Heterotopic urinary bladder with a communicating reservoir.

A heterotopic bladder attached to an Ommaya reservoir was transplanted to the back of a syngeneic rat. Following transplantation, the mucosa underwent ischemic necrosis. However, it was rapidly reepithelialized in 2 weeks as a result of spreading of the epithelium originating from the ureterotrigonal region. By light microscopy the regenerated epithelium was indistinguishable from the normal transitional epithelium, and the cannula connecting the reservoir to the bladder remained patent throughout the observation period of 22 weeks. One bladder, when examined at 22 weeks, contained a transitional cell papilloma with squamous metaplasia. Although further study is needed, this model is potentially useful in studies related to bladder carcinogenesis.