Ultrasonographic measurements
We manually measured the perimeter (cm) of the cross-section area of the gastric antrum using ultrasonography (SonoSite, Inc., Bothwell, WA, USA) with a low frequency (2–5 MHz) convex transducer in the abdominal view mode, and we automatically calculated the CSA (cmThe perimeter (the outermost serosa layer border) of a single section of the gastric antrum was imaged in a parasagittal plane in the epigastric area using the left lobe of the liver, the descending aorta, and the superior mesenteric artery as internal landmarks (Fig. 
Example of gastral antrum images on ultrasonography. A, antrum of stomach; L, left lobe of liver; Ao, descending aorta; SMA, superior mesenteric artery; P, pancreas