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MS ExplainedBladder problems

Types of bladder problem

  • Frequency - an increase in the number of times someone needs to urinate in a day
  • Urgency - the feeling of having to empty the bladder immediately, an inability to 'hold on'
  • Hesitancy - the difficulty in starting to urinate
  • Incontinence - the inability to hold urine in the bladder until an appropriate time

The wall of the bladder consists of muscle called the detrusor muscle, which stretches to store urine. At the base of the bladder is a valve called the urethral sphincter, which opens to let urine out.

The average capacity of the bladder is between 300 and 500ml (about three quarters of a pint). On average, an individual produces about 1ml of urine every minute.

The urge to empty the bladder usually occurs when it contains about 200ml. At this point the bladder is expanded enough to stimulate nerve endings in the detrusor muscle. This triggers a message to an area of the spinal cord that controls the reflex action that causes the bladder to contract. A message is also sent to the brain, signalling the need to urinate. When the brain assesses that it is appropriate to do so it passes simultaneous messages back through the spinal cord telling the valve to open and the detrusor muscle to contract, and urine is passed. Normally this occurs four to six times a day.

Damage to areas of the spinal cord or brain that control phases of this process can cause different types of problem.

diagram of the healthy bladder

Normal function
The bladder triggers a message to the reflex area of the spinal cord and a message is also sent to the brain. The brain passes instructions to the bladder

Failure to store

In this situation, damage occurs to the spinal cord between the area controlling the bladder reflex and the brain. When this happens, the controlling message from the brain is interrupted and the reflex action means the bladder will empty automatically. For the individual this means they will need to go to the toilet often (frequency), but usually with little or no notice (urgency), resulting in incontinence.

diagram of the bladder with failure to store

Failure to store
Damage occurs between area controlling the bladder reflex and the brain

Failure to empty

This happens when the scarring occurs in the reflex area of the spinal cord interrupting the instruction to empty the bladder. This means that even when someone goes to the toilet, they find it difficult to pass urine (hesitancy). The bladder does not empty properly and keeps filling beyond its normal level until it overflows. This leads to frequent, urgent needs to go to the toilet, often accompanied by overflow incontinence.

diagram of the bladder with failure to empty

Failure to empty
Scarring occurs in the reflex area of the spinal cord interrupting the instruction to empty the bladder

Combination of failure to store and failure to empty

This occurs when scarring causes a loss of coordination between the contracting of the bladder and the opening of the valve. Depending on where the damage occurs this can either mean:

  • the bladder contracts but the valve remains closed, so that urine can not be released - the individual feels a strong urge to go to the toilet (urgency) but is unable to properly empty their bladder (hesitancy)
  • the bladder relaxes and the valve opens resulting in an inability to store any urine - which causes incontinence.

Rather than helping the problem, reducing fluid intake can in fact make bladder symptoms worse. If the body does not have sufficient fluid, urine becomes concentrated and flow slows down. This allows painful crystals to form and bacteria to grow, which can lead to infections developing.

Difficulty with bladder control and with walking often go together in MS. The wiring of the nervous system means that the connections to the bladder from the spinal cord come below those to the legs. If there is damage to the nerves further up the spinal cord, both functions can be affected.

More information from the MS Trust
Bladder management factsheet
Next page - Bowel problems