Patients were aged between 63 and 78 years and presented,
as risk factors,
hypertension (n:7,
100 %),
smoke habit (n:1,
14%) and dislypidemia (n:1,
14%).
Five of the eight aneurysms were placed
on left renal artery (63%) ,
three on right side (37%) and all lesions presented the following characteristics: diameter of the sac between 29 and 55 mm (mean = 32.5 5 mm ) (Table I) characterized by a saccular shape (100%),
presence of an associated stenosis in two of the eight lesions (25%),
average length of the renal artery behind and forward the neck of the aneurysm of 9 ± 3 mm,
average length of the neck of 5 ± 2 mm and average diameters of 3 ± 2mm,
thrombosis was present in two lesions while calcifications on aneurysm wall in one patient.
No patients showed direct or indirect signs of active or recent bleeding. Technical success was obtained in all patients (100%) and no specific complications related to the procedure,
as device dislodgement,
renal parenchyma ischemia,
type II endoleak and aneurysm reperfusion,
and no complications related to the endovascular procedure,
as hematoma,
haemorrhage and infections occurred.
All lesions were placed in the middle part of renal artery and no renal branches were sacrificed during stent deployment.
Mean follow up time was 28±5 months, although two patients were lost after two years follow-up.
At follow up the instrumental exams have shown covered stents patency,
absence of endoleaks,
no re-stenosis inside the vessels and a decrease of the aneurysm diameters ( 10% at 6 month,
15% at 12 month follow up).
In only one patient (14%),
where the Advanta covered stent was deployed,
a restricted area on superior pole of the right kidney characterized by an absent contrast enhancement was observed in CTA at six months follow-up and unchanged in the following CTA examinations.
This lesion was not present
in the CTA at 1 month follow-up and was probably caused by suspension of the after-procedural double anti-aggregation therapy,
due to surgical removal of bladder polyp at 4 weeks since endovascular procedure.
However the stent-graft remain patent at long-term follow-up and a slight
increase of blood pressure as unique clinical sign was observed (patient 2).
Clinical improvement was achieved in all patients,
especially headache and dizziness which were not observed in follow-up period,
and backache which disappeared in approximately 2 weeks.
All patients didn’t show any micro- or macro-haematuria episode immediately after procedure.
We achieved a decrease of blood pressure (103.9±26.6 mmHg at 3 months,
106.4±27 mmHg at 12 months follow-up) and drug therapy adaptation with an improvement of drugs posology (0.9±0.8 at 3 months,
0.4±0.5 at 12 months follow-up) (Table II).
The GFR significantly increased in all patients at 6 months after the procedure,
and it slightly increased after 12 and 24 months (table II).
The traditional treatment of renal artery aneurysm is represented by surgery,
especially aneuysmorrhaphy,
aortorenal bypass,
renorenal interposition,
patch angioplasty,
ex vivo repair and reinplantation,
and nephrectomy (02,04,16),
with a mortality and morbidity rate estimated in about 10% in excellent center (23).
Potential complications include death,
need for nephrectomy,
branch occlusion,
ureteral stricture,
or postoperative graft occlusion (04).
The percutaneous endovascular treatment involves the exclusion of the aneurysm with covered stent or metallic microcoil deployment (02,11,12,19,21-27).
Coils can be placed within the aneurysm to develop thrombosis of the lesion and to maintain the blood flow in the renal artery or,
in aneurysm difficult to reach,
they can be placed in the feeding artery with subsequent parenchyma ischemia.
Some authors,
like Rao Gutta et Al and Klein et Al,
showed good results obtained with microcoils (16,19),
but the distal embolization risk may reach high percentage,
up to 21%,
with the subsequent end-organ infarct (06,08,12-14,20,21).
Moreover other coil-related complications are described,
as continuous transmission of blood pressure inside
the sac with high rupture risk exposure (12,13,20) and the occurrence of recanalization,
between 9 and 42.9%,
which can cause enlargement of the aneurismatic sac,
due to the underfilling following the presence of mural thrombus (06,
10,
28).
However,
coils placement should be considered as primary treatment in patients with aneurysms positioned in the distal branches and with complex anatomy.
The graft stent deployment allows the exclusion of the aneurysm with a low rupture and dissection risk,
and a low peri- and post-procedure complications rate with a high technical success rate (02,11-13,21-27).
In accordance to the classification of RAAs reported by Rundback et al.
(11,13,26),
in our opinion, saccular aneurysms arising from the main branch with a small neck (type 1) have to be treated percutaneously using covered stent.
The type 1 aneurysm,
following Rundback classification,
is
characterized by a sacciform anatomy,
a narrow and wide neck,
with a juxtarenal position,
remote from bifurcation of the main branch and outside the kidney.
Furthermore,
in these aneurysms,
a sufficient requested sealing zone for stent placement was present (10,15).
In this fashion,
it is possible to preserve renal perfusion and,
at the same time,
to treat stenosis and RAA (7). Stent-grafts have the advantage of excluding the aneurysm from systemic blood flow.
This technique allow to maintain the flow to the target organ and to exclude completely the aneurismatic
sac; in fact incomplete embolization could cause aneurysm reperfusion,
with a new needed procedure,
and altered arterial flow with subsequent renal ischemic suffering and arterial hypertension (05-07).
Some limitations about stent deployment are present in literature,
especially
in vessel with a diameter lower than 6 mm and tortuous anatomy due to covered stents bulky and stiff structure (05,06,09,10,28).
However no studies with long term follow up are available for covered stent placement in renal arteries.
Sprouse et Al.
followed up to 2 years a case of covered
stent placed in a renal artery for a venous fistula with good results and longer term studies of covered stents in coronary arteries have shown excellent outcome with late restenosis rate of 28% at 10 years (29) .
In our case history with long-term follow-up,
no cases of restenosis occurred.
About the bulky and stiff structure of the placed devices,
we facilitated the advancement of the covered stent in complex anatomy vessels with two guidewires in renal artery and a transbrachial approach in order to achieve a stable carrier system,
a sufficient pushability and a better control over the shaft.
Rossi et al and Laganà et al.
reported a stiff guidewire placement to obviate to these drawbacks (10,14). The graft stent choice depends on vessel anatomy,
technical characteristics of the devices and experience of the author.
In our experience we used self- and balloon-expandable graft-stent,
in particular Symbiot,
Jostent peripheral stent-graft,
Advanta V12 and Direct-stent. The Jostent peripheral stent-graft,
Advanta V12 and Direct-stent stent-graft are balloon expandable stents which should be used in vessels with simple anatomy and large diameter.
The advantages
involve a precise deployment on the site of lesion with an high radial strength that allows a total exclusion of the aneurysm and,
moreover,
in patient with renal stenosis,
allows the physiologic
vessel patency restore.
A disadvantage in balloon expandable stent placement is the high profile of the device,
compared to the self-expandable device,
which requires a protection sheath and a guide catheter with larger size (02).
The high profile,
about 7 Fr or more,
except Advanta V12 device, represents a limitation in patients with vasculopathy,
because the device can determine a trauma in the passage through its endovascular route,
especially at the level of renal artery ostium where a
possible trauma can evolve in dissection and,
afterwards,
in occlusion (26).
We have tried to limit this complication by the use of Destination sheath reducing the sizes of the guiding catheter.
The vessel occlusion can also be a result of a dislodgement or migration of the stent,
when the stent is
placed on the ostium of a segmental artery,
or when the stent remains undeployed inside the vessel 02.
In our experience we used in two cases Jostent peripheral stent-graft,
in two cases Direct-stent stent-graft,
in one case the Advanta V12.
In medical literature some authors used Jostent peripheral stent-graft with good results in term of precise placement,
exclusion of aneurismatic sac and clinical improvement (04,11,14,21-24).
In particular Jostent placement was reported by Tan et al.
and Pershad et al.
in case reports in which the deployment has been performed in distal renal bifurcation,
resulting in the sacrifice of a distal branch vessel with subsequent partial renal parenchyma ischemia with poor patient discomfort (04,21).
In the cited studies complications during Jostent deployment are not underlined.
To the best of our knowledge any Advanta V12 and Direct-stent weren’t placed in patients with primary renal artery aneurysm.
Concerning the self expandable stent,
Symbiot stent is deployed in renal artery with a complex anatomy,
because it is simpler than other devices to advance in tortuous vessels for the lower dimension and major flexibility,
excellent especially in vasculopathic patients.
However,
due to its structure,
it is characterized by a low tensile strength body and,
consequently,
a weaker adhesion to vessel wall,
which require some dilatations after placement.
Moreover the disadvantages are determined by a difficult deployment,
due to possible foreshortening and dislodgment of the stent which can determine,
ultimately,
occlusion.
In our experience we used the Symbiot stent in three patients.
Two stents were placed in one patient in both renal arteries because the presence of bilateral aneurysms.
In medical literature a Fluency device deployment was described by Klonaris et al,
even if this self-expandable stent-graft has a higher caliber and requests a simpler vessel anatomy to be advanced and deployed (02).
The presence of clinical symptoms and the position of lesions on middle segment of the renal artery represent not common features in this pathology,
reflecting a lack of power of our sample size.
In this setting it is difficult to apply our results on general population,
however we obtained about the long term follow up of covered stent placement in renal arteries.