Transrectal ultrasonography: interpretation of normal intestinal wall structure for the preoperative staging of rectal cancer.

An in vitro ultrasonographic study was carried out to four polyethylene membranes of different thicknesses and on four normal surgical specimens from the rectal wall, to assess its various layers and their anatomical structure. Three different techniques were used, and an electronic equipment measured the thickness of the membranes and of the surgical specimens. Polyethylene membranes less than 1000 microns thick gave linear echoes; the 1000-microns-thick membrane gave a three-layer image--two hyperechogenic layers separated by a hypoechogenic one.