Partial resection of the urinary bladder in swine and sheep and replacement of the resected segment by biologically inert patches

Abstract

This study was performed to examine the adequacy of biological inert patches as a substitute material for the construction of urinary bladder replacement tissue. An animal model experiment was conducted in six sheep and six swine. In all animals partial resection of the urinary bladder was performed; round or oval-shaped, 5–6 cm in diameter. Patches of the same shape, 4–5 cm in diameter were used. Two types of patches, polytetrafluorethylene and small intestinal submucosa were tested in the experiment, sewn with an absorbable 4-0 polydioxanone suture. Following 16 weeks the animals were euthanized followed by autopsy and histologic analysis. All animals showed evidence of bladder regeneration at the replaced segment. The patches were found to be contracted to 12–20 mm in length and 8–10 mm in width, attached to the bladder mucosa with their smaller base and protruding into the bladder lumen. In some animals, no shrunk patches were found, suggesting they had been passed out by urine. Histologically, fibrous tissue completely replacing the substitute tissue was identified with endothelial-lined luminal surface and submucosal and serosal ingrowth of new blood vessels. The replacement tissue showed no evidence of muscle layer ingrowth. Bladder capacity was also measured and no significant decrease was recorded. Our experiment demonstrated the formation of replacement tissue at the site of graft implantation, which allows the resection of a larger portion of bladder without decreasing its capacity and thus constitutes a very good method for surgical treatment of urinary bladder tumours and other defects.