Spontaneous urinary calculus in young LEW rats caused by Corynebacterium renale

Spontaneous urinary calculus was observed in only 27% of female LEW rats among nine inbred strains maintained in the Institute for Animal Experimentation. The condition occurred between 3 and 9 weeks of age with loss of weight, enlargement of the os urethral externum, anuria and general marasmus. All of the affected rats died from anuria 3 to 4 days after the onset. The affected rats had one to ten infected stones or many fine crystals of sand, which consisted of magnesium ammonium phosphate, in the urinary bladder and/or urethra. Analysis of microorganisms revealed that Corynebacterium renale, known as a causative agent of bovine pyelonephritis, was the most probable candidate for producing infection stones. This is the first report that the rat is spontaneously infected with C. renale. This could be a useful animal model for human urinary calculus and also for C. renale infection in the field of veterinary science.