Evolving clinical applications of contrast-enhanced ultrasound (CEUS) in the abdominal aorta

Abstract

Ultrasound (US) represents the initial modality in the workup of abdominal aortic pathology based on the plethora of advantages including widespread availability, low cost, safety profile and repeatability. However, US has inherent limitations including limited spatial information of pathologic processes to neighboring structures, lower sensitivity to slow blood flow and aortic luminal irregularities. For evaluation of aortic pathology angiography has long been considered the gold standard. Non-invasive cross-sectional imaging techniques like computed tomography angiography (CTA) and magnetic resonance angiography (MRA) have gradually replaced interventional angiography for the evaluation of aorta, currently being regarded as the diagnostic imaging modalities of choice for diagnosis of virtually every aortic disease. Interventional angiography is currently primarily performed for treatment purposes of aortic pathology. The introduction of microbubbles as ultrasonographic contrast agents has rendered contrast-enhanced ultrasound (CEUS) an evolving valuable complementary technique with markedly increased diagnostic accuracy for certain aortic applications. CEUS is characterized by the potential to be performed in patients with impaired renal function. Due to its superior spatial and temporal resolution, ability for prolonged scanning and dynamic and real-time imaging, it provides clinically significant additional information compared to the standard Duplex US. The purpose of this paper is to discuss the currently available literature regarding abdominal aortic applications of CEUS, briefly elaborate on CEUS technique and safety and present cases in order to illustrate the added value in aortic pathologies. Conditions discussed include abdominal aortic aneurysm (AAA), aneurysm rupture, aneurysm surveillance after endovascular repair, dissection and aortitis.

Keywords: Aneurysm; aorta; aortitis; endoleak; ultrasonography.

Figure 1

An 80-year-old male patient underwent EVAR 1 year ago. On standard ultrasound shrinking of the aneurysm sack from 6 to 4.8 cm (maximal diameter) could be documented. CEUS revealed an endoleak type 2 with collateral flow through the inferior mesenteric artery. (A) CEUS imaging on cross-sectional view 31 seconds after contrast agent bolus injection (SonoVue 1 mL) with enhancement of both stent grafts. (B) CEUS imaging on cross-sectional view 40 s after contrast agent bolus injection with additional enhancement of the ventral part of the aneurysm sac (endoleak). (C) CEUS imaging on longitudinal few with endoleak filling from the inferior mesenteric artery (endoleak type 2). No further treatment was performed based on the shrinking of the aneurysmal sac. One year later further shrinking could be documented to a diameter of 4.4 cm. (D) On CEUS imaging no endoleak could be demonstrated due to spontaneously occlusion of the endoleak. EVAR, endovascular aneurysm repair; CEUS, contrast-enhanced ultrasound.

Figure 2

An 83-year-old male patient underwent EVAR 2 years ago. (A) Color coded Duplex follow-up ultrasound revealed no endoleak; (B) additional CEUS imaging revealed low flow endoleak type 2 with collateral flow through a lumbar artery. EVAR, endovascular aneurysm repair; CEUS, contrast-enhanced ultrasound.

Figure 3

An 85-year-old male patient underwent EVAR 6 years ago. (A) Color coded Duplex follow-up ultrasound revealed no endoleak; (B) additional CEUS imaging revealed low flow endoleak type 2 with collateral flow through a lumbar artery. EVAR, endovascular aneurysm repair; CEUS, contrast-enhanced ultrasound.

Figure 4

A 70-year-old male patient underwent EVAR 6 months ago. Standard and CEUS revealed an endoleak type I with collateral flow through a lumbar artery. (A) Duplex ultrasound with typical to-and-fro signal in the region of a lumbal artery; (B) CEUS imaging revealed a huge enhancement within the aneurysm sac; (C) catheter based embolization of the endoleak by using micro-catheter through the internal iliac artery and lumbal artery with Onyx and Histoacryl; (D) CEUS imaging after the intervention revealed no endoleak. EVAR, endovascular aneurysm repair; CEUS, contrast-enhanced ultrasound.

Figure 5

An 84-year-old female patient underwent EVAR 5 years ago. Follow-up imaging studies revealed an increase of the aneurysma sac during the last year. CEUS imaging demonstrated an endoleak type 2 with collateral flow through a lumbar artery. (A) CEUS imaging on cross-sectional few 30 s after bolus injection (1 mL SonoVue) with enhancement of the aneurysm sac starting from a lumbar artery; (B) enhancement of the endoleak within the aneurysm sac; (C) transabdominal direct punctuation of the endoleak and embolization with Onyx; (D) CEUS imaging during the procedure demonstrated complete occlusion of the endoleak. EVAR, endovascular aneurysm repair; CEUS, contrast-enhanced ultrasound.

Figure 6

A 70-year-old female patient with abdominal pain had diagnosis of chronic peri-aortitis one month ago. Since then oral therapy with prednisone 60 mg per day were started. Follow-up standard B-mode ultrasound revealed persistent peri-aortal hypoechoic tissue around the ventral part of the abdominal aorta on the cross-sectional few (A) and longitudinal view (B). Corresponding CEUS imaging even better delineate this periaortic vessel wall thickening (C and D). Only moderate enhancement within this tissue on CEUS imaging could be demonstrated based on a decreased inflammatory activation due to the anti-inflammatory treatment. CEUS, contrast-enhanced ultrasound.