After an endoluminal graft repair all bloodflow is ideally excluded from the AAA allowing thrombosis of the AAA outside of the stent graft. An endoleak is an area of the AAA that has been excluded by the endoluminal graft that nonetheless continues to have bloodflow. With an endoleak a treated aneurysm may continue to grow and eventually rupture. Signs of an endoleak can include flow seen outside the graft lumen or an increasing size of the aneurysm post repair. However, ultrasound is not sensitive and the signs can be subtle. Pulsatility of the sac reduces post repair, but still occurs even without an endoleak.

A contrast enhanced multiphase CT examination is used to diagnose the specific type of endoleak and should be the initial choice of investigation if a postoperative complication is suspected. There are 4 types of endoleaks of which two require immediate treatment when diagnosed. Endoleaks occur in approximately a third of AAA’s treated with endoluminal grafts and generally patients have yearly routine imaging surveillance.

There is a 7cm AAA. There is mural thrombus so the lumen is 3cm.

The lumen size has very little relation to whether any symptoms are due to the AAA, and the short term risk of rupture. Lumen size may have a small effect in the long term rate of growth (and therefore rupture). However, in the emergency setting this is irrelevant so the lumen size can be ignored.

When performing ultrasound you may see findings that you were not expecting or are unsure of. In these cases, it is appropriate to seek more experienced advice or further imaging, always remembering and using your clinical judgement. In this case an urgent CT confirmed sigmoid perforation. The aorta is retroperitoneal, so most ruptures do not cause free fluid (if they then rupture into the peritoneal cavity, the tamponade effect is lost and the patient usually rapidly exsanguinates). Although free fluid with particulate matter could represent an aortic rupture with fibrin and clot, if this were the case the patient would be expected to be moribund.

The proximal abdominal aorta can be seen but the distal aorta cannot be adequately visualised, so an AAA cannot be excluded. An “inderminate” finding should be expected in 10-20% of scans when performed by less experienced users.

If the aorta cannot be visualised using the normal abdominal window, then try a lateral approach (along the edge of the rectus sheath, usually requires quite a lot of pressure, find the spine then fan the beam anteriorly until you find the aorta as shown in the video loop) or using the kidney as a window (in this case there is also hydronephrosis from the renal calculus that was the cause of this patient’s symptoms).

Aortic dissection – there is an echogenic flap with in the lumen. It does not have the appearance of an artefact

Initial management of distal dissection is control of blood pressure with analgesia, B blockers and other anti-hypertensives. CT should be performed to confirm the diagnosis and the extent of the dissection as if the ascending aorta is involved (type A) then cardiothoracic repair may be required.

The brighter than normal endoluminal stent can be seen, most easily below the level of the ‘trouser legs’ which sit inside the native aorta (above the native aorta bifurcation)

Ultrasound may show findings diagnostic of endovascular stent leak or complication such as:
large endovascular leaks may be seen with colour doppler ultrasound,
if the native aorta is larger than on previous images it suggests endovascular leak,
retroperitoneal haematoma suggests rupture due to endovascular leak.
However, the absence of these does not exclude endovascular stent complications, and it is often technically challenging to see these findings (beyond the scope of basic ultrasound users). Ultrasound thus has a very limited role in the evaluation of an acutely unwell patient who has had an endovascular repair. In this case, there was no leak and the aneurysm diameter was stable.