Evaluation of acetic acid-induced gastric ulcers in rats by scanning acoustic microscopy.

To clarify the mechanism of gastric ulcer recurrence, we studied acetic acid-induced gastric ulcers. The healing of these gastric ulcers was then studied for 4-21 weeks after the injection. Forty-eight ulcers were examined by macroscopic observation and scanning acoustic microscopy (SAM) and by histologic study of the ulcers. SAM has a higher radio frequency and provides more detailed information about the gastric wall than endoscopic ultrasonography (EUS). Thirteen healed and 35 non-healed gastric ulcers were observed by macroscopic observation over 4-21 weeks. SAM enabled us to observe the normal gastric wall of the rat in five different layers. The SAM echo patterns of the healed ulcers were all one pattern. On the other hand, we were able to classify the echo patterns of the non-healed ulcers into two different patterns; one pattern consisted of a high-echogenic region in the first and second layers with an underlying relatively high echogenic region in a horizontal pattern. The other pattern showed a poorly defined and spotted low-echogenic region in the first and second layers which fanned out toward the fifth layer. However, these two different ulcers could not be distinguished macroscopically. Histologic findings supported the results of the SAM study which showed one pattern in healed ulcers and two patterns in non-healed ulcers. In the non-healed ulcers the two different patterns may be ascribed to the proliferation of collagen fibers. SAM makes it possible to image the proliferation of collagen fibers and identify the two different types with an accuracy of 97%.(ABSTRACT TRUNCATED AT 250 WORDS)