Continence in spina bifida: bladder and bowel

 

THE BLADDER

The urinary system is one of the most vital in the human body. It has 2 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, 2 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 2 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 kidney.

 

The bladder is a muscular lined sac with a capacity of about 300-400 mL for a 12-year-old child. A 3- or 4-year-old has about half this capacity. When the bladder becomes fully expanded and cannot store any more urine, sensory receptors alert the brain and the brain sends a message to the bladder muscles to contract.

When the bladder contracts pressure builds up and urine is pushed out through a short tube, called the urethra, and is discharged from the body.

The urethra is surrounded by a circular muscle, the urinary sphincter, that tightens to hold the urine in, or relaxes to allow urine to empty from the bladder and leave the body. This sphincter muscle is voluntary, allowing a person to choose when to urinate.

 

How spina bifida affects the urinary system

A person with spina bifida is usually born with an undamaged urinary system but, over time, paralysis leads to a condition known as neurogenic bladder. This form of incontinence is associated with partial or complete involuntary urination and is caused by damage to the nerves in the sacral area.

 

Nerve damage can result in impairment to one or more of the following: the bladder, the urinary sphincter or the muscular flap attached to the ureter.

The neurogenic bladder can be either flaccid or spastic. A flaccid bladder is limp and cannot contract completely to force urine out. When the flaccid bladder becomes full, excess urine spills over and flows out of the body through the urethra. Urine dribbles out continually and when excess pressure is put on the bladder, such as when laughing or crying, this dribbling becomes more severe. However, the bladder never empties completely and some (residual) urine always remains.

Unlike the flaccid bladder, the spastic bladder does not store urine at all. The muscles that line this type of bladder are extremely sensitive and irritable. They contract and expel urine immediately after it enters the bladder. Even though the bladder is continually contracting, some urine almost always remains in the bladder.

The bladder is also influenced by the control of the urinary sphincter. If nerve damage exists, the sphincter muscle can be either too tight or too loose. When the sphincter muscle is tight, urine becomes trapped in the bladder and is often forced back up the ureters to the kidney. If the sphincter muscle is too loose, however, urine continually leaks out of the body.

The function of the bladder is also influenced by pressure. Pressure is needed to force urine out. Low pressure in the bladder will result in incomplete emptying; high pressure can force urine into the ureters and kidneys (reflux).

This backward flow of urine can be very damaging to the urinary system and especially the kidneys. Normally, a muscular flap on the ureters closes and once the urine flows out of the kidneys, it cannot flow back. However, the muscles that control this flap are often damaged and instead of following the path from the kidneys to the bladder and outside of the body, the urine flows back up the ureters to the kidney.

It is very important for a person's 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. Repeated, severe infections, over time, substantially damage the kidneys and impair their filtering capabilities.

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 signs — pain while urinating, for example — of a urinary tract infection.

With spina bifida, urinary incontinence will usually affect those children who have the most severe type (myelomeningocele). It also occasionally affects those children with the less severe types of spina bifida (occulta & meningocele).

 

How urinary incontinence is managed

 

  • Medication.
  • A toilet timing/training programme. The keyword is regularity.
  • Adapted clothing and specific incontinence products e.g. pads, shields.
  • Possible surgery e.g. bladder augmentation, artificial sphincter, perineal urethrostomy.
  • Clean intermittent catheterisation.

N.B. Usually some combination of the above suggestions is required for successful urinary continence management.

 

Clean intermittent catheterisation (CIC)

This is a process by which the bladder is drained several times daily with a catheter using a clean but non-sterile technique. It is a non-medical procedure.

 

The aim of clean intermittent catheterisation is to help manage the abnormal bladder function by improving bladder emptying, reducing urinary leakage (wetting) and assisting in protecting the kidneys from damage.

The development of independent clean intermittent catheterisation skills is usually encouraged at kindy and preschool and formalised at primary school. It is generally accepted that most children learn self-catheterisation and are basically independent by 8 years of age (Grade 3).

It is usually expected that children will see appropriate doctors regularly, to monitor kidney and bladder function.

 

THE BOWEL

The human body is designed to rid itself of waste products which it cannot utilise. If we do not rid ourselves of waste material we can become very ill. The organs which help our body cleanse itself of waste are part of the lower digestive system and are known as the ‘bowels’.

 

 

How the bowel system works

The bowel consists of the small intestine, the large intestine, the rectum, internal and external anal sphincters and the anal canal. The large intestine stores the waste material. At regular, uncontrolled intervals this waste is pushed down from the large intestine into the rectum by a series of waves and contractions known as peristalsis.

 

The internal anal sphincter, which is a muscle located below the rectum, opens automatically when it senses that there are faeces in the rectum. Nerves located in the anal canal send a message to the brain that we should have a bowel movement. The bowel movement does not occur at that particular moment because of the external sphincter, a muscle we usually learn to control between the ages of one and 3 years. When it is convenient (e.g. when we are sitting on a toilet), this muscle will relax and a combination of rectal contractions and tightening of the stomach muscles will push faeces out of the body.

 

How spina bifida affects the bowel

Almost all people born with spina bifida have bowel problems. As with most of the conditions associated with spina bifida, bowel problems are a result of damaged nerves in the lowest level of the spinal cord. Nerve damage generally affects 3 areas of the bowel:

 

  • the external anal sphincter;
  • the mechanism which tells us that the rectum is full; and
  • the muscles which aid the body in removing faecal waste.

In a normally operating bowel the external sphincter will contract when the rectum is full and hold the faeces in the anal canal. However, because there is little or no control over the external anal sphincter for a person with spina bifida, faeces are often forced out of the body at an inappropriate time.

Limited sensation affects the ability to realise when the rectum is full. Nerve damage prevents the brain from receiving the message to empty the bowels. If it is not realised that the bowel is full and there is no control of the external sphincter then the bowels may open when it is least expected.

Many people with spina bifida have weak stomach and pelvic muscles. These muscles are used to push the stool out of the body. The combination of limited sensation in the nerves of the lower digestive system and weak muscles can lead to a series of problems such as constipation, impaction, or rectal prolapse.

Being constipated can make one feel nauseated and grouchy and, generally, very sick. Constipation occurs when the stool is unable to be removed from the body and becomes hardened because the water it contains is absorbed back into the body.

 

How bowel continence is managed

 

  • Eating a diet high in fibre and drinking plenty of water.
  • Medication.
  • A toilet timing/training programme. The keyword is regularity.
  • Enemas e.g. bowel washout.
  • Manual evacuation.
  • Exercise.
  • Surgical procedures e.g. Mitrofanoff Antegrade Colonic Enema (MACE).

The overall aims of bowel management programmes include:

  • the reduction of incontinence by establishing regular bowel evacuation;
  • the reduction of the risk of a megacolon; and
  • the achievement of social continence and independence and confidence in bowel management strategies.

 
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