Significance of a common extended mucosal interface observed in transverse small intestine sonograms

An echogenic stripe can be seen through the mucosal layer on either side of the ultrasonographic image of a bowel loop in cross-section. The mucosa is a continuous layer surrounding the intestinal lumen; thus it should appear as a continuous hypoechoic band with no bright stripe in it. The purpose of this study was to investigate the origin of this stripe and to determine whether it is an artifact. Intestinal cross-sectional images were obtained using different transducer types and frequencies. In vivo and in vitro, different angles of insonification were used and, in vitro, bowel loops were also fluid filled during an ultrasonographic examination, to assess the potential influence of intestinal shape and position on this stripe. Some of these loops were evaluated histologically to determine if the echogenic stripe had a histologic basis. The echogenic stripe was present only when the loop was flattened. It remained on each side of the maximal cross-sectional width and disappeared when this width was parallel to the ultrasound beam, or when the bowel loop had a completely round shape and was dilated. There was no influence of transducer type, shape, or frequency on the appearance of the line. Histologically, uneven and larger distance between the mucosal villi could be seen on either side of the bowel loop corresponding to the location of the echogenic stripe seen on the ultrasonographic images. In conclusion, the occasional echogenic stripe represents an interface within the mucosa due to altered position of villi on either side of the maximal intestinal cross-sectional width in collapsed bowel segment.