CT is the preferred method,
because its availability,
speed and spatial resolution,
although there are many descriptions using ultrasound/doppler or enhanced MRI.
We found an article using unenhanced CT with aneurysm volumetric calculation,
considered to be normal a maximum increase of 2% by volume,
due to error from estimation,
and in case of a variation of >2%,
the patient should be evaluated with standard enhanced CT technique.
Studies describe o recommend to assess at 1st month,
3rd month,
6th month and if no abnormalities are detected,
continue with annual examinations,
leaks with no significant sac enlargement can be assessed every 6 months until two years,
unless it is demonstrated that needs revision.
Our protocol consists: the first study includes an unenhanced CT and an arterial phase; follow up studies include only the arterial acquisition.
We study our patients in a Brilliance 64-slice CT (Philips,
Amsterdam The Netherlands) with 120kV,
250-300mA/s,
with bolus detection technique in the descending aorta,
(150HU threshold),
a gantry rotation speed of 0.5s,
a pitch of 0.983,
with reconstruction protocol of 2 mm.
slab thick with overlap of 1 mm.
(1mm real resolution in Z axis).
The studies were performed with 70-80ml of 400mg/ml Iomeprol (Iomeron ®,
Rovi,
Madrid,
Spain) with bolus chase with 50mL of normal saline,
using a power injector.
In the first study,
we must identify the position of the endoprothesis components and the existence of new images that can be considered normal or pathological.
Usual aftercare findings,
not pathological:
1.
- The proximal anchoring zone of the prosthesis,
is in the origin of the renal arteries: a relatively frequent finding and carries no long-term complications in most cases.
Fig. 1
2.
- Periprosthetic diffuse hyperdensity (between the prosthesis and the aneurysm mural thrombus),
must be present in the precontrast study,
and appears to be due to acute thrombosis of the periprosthetic aneurysmatic lumen.
Fig. 2
3.
- Appearance of high density images in the mural thrombus,
may be due to aortic calcium plaques that have been moved during treatment.
Fig. 3
It is important to compare with the baseline study (without contrast),
and thus,
distinguish them from leaking.
4.
– Periprosthetic gas in the aneurysm sac,
is usually a finding,
does not imply any morbidity.
Fig. 4
5.
- It is essential to become familiar,
with the type of endoprothesis,
that was used in each patient,
since different radiological references or structure may suggest that there are fractures or that an inadequate assembly exists between the different components,
it is important to remember that the coated part of the prosthesis usually have markings that delimit it,
since this material is not visible with CT.
Fig. 5
Endoleaks or leaks are the existence of contrast material outside the prosthesis.
There are five types:
- Type I: may be proximal (type Ia) or distal (type Ib) are those which occur secondary to inadequate anchoring of the prosthesis to the walls of the neck,
or between the iliac extensions.
Usually produce increased aneurysm size and tension and require early treatment.
Repair is usually done with a balloon or extension of the prosthesis.
In prosthetic unilateral aorto-iliac bypass,
with femorofemoral bypass and proximal occlusion of the unused iliac,
patency of this,
it is considered a leak type Ic,
promptly treatment is recommended too.
Fig. 6
- Type II: are due to retrograde filling from arteries covered by the stent (typical of the inferior mesenteric artery or lumbar aortic branches).
They carry low risk and are usually followed to assess,
whether they enlarge or close spontaneously (common).
Is important to verify that aneurysm diameter stays stable.
Fig. 7
- Type III: caused by failure of the coupling portions of the stent,
in those cases in which the prosthesis is a bilateral aorto-iliac,
may occur between the extension prosthesis and the iliac extensions,
a fractured stent could will produce the same problem.
They may also be caused by improper handling of the prosthesis.
Also require early treatment,
since they involve risk of aneurysm growth.
Fig. 8
- Type IV: described as a cloudy or hazy classic enhancement in intraoperative angiography,
occurred with the first materials used,
not being used in the new prosthesis and which at present,
are rare,
also would require early treatment.
- Type V: endotension: the only evidence of treatment failure is an significantly increasing size of the aneurysm,
when compared with past controls.
Could be assessed with other techniques,
including arteriography,
contrast enhanced ultrasound (CEUS) or MRI.
Adding dynamic evaluation,
with MRI and US (saving radiation),
could help to identify the possible false negative CT Angiography.
Fig. 9
Other complications that can occur:
1.
- Reduced kidney size,
although rare,
a significant stenosis of a renal artery,
that´s only noticed with progressive renal parenchymal atrophy.
Fig. 10
2.
- Stent thrombosis: affecting the body or limbs of the prosthesis.
Must be distinguished from those cases in which the vascular plug used to occlude an iliac common artery,
could look like a stent,
in a patient with unilateral aorto-iliac bypass.
3.
- Bilateral occlusion / thrombosis of hypogastric: may occur in patients with very tortuous anatomy or advanced peripheral artery disease.
This issue must be sought and reported and also any signs of abdominal visceral pathology (mainly left colitis).
There are reports of ischemic colitis,
in patients with occlusion of an enlarged inferior mesenteric artery (IMA),
which could be a sign of a pre-existing significant stenosis,
in celiac trunk or superior mesenteric artery or hypogastric,
and thus causing visceral ischemia.
The identification of these complications will guide a review or repair intervention,
allowing reinstate or extend the usefulness and functionality of treatment.
A rare situation but with serious morbidity and mortality is associated prosthetic infection,
can be classified as:
- Early (before 4 months after surgery) clinically manifests as an acute infection,
high fever,
systemic compromise,
leukocytosis and increased acute phase reactants (blood cultures are of limited use).
- Late (more than 4 months postoperatively) cases have been described in which the diagnosis was made between 7 days and 10 years.
The clinical situation is often characterized by pseudoaneurysms,
gastrointestinal bleeding associated with aorto-enteric fistula,
hydronephrosis,
osteomyelitis or periaortic fibrosis,
usually in the absence of fever.
We suspect the existence of an infection when there is periaortic tissue stranding,
with loss of cleavage planes with the surrounding tissues,
if a soft tissue density exists,
a progressive peri-aortic gas collection,
or when changes occur to the sac in an accelerated evolution.
While these findings may be suggestive,
traditionally used scintigraphy with 99mTc-labeled leukocytes,
or pre-antibiotic diagnostic aspiration and more recently,
PET-CT to establish its inflammatory origin.