Tissue reaction of the rabbit urinary bladder to tension-free vaginal tape and porcine small intestinal submucosa

Objectives To compare the histological tissue reactions of urinary bladder in close contact with polypropylene mesh tension-free vaginal tape (TVT) or porcine small intestinal submucosal (SIS) grafts, as the commercial availability of various materials has considerably simplified sling procedures for treating urinary incontinence, but erosion and infection after using artificial sling materials remain an important concern. Materials and methods Thirty female New Zealand rabbits were randomized to three groups, i.e. group A (TVT, 12 animals), group B (SIS, 12) and group C (surgical control, six). Through a laparotomy under anaesthesia and an aseptic technique, the bladder was approached at its dome, where a 0.5 x 1 cm piece of TVT or SIS was fixed in direct contact with the bladder wall. The control group underwent only bladder manipulation with no material applied. Half the animals in each group were killed after 6 weeks and the other half after 12 weeks. The urinary bladder was harvested and examined histologically. Results The grafts in both groups were characterized by dense foreign-body type reactions and were mostly attached loosely to the bladder wall by a thin layer of fibrovascular tissue. More importantly, the bladder wall reactions showed no inflammation in all 12 animals in group A (TVT) but three of them had various grades of fibrosis. There was severe transmural inflammation in one animal in group B (SIS); one rabbit had grade I and two had grade II fibrosis. The controls, as expected, showed no bladder wall reactions. Conclusion In this descriptive analysis of reaction types elicited on the urinary bladder by these grafts, both materials appeared to be safe. Although TVT elicited fewer and less severe adverse reactions, no statistical conclusions can be drawn. The clinical significance of these findings should emerge from long-term clinical data when they become available.