Degenerative Changes of Afferent Neurons in the Lumbosacral Dorsal Root Ganglia Following Complete Urethral Obstruction in Guinea Pigs

OBJECTIVE: The ultrastructural changes in the bladder afferent neurons were examined in the guinea pig following acute complete urethral obstruction. MATERIAL AND METHODS: Complete urethral ligation was carried out in nine guinea pigs under anaesthesia and the animals were sacrificed at 12, 24 and 48 h postoperatively. Three sham-operated animals were sacrificed at 48 h postoperatively as controls. The dorsal root ganglia (DRG) at L6, S1 and S2 spinal segments of the animals in each group were removed and processed for electron microscopic study. RESULTS: In the control groups, all the DRG neurons at L6-S2 segments appeared normal. At 12 h after urethral ligation, a few neurons in the DRG at various segments showed signs of structural changes, notably the mitochondria. Mitochondrial swelling was more pronounced at 24 h, and by 48 h most of them became vacuolated and lysed. It was estimated by semiquantitative study that 18.6% and 22% of DRG neuronal profiles at 24 and 48 h, respectively, displayed severe mitochondrial swelling and vacuolation. CONCLUSIONS: The observed degenerative changes in DRG neurons following complete urethral obstruction may be a cellular reaction in response to the axonal injury elicited by bladder overdistension. This may account for alterations in visceral sensation in patients with acute urinary retention.