Urothelial hyperplasia and neoplasia: a response to chronic urinary tract infections in rats.

The rat was used as an animal model to examine the effect of foreign bodies and long term infection (24 weeks) on bladder epithelium. Stainless steel wire implants and multiple injections of Escherichia coli were compared to control rat bladders by gross observation, light microscopy and scanning electron microscopy. Hyperplastic alterations, (papilloma, von Brunn's nests), dysplasia (squamous metaplasia, microvilli) and early lesions consistent with neoplasia occurred in rats with bladder implants and multiple bacterial injections but not in controls. Epithelial changes were not associated with sterile bladder implants. Bladder papillomata could be observed as early as 2 weeks in rats having both an implant and an infection, but the majority of hyperplastic and early neoplastic-like changes occurred after 6 weeks. Long-term infections, both with and without a bladder implant, can lead to lesions consistent with neoplasia in bladder epithelium.