DEFINITION

Aneurysm is a permanent dilation of an arterial tract; normally an arterial segment is considered aneurysmatic when its diameter reaches twice that considered normal. This pathology can affect all the arteries of the organism but more frequently the aortic, iliac, femoral-popliteal district and, at the visceral level, the splenic, renal and superior mesenteric arteries and the celiac tripod. Carotid and subclavian districts or any other artery are more rarely affected. In the case of involvement of the aorta, an aneurysm is referred to when the dilatation is greater than 50% of the normal diameter (corresponding in a 60-year old adult male to about 2 cm and in the same age woman at slightly smaller dimensions).

FREQUENCY: the most frequent aneurysm is the aortic or subrenal aortoiliac aneurysm (85%); less frequently the aneurysm can also affect the origin of the renal arteries. It affects 3-6% of the general population aged 65 to 74 and most frequently men. The frequency has increased, mainly due to the improvement of diagnostic techniques and to the lengthening of the average lifespan of the individual.

CAUSES: The most frequent cause of abdominal aorta aneurysm is atherosclerosis, although there may be other rare causes, including previous traumas and infections.

NATURAL EVOLUTION OF THE CONDITION

The natural evolution of aneurysms is the progressive increase in its diameter, with a consequent increase in the risk of rupture. The larger the aneurysm, the faster its growth, and the higher the risk of rupture. The rupture of an aorto-iliac tract aneurysm or visceral vessels is a dramatic event that leads to the death of the patient in a high percentage of cases, even if operated on urgently. In most cases, thrombi may form inside the aneurysm, which may become detached and be dragged by the bloodstream, occluding the smaller vessels (embolism), or these same thrombi may clump together, causing complete obstruction of the aneurysm over time (thrombosis); such events occur rather rarely in aorta aneurysms. Less frequent complications are the fistulisation (their opening) in the viscera of the digestive tract (e.g. intestine) or in other venous vessels (e.g. the vena cava); these complications involve a high level of mortality. DIAGNOSIS: the diagnosis is in 75% of cases made by chance, and can be by means of a medical examination (relief of pulsating swelling) or during diagnostic investigations carried out for other reasons (e.g. ultrasound, X-ray, CT).

TREATMENT INDICATIONS

The aneurysm does not always have to be corrected surgically. Surgical/endovascular treatment is the most effective strategy, as medical therapy is mostly unable to prevent or limit the evolution of the disease and any complications of the disease already described. In most cases, treatment is designed to prevent complications. This practice should be aimed at aneurysms that present a greater risk of rupture, thrombosis, and embolisation, although it is necessary to balance the risk/benefit ratio, considering the age and life expectancy of the patient, as well as the state and functionality of all organs and systems, with particular attention to renal, cardiac, cerebral and respiratory functions. Furthermore, treatment is always advisable if the aneurysm causes symptoms (abdominal and/or lumbar pain, signs of compression of the surrounding structures, embolism and/or thrombosis), in the absence of other specific pathologies that justify the symptoms. In the presence of a ruptured aneurysm, or one that is in the phase of imminent rupture, urgent intervention is all the more advisable in an absolute way, even if it carries much higher risks than elective treatment. 3 Therefore, the decision whether or not to correct an aneurysm, and by what method, occurs after the evaluation of the characteristics of the aneurysm itself, of the possible presence of involvement of the contiguous vessels (renal arteries, iliac and femoral arteries) and of the patient’s general state of health. Ultimately, a multidisciplinary evaluation involving not only the surgeon but also other professionals is necessary in order to reach the decision of the intervention. If, at the end of the diagnostic procedure, the patient is not considered to be susceptible to treatment, and/or if the patient refuses to undergo surgical treatment, surveillance of the aneurysm itself is recommended, whilst paying attention to the appearance of any symptoms that may indicate its evolution, and in any case by means of investigations such as ultrasound, to be carried out at intervals defined by the specialist. In the case of abdominal aorta aneurysm (AAA), the current indication for treatment is for aneurysms with a diameter greater than 5.5 cm; in patients with concomitant iliac aneurysm, treatment is advisable where there is the presence of lesions greater than 3 cm in diameter at the iliac site, regardless of the diameter of the aorta. There is also an indication to treat aneurysms with diameters between 5 and 5.4 cm, especially if the patient is female, if there are no major comorbidities, if there is no high procedural risk and if the life expectancy is at least 3 years. Finally, an intervention is also advisable for smaller diameter aneurysms in certain unique situations: rapid growth, morphological aspects indicating an increased risk of rupture.