The Spastic (Reflex) and Flaccid Bladder


Types of Bladder Following a Spinal Cord Injury

Following a spinal cord injury the bladder will usually be affected in one of two ways. The bladder will either react with a reflex action to empty the bladder called a spastic or reflex bladder, or the bladder will not contract when full, and will be said to be a Flaccid bladder.

The spastic (reflex) bladder usually occurs in spinal cord injuries of T12 and above.

The flaccid bladder usually occurs below spinal cord injuries of T12 to L1, where the spinal cord injury is in the cauda equina area of the spinal cord.

The Spastic (Reflex) Bladder

The spastic (reflex) bladder occurs when the stretch receptors in the bladder wall are triggered from a full or filling bladder, sending signals to the spinal cord. In the spinal cord these messages stimulate the motor nerves which are responsible for telling the bladder muscle (detrusor) to contract, thus emptying the bladder. This combined action of sensory and motor nerves passing signals within the spinal cord related to the bladder is called the micturition reflex – the reflex that allows the storage and release of urine as required. At the same time other nerve cells in the spinal cord are stimulated and send messages to the sphincter muscle to relax. This is an automatic involuntary action, and the person has no control over when the bladder will empty.

Sometimes the sphincter muscles will not relax properly when the bladder contracts, and this can lead to a condition called dyssynergia. dyssynergia can be treated by medication to relax the sphincter muscle, or by surgical procedures to open the sphincter. One danger of dyssynergia is that it can lead to an overfull bladder, which could damage the kidneys from a reflux of urine.

The Flaccid Bladder

The flaccid bladder occurs when signals from the stretch receptors in the bladder wall, do not tell the detrusor muscles to contract in a reflex action to empty the bladder when full. This can lead to the bladder being over stretched, and in extreme cases ruptured. Over stretching of the bladder can cause damage to the bladder wall, and cause infections.

If a flaccid bladder is not emptied, and is left to constantly overfill, pressure within the bladder can reach dangerous levels and damage the kidneys in a condition called "reflux" where urine is forced back into the kidneys through the ureters from the bladder.

  • Bladder Nerve Innervation Diagram