Ureteral tissue expansion for bladder augmentation.

PURPOSE

Ureteral augmentation is an effective method of bladder reconstruction using the native urothelium of a megaureter. Clinically this procedure is contingent on the presence of an enlarged ureter. We have iatrogenically produced a segmental megaureter, while preserving renal function in a pig model. The urothelium of the enlarged ureter was then used for augmentation cystoplasty.

MATERIALS AND METHODS

A tissue expander suitable for insertion into the lumen of the ureter was constructed. The tissue expander was passed antegrade through a flank incision of 8 pigs, and a separate nephrostomy tube was left in place. During the ensuing 1 to 4 weeks the pigs 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 ureter, opened and anastomosed to the bladder. The continuity of the left ureter was restored by primary ureteroureterostomy. The animals underwent cystograms at 1 and 4 weeks and were sacrificed 4 weeks after augmentation. Tissue was harvested for gross and microscopic histology.

RESULTS

Of the 8 pigs starting the protocol 5 underwent successful ureteral tissue expansion followed by bladder augmentation. Tissue expansion was performed from 1 to 4 weeks, and 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 evidence of discomfort or failure to thrive. All 5 animals underwent successful ureteral augmentation with primary ureteroureterostomy. Tissue expansion volumes of approximately 250 cc were optimal for tissue management and ease of augmentation. Cystograms of all augmented animals showed increased bladder capacity with filling of the ureteral segment. Histological examination of the ureteral augmentation revealed preservation and regeneration of the urothelial mucosa.

CONCLUSIONS

The use of a tissue expander in the lumen of the ureter is a novel method of generating urothelium for use in bladder augmentation. It may provide an alternative to bowel in patients who require bladder augmentation. Long-term studies are currently under way.