Detubularization-induced contractile response change of the ileum following ileocystoplasty

We reported previously that following ileocystoplasty the structure and pharmacologic response of the implanted ileum changes towards that of the bladder. Specifically, the relaxation response to alpha adrenergic (methoxamine) and purinergic (ATP) stimulation reverses to a contractile response one month after the ileal segment is surgically made part of the urinary bladder. The present study was designed to investigate possible signals for this change and also to determine whether bladder responses would mimic the ileum if surgically interposed into the ileal stream. Rabbits in group 1 underwent bladder interposition into the functioning terminal ileum, rabbits in group 2 underwent tubularized ileocystoplasty and rabbits in group 3 underwent detubularized ileocystoplasty with urinary diversion. Twelve rabbits survived and were available for evaluation; five in group 1, three in group 2 and four in group 3. Analysis was done six weeks after surgery. In group 1 animals, the interposed bladder showed epithelial changes towards ileum and also a change in its in-vitro contractile responses towards that of ileum. In group 2 animals the tubular cystoplastic ileum showed minimal functional and morphologic changes. In group 3 animals, the defunctionalized, detubular cystoplastic ileum showed alpha adrenergic and purinergic response changes towards bladder. These results indicate that detubularization with interruption in the arrangement of smooth muscle fibers as well as the breach in the integrity of neuronal connections is likely to be the primary signal for the change in the ileum towards bladder induced by cystoplasty. The results can not rule out reinnervation of the intestinal segment by bladder nerves. In addition these data demonstrate that the pharmacologic response of the bladder changes towards the ileum within six weeks after the bladder is surgically made part of the ileum.