Reactions to vesical foreign bodies in two strains of rats.

Foreign bodies in the urinary tract induce uroliths. This study examined reactions to vesical foreign bodies in Brattleboro rats manifesting diabetes insipidus and Sprague-Dawley rats. A silk suture was placed in the bladder of these rats and the occurrence of vesical uroliths, stone composition, and mucosal morphology were examined. Sprague-Dawley rats readily formed bladder stones in addition to a urolith formed over the suture, but there was little evidence that Brattleboro rats developed similar stones. Stone composition was primarily ammonium magnesium phosphate. The mucosal reactive hyperplasia was pronounced in the Sprague-Dawley, but was negligible in the Brattleboro rats. In conclusion, vesical foreign bodies readily induced uroliths in Sprague-Dawley rats, but there was no similar evidence in Brattleboro rats. It is suggested that the excessive diuresis of the latter may play a major role for this resistance to form stones, but the precise mechanisms of it are complex and remain to be explored.