related to the renal function. Major medical societies both in Europe and in North America have developed guidelines for the usage of GBCA. Since the establishment of these guidelines and the increased general awareness of this condition, the occurrence of NSF has been nearly eliminated. Giving an overview over the current knowledge of NSF pathobiochemistry, pathogenesis and treatment options this review focuses on the guidelines of the European Medicines Agency, the European Society of Urogenital Radiology, the FDA and the American College of Radiology from 2008 up to 2011 and the transfer of this knowledge into every day practice.