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 gu inea pigs under anaesthesia and the animals were sacrificed at 12, 24 and 4 8 h postoperatively. Three sham-operated animals were sacrificed at 48 h po stoperatively as controls. The dorsal root ganglia (DRG) at L6, S1 and S2 s pinal segments of the animals in each group were removed and processed for electron microscopic study. Results: In the control groups, all the DRG neu rons 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 chang es, notably the mitochondria. Mitochondrial swelling was more pronounced at 24 h, and by 48 h most of them became vacuolated and lysed. It was estimat ed by semiquantitative study that 18.6% and 22% of DRG neuronal profiles at 24 and 48 h, respectively, displayed severe mitochondrial swelling and vac uolation. Conclusions: The observed degenerative changes in DRG neurons fol lowing 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 retent ion.