The histological response to auto-augmentation gastrocystoplasty (AAGC) in a sheep model

Abstract

A number of surgical techniques have been used (with variable success) to increase bladder size in patients with reduced bladder volumes. Sewing vascularized flaps of intestinal muscularis propria into opened bladders has had limited success due to subsequent fibrosis, and full thickness gastric flaps in the absense of autoaugmentation have resulted in ulcerative cystitis. The following study in 16 sheep over an 8 month period describes the local histologic response to a new technique in which exposed bladder subepithelial connective tissue and mucosa was covered with a demucosalised gastric muscularis propria flap (AAGC). In the initial postoperative stages the dome of the bladder was formed by an inner pouch of viable subepithelial connective tissue and mucosa with a covering of fibrin, opposed to fibrin coated submucosa of the gastric flap. At the end of the first week the 2 layers had fused, and there was a marked chronic inflammatory Infiltrate with granulation tissue formation at the anastomosis site of the bladder and gastric muscle coats. Multinucleated foreign body type giant cells surrounded suture material. By 4 wks the inflammation was beginning to subside and dystrophic calcification was found only in the areas of granulomatous inflammation at the anastomosis site. From 8 wks through to 8 mths there remained only a very mild granulomatous inflammation around suture material, with no significant inflammation in any of the layers of the autoaugmentation or gastrocystopiasty . At every stage, all layers of the bladder and stomach patch remained viable, the kidneys were unremarkable and the residual stomach showed no treatment-related changes. Contrast and urodynamic studies demonstrated normal function and improved bladder volume. Thus, in demonstrating continued viability with minimal fibrous scarring in the augmented sheep bladder, this study lends support to the further application of autoaugmentation gastrocytoplasty in the treatment of bladder volume disorders.