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Atlas of Human Body Ultrasound Scanning_ Methods and Diagnostic Applications ( PDFDrive ).pdf
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Z. Xu et al.

 

 

4.3\ Long-Axis View

of the Superior Mesenteric

Artery

 

SMA

CA

LRV

 

 

Ao

L

 

SMA

CA

LRV

 

Ao

 

Fig. 9.15  Long-axis view of the superior mesenteric artery

4.3.1\ Scanning Method

The patient should be on an empty stomach for more than 8 h, and should be in a supine position.

The probe is placed vertically 1–2 cm to the left of the midsagittal line, or the probe is rotated to a horizontal position after acquisition of the transverse section of the SMA.

4.3.2\ Section Structure

SMA, CA, Ao, left renal vein; the superior surface of the opening of the SMA is 1–6 mm lower than the inferior border of the opening of the CA.

4.3.3\ Measurement Method and Normal Value

On this section, the diameter of the SMA is about 0.77 cm; the lumen may enlarge after a meal. This section is also used to measure the angle between the SMA and the Ao; the normal range of this angle is 40 °–60°.

4.3.4\ Clinical Application Value

Plaque on the artery wall may be seen on this section in patients with arteriosclerosis; if there is a stenosis, narrowing of the blood flow and aliasing may be shown on this view.

In the case of a small SMA-Ao angle is a clue to diagnosing the “nutcracker” phenomenon and SMA compression syndrome. In the case of a large SMA-Ao angle caused by elevation of the SMA by a mass is helpful to determine if the mass arises from the retroperitoneal region.