A newly designed model for infection-induced bladder stone formation in the rat.

A newly designed urolithiasis model for rats, inducing a mild urinary tract infection, exhibiting reduced renal damage without pyelonephritis and causing reliable stone formation, was established. This was accomplished by implanting a zinc disc in the bladder and then performing transvesical inoculation of Proteus mirabilis into the bladder. Five days after challenge with 10(7) colony forming units (CFU) of P. mirabilis in each rat, the number of organisms in the bladder urine reached a level of over 10(5) colony forming units per ml. The infection was mostly restricted to the urinary tract organs. Infectious bladder stones were formed 5 days after infection and developed day by day, weighing 88.3 +/- 18.8 mg. on the 21st day. Blood urea nitrogen values stayed in the normal range in all test animals during this experiment. The main composition of the stones formed was shown to be struvite (MgNH4PO4 X 6H2O).