Effect of seromuscular colocystoplasty lined with urothelium and partial detrusorectomy on a new canine model of reduced bladder capacity.

We developed a canine model of reduced bladder capacity by spraying talc on the outer surface of the detrusor after peeling the peritoneum from the bladder. This method was effective to reduce bladder capacity to almost a third of normal and this reduction persisted for the 6-month followup. On this model we performed detrusorectomy (auto-augmentation) and seromuscular colocystoplasty, and compared the results. Following detrusorectomy in talc bladder dogs bladder capacity failed to increase significantly at 3 months and 6 months. In contrast, seromuscular colocystoplasty caused a significant increase in bladder capacity in talc bladder dogs that was sustained for the 6-month followup. We also performed detrusorectomy in dogs with normal bladders and observed a progressive decrease in bladder capacity, which became significant at 6 months. Histology of the bladders after sacrifice revealed that talc induces a desmoplastic reaction around the detrusor that limits bladder distensibility and reduces its capacity. With detrusorectomy the perivesical fibrotic layer induced by talc and the detrusor were effectively removed but a thin layer of fibrosis developed between the bladder mucosa and the peritoneum that may account for the lack of improvement in bladder capacity. Identical observations were made after detrusorectomy in normal bladders. In contrast, following seromuscular colocystoplasty the bladder mucosa was adjacent to the submucosa of the colonic patch without fibrosis, a finding that may account for the restoration of bladder capacity. These experiments confirm previous experimental and clinical observations about seromuscular colocystoplasty, and suggest that it may result in better long-term results than simple auto-augmentation.