International Journal of Nephrology for rupture and bleeding [8]. There is also an increased risk of bleeding each time after insertion and removal of dialysis needles [9]. This is because the vessel wall is thinned in an aneurysm and is easily injured and prone to bleeding and rupture [10]. Cannulation should not be continued along any type of aneurysm, particularly in patients for whom the skin layer within the aneurysm is thin and prone to infection, a sign of impending perforation [11]. Long-standing high blood ﬂow rates through an AV ﬁstula results in shear forces that cause damage to the elastic ﬁbers of the internal elastic lamina. The high ﬂow rates and the resulting shear forces from repeated dialysis treatments limit time for healing, thereby causing destruction of the venous wall and aneurysm formation [12]. Arteriovenous ﬁstula aneurysms may be false aneurysms or venous aneurysms [13]. False aneurysms are hematomas located outside the vessel wall, formed due to a leaking hole in the artery and are most often due to iatrogenic trauma, primarily repeated needle punctures. Infection of a false aneurysm increases the risk of rupture and bleeding as the vessel wall is already thin. Risk for bleeding and hematoma formation is greatest in the early stages of use of a ﬁstula and greater in brachiobasilic ﬁstulae than ﬁstulae at the wrist or elbow [11]. Venous aneurysms occur when repeated trauma to the venous wall is coupled with complete stenosis. The increased venous resistance leads to progressive enlargement of the venous aneurysm, thus increasing the risk of rupture [13]. True aneurysms are fusiform, develop slowly over several years, and lie beneath intact, nonulcerated skin making them less prone to infection and rupture. On the contrary, pseudoa- neurysms are usually saccular with thinning of overlying skin and develop over a short period of time, making them more prone to rupture and infection [14]. Aneurysms are at risk for rupture if they are large and rapidly expanding, if there is thinning of overlying skin exposing the underlying ﬁstula and if there are signs of local infection [15, 16]. The occurrence of large aneurysms, in addition to threatening the function of the AVF, may ultimately rupture with catastrophic sequelae. However surgical options to repair such large aneurysms are limited and often involve loss of the AVF. Endovascular procedures such as angioplasty and stenting have been increasingly used to treat vascular access dysfunction and to prolong the life of an AVF [17]. 3.2. Stenosis. Venous stenosis within the perianastomotic region is the leading cause of vascular access dysfunction [18]. The basic underlying mechanism of venous stenosis is neointimal hyperplasia due to cytokine production, cellular proliferation, and microvessel formation [19]. This is trig- gered by high intraluminal pressure, turbulent blood ﬂow, vascular calciﬁcation, endothelial injury, and increased levels of ﬁbronectin [20, 21]. Development of stenosis of AV ﬁstula is also inﬂuenced by venous capacitance, surgical technique, and the site of the AV ﬁstula. In hemodialysis patients, a native AV ﬁstula is the vascular access of choice owing to its superior patency and 3 low complication rates. Venous stenosis per se does not lead to blood loss but can be complicated by aneurysm formation with subsequent rupture and blood loss. Aneurysms are observed within the ﬁrst postanastomotic venous segment in the presence of a hemodynamically relevant stenosis in the juxta-anastomotic position The therapy of choice is a new AV anastomosis using a healthy venous segment located a few centimeters more proximally, but as close to the former anastomosis as possible, to preserve the maximum area for cannulation. 3.3. Infections. Vascular access site infection is considered to be the most challenging complication and the major cause of morbidity and mortality among chronic hemodialysis patients [22]. It is also an important cause for AV ﬁstula failure. The source of sepsis in the dialysis population is largely related to vascular access. Infection rate is highest with temporary central vein catheter followed by tunneled central vein catheter and prosthetic AV grafts and is least with pri- mary AV ﬁstulas [23–27]. Common factors associated with increased AVF and AV graft infection include prior episode of bacteremia, immunosuppression, poor personal hygiene, poor aseptic techniques during cannulation, repeated can- nulations, defects in neointimal lining, nasal staphylococcus aureus carriage, diabetes mellitus, uremia, and age of ﬁstula [22, 28]. Blood loss due to infections of AV ﬁstulas results from vessel wall weakening leading to aneurysm formation and rupture. Preexisting aneurysms can rupture secondary to superimposed infections. Surgical debridement of localized infections can also result in signiﬁcant blood loss. Utilization of antibacterial soap followed by either 70% alcohol or 10% povidone iodine has been shown to reduce the risk of infections from needle cannulations [9]. A study showed a slightly greater incidence of AV ﬁstula infections with the button hole technique for cannulation when compared with the rope ladder technique [29]. Recognizing and correcting the modiﬁable risk factors for infection will help minimize the incidence of AV ﬁstula infection and thereby decrease the risk of access blood loss due to aneurysm rupture. 3.4. Trauma. The most common trauma to AV ﬁstulas is repeated needle cannulations during dialysis. Dialysis technicians and patients are taught to rotate needle insertion sites during each dialysis. Proper cannulation is a vital and fundamental skill that every hemodialysis nurse should master. First cannulation should be carried out by nurses who have great expertise [11, 30]. To reduce the bleeding time after needle withdrawal, all superﬁcial AV ﬁstulas should be cannulated at an angle of 25 degrees [31]. There are 3 diﬀerent cannulation techniques which include rope ladder, button hole, and area puncture. In the rope ladder technique, puncture sites are spread along the length of the vascular access, starting distally, and proceeding proximally. This is the most popular method. The button hole technique consists of puncturing the same site, in the same direction and at the same angle and depth. The initial few punctures are made using a sharp needle