The bladder
The urinary system is one of the most vital in the human body. It has two functions: to filter waste and excess water from our blood to form urine and to return salt and other important chemicals to the blood. It is of extreme importance to your health that the urinary system functions properly.

How the urinary system works
The urinary system consists of a pair of kidneys, two ureters, a bladder, a urinary sphincter muscle, and a urethra. The kidneys are made of special filtering tissue through which all of the body's blood passes several times a day. They strain the useful material from the blood and send excess water and waste material down two thin tubes (ureters) to the bladder. Each ureter has a flap of skin on the end of it which closes to prevent urine from flowing backwards up the ureters into the kidneys.

 

Diagram of normal emptying of bladder compared to a bladder emptying incompletely

The bladder is a muscle lined sac. The muscle, called the detrusor, remains relaxed creating a low pressure reservoir for the urine until urination occurs. A 12 year old’s bladder capacity is about 300 - 400 mls. A 3 or 4 year old’s is about half this. The outlet from the bladder is a small tube called the urethra. It is longer in boys than girls, because it passes through the penis. The urethra is surrounded by two small circular muscles called sphincters, which remain contracted until urination. One of these operates involuntarily, and the other voluntarily, ie we can control it.

When the bladder is full sensory receptors tell the brain via the nerves in the spinal cord that the bladder needs emptying. When the person is ready to go to the toilet, the brain sends messages via the nerve pathways to the bladder muscle and sphincter. It coordinates the contracting of the bladder muscle with the relaxation of the sphincter muscle. This discharges the urine from the body.

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How spina bifida affect the urinary system
A person with spina bifida is usually born with an undamaged urinary system but with an interrupted nerve supply between it and the brain. This is called neurogenic or neuropathic bladder.

Nerve damage can result in impairment to either or both the bladder muscle and the urinary sphincters. The bladder muscle can be such that it cannot contract (ie it is always relaxed) or overactive and the sphincters (especially, the voluntarily controlled one) uncontrollable and either too relaxed or too tight. It is rare for the bladder muscle to be flaccid and the sphincter muscle too tight.

There are basically three common scenarios.

1. A bladder with a muscle which cannot contract combined with a sphincter which is too relaxed. This is the most common situation for people with spina bifida. The result is constant dribbling of urine, but not always complete emptying of the bladder.
2. An overactive bladder with a sphincter which is too relaxed. This also results in unpredictable discharge of urine and incomplete bladder emptying.
3. An overactive bladder with a sphincter which does not relax. This is a dangerous situation because when the bladder contracts, the urine cannot get past the tight sphincter and is forced through the small valves at the bottom of the ureters back up into the kidneys. As well as the damage that this high pressure can do to the urinary system, urine in the kidneys can cause serious kidney infections. Repeated infections substantially damage the kidneys and impair their filtering capabilities, leading to a reduced ability to filter wastes from the body.

It is very important for health that the bladder is completely emptied regularly. Urine that remains in the bladder provides an excellent breeding ground for bacteria which thrive in warm, damp conditions.

The signs of a urinary tract infection are cloudy or discoloured urine, fever, chills and shakes, headache, fatigue, nausea pain and an increased frequency and need to urinate. A person with spina bifida who has paralysis in the lower extremities should monitor the appearance of their urine carefully since they may not be able to feel the first warning sign of a urinary tract infection, pain while urinating.

Urinary incontinence will usually affect those children who have the most serious type of spina bifida, myelomeningocele. It may also affect those children with the less serious types of spina bifida, spina bifida occulta and meningocele.

How urinary continence is managed

• Almost always with clean intermittent catheterisation
• Medication to relax the bladder muscle
• A toilet timing and training program. The key is regularity.
• Continence products eg pads and shields
• Surgical procedures eg bladder augmentation, insertion of an artificial sphincter, the creation of a perineal urethrostomy

N.B. A combination of the above suggestions is usually required for successful urinary continence management.

The key to a healthy urinary system is FREQUENT COMPLETE EMPTYING.

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Clean intermittent catheterisation (CIC)
Clean intermittent catheterisation is the process in which the bladder is drained several times a day (usually every 4 hours during waking hours) with a catheter using a clean but non-sterile technique.

Clean intermittent catheterisation helps the urinary system by facilitating complete bladder emptying, reducing constant urinary leakage and protecting the kidneys from damage.

Training in independent clean intermittent catheterisation is usually started when a child is at kindergarten or preschool. Most children are basically independent by 8 years of age.

Children should still see their urologist or paediatrician regularly to monitor kidney and bladder function.

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