**1. Introduction**

108 Aneurysm

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By definition AAA is dilatation in diameter of the main arterial vessel in abdomenabdominal aorta for over 50% compared to expected normal diameter (1). This dilatation is caused by gradual decrease in elasticity and consistence of aortic wall, usually including weakness in middle layer of aortic wall (tunica media), which leads to extension of extern layer (tunica adventitia) and/or inner layer (tunica intima) (2,3). Blood that is pumped through aorta under pressure, gradually stretches this weakened wall and most often creates aneurysmatic dilatation.

The disease is most often found in elderly population (4). In 5% of population older than 65, presence of AAA is confirmed (4,5). It has been noticed that this disease is about 6 times more frequent in males than in female population (6).

Over time, most of AAA (around 80%) increases in diameter (2,6). It is not possible to foresee which aneurysm will increase and which one will remain stable. In most cases, the growth of aneurysm is slow. Aneurysms measuring 5 or more cm in diameter increase for 4-8mm annually (7). Aneurysms with greatest diameter of 4-5 cm grow 3-7mm annually, while those smaller than 4 cm in diameter grow 2-5 mm on average (7,8). This long-term disease presents with nonspecific symptoms and is often unpredictable. The most frequent complication and leading cause of mortality (over 80%) in patients with AAA is rupture.

In many epidemiologic studies it has been noticed that persons with positive family anamnesis for this disease, have significantly higher risk of developing the aneurysm and its rupture. Furthermore, other risk factors for aneurysm have been identified, such as obesity, hypertension, smoking and elevated blood cholesterol level (9-14). The role od diabetes

mellitus, which is a well known risk factor in development of occlusive disease of blood vessels, in terms of aneurysm development remains controversial (15-20).

There are two current therapeutic approaches. The first one is surgery and the other is endovascular (Endovascular Aortic Repair – EVAR). In about half of the patients with intact aneurysm, as well as in those with ruptured one, endovascular approach can be applied. Advantages of endovasular treatment are avoiding general anesthesia, laparotomy and clamping the aorta. The procedure lasts shorter and recovery is fast. However, there are some disadvantages or technical limitations of this procedure. It is not possible to place the graft if proximal neck of the anuerysm is smaller than 15mm and conical in shape (21,22), because origins of renal arteries could be covered. Also, the neck of the aneurysm should be orientated at the angle no smaller than 60º towards the sagittal plane of the aorta, iliac arteries must not be tortuous and must measure at least 9 mm in diameter (23,24). During relatively short period of clinical application and development of EVAR (from 1991) the problem of frequently inadequate commercially available aortic stent-grafts for yellow race and patients with low BMI (21) has arised. The appliation of EVAR in yellow race patients showed that only 23-42% grafts, with fabrically defined dimensions, are adequate, in 23-46% they need certain corrections, while in about 30% of patients there is a contraindication for stent placement (25,26,27,28). Contemporary experience in the application of EVAR showed that overall number of complications is relatively high, even up to 30-40%. Also, one of the reasons is a not precise enough preprocedural morphologic evaluation of AAA and early diagnostics of postprocedural complications.

Modern generations od multidetector CT units (generation 16 slice, 2004 to 64 slice detectors-2007), offered a new visualisation quality and possibility to obtain more relevant diagnostic information compared to DSA. MDCT aortography reaffirmed the significance of preprocedural evaluation which ensures obtaining numerous and high quality information in each and every situation, considering the place of graft insertion, graft design and overall indication for EVAR, as well as relevant postprocedural evaluation and early diagnstics of possible complications.

During last 3 years, MDCT units with 10-times lower exponential doses per examination were constructed (29-35). At the same time, routine use of high-resolution ultrasonography as non-ionizing morphologic imaging enabled screening programmes for AAA in elderly and high-risk populaton, that are conducted and in progress in many countries (36,37,38).
