1.3\ Transverse View

of the Abdominal Aorta

SMV

SMA

IVC Ao

Fig. 9.3  Transverse view of the abdominal aorta

1.3.1\ Scanning Method

The patient should be on an empty stomach for 8–12 h, and should be in a supine position. The probe is placed transversely on the midsagittal line of the abdomen. Continuous scanning is performed from the subxyphoid area to the level of the end of the Ao.

1.3.2\ Section Structure

Transverse section of the Ao, IVC, superior mesenteric artery (SMA), and superior mesenteric vein (SMV).

1.3.3\ Measurement Method and Normal Value

The anterior–posterior and transverse (left–right) diameters are measured on the maximum transverse section, with cursors placed at the inner surface of the artery wall, from one side to the other.

1.3.4\ Clinical Application Value

On this section, the whole Ao is evaluated to exclude a stenosis or dilation of the lumen. An aneurysm can be diagnosed if a lumen dilation above 50% is observed. Regular monitoring of the aneurysm size is preferred. The structure of the Ao should be evaluated on this section; ­thickening of the artery wall and a stenosis of the lumen can be observed in the Ao involving Takayasu arteritis. In arteriosclerosis, asymmetrical thickening and echo change of the inner middle layer is commonly observed.

1.3.5\ Notice

The axial resolution of ultrasound is better than the lateral resolution; therefore, on the transverse view, the measurement of the anterior–poste- rior diameter is more accurate than that of the transverse diameter; the larger diameter should be used as the diameter of the Ao. For measurement of the residual lumen, the errors may be prominent on both transverse and longitudinal sections; combination with color Doppler evaluation is useful in reducing the error. Relatively speaking, measurement on the transverse section is more accurate than that on the longitudinal section.