The patient had undergone percutaneous transfemoral placement of a stent graft for a 47mm large aneurysm of the abdominal aorta (below the level of the renal arteries). At that time, no complication or difficulty developed and a negative Computed Tomography (CT) survey had been obtained three days later.
The patient was asymptomatic at the time of our observation. A 3-month follow-up ultrasound (US) examination was requested. The sac had slightly increased in size (transverse diameter 51mm). The aorto-iliac graft could be recognised in place but a subtle inhomogeneity of the periprosthetic thrombus was noted. The operator decided to immediately perform a contrast-enhanced US examination.
The study was carried out with contrast-specific software (Contrast Tuned ImagingTM, CnTI – Esaote, Genoa, Italy) and a devoted US unit (EsaTuneTM, Esaote). The following parameters were used: 3.5MHz frequency (convex probe), low-power beam (mechanical index 0.08, derated pressure 50MPa), beam focus at the deeper aspect of the region of interest, continuous acquisition mode (starting immediately after the contrast agent injection and lasting for 5 minutes).
A sulphur-exafluoride-based agent (SonoVueTM, Bracco, Milan, Italy) was rapidly injected through a 20G needle and an antecubital vein. A volume of 2.4mL was administered and a 5mL saline flush followed.
About 20 seconds after the injection, immediately after endoprosthesis lumen opacification, an evident inflow within the aneurysmal sac was noted. This contrast leakage appeared at the mid-level of the sac, with no relationship to the proximal and distal ends of the graft. It arose from the posterior aspect of the prosthesis, then spread anteriorly. The sac enhancement persisted for several minutes though intermittent high-intensity flashes were needed to renew the luminal and the sac contrast signal. This enhancement corresponded to the level of baseline US inhomogeneity. No outflow sign was found.
A confirmatory biphasic CT study was performed 2 days later. A Somatom Plus 4 Expert unit (Siemens, Erlangen, Germany) was used. The following scanning parameters were employed: 0.75 revolution time, 3mm thickness, 4.5mm table feed, 1mm reconstruction interval, 25sec start delay (early phase), 120sec start delay (late phase). A breath-hold acquisition from the level of the coeliac trunk to the level of the external iliac arteries was obtained.
A non-ionic contrast agent (iomeprol, Bracco) was injected via a 20G peripheral vein needle and an automatic injector (Angiomat 6000, Liebel-Flarsheim, Cincinnati, USA): 130mL volume, 350mgI/mL concentration, and 4mL/sec rate.
No relevant abnormality could be detected on non-enhanced scans. On CT angiography images a clear contrast medium leakage was detectable, coming from the posterior face of the mid-level left prosthetic channel. No significant collateral feeding vessel was found and no evidence of out-flow was present.
The patient underwent endovascular secondary graft implantation within the aortic sac and recovered without any complication.