1 Department of Diagnostic Radiology, Tübingen University Hospital, Tübingen, 2 Department of Internal Medicine II, Nephrology and Dialysis, St Josephs Hospital, Berlin and 3 Center for Diagnostic Radiology and Minimally Invasive Therapy, Jewish Hospital Berlin, Berlin, Germany
Correspondence and offprint requests to: Dr Benjamin Wiesinger, Department of Diagnostic Radiology, Hoppe Seylerstr. 3, D-72076 Tübingen, Germany. Email: benjamin.wiesinger{at}med.uni-tuebingen.de
Keywords: arteriovenous fistula; percutaneous embolization; renal malformations; stent; thrombosis
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Introduction |
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We describe the diagnostic, therapeutic and follow-up radiological findings in an unusual case, highlighting a possible complication after embolization therapy in a patient with von Willebrand factor (vWF) syndrome.
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Case |
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Via a left common femoral approach, a Cordis 7French (F) renal double curve (RDC) guiding catheter was introduced in the saccular part of the aneurysm using a 0.035 inch wire (Figure 2a). A 5F Cordis Cobra catheter was subsequently used for the imaging of the whole aneurysm. Thereafter, the Cobra catheter was removed and the 0.035 inch wire was exchanged for a 0.018 inch steel core wire. The RDC catheter was drawn back to the neck of the aneurysm and a Cordis PRECISE stent, diameter 10 mm and 40 mm in length, was advanced in the arterial part of the pathology covering the AVF; this was placed without post-dilatation. The stent bridged the wide neck of the aneurysm and was implanted for prevention of coil dislodgment. A covered stent was not used to prevent compromise of the blood flow in the several side branches visualized with angiography. After stenting, the renal artery was superselectively catheterized with a Cordis Maastransit Microcatheter via the 0.018 inch wire and coiling was performed for the renal artery aneurysm through the stent struts of the previously implanted PRECISE stent. In total, 27 fibred complex helical platinum coils from Boston Scientific, with 3 and 4 mm in the helical configuration and an original length of 30 mm were used to achieve complete stasis in the arterial aneurysm. Thereafter, 0.8 ml of histoacryl (tissue adhesive substance enbucrilat, n-butyl-cyanoacrylate) and lipiodol (oily contrast media) in a mixture of 1:2 was admistered into the coiled area. After a control angiogram with a 7F Cordis Prostar catheter and the application of a closer system (Abbott, USA), the procedure ended without any complications (Figure 2b).
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Discussion |
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In contrast, a possible aetiology for renal arteriovenous malformations (AVMs) is thought to be a pre-existing renal arterial aneurysm, which has eroded into an adjacent vein. AVMs are classified as congenital or idiopathic [3,4].
Congenital AVMs constitute 20% of the total AV communications. They are often located near the collecting system and are described as cirsoid with multiple AV communications; they commonly present clinically with gross haematuria. Idiopathic malformations as in our case are rare, with only
5% of all renal AV communications. They are characterized as single cavernous channels with defined aneurysmal arterial and venous elements. Their clinical appearance is often associated with abdominal bruit, hypertension and/or high-output cardiac failure.
A useful diagnostic tool is ultrasound with colour Doppler imaging and contrast-enhanced CT or magnetic resonance imaging (MRI), whereas arteriography best demonstrates the detailed anatomy of the feeding and draining vessels and is necessary for the accurate planning of the intervention.
The indication for the treatment of such lesions is the presence of clinical symptoms such as flank bruit and pain, haematuria, uncontrolled hypertension and high-output cardiac failure or the prevention of vessel rupture. Respectively, treatment would consist of an occlusion of the fistula if problems are primarily volume associated or in a switch-off of the arterial aneurysmal part to prevent eventual rupture. Risk of rupture in AVMs is supposed to be slight, but a rupture rate of up to 24% is described for single arterial aneurysms larger than 2 cm in diameter [5]. Dzsinich et al. recommend not to treat small non-symptomatic renal arterial aneurysms <1.5 cm or those with circumferential calcification [1]. However, asymptomatic ones of >2.5 cm in diameter [1], or symptomatic ones as well as those aneurysms with documented expansion, peripheral renal parenchymal embolization and those in women anticipating pregnancy should be treated to prevent rupture.
As our patient did not have volume-associated problems, such as cardiac compromise but presented with a documented expansion of size of the arterial aneurysm beyond the critical margin, it was decided to embolize only the arterial aneurysmal part of the malformation without damaging the renal parenchyma. The aim was to prevent a possible rupture and not to occlude the fistula, which, by increasing the pressure in the arterial part, would have impaired the risk of rupture. Additionally, endovascular embolization therapy was thought to minimize the risk of post-operative inadequate coagulation/bleeding especially due to the vWF syndrome of the patient relative to an alternative surgical approach.
Successful endovascular repair and embolization has been described in some case reports for renal AVMs and renal artery aneurysms [2,3,6,7]. In terms of embolization, there are a number of options available. Some AVMs have been treated successfully with superselective embolization therapy, for example in pregnant women [3], with, for example, metallic coils. However, there are few reports on successful endovascular treatment of renal artery aneurysms such as, for example, in wide neck aneurysms with a TrisPan coil (neck-bridge device developed by Boston Scientific Target) and Guglielmi detachable coils [6] or in a patient with fibromuscular dysplasia treated with a Jostent stent-graft [7]. In this patient, satisfying long-term patency results and a successful aneurysm exclusion were seen at 16 months after stenting with a Jostent [7], suggesting long-term validity.
In our case, we used a non-covered stent in order not to compromise blood flow via the side branches visualized in the angiography. In order to obtain stasis in the aneurysmal blood flow, we had to embolize the saccular part through the stent struts. We believe that particulate emboli alone, such as polyvinyl alcohol, absorbable gelatin sponges and gelatin spheres, are not suitable for embolization of large aneurysms unless used in combination with other occlusive devices such as metallic coils. We also believe that use of particles would not be likely to result in occlusion of such aneurysms, even with a tight coil nest, and would have the potential for embolization to the lungs. We thus preferred commercial platinum coils to begin a coil nest.
We required deployment of 27 complex helical 3 and 4 mm platinum coils and the administration of 0.8 ml of histoacryl and lipiodol in a 1:2 mixture to decrease the aneurymal flow significantly. Thrombin could probably have passed through the coil nest and the stent struts and may have caused serious systemic thromboembolic complications such as pulmonary embolization or renal infarction by embolization material displacement. Potentially, coils could also serve as a nidus for pulmonary embolism [8], but the stent struts were thought to serve as a barrier and would prevent this complication.
In our case, we unfortunately saw an extensive thrombosis detected by CT as a useful tool for general diagnostic screening and the detection of vascular patency. Fever and infection signs were thought to have occurred mainly secondary to the parenchymal infarction and thrombosis and not through primary renal infection where the development of a thrombus is generally also possible as a complication [9]. Angiography and local thrombolysis would have been considered, especially if the stented arterial part were occluded, but the possible effects of a local thrombolysis were feared considering the patient's coagulation disorder. Probably there was thrombus development starting in the arterial embolized part of the malformation, appositionally growing through the AVF into the venous part of the malformation. Thrombus formation might have been started because of a possible partial protrusion of several coils through the mesh of the stent, the thrombogenicity of the embolization material and the relative post-interventional stasis and changed haemodynamics. Additionally, the low dose and not full dose post-interventional heparinization together with probable vWF-related alterations in coagulation might have played a significant role. Generally we believe that sufficient post-interventional anticoagulation and an accurate selection of embolic agents/particles should be mandatory. It is surely advantageous to use as few embolic agents/particles as possible to prevent thrombus formation, and probably longer coils could have secured better positioning inside the aneurysm to prevent an eventual partial protrusion as an accelerator for local thrombosis. In the literature, inferior vena cava thrombosis after embolization therapy is extremely rare. Harada et al. reported a case of a 50-year-old woman with renal AVM treated with transarterial embolization who developed ipsilateral flank pain and haematuria 12 months after treatment. As malignancy could not be ruled out, a nephrectomy was performed. During nephrectomy, an extensive AVM and inferior vena cava thrombus was palpable and an additional thrombectomy was performed [10].
Nevertheless, while considering these points, we believe that catheter angiography should be the first choice of intervention, not only for the occlusion of AVMs but also in the occlusion of dangerous aneurysms.
Conflict of interest statement. None declared.
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References |
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