Spinal cord injuries and the bladder

There are two different clinical conditions to consider in relation to spinal cord lesions and bladder function and these are ‘reflex bladder’ and ‘flaccid bladder’. They are determined by the level of damage to the spinal cord.

Reflex bladder

This results when the spinal cord is completely severed above T12.

How does this affect the individual?

• The sensory signals from the bladder wall are unable to reach the brain, therefore there is no awareness of bladder filling
• There are no descending messages to control the external urethral sphincter, therefore the urethral sphincter is constantly relaxed
• There is a functioning spinal reflex. The parasympathetic nerves cause the detrusor muscle to contract in response to the bladder wall stretching, therefore the bladder automatically empties as it fills, known as a reflex bladder

Flaccid bladder

This results when the spinal cord is completely severed below T12.

How does this affect the individual?

• A complete spinal cord lesion below T12 will damage the parasympathetic outflow of the bladder, therefore the detrusor muscle will be unable to contract, it will be paralysed
• The spinal reflex will not function
• The bladder will fill uncontrollably, the bladder will become abnormally distended and overflow incontinence will occur

Clinical practice point. Bladder dysfunction in a person with spinal cord injury puts them at serious risk of complications such as autonomic dysreflexia and urinary tract infection (UTI), both of which can be fatal.

Your task

Find a definition of autonomic dysreflexia and add it to your glossary.

Describe the symptoms, consequences and treatment of autonomic dysreflexia.