Detection of abdominal aortic aneurysm is an absolute indication for surgical treatment. A radical type of operation is resection of the abdominal aortic aneurysm, followed by replacement of the resected area with a homograft. The operation is performed through a laparotomy incision. With the involvement of the iliac arteries in the aneurysm, a bifurcation aorto-iliac prosthesis is indicated. The average mortality in open surgery is 3.8-8.2%.
Contraindications to elective surgery are recent (less than 1 month) myocardial infarction, stroke (up to 6 weeks), severe cardiopulmonary insufficiency, renal failure, common occlusive lesion of the iliac and femoral arteries. When an abdominal aortic aneurysm is torn or ruptured, resection is performed for health reasons.
To modern low-traumatic methods of abdominal aortic aneurysm surgery, aortic endoprosthetics with the help of an implantable stent-graft is considered. A surgical procedure is performed in an x-ray operating room through a small incision in the femoral artery; the course of the operation is controlled by X-ray television. Installing the stent-graft allows you to isolate the aneurysmal bag, thereby preventing the possibility of its rupture, and at the same time creates a new channel for blood flow. The advantages of endovascular intervention are minimal invasiveness, less risk of developing postoperative complications, quick recovery. However, according to the literature, in 10% of cases there is a distal migration of endovascular stents.
Aneurysm of the abdominal aorta is a pathological expansion of the abdominal aorta in the form of protrusion of its wall in the area from the XII thoracic to the IV – V lumbar vertebra. In cardiology and angiosurgery, the proportion of abdominal aortic aneurysms accounts for up to 95% of all aneurysmal changes in the vessels. Among men older than 60 years, abdominal aortic aneurysm is diagnosed in 2-5% of cases. Despite a possible asymptomatic course, abdominal aortic aneurysm is prone to progression; on average, its diameter increases by 10% per year, which often leads to a thinning and rupture of a fatal aneurysm. In the list of the most common causes of death an abdominal aortic aneurysm ranks 15th.
Causes of abdominal aortic aneurysm
According to research, the main etiological factor of aortic aneurysms (aortic arch aneurysms, thoracic aortic aneurysms, abdominal aortic aneurysms) is atherosclerosis. In the structure of the causes of acquired aortic aneurysms, it accounts for 80-90% of cases.
The rarer acquired origin of abdominal aortic aneurysms is associated with inflammatory processes: non-specific aortoarteritis, specific vascular lesions in syphilis, tuberculosis, salmonellosis, mycoplasmosis, rheumatism.
A prerequisite for the subsequent formation of abdominal aortic aneurysm may be fibrous-muscular dysplasia – congenital inferiority of the aortic wall.
The rapid development of vascular surgery in recent decades has led to an increase in the number of iatrogenic abdominal aortic aneurysms associated with technical errors in performing angiography, reconstructive operations (aortic dilatation / stenting, thromboembolectomy, prosthetics). Closed abdominal or spinal injuries can contribute to the occurrence of traumatic abdominal aortic aneurysms.
About 75% of patients with abdominal aortic aneurysms are smokers; at the same time, the risk of developing aneurysm increases in proportion to the smoking experience and the number of daily cigarettes smoked. Age over 60 years old, male gender and the presence of similar problems in family members increase the risk of abdominal aortic aneurysm formation by a factor of 5-6.
The likelihood of rupture of the abdominal aortic aneurysm is higher in patients suffering from arterial hypertension and chronic lung diseases. In addition, the shape and size of the aneurysmal bag matters. It is proved that asymmetric aneurysms are more susceptible to rupture than symmetric ones, and with an aneurysm diameter of more than 9 cm, the mortality rate from rupture of the aneurysmal sac and intra-abdominal bleeding reaches 75%.
Pathogenesis of abdominal aortic aneurysm
In the development of abdominal aortic aneurysm, inflammatory and degenerative atherosclerotic processes in the aortic wall play a role.
The inflammatory response in the aortic wall arises as an immune response to the introduction of an unknown antigen. At the same time, infiltration of the aortic wall by macrophages, B and T lymphocytes develops, production of cytokines increases, and proteolytic activity increases. The cascade of these reactions, in turn, leads to degradation of the extracellular matrix in the middle layer of the aorta, which is manifested in an increase in the content of collagen and a decrease in elastin. In place of smooth muscle cells and elastic membranes, cyst-like cavities are formed, as a result of which the strength of the aorta wall decreases.
Inflammatory and degenerative changes are accompanied by a thickening of the walls of the aneurysmal sac, the occurrence of intense perianeurysmal and postaneurysmal fibrosis, fusion and the involvement of the surrounding aneurysm organs in the inflammatory process.
Classification of abdominal aortic aneurysm
The anatomical classification of abdominal aortic aneurysms is of the greatest clinical value, according to which infrarenal aneurysms are distinguished, located below the discharge of the renal arteries (95%) and suprarenal with localization above the renal arteries.
According to the shape of the protrusion of the vessel wall, there are saccular, diffuse spindle-shaped and dissecting aneurysms of the abdominal aorta; on the wall structure, true and false aneurysms.
Taking into account the etiological factors, abdominal aortic aneurysms are divided into congenital and acquired. The latter may have non-inflammatory etiology (atherosclerotic, traumatic) and inflammatory (infectious, syphilitic, infectious-allergic).
According to the variant of the clinical course of aneurysm of the abdominal aorta is uncomplicated and complicated (exfoliating, torn, thrombosed). The diameter of the abdominal aortic aneurysm suggests a small (3-5 cm), medium (5-7 cm), large (over 7 cm) and a giant aneurysm (with a diameter of 8-10 times the diameter of the infrarenal aorta).
Based on the prevalence of A.A. Pokrovsky et al. There are 4 types of abdominal aortic aneurysm:
- I – infrarenal aneurysm with a distal and proximal isthmus sufficient in length;
- II – infrarenal aneurysm with a sufficiently long proximal isthmus; extends to aortic bifurcation;
- III – infrarenal aneurysm involving bifurcation of the aorta and the iliac arteries;
- IV – infra-and suprarenal (total) abdominal aortic aneurysm
Symptoms of abdominal aortic aneurysm
In case of uncomplicated abdominal aortic aneurysm, there are no subjective symptoms of the disease. In these cases, the aneurysm can be diagnosed by chance on abdominal palpation, ultrasound, abdominal radiography, diagnostic laparoscopy for another abdominal pathology.
The most typical clinical manifestations of abdominal aortic aneurysm are constant or periodic aching, dull pains in mesogaster or the left half of the abdomen, which is associated with the pressure of the growing aneurysm on the nerve roots and plexuses in the retroperitoneal space. Pain often radiates to the lumbar, sacral, or groin area. Sometimes pains are so intense that for their relief, analgesics are required. Pain syndrome can be regarded as an attack of renal colic, acute pancreatitis, or radiculitis.
Some patients in the absence of pain notes a feeling of heaviness, distention in the abdomen or increased pulsation. Nausea, belching, vomiting, flatulence, and constipation may occur as a result of mechanical compression by the aneurysm of the abdominal aorta of the stomach and duodenum.
Urological syndrome in abdominal aortic aneurysm may be due to compression of the ureter, kidney dislocation and manifests hematuria, dysuric disorders. In some cases, compression of the testicular veins and arteries is accompanied by the development of a painful symptom complex in the testes and varicocele.
Isioradicular syndrome associated with compression of the nerve roots of the spinal cord or vertebrae. It is characterized by lower back pain, sensory and movement disorders in the lower limbs.
With abdominal aortic aneurysm, chronic ischemia of the lower extremities may develop, occurring with symptoms of intermittent claudication and trophic disorders.
An isolated dissecting abdominal aortic aneurysm is extremely rare; more often, it is a continuation of the thoracic aortic dissection.
Symptoms of aneurysm rupture
A rupture of the abdominal aortic aneurysm is accompanied by a clinic of an acute abdomen and in a relatively short time can lead to a tragic outcome.
The symptom complex of the abdominal aorta rupture is accompanied by a characteristic triad: pain in the abdomen and lumbar region, collapse, increased pulsation in the abdominal cavity.
The features of the clinic for rupture of an abdominal aortic aneurysm are determined by the direction of the rupture (into the retroperitoneal space, free abdominal cavity, inferior vena cava, duodenum, bladder).
Retroperitoneal rupture of abdominal aortic aneurysm is characterized by pain of a permanent nature. With the spread of retroperitoneal hematoma in the pelvic region, there is an irradiation of pain in the thigh, groin, perineum. High hematoma may simulate cardiac pain. The amount of blood poured into the free abdominal cavity in case of retroperitoneal aneurysm rupture, as a rule, is small – about 200 ml.
When intraperitoneal localization of a ruptured abdominal aortic aneurysm, a massive hemoperitoneum clinic develops: hemorrhagic shock phenomena are rapidly increasing – sharp pallor of the skin, cold sweat, weakness, filamentous, frequent pulse, hypotension. There is a sharp bloating and soreness of the abdomen in all departments, a spilled symptom of Shchetkin-Blumberg. Percussion is determined by the presence of free fluid in the abdominal cavity. A fatal outcome with this type of rupture of the abdominal aortic aneurysm occurs very quickly.
The breakthrough of the abdominal aortic aneurysm in the inferior vena cava is accompanied by weakness, shortness of breath, tachycardia; swelling of the lower extremities is typical. Local symptoms include abdominal and lower back pain, a pulsating abdominal mass, over which systolic-diastolic murmur is heard. These symptoms increase gradually, leading to severe heart failure.
When an abdominal aortic aneurysm ruptures in the duodenum, a profuse gastrointestinal bleeding clinic develops with a sudden collapse, bloody vomiting, and melena. In diagnostic terms, this variant of the rupture is difficult to distinguish from gastrointestinal bleeding of a different etiology.
Diagnosis of abdominal aortic aneurysm
In some cases, the presence of an abdominal aortic aneurysm can be suspected by general examination, palpation and auscultation of the abdomen. For identification of family forms of abdominal aortic aneurysm, a thorough history should be collected.
When examining lean patients in the prone position, an increased pulsation of the aneurysm through the anterior abdominal wall can be determined. On palpation in the upper abdomen on the left, a painless, pulsating, dense-elastic formation is detected. During auscultation of abdominal aortic aneurysm systolic murmur is heard.
The most accessible method for the diagnosis of abdominal aortic aneurysm is a radiographic survey of the abdominal cavity, which allows visualization of the shadow of the aneurysm and the calcification of its walls. At present, USDG, duplex scanning of the abdominal aorta and its branches is widely used in angiology. The accuracy of ultrasound detection of abdominal aortic aneurysm is close to 100%. With the help of ultrasound is determined by the state of the aortic wall, the prevalence and localization of the aneurysm, the place of rupture.
CT or MSCT of the abdominal aorta allows to obtain an image of the lumen of the aneurysm, calcification, dissection, intramesh thrombosis; identify the threat of rupture or an accomplished rupture.
In addition to these methods, aortography, intravenous urography, and diagnostic laparoscopy are used in the diagnosis of abdominal aortic aneurysm.
Prognosis and prevention of abdominal aortic aneurysm
Aneurysm of the abdominal aorta is a treacherous and unpredictable vascular pathology. The probability of death from rupture of a large aneurysm is more than 75%. At the same time, from 30 to 50% of patients die even at the prehospital stage.
In recent years, cardiac surgery has seen significant progress in the diagnosis and treatment of abdominal aortic aneurysm: the number of diagnostic errors has decreased, and the number of patients undergoing surgical treatment has expanded. First of all, it is connected with the use of modern imaging studies and the introduction of aortic aneurysm in endoprosthesis replacement.
In order to prevent a potential threat of abdominal aortic aneurysm, people suffering from atherosclerosis or having a family history of this disease should be regularly examined. The important role played by the rejection of unhealthy habits (smoking). Patients who have undergone surgery for abdominal aortic aneurysm need to be followed by a vascular surgeon, regular ultrasound and CT scans.