The diagnostic significance of left auricular thrombus in F344/N rats

In the process of assessing the main cause of death in F344/N rats from the aging farm of our institute, we have often found left auricular thrombus i n autopsy cases of moribund animals. In 319 autopsy cases, 45 were of left auricular thrombus and 44 were accompanied by hematopoietic neoplasms, incl uding overt leukemia and a pre-leukemic condition of leukemia. In cases wit hout splenomegaly, this lesion was found in 13 of 21 animals (61.9%) wherea s, in cases with splenomegaly, 31 of 239 were positive for this lesion (13. 0%). Thus, left auricular thrombus may be an important macroscopic diagnost ic criteria of hematopoietic neoplasms, especially when splenomegaly is abs ent. Furthermore, this lesion tended to arise in aged animals despite the p resence of splenomegaly. These results would therefore greatly contribute t o aging science by confirming the health condition of experimental rats and the accuracy of subsequent results. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.