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Objective To determine the ultrasonographic characteristics of liver metastases induced in a rat model; to evaluate the usefulness of ultrasonography in the noninvasive evaluation of tumor infiltration. Material and methods We seeded the livers of 46 WAG/RijCrl rats with CC-531 syngeneic colorectal carcinoma cells by intrasplenic inoculation. At 21, 28, 35, 42, 70 days after tumor seeding, we performed a series of ultrasonographic examinations to evaluate tumor induction in different groups of animals: 37 rats were studied with a 10 MHz linear probe and 9 were studied with a 6–18 MHz multifrequency probe. The following signs were considered indicative of tumor development: intrahepatic nodules, sinuate liver borders, lobe enlargement, and extrahepatic masses. Ultrasonographic findings were verified at autopsy. We determined the number of implants, size (less than 3 mm, between 3 and 7 mm, or greater than 7 mm), and lobe location for each technique. Results Compared to the autopsy results, ultrasonography detected 64% of the animals with disease. All the extrahepatic masses were correctly diagnosed. Metastases were identified in 90% of the rats with lesions greater than 7 mm, in 75% of those with implants between 3 and 7 mm, and in 25% of those with lesions less than 3 mm. In the group in which we used the 6–18 MHz probe, we detected 50% of the lesions less than 3 mm. Conclusion Ultrasonography was useful for monitoring the experimental model and enabled the noninvasive oncologic evaluation of the rat liver with reasonable sensitivity. |
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