[An unusual lithiasic nidus. Review of bladder lithogenesis caused by foreign bodies]

We report on an 88-year-old male patient with a bladder stone that had been incidentally detected and found to contain a foreign body, which was shown to be a urethral dilator on microscopic and chemical analyses. The calculi had three well-defined layers with clearly infective features. The literature on bladder stone formation is reviewed and the clinical features and treatment are discussed.