After spinal cord injury the bladder is referred to as a Neurogenic Bladder. This means nervous system control of the bladder has been lost as a result of the injury. This loss of nervous system control, in turn, means that, while the bladder fills with urine, the message that the bladder is full cannot reach the brain. This message is blocked at the level of injury, and you are no longer able to feel the urge to urinate.
The muscle activities of the bladder and external sphincter muscle are also affected by the injury. The bladder may be hypertonic, or spastic. The bladder will tighten and spasm as it fills and if the sphincter muscle will relax, these spasms (or contractions) may expel urine. If the sphincter muscle will not relax, voiding may not occur.
If urination occurs, it is called Reflex voiding, and is produced by a reflex that is still intact after the injury. When the bladder fills, nerve impulses are sent into the spinal cord at S2-3-4 and a responding Nerve Impulse is sent back to the bladder in a reflex that causes the bladder to contract.
This reflex may be destroyed and the bladder can be hypotonic, or flaccid, in patients with lower-level injuries (generally T-12 or lower). In this case, the bladder remains relaxed and stretches as it fills, but has no contractions to empty urine.
Whatever the altered function of the neurogenic bladder, the most important issue is one of control. The bladder has a Disability, and you have lost conscious and subconscious control over the storage function of the bladder. The bladder can no longer control the amount of urine it stores and control of the voiding process may be interrupted. Because of this disability, urinary tract complications can occur if the bladder is not managed properly.
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