Only 11 patients (29.7%) met the classical criteria for alkaline encrusted cystitis. They had an initial or predisposing bladder lesion, irritative symptoms, passed calcareous material, a demonstrated or suspected urinary infection from ureolytic pathogens and alkaline urine. The remaining 26 patients (70.2%) with histologically demonstrated encrustations on the bladder wall did not meet the foregoing criteria