Urolithiasis in rats with diabetes insipidus (Brattleboro strain rats)

Brattleboro strain rats homozygous for hypothalamic diabetes insipidus (DI rat) excrete nearly their body weight per day in dilute urine and yet can form bladders stones composed of struvite and apatite. Studies were undertaken to investigate this apparent paradox. The results show that DI rat urine is indeed undersaturated with respect to struvite and apatite. However, chronic infection of DI rat urine with a urease-containing organism (Proteus mirabilis) results in the rapid formation of large struvite/apatite bladder stones. It is concluded that the Brattleboro strain DI rat, like man and unlike other rats, forms struvite/apatite calculi only in the presence at chronic urinary tract infection.