Master of Science (MS)


Biomedical and Veterinary Medical Sciences - Veterinary Clinical Sciences

Document Type



Five intestinal layers are commonly described ultrasonographically in dogs. However, current high-frequency endosonography allows the identification of 9 layers in people. The aim of this study was to describe ex vivo small intestinal layering in dogs and correlate ultrasonographic layering with histological layers. Our hypothesis was that, similar to findings in humans, discrepancies exist in thickness and visibility of intestinal layers between histology and ultrasound in dogs. Twelve adult dogs were included in the study. They were euthanized for reasons unrelated to gastrointestinal disease, but extensive medical history was unavailable. Duodenum, jejunum and ileum samples were resected immediately after euthanasia. Ultrasonographic images were acquired post-mortem and two needles, pinned on each side of the sample, were used to denote where transverse images were acquired, and histological sections were obtained accordingly. Comparison of ultrasonographic and histological layer thicknesses was performed statistically and subjectively, and intestinal layer echogenicity as well as presence of additional ultrasonographic layers were evaluated and compared with histological findings. No significant statistical differences were noted between the ultrasonographic and histological small intestinal layer thicknesses. In addition to the five established layers, an additional hyperechoic line was observed within the muscularis of all samples, and corresponded histologically to the interface between the longitudinal and circular smooth muscle fibers of the muscularis. In 4 ileum samples, an additional hyperechoic thin mucosal line was observed parallel to the submucosa, corresponding histologically to submucosal lymphoid follicle hyperplasia (Peyer’s patches). Finally, a variably intense hyperechoic line was visible at the inner aspect of the mucosa of every sample. This ultrasonographic layer corresponded to the mucosal villi on histology, and its degree of hyperechogenicity was related to the degree of lacteal dilation observed histologically. In contrary to our hypothesis, statistical differences between ultrasonographic and histological small intestinal layers were not shown. It was also established that additional intestinal ultrasonographic layers could be observed ex vivo. Some of these layers were considered to be normal histological interfaces, such as the interface between the circular and longitudinal muscularis layers, while some were correlated with histopathological findings, such as mucosal lacteal dilation or submucosal lymphoid follicle hyperplasia.



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Committee Chair

Gaschen, Lorrie