Abdominal aorta in norm and pathology

Normal abdominal aorta

The normal adult aorta in cross 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 the bifurcation. The transverse and vertical diameters of the section should be the same.

Measurements should be taken at different levels along the entire length of the aorta. Any significant increase in the diameter of the lower section is pathological.

Aortic displacement

The aorta may be displaced by scoliosis, retroperitoneal tumors, or involvement of the para-aortic lymph nodes; in some cases this may simulate an aneurysm. Careful transverse scanning is necessary to identify a pulsating aorta: lymph nodes or other extra-aortic lesions will be visualized posteriorly or around the aorta.

If the aorta has a diameter of more than 5 cm in cross-section, urgent medical attention is required. There is a high risk of rupture of an aorta of this diameter.

Aortic aneurysm

A significant increase in the aortic diameter in the lower parts (towards the pelvis) is pathological; detection of an increase in the aortic diameter above normal values is also highly suspicious for aneurysmal dilatation. However, it is necessary to differentiate aneurysm from aortic dissection, and in elderly patients significant tortuosity of the aorta may mask aneurysm. An aneurysm may be diffuse or localized, symmetrical or asymmetrical. Internal reflected echoes appear in the presence of a clot (thrombus), which may cause narrowing of the lumen. If a thrombus is detected in the lumen, the vessel measurement should include both the thrombus and the echo-negative lumen of the vessel. It is also important to measure the length of the pathologically changed section.

Also, a horseshoe kidney, a retroperitoneal tumor, or altered lymph nodes may be clinically mistaken for a pulsating aneurysm. A horseshoe kidney may appear anechoic and pulsating, since the isthmus lies on the aorta. Cross-sections and, if necessary, oblique sections will help differentiate the aorta and renal structure.

The cross-sectional area of the aorta at any level should not exceed 3 cm. If the diameter is greater than 5 cm or if the aneurysm increases rapidly in size (an increase of more than 1 cm per year is considered rapid), there is a significant likelihood of dissection.

If fluid leaks are detected in the area of the aortic aneurysm and the patient experiences pain, the situation is considered very serious. This may indicate dissection with blood leakage.

Aortic dissection

Dissection may occur at any level of the aorta, either short or long. Most commonly, dissection may occur in the thoracic aorta, which is difficult to visualize using ultrasound. Aortic dissection may create the illusion of aortic doubling or lumen doubling. The presence of a thrombus in the lumen may significantly mask the dissection, as the aortic lumen will be narrowed.

In any case, if there is a change in the diameter of the aorta, either a decrease or an increase, dissection may be suspected. Longitudinal and transverse sections are very important to determine the full length of the dissection area; it is also necessary to make oblique sections to clarify the extent of the process.

When an aortic aneurysm or aortic dissection is detected, the renal arteries must first be visualized and determined before surgery whether they are affected by the process or not. If possible, the condition of the iliac arteries must also be determined.

Aortic stenosis

Each local narrowing of the aorta is significant and should be visualized and measured in two planes, using longitudinal and cross-sectional sections, to determine the extent of the process.

Atheromatous calcification may be seen throughout the aorta. If possible, the aorta should be followed beyond the bifurcation into the right and left iliac arteries, which should also be examined for stenosis or dilation.

In elderly patients, the aorta may be tortuous and narrowed as a result of atherosclerosis, which may be focal or diffuse. Calcification of the aortic wall creates hyperechoic areas with acoustic shadowing. Thrombosis may develop, especially at the level of the aortic bifurcation, with subsequent occlusion of the vessel. In some cases, Doppler ultrasonography or aortography (contrast radiography) is necessary. All sections of the aorta must be examined before a diagnosis of stenosis or dilation can be made.

Aortic prosthesis

If the patient has had an aortic graft, it is important to determine the location and size of the graft sonographically, using cross-sectional views to rule out dissection or blood leakage. Fluid adjacent to the graft may be due to bleeding, but it may also be due to localized swelling or inflammation following surgery. Correlation between clinical findings and ultrasound examination is necessary. In all cases, the full length of the graft and the condition of the aorta above and below it should be determined.

Non-specific aortitis

Aneurysms in nonspecific aortitis are more common in women under 35, but are sometimes detected in children. Aortitis can affect any part of the descending aorta and can cause tubular dilation, asymmetric dilation, or stenosis. A thorough examination in the projection of the renal arteries is necessary to detect lesions. Patients with aortitis should undergo ultrasound examination every 6 months, since the stenosis area can subsequently dilate and become an aneurysm. Since echography does not provide visualization of the thoracic aorta, aortography is necessary to determine the condition of the aorta along its entire length from the aortic valve to the aortic bifurcation and determine the condition of the main branches.

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