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English: Abdominal ultrasound in the axial plane at the level of the navel of a 31 year old man, showing normal anatomy. It uses compression to decrease the distance to the aorta for better visualization, resulting in flat shapes of the inferior mesenteric vein and the inferior vena cava.
This is thought to be due to the large size of its principal branches. At the 11th rib, the diameter is 122mm long and 55mm wide and this is because of the constant pressure. [2] The abdominal aorta is clinically divided into 2 segments: The suprarenal abdominal or paravisceral segment, inferior to the diaphragm but superior to the renal arteries.
Abdominal aortic aneurysms are commonly divided according to their size and symptomatology. An aneurysm is usually defined as an outer aortic diameter over 3 cm (normal diameter of the aorta is around 2 cm), [43] or more than 50% of normal diameter. [44] If the outer diameter exceeds 5.5 cm, the aneurysm is considered to be large. [42]
Fetal: Anteroposterior diameter of less than 4 mm in fetuses up to 32 weeks of gestational age and 7 mm afterwards. [ 17 ] Adults: cutoff values defined differently by different sources, with anteroposterior diameters ranging between 10 and 20 mm. [ 18 ] About 13% of normal healthy adults have a transverse pelvic diameter of over 10 mm. [ 19 ]
Abdominal aortic aneurysms are commonly divided according to their size and symptomatology. An aneurysm is usually defined as an outer aortic diameter over 3 cm (normal diameter of the aorta is around 2 cm), [17] or more than 50% of normal diameter that of a healthy individual of the same sex and age.
An aortic aneurysm is an enlargement (dilatation) of the aorta to greater than 1.5 times normal size. [1] Typically, there are no symptoms except when the aneurysm dissects or ruptures, which causes sudden, severe pain in the abdomen and lower back. [2] [3] The etiology remains an area of active research.
Abdominal ultrasound can be used to diagnose abnormalities in various internal organs, such as the kidneys, [1] liver, gallbladder, pancreas, spleen and abdominal aorta. If Doppler ultrasonography is added, the blood flow inside blood vessels can be evaluated as well (for example, to look for renal artery stenosis).
As the blood moves into the aortic arch, the area with the highest velocity tends to be on the inner wall. Helical flow within the ascending aorta and aortic arch help to reduce flow stagnation and increase oxygen transport. [4] As the blood moves into the descending aorta, rotations in the flow are less present.