Case report on situs inversus totalis in two Sprague-Dawley rats.

We macro- and microscopically examined two cases of congenital visceral transposition (situs inversus totalis) in SD rats. We also investigated the possibility of situs inversus in association with immotile-cilia syndrome. The rats had grown normally with no clinical signs of disease. Although all organs including the vascular system were located opposite to the normal position and displayed a mirror image on macroscopic observation, no abnormality was found in any of the organs on microscopic examination. Electron-microscopic observation revealed in neither animal any structural abnormalities of the cilia and flagella, which are one of the diagnostic characterizations of immotile-cilia syndrome. Congenital transposition of the viscera is rare and there are few reports examining complications with situs inversus in rats. This report will be helpful in accumulating information on this condition.