Bladder management after spinal cord injury
The urinary system includes the kidneys, ureters, bladder and urethra. While the kidneys and ureters continue to work normally after a spinal cord injury (SCI), bladder function and micturition (urination) is impacted and will need to be managed. This section provides an overview of bladder function and micturition and how it changes following SCI.
The kidneys, ureters and bladder.
Bladder function
The kidneys produce approximately 1.7 litres of urine each day, which passes to the bladder via the ureters. What follows is a two-step process:
Bladder filling
- Bladder filling requires detrusor relaxation and pelvic floor contraction. The capacity of a normal bladder is approximately 500ml.
- The first sensation to void occurs at approximately 250ml. The frontal cortex can initiate or suppress void volition and maintain continence by limiting voiding to desired times.
- A normal desire to void is triggered by the progressive distention of the bladder, leading to increasing afferent input to the sacral and pontine micturition centres, which then initiates detrusor contraction and sphincter relaxation.
Micturition
To allow micturition, the pelvic floor and sphincters relax and the detrusor contracts. The pontine micturition centre mediates the coordination of detrusor contraction and sphincter relaxation.
Micturition requires:
- An intact nerve pathway.
- Normal muscle tone (detrusor, sphincter and pelvic floor).
- The absence of any obstruction.
- Normal bladder capacity.
Bladder filling and micturition after spinal cord injury
An SCI disrupts communication between the sacral micturition centre in the spinal cord, and the pons and cerebrum in the brain. This results in the loss of coordinated bladder filling and emptying. An SCI can affect bladder function in different ways depending on the level of the injury. Most people with SCI have some degree of bladder dysfunction.
Stages of bladder filling and desire to urinate