Abdominal aorta in norm and in pathology

Normal abdominal aorta

The normal aorta of an adult in a transverse section is measured by the maximum internal diameter, which ranges from 3 cm at the level of the xiphoid process to 1 cm at the level of bifurcation. The transverse and vertical cut diameters must be the same.

Measurements should be performed at different levels along the entire length of the aorta. Any significant increase in diameter below the located department is a pathology.

Aortic displacement 

The aorta can be displaced in scoliosis, retroperitoneal tumors, or lesion of para-aortic lymph nodes; in some cases it can simulate an aneurysm. A thorough transverse scan is needed to identify the pulsating aorta: lymph nodes or other extrasaortic lesions will be visualized behind or around the aorta.

If the aorta has a diameter of more than 5 cm in the cross section, urgent attention should be paid to the clinicians. There is a high risk of aortic rupture of this diameter.

Aortic aneurysm

A significant increase in the diameter of the aorta in the lower located areas (towards the pelvis) is pathological; the detection of an increase in the diameter of the aorta above normal values is also very suspicious of an aneurysmal enlargement. Nevertheless, it is necessary to differentiate the aneurysm from aortic dissection, and in elderly patients a significant tortuosity of the aorta can mask the aneurysm. The aneurysm can be diffuse or local, symmetric and asymmetric. Internal reflected echoes appear in the presence of a clot (thrombus), which can cause a narrowing of the lumen. If a thrombus is detected in the lumen, the measurement of the vessel must include both a thrombus and a zhonegativny lumen of the vessel. It is also important to measure the length of the pathologically altered site.

Also for a pulsating aneurysm, it is clinically possible to take a "horseshoe-shaped kidney", a tumor of the retroperitoneal space, altered lymph nodes. The horseshoe kidney may look anechogenic and pulsating, since the isthmus lies on the aorta. Cross sections and, if necessary, slices at an angle will help differentiate the aorta and the renal structure.

The aortic cross section at any level should not exceed 3 cm. If the diameter is more than 5 cm or if the aneurysm sharply increases in size (an increase of more than 1 cm per year is considered rapid), there is a significant likelihood of stratification.

When identifying fluid swells in the area of the aortic aneurysm and in the presence of pain in the patient, the situation is regarded as very serious. This can mean a stratification with leakage of blood.

Aortic dissection

Stratification can occur at any level of the aorta on a short or long stretch. More often, the bundle can take place in the thoracic aorta, which is difficult to visualize with ultrasound. Aortic dissection can create the illusion of doubling the aorta or doubling the lumen. The presence of a thrombus in the lumen can largely mask the bundle, since the aortic lumen will be narrowed.

In any case, if there is a change in the diameter of the aorta, both a reduction and an increase in it, a stratification may be suspected. Longitudinal and transverse sections are very important for determining the total length of the patch; It is also necessary to make oblique slices to clarify the prevalence of the process.

When an aortic aneurysm or aortic dissection is detected, it is first necessary to visualize the renal arteries and determine before the surgical intervention whether they are affected by the process or not. If possible, it is also necessary to determine the condition of the iliac arteries.

Constriction of the aorta

Each local aortic constriction is significant and should be visualized and measured in two planes, using longitudinal and transverse sections to determine the prevalence of the process.

Atheromatous calcification can be detected throughout the aorta. If possible, it is necessary to track the aorta after bifurcation along the right and left iliac arteries, which should also be examined for stenosis or enlargement.

In elderly patients, the aorta can be convoluted and narrowed as a result of atherosclerosis, which can be focal or diffuse. Calcification of the aortic wall creates hyperechoic areas with an acoustic shadow. Thrombosis may develop, especially at the level of the aortic bifurcation, followed by occlusion of the vessel. In some cases, Doppler examination or aortography (contrast radiography) is necessary. Before making a diagnosis of stenosis or enlargement, it is necessary to examine all the departments of the aorta.

Aortic prosthesis

If the patient underwent surgery for aortic prosthesis, it is important to echographically determine the location and size of the prosthesis, using transverse sections to eliminate delamination or leakage of blood. The fluid near the transplant may be a consequence of bleeding, but it can also be the result of limited edema or inflammation after surgery. It is necessary to make a correlation between the clinical data and the results of ultrasound. In all cases, it is necessary to determine the total length of the prosthesis, as well as the condition of the aorta above and below it.

Nonspecific aortitis

Aneurysms with nonspecific aortitis are more common in women under 35 years of age, but sometimes they are detected in children. Aortic can affect any part of the descending aorta and can cause tubular expansion, asymmetric enlargement or stenosis. For the detection of lesions, a thorough examination in the projection of the renal arteries is necessary. Patients with aortitis need to perform an ultrasound every 6 months, since the stenosis site can then be dilated and become an aneurysm. Since the echography does not provide visualization of the thoracic aorta, it is necessary to perform aortography to determine the state of the aorta all the way from the aortic valve to the aortic bifurcation and to determine the state of the major branches.

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