Aneurysm of the abdominal aorta

Aneurysms of the abdominal aorta account for about three-quarters of the aortic aneurysm, they affect 0.5-3.2% of the population. Prevalence in men is 3 times greater than that of women.

Aneurysms of the abdominal aorta usually begin below the retraction of the renal arteries, but can capture the mouth of the renal arteries; approximately 50% of the iliac artery. In general, the diameter of the aorta> 3 cm indicates an aneurysm of the abdominal aorta. Most aneurysms of the abdominal aorta are spindle-shaped, some are sacciform. Many can contain laminar thrombi. Aneurysms of the abdominal aorta involve all layers of the aorta and do not lead to delamination, however, the stratification of the thoracic aorta can extend to the distal part of the abdominal aorta.

[1], [2], [3], [4], [5]

Causes of an aneurysm of the abdominal aorta

The most frequent cause of weakness of the arterial wall is usually associated with atherosclerosis. Other causes include trauma, vasculitis, cystic necrosis of the middle shell and postoperative destruction of the anastomosis. Sometimes syphilis and a local bacterial or fungal infection (usually due to sepsis or infective endocarditis ) lead to weakening of the arterial wall and the formation of infected (mycotic) aneurysms.

Smoking is the most significant risk factor. Other factors include arterial hypertension, older age (the maximum frequency is recorded at the age of 70-80 years), family history (in 15-25% of cases), belonging to the Caucasian peoples and the male gender.

[6], [7], [8], [9], [10]

Symptoms of an aneurysm of the abdominal aorta

Most aneurysms of the abdominal aorta are asymptomatic. If there are clinical manifestations, they can be nonspecific. As the aneurysms of the abdominal aorta are enlarged, they can inflict pain, which is stable, deep, aching, internal and is most noticeable in the lumbosacral region. Patients may notice a visible abdominal ripple. Rapidly increasing aneurysms prone to rupture often cause symptoms, but most aneurysms grow slowly and asymptomatically.

In some cases, an aneurysm can palpate, like pulsating mass, depending on its size and the constitution of the patient. The probability that a patient with a pulsating palpable volume formation has an aneurysm measuring> 3 cm is approximately 40% (positive prognostic significance). An aneurysm may produce systolic murmur. If there was no instantaneous death from the rupture of the aneurysm of the abdominal aorta, patients in such an acute situation usually feel pain in the abdomen or lower back, they have arterial hypotension and tachycardia. In the history there can be a mention of the recent trauma of the upper abdomen.

With mute aneurysm of the abdominal aorta, symptoms of complications can sometimes be found (eg pain in the limb due to embolism or thrombosis of organ vessels) or underlying disease (eg, fever, malaise, weight loss due to an infection process or vasculitis). Sometimes large aneurysms of the abdominal aorta lead to disseminated intravascular coagulation, possibly because large areas of the anomalous endothelium initiate rapid thrombosis and consumption of coagulation factors.

Diagnosis of an aneurysm of the abdominal aorta

Most abdominal aortic aneurysms are diagnosed accidentally, during a physical examination or when abdominal ultrasound, CT or MRI is performed. Aneurysms of the abdominal aorta should be assumed in elderly patients who suffer from acute pain in the abdomen or loin, regardless of the presence or absence of palpable pulsating formation.

If the symptoms and results of an objective examination suggest an aneurysm of the abdominal aorta, ultrasound of the abdominal cavity or CT is performed (usually the method of choice). In hemodynamically unstable patients with an alleged aneurysm rupture, ultrasound provides rapid bedside diagnosis, but intestinal gases and bloating may reduce its accuracy. Laboratory tests, including a general blood test, electrolyte blood composition, urea and creatinine content, coagulogram, blood group determination and compatibility tests, are performed in preparation for a possible surgical procedure.

If there is no suspicion of a rupture, CT angiography (CTA) or magnetic resonance angiography (MRA) can more accurately characterize the size of the aneurysm and its anatomical features. If the thrombus lining the aneurysm wall, with KTA, its true size can be underestimated. In this case, a non-contrast CT can provide a more accurate estimate. Aortography is essential if it is suspected that the kidney or iliac arteries are involved in the process, and if endovascular stenting (endograft) is expected.

Survey radiography of the abdominal cavity has neither sensitivity nor specificity; however, if it is performed for a different purpose, one can see the calcification of the aorta and the walls of the aneurysm. If there was a suspicion of a mycotic aneurysm, a bacteriological examination was performed to obtain bacterial and fungal blood cultures.

[11], [12], [13], [14]

Treatment of an aneurysm of the abdominal aorta

Some abdominal aortic aneurysms gradually increase at a constant rate (2-3 mm / year), while others increase in leaps and bounds, for unknown reasons approximately 20% of an aneurysm indefinitely has constant dimensions. The need for treatment is associated with a size that correlates with the risk of rupture.

The size of the abdominal aortic aneurysm and the risk of rupture *

Diameter of ABA, cm	Risk of rupture,% / year
<4	0
4-4.9	1
5-5.9 *	5-10
6-6,9	10-20
7-7.9	20-40
> 8	30-50

* Surgical treatment is considered a method of choice for aneurysms measuring> 5.0-5.5 cm.

The rupture of the aneurysm of the abdominal aorta is an indication for immediate surgical intervention. Without treatment, mortality is approaching 100%. Against the backdrop of treatment, mortality is approximately 50%. The figures are so high, because many patients have concomitant thrombosis of the coronary vessels, cerebrovascular and peripheral atherosclerosis. Patients who develop hemorrhagic shock, need to restore the volume of circulating fluid and blood transfusion, but the average arterial pressure can not be raised> 70-80 mm Hg. Because bleeding can increase. Preoperative AH monitoring is important.

Surgical treatment is indicated for aneurysms> 5-5.5 cm (when the risk of rupture exceeds 5-10% per year), if this is not prevented by associated pathological conditions. Additional indications for surgical treatment include an aneurysm size increase> 0.5 cm for 6 months regardless of size, chronic abdominal pain, thromboembolic complications or an aneurysm of the iliac or femoral artery that causes ischemia of the lower limb. Before the treatment it is necessary to investigate the state of the coronary arteries (for the exclusion of IHD), because in many patients with an aneurysm of the abdominal aorta there is generalized atherosclerosis, and surgical intervention creates a high risk of cardiovascular complications. Appropriate medical therapy for IHD or revascularization is very important to reduce morbidity and mortality in the treatment of an aneurysm of the abdominal aorta.

Surgical treatment consists of replacing the aneurysmal part of the abdominal aorta with a synthetic graft. If ileal arteries are involved, the graft should be large enough to capture them. If the aneurysm extends above the renal arteries, these arteries should be reimplanted into a prosthesis or a bypass shunt.

Placement of an endoprosthesis within the aneurysm lumen through the femoral artery is a less traumatic alternative treatment method, used at a high operational risk of complications. This procedure excludes an aneurysm from the systemic blood flow and reduces the risk of rupture. The aneurysm is eventually closed by thrombotic masses, and 50% of aneurysms decreases in diameter. Short-term results are good, but long-term results are unknown. Complications include bending, thrombosis, displacement of the endoprosthesis and the formation of a constant flow of blood into the aneurysmal space after the endoprosthesis is installed. Thus, follow-up after the endotransplant should be more thorough (examinations are performed more often) than after traditional prosthetics. If there are no complications, visualization studies are recommended after 1 month, 6 months, 12 months and every year thereafter. Complex anatomical features (for example, a short aneurysm neck below the renal arteries, pronounced arterial tortuosity) lead to the impossibility of implantation of an endoprosthesis in 30-50% of patients.

Prosthetics of aneurysms <5 cm in size do not appear to improve survival. With such aneurysms, follow-up with ultrasound or CT scan at 6-12 months before their increase to the extent that they consider it an indication of prosthetics. The duration of control for accidentally detected aneurysms that occur asymptomatically is not established. Control of risk factors for atherosclerosis, especially smoking cessation and the use of antihypertensive agents, is very important. If a small or medium aneurysm becomes more than 5.5 cm, and the preoperative risk of developing complications is lower than the estimated risk of a rupture, surgical treatment is prescribed. The risk of a gap in comparison with the preoperative risk of complications should be discussed in a detailed conversation with the patient.

The treatment of mycotic aneurysms consists of active antibacterial therapy directed at the microorganism, and the subsequent removal of the aneurysm. Early diagnosis and treatment improve the result.