Bladder augmentation with different forms of intestinal grafts: an experimental study in the pig

Objective To create an experimental animal model to examine changes in bladder volume and histology after bladder augmentation in growing individuals and from the model, evaluate a method using demucosalized intestinal grafts and short-term bladder drainage. Materials and methods The study comprised 21 piglets: in group 1, seven underwent a sham operation; in group 2, seven piglets underwent bladder augmentation with full-thickness caecum after a major bladder resection; in group 3 seven underwent the same procedure but with demucosalized caecum. The bladder volume and area of the intestinal segment were measured peroperatively and when the animals were killed 2 months later. Bladder specimens were taken for histological examination. Results The mean preoperative bladder volumes were similar among the groups; in the control group, volumes increased from 58 to 165 mL and in group 2 from 63 to 255 mL, with an increase in area of the intestinal segment from 59 to 138 cm2 . In group 3 the volume was unchanged, from 63 to 71 mL, with a decrease in area from 58 to 5 cm2 . Control bladders showed normal urothelium with neutral mucins and sialomucins. In group 2, there was metaplasia in the border between urothelium and colonic epithelium, with enhancement of sialo- and sulphomucins. Demucosalization resulted in extensive fibrosis, with a monolayer of urothelial cells showing metaplasia. Conclusions The experimental model was successful; the observed changes in bladder volume correlated well with the fate of the intestinal implant, because the bladder resection was major. This is essential, as the bladder remnant has some growth potential. Full-thickness grafts grew faster than the normal bladder. Mechanical demucosalization, including submucosa, results in shrinkage despite short-term drainage. Glandular metaplasia, with production of sialomucins and sulphomucins, occurs at the junction between bladder and colon, irrespective of mucosal removal.