URETERAL TISSUE EXPANSION FOR BLADDER AUGMENTATION

Purpose: Ureteral augmentation is an effective method of bladder recon struction using the native urothelium of a megaureter. Clinically this procedure is contingent on the presence of an enlarged ureter. We hav e iatrogenically produced a segmental megaureter, while preserving ren al function in a pig model. The urothelium of the enlarged ureter was then used for augmentation cystoplasty. Materials and Methods: A tissu e expander suitable for insertion into the lumen of the ureter was con structed. The tissue expander was passed antegrade through a flank inc ision of 8 pigs, and a separate nephrostomy tube was left in place. Du ring the ensuing 1 to 4 weeks the pig; underwent daily dilation of the tissue expander without anesthesia. After dilation the pigs underwent ureteral augmentation of the bladder. The segment of expanded ureter was isolated from the native meter, opened and anastomosed to the blad der. The continuity of the left ureter was restored by primary uretero ureterostomy. The animals underwent cystograms at 1 and 4 weeks and we re sacrificed 4 weeks after augmentation. Tissue was harvested for gro ss and microscopic histology. Results: Of the 8 pigs starting the prot ocol 5 underwent successful ureteral tissue expansion followed by blad der augmentation. Tissue expansion was performed from 1 to 4 weeks, an d volumes of 150 to 1,000 cc were obtained. Two to 3 weeks of dilation was optimal to achieve ease of dilation, and no animal showed evidenc e of discomfort or failure to thrive. All 5 animals underwent successf ul ureteral augmentation with primary ureteroureterostomy. Tissue expa nsion volumes of approximately 250 cc were optimal for tissue manageme nt and ease of augmentation. Cystograms of all augmented animals showe d increased bladder capacity with filling of the ureteral segment. His tological examination of the ureteral augmentation revealed preservati on and regeneration of the urothelial mucosa. Conclusions: The use of a tissue expander in the lumen of the ureter is a novel method of gene rating urothelium for use in bladder augmentation. It may provide an a lternative to bowel in patients who require bladder augmentation. Long -term studies are currently under way.