Contrast ultrasound (CEUS) contrast-enhanced ultrasound -is a non-invasive and non-ionizing radiological imaging method with the use of a contrast medium.
Compared to conventional ultrasound, it enables better visualization of pathological changes in the liver and extrahepatic organs (most often the aorta, kidneys and spleen), both in adults and in children.
CEUS is an important part of the diagnostic and therapeutic procedure in monitoring complications after endovascular treatment of pathological changes in the aorta (eng. -endovascular aortic repair, EVAR). Its main indication is detection and monitoring endoleak after EVAR.
Procedure
Recommendations from the literature are to use a convex ultrasound probe with a frequency of 1 to 9 MHz with a low mechanical index (from 0.06 to 1.0). 1 to 2.4 mL of contrast agent is administered in the form of a bolus through the previously placed intravenous route and cannula of 18 to 20 G, and then 5 to 10 mL of physiological solution is administered.
The cannula must be placed parallel to the blood stream, never at an angle, because in this way the contrast microbubbles will rupture during contrast administration.
It is recommended to use the double bolus technique – 1 mL is used to assess the patency of the set of the stent-graft and locating the endoleakand with an interval of five minutes, another 1 mL is applied to assess the type endoleak (I to V). SonoVue® (sulfur hexafluoride) is the only approved contrast agent for follow-up CEUS examinations after EVAR.
The rate of documented side effects (headache, skin redness, palpitations, paresthesias, hypotension, nausea, vomiting, abdominal pain) is very low (0.125%), and the rate of life-threatening side effects, such as anaphylactic reaction, is even lower (0, 0086%).
Who is contrast ultrasound intended for?
CEUS is safe for patients with impaired renal function because the contrast agent is eliminated from the body through the respiratory tract. CEUS is contraindicated in patients with increased sensitivity to sulfur-hexafluoride, right-left shunt, advanced pulmonary and systemic hypertension, and acute respiratory distress syndrome.
Special caution is required in patients with unstable ischemic heart disease, a recent episode of acute coronary events, heart failure, arrhythmias or acute inflammatory events in the body.
Patient monitoring
In the algorithm of monitoring patients after EVAR, the gold standard is still computerized tomographic angiography (CTA) which needs to be done 30 days after EVAR.
In the case of a normal finding, the CTA is repeated in 12 months, and in the case of a pathological finding, the search must be repeated in 6 months, that is, according to the clinical indication, a reintervention can be performed.
If the condition of the aorta is stable after the first year of control CTAs, further follow-up with CEUS is recommended, and CTA should be performed once every 5 years. The goal is to reduce the use of contrast media with a potentially nephrotoxic effect and cumulative exposure to ionizing radiation.