Identification of the layers of the bladder wall on high-frequency endoluminal ultrasonography by a needle puncture experiment.

The purpose of this study was to identify the layers of the bladder wall on high-frequency endoluminal ultrasonography (ELUS). We performed a needle puncture experiment using five normal pig bladders. The histologic layer structure was compared with the ELUS images obtained using a 30-MHz miniature transducer. The bladder wall was depicted as five layers by ELUS and these corresponded to the histologic layers. The first layer (hyperechoic) was a margin echo that included the epithelium and the upper part of the lamina propria. The second layer (hypoechoic) corresponded to the lamina propria and the third layer (hyperechoic) was a margin echo that included the upper part of the muscle layer. The fourth layer (hypoechoic) corresponded to the muscle layer, and the fifth layer (hyperechoic) was a margin echo that included the upper part of the adventitia.