Effect of prolonged experimental distension on the function and ultrastructure of the canine urinary bladder.

Urinary bladder distension was induced for 10 hours in dogs and micturition tests were made before over-stretching, immediately afterwards and 5 days later. Compliance and residual urine had increased and maximum pressure during voiding had decreased immediately after retention, but returned to normal after 5 days. Biopses for light microscopic and electronmicroscopic investigation taken from the anterior wall of the bladder on the fifth day showed submucosal haemorrhages and some necrosis. The consistent finding on electron microscopy was Schwann cell oedema, which was seen within the cytoplasm and between the cytoplasmic processes of the Schwann cells. Axonal degeneration was also a common finding. These anatomical changes, although found at the moment of functional recovery, may be linked to impaired conductivity of the nerves in the bladder wall, at least partly, causing its impaired function. Recovery of function occurs quite rapidly in healthy bladders.