The sonographic appearance of the normal gastric wall: an in vitro study.

In order to evaluate the real number and anatomical correspondence of the ultrasonographically recognizable layers within the gastric wall, we used a high frequency (7.5 MHz) rotating transducer to examine five surgical specimens of the stomach suspended in a water bath. Five layers were always clearly distinguishable within the gastric wall, whose thickness was 3-6 mm. Fine needles and lancets were localized at the level of the 3rd hyperechoic layer when inserted in the submucosa and in the 4th hypoechoic layer when inserted in the muscolaris propria. Thin echogenic bands were always displayed on both sides of other homogeneous tissues (spleen, myometrium) suspended in water. On the basis of these findings and also taking in account the physical laws of ultrasound interactions with tissues, we conclude that the 1st and the 5th hyperechoic layers are partially generated by ultrasound reflection at the interface liquid/wall. The 2nd hypoechoic layer corresponds to the deepest part of the mucosa; the 3rd hyperechoic to the submucosa and the submucosa/muscularis propria interface and the 4th hypoechoic layer to the muscularis propria.