Ultrasound outperforms CTA in endoleak classification

Contrast-enhanced ultrasound may offer more sensitive and more detailed detection of endoleaks for aortic stent-grafts than CT angiography, according to research presented at the 2006 RSNA meeting. The two techniques might best be used in combination, said researchers from the University of Insubria in Varese, Italy.

Dr. Gianpaolo Carrafiello and colleagues performed both CTA and CE ultrasound on 32 patients with 33 endoleaks from 2002 to 2006. Endoleaks around stents were identified and evaluated during regular follow-up care using CTA, the current standard. Patients then underwent CE ultrasound with a second-generation contrast agent (Sonovue) to compare the two methods.

CE ultrasound and CTA classifications agreed in 26 of the 33 cases. All were type II endoleaks, which are the most common type and need continued monitoring, although some resolve without intervention.

Digital subtraction angiography was used in the seven cases in which CTA and CE ultrasound results conflicted. CTA classified two leaks as type II that CE ultrasound classified as type I. Type I endoleaks need immediate intervention, and DSA later confirmed the ultrasound classification. Three endoleaks were classified as type III by CTA but type II by ultrasound. Type III endoleaks, which are more rare, require repair with an additional endograft. Once again, DSA confirmed the ultrasound classification. Finally, CTA missed two type II endoleaks that ultrasound detected and DSA confirmed.

The authors concluded that CE ultrasound is more specific than CTA in the classification of endoleaks. CE ultrasound shows blood flow in real-time, making it easier to pin down the origin of endoleaks, clarify their type, and allow more precise therapeutic planning. CTA does have advantages over ultrasound, however.

"CT angiography enables a more precise evaluation of aneurysm morphologic changes, aneurysm sac diameter, graft anchorage, and integrity that is unobtainable with ultrasonography," Carrafiello said.

CE ultrasound has more limited costs and avoids exposure to ionizing radiation, but obesity and bowel gas can interfere with the procedure and patient collaboration is required.

"Contrast-enhanced ultrasound could be used along with CT angiography when the latter reveals the presence of an endoleak, to provide a better characterization of it or to monitor a type II endoleak, reducing the use of CT angiography with consequent reduction of costs and exposure to radiation," Carrafiello said.