Nerve transfer for restoration of lower motor neuron‐lesioned bladder function: Correlation between histological changes and nerve evoked contractions

We determined the effect of pelvic organ decentralization and reinnervation one year later on urinary bladder histology and function. Twelve dogs underwent decentralization by bilateral transection of coccygeal and sacral (S) spinal roots, dorsal roots of lumbar (L)7, and hypogastric nerves. One was euthanized at 11 and three at 18‐21 months post‐decentralization. Eight were reinnervated 9‐13 months post‐decentralization with obturator‐to‐pelvic nerve and sciatic‐to‐pudendal nerve transfer, then euthanized 8‐12 months later. Controls included 11 sham‐operated and 3 unoperated animals. Before euthanasia, pelvic or transferred nerves and L1‐S3 spinal roots were stimulated and maximum detrusor pressure (MDP) recorded. Bladder specimens were collected for histological and ex vivo smooth muscle contractility studies. Decentralized and reinnervated animals showed loss of urothelium integrity, fewer intramural ganglia, and more inflammation and collagen, than controls, although percent muscle was maintained. In reinnervated animals, pgp9.5+ axon density was higher, compared to decentralized animals. Ex vivo smooth muscle contractions in response to KCl correlated positively with submucosal inflammation, detrusor muscle thickness and pgp9.5+ axon density. In vivo , decentralized and reinnervated animals showed lower MDP than controls after stimulation of transferred or pelvic nerves and L7‐S3 roots. Reinnervated animals showed higher MDP after stimulation of L1‐L6 roots, compared to L7‐S3 roots. MDP correlated negatively with detrusor collagen and inflammation, and positively with pgp9.5+ axon density and intramural ganglia numbers. Although percent muscle and some bladder smooth muscle function was maintained in reinnervated animals, perhaps due to the innervation change, enhanced collagen deposition and inflammation were associated with decreased contractile function.