Key result
The bright specular echoes of the diaphragm on ultrasound are due almost exclusively to the parietal pleura and peritoneum, while the diaphragmatic muscle produces only low-level scattered echoes.
This in vitro study demonstrates that the bright echogenic appearance of the diaphragm on ultrasound is primarily due to its membranes rather than the muscle tissue.
The brightly echogenic appearance of the diaphragm on routine clinical scans is not easily reconciled with the well-documented echo-poor appearance of muscle elsewhere in the body. A series of specimens of normal human diaphragm freshly excised at autopsy were suspended in a water bath. Articulated arm scans were done varying the angle of the incident beam to the specimen by 5-degree increments and recording the maximum attenuation which allowed visualization (ie, an extinction point). This was accomplished for intact diaphragm, peritoneal membrane alone, and diaphragmatic muscle alone with both membranes stripped. The bright specular echoes seen are due almost exclusively to the membranes (parietal pleura and peritoneum) and the diaphragmatic muscle itself produces only low-level scattered echoes as elsewhere. However, these scattered echoes account for persistent visualization of the diaphragm at steep angles of the incident beam. A considerable portion of the in vivo thickness of the diaphragmatic echo complex is, therefore, produced by diaphragm-lung interface.
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Fried et al. (1985) studied Normal human diaphragm. Ultrasound scanning at varying angles was evaluated on Maximum attenuation allowing visualization (extinction point) and source of specular echoes. The bright specular echoes of the diaphragm on ultrasound are due almost exclusively to the parietal pleura and peritoneum, while the diaphragmatic muscle produces only low-level scattered echoes.
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