1Department of Diagnostic Radiology, Kyung Hee University Hospital, Korea. 2Department of Pathology, Kyung Hee University Hospital, Korea.
Published online: January 1, 2001.
ABSTRACT
PURPOSE: To evaluate the change of the wall of obstructed small bowel loop on ultrasonography (US), the changes of pre- and post-obstructed segments were examined by using US and correlated with histopathologic findings. MATERIALS and METHODS: Small bowel loops of seven rabbits were caused to be obstructed by surgery. One of them was sacrified after 12 hours, and six were after 24 hours. The bowel loop of about 10cm in length was cut and removed from obstructed site for evaluation with US and correlation with histopathologic findings. One control was also included and correlated by the same way, without bowel obstruction. After US examination, the bowel loops were opened at the mesenteric border. They were mounted into hard paper, and put in a plastic pail filled with 2 liters of physiologic saline. The specimens were imaged with a 10 MHz linear array transducer with high definition zoom. After sonographic examination, the specimens were fixed with 10% formalin solution and stained by hematoxylin-eosin. RESULTS: The segments of small bowel showed three layers on US, which were hyperechoic, hypoechoic, and hyperechoic from the mucosal surface. The total thickness of the pre-obstructed segments was 1.65 +/-0.15 mm, and of post-obstructed was 1.62 +/-0.14mm ; there was no significant difference (p>0.05). The ratio of the second hypoechoic layer to total thickness was 23% at pre-obstructed segments, 17% at post-obstructed, and 7% at the control. Under microscopic examination, the total thickness of the pre-obstructed segments was measured as 0 . 9 5 +/-0.12mm, and that of the post-obstructed was measured as 0.9 +/- 0.11mm; there was no significant difference (p>0.05). The total thickness on US was about 0.7mm thicker than that in microscopic findings, so considering the ratio of each layers, the first hyperechoic and the second hypoechoic layers were assumed to be mucosal layer, and the third hyperechoic layer was assumed to be submucosal and muscle layers. Histopathologic findings of both pre- and post-obstructed segments revealed increased goblet cells, lymphatic dilatation of villi at the mucosal layer, fibrosis, edema, hemorrhage, and infiltration of inflammatory cells at the submucosal layer. Only in pre-obstructed segments, the muscle layer showed muscle cell hypertrophy, a decreasing of interspace between inner circular and outer longitudinal muscle layers and also among intermuscular fibers. Hemorrhage, edema, and inflammatory cells infiltration were also observed in the muscle layer. CONCLUSION: There was no increased wall thickness of the pre-obstructed segments, and the proportion of the second hypoechoic layer was increased. The histopathologic finding of it corresponded to the lymphatic dilatation of the mucosal layer.
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