Download this article's Factoid in PDF (& PPT for Gold Subscribers)

Second-generation contrast-enhanced ultrasound is nearly as effective as computed tomographic angiography (CTA) for detecting endoleaks in patients who have undergone endovascular repair of abdominal aortic aneurysms (EVAR). The noninvasive tool can be integrated into follow-up in select, stable patient populations, thereby reducing exposure to radiation, according to a small prospective study published online May 15, 2012, ahead of print in Radiology.

Rosa Gilabert, MD, PhD, of the University of Barcelona (Barcelona, Spain), and colleagues performed CTA and contrast-enhanced ultrasound on 35 patients at 1 and 6 months after EVAR. The tests were repeated yearly thereafter. The sensitivity and specificity as well as the positive and negative predictive values for detecting endoleaks were calculated using CTA as the reference standard.

Angiography was performed in patients who had type II endoleaks with an increase in aneurysm sac size as well as in patients with type I or type III endoleaks.

No Clinically Significant Endoleak Overlooked

Overall, 126 CTA and contrast-enhanced ultrasound tests were performed. CTA detected 34 leaks in 16 patients, while ultrasound detected 33 of the 34 leaks. Both methods achieved similar levels of accuracy (table 1).

Table 1. Endoleak Detection with Contrast-Enhanced Ultrasound

In an e-mail communication with TCTMD, Dr. Gilabert said the only endoleak missed by contrast-enhanced ultrasound “was a small one detected in a patient with a stable aneurysm sac size. And it was identified by ultrasound in the next follow-up study.”

She added that 7 endoleaks were misclassified using ultrasound. “In four of them, the time span between the CTA and contrast-enhanced ultrasound was greater than 2 weeks, and the dynamic nature of the endoleaks [could explain the discrepancy],” Dr. Gilabert said. “According to these results, once an endoleak is diagnosed by contrast-enhanced ultrasound, a CTA can be carried out in order to confirm its origin. This is basic [practice] in cases in which aneurysm sac size increases and angiographic intervention is mandatory.”

A Viable Alternative to CTA

According to Dr. Gilabert the results of the study “support the use of contrast-enhanced ultrasound in EVAR follow-up as an alternative diagnostic tool to CTA, not a replacement.”

She noted several appropriate scenarios for the use of ultrasound, such as patients with suboptimal renal function precluding the administration of iodinated contrast material or in the follow-up of patients with stable or decreasing aneurysm sac size and no evidence of endoleak on CTA 1 year after EVAR.

“The clinical practice guidelines of the European Society for Vascular Surgery support [follow-up using] color Doppler ultrasound together with plain abdominal radiographs, if at 12 months after EVAR there is no endoleak and a stable or shrinking aneurysm sac. Aneurysm sac diameter, endograft patency, and endoleak can be assessed by color Doppler ultrasound, while plain abdominal radiographs allow [for] the evaluation of endograft characteristics not identifiable by color Doppler ultrasound, such as graft migration and limb kinking,” Dr. Gilabert continued. “Contrast-enhanced ultrasound also [aids in the evaluation of] endograft patency, but it has a greater sensitivity in endoleak detection. The performance of contrast-enhanced ultrasound together with plain abdominal radiographs will offer a more comprehensive EVAR surveillance without the risks associated with repeated CTA surveillance studies.”

Benefits of Avoiding CTA

According to Dr. Gilabert minimizing the use of CTA not only reduces patient exposure to radiation but also helps preserve renal function.

“Atherosclerosis is a systemic disease that affects all arterial beds, thus impaired renal function is not uncommon in patients undergoing EVAR,” she added. “EVAR attenuates the perioperative renal injury associated with open repair; but in the long term, renal function deteriorates more quickly after EVAR, and the fall in glomerular filtration rate is independently associated with EVAR when compared with open repair. [One] possible explanation for this deterioration . . . [is] the repeated renal contrast agent injury that results from intensive CT follow-up.”

Still, she noted, contrast-enhanced ultrasound is not for everyone. Contraindications to the administration of the contrast agent include heart failure, right-to-left shunt, severe chronic bronchopulmonary disorder, severe pulmonary hypertension, and uncontrolled hypertension. In addition, obesity and gas-filled bowel can interfere with a contrast-enhanced ultrasound evaluation.

Related Stories:

• CT and MRA for Endovascular Repair
• Imaging and Intervention in Aortic Aneurysms

Click here for a listing of companies that provide support to the Cardiovascular Research Foundation, owner and operator of TCTMD.