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The AVP is a device designed and produced by St. Jude since 2004 for the embolization of peripheral arterial and venous vessels of various sizes. Over the years, several models have been designed that have progressively implemented the therapeutic possibilities of this family of devices. Currently, there are 4 models that share two common components: a vascular plug and a delivery wire. In addition, all devices have a self-expanding system, a platinum radiopaque marker, and a controlled and fast release mechanism. The structural characteristics of the different types of AVP are as follows: AVP I has a single lobe and single layer, AVP II has 3 lobes and multilayer, AVP III is bilobed and multilayer, and AVP IV is bilobed and single layer [2]. The indications are different: AVP I is indicated for vessels that have a reduced landing area, AVP II is very ductile due to the variability of available calibers and is indicated when rapid occlusion of the flow is required; contraindicated when there is a poor “landing zone”, the AVP III is used in medium-sized vessels, with a tortuous course and which have a high flow. AVP IV, available from 2009, with sizes from 4 to 8 mm represents the recent solution of the AVP family. The device can be released through a diagnostic 5-Fr catheter with compatible guide 0.038, and the structural characteristics allow both the release in irregular course vessels and a rapid occlusion of the target [2, 3]. The literature is very vast regarding the use of the different types of devices of the AVP family in various treatments such as in FAV, aneurysms, portal vein embolization, and post EVAR endoleak. Furthermore, cases of occlusions of splanchnic and bronchial branches as well as in the treatment of superficial FAV in hemodialysis are also described. Although there are a small number of scientific works that describe the release of AVP in the embolization of the renal vessels, their use is becoming increasingly widespread and routine [2, 4, 5]. The embolization of the renal arteries represents the gold standard for acute bleeding; it is a valid support for the treatment of arteriovenous fistula and for the therapeutic management of large hypervascularized renal heteroplastic masses but it is strongly recommended also in cases of vascular malformations [1,2,3,4,5,6]. In pre-operative planning, knowledge of normal anatomy and renal artery variants found in 30% of the population is fundamental. In addition to the knowledge of the anatomy of the vessels, it is essential to have information on the values of hemoglobin; hematocrit; renal, cardiac, and hepatic function; and coagulation indices [4]. Renal venous arterial malformations are even rarer and can benefit from an endovascular treatment which, however, as with MAV from other districts, is not always decisive, frequently requiring more sessions. The embolizing material to be used is chosen based on the size, course, and flow of the vessel. The use, even combined, of embolizing materials such as fibrin, PVA, EVOH, and microcoils is mainly indicated for the embolization of peripheral distal vessels of small caliber. They are widely used in case of distal pseudoaneurysms or bleeding. The coils and plugs are mainly indicated for the occlusion of medium-proximal vessels. The plugs, although still not widespread in the clinical setting, have a precise release system as well as a low risk of migration; often, a single plug is required for a complete occlusion.
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Indications for embolization in the therapeutic management of neoplastic renal masses include palliative treatments for mass reduction and hemorrhagic risk in patients candidates for total or partial nephrectomy or radio-ablation treatments as well as for control of hematuria and/or active intra- and peri-injury bleeding. Non-traumatic kidney bleeding is a rare event, but it can be very life-threatening. It is a very frequent event in large benign or malignant neoplasms (61%); among these, it is very frequent in angiomyolipoma (29%) and renal cell carcinoma (26%) [7, 8]. The ischemia produced by the pre-operative endovascular procedure also involves the formation of a clearer edematous cleavage plan between the mass and the nearby tissues allowing the surgeon a more rapid and precise removal; this condition is more pronounced especially within 72 h of the procedure. The ischemic syndrome can be of various entities mainly characterized by leukocytosis, nausea, vomiting, and fever [9, 10]. However, a risk-benefit assessment is essential before each procedure [9, 10].
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Kidney biopsy is a minimally invasive method. However, it can give major and minor complications. Minor complications are hematuria, small peri-renal hematomas, arteriovenous fistulas, and pain that resolves spontaneously. The major complications related to massive bleeding with hemodynamic instability, high-flow arteriovenous fistulas, macro-ematura, and voluminous peri-renal hematomas. Bleeding is the most frequent complication. It occurs in 12–24 h after the biopsy. The literature remarks variable complication rates, from 5 to 16% of cases including 9–13% of hematuria. Blood transfusion is essential in 0.1–3% of cases [11, 12]. Several studies have reported incidences of complications of 7.4–11% after kidney biopsy. Renal arteriovenous fistulas represent a pathological condition characterized by an abnormal connection between an arterial and venous vessel. They are classified according to etiology into idiopathic, acquired, and congenital. Idiopathic and congenital forms represent 30% of all renal fistulas [13, 14]. Acquired fistula can be secondary to traumatic events, carcinoma, arteritis, and biopsy [13, 14]. Most renal arteriovenous fistulas due to renal biopsy are asymptomatic and resolve spontaneously within 2 years, but some may be symptomatic and require interventional treatment [15]. The treatment has been surgical for years with a partial or total nephrectomy and ligation of the arterial vessel [13, 14, 16]. Endovascular treatment allows to occlude the afferent vessel and has progressively replaced surgery therapy.