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Dehydration in children

Dehydration means not enough fluid in a child's body. This can result from vomiting, diarrhoea, not drinking, or any combination of these three. Sweating or urinating too much can also cause dehydration, although this is far less common. Infants and small children are much more likely to become dehydrated than older children or adults.

Causes of dehydration in children

  • Dehydration is most often caused by a viral infection that causes fever, diarrhoea, vomiting and a decreased ability to drink or eat.
  • Common viral infections causing vomiting and diarrhoea include rotavirus and winter vomiting disease (norovirus).
  • Sometimes sores in a child's mouth caused by a virus make it painful to eat or drink, helping to cause or worsen dehydration.
  • More serious bacterial infections can make a child less likely to eat and may cause vomiting and diarrhoea.
  • Common bacterial infections include Salmonella, E coli, Campylobacter, and C.difficile.
  • Parasitic infections such as Giardia lamblia cause the condition known as giardiasis.
  • Increased sweating due to a very hot environment can cause dehydration.
  • Excessive urination caused by unrecognised or poorly treated diabetes (not taking insulin) is another cause.

Symptoms of dehydration in children

You should be concerned if your child has an excessive loss of fluid from vomiting or diarrhoea, or if the child refuses to eat or drink.

Signs of dehydration:

  • Sunken eyes
  • Decreased frequency of urination or dry nappies
  • Sunken soft spot on the top of the head in babies (called the fontanelle)
  • No tears when the child cries
  • Dry or sticky mucous membranes (the lining of the mouth or tongue)
  • Lethargy (less activity than normal)
  • Irritability (more crying, fussiness)

When to seek medical care:

Seek urgent medical advice if your child has any of the following:

  • Dry mouth
  • Crying without tears
  • No urine output in 4-6 hours
  • Sunken eyes
  • Blood in the stool
  • Abdominal pain
  • Vomiting for more than 24 hours, or vomiting that is consistently green in colour
  • Fever higher than 39 Celsius (103°F)
  • Less activity than usual
  • Urination much more than usual

Call 999 or go to a hospital’s Accident and Emergency Department in these situations:

  • If your child is lethargic (difficult to awaken)
  • If your child is complaining of severe abdominal pain

Examinations and tests

The doctor will perform a thorough history and physical examination in an effort to determine the cause of dehydration, as well as to find out how severe the dehydration is. He or she will look for evidence of dehydration, as well as signs of illnesses that may cause dehydration.

Certain tests may be performed.

  • A full blood count may identify seriousness or type of infection.
  • Blood cultures may identify the type of bacterial infection.
  • Blood chemistry may identify any electrolyte abnormality caused by vomiting and diarrhoea, and may identify imbalances in body chemistry caused by illness.
  • Urinalysis may identify bladder infection, give evidence of severity of dehydration, and may identify sugar and ketones in urine (evidence of uncontrolled diabetes).
  • In some cases, the doctor may arrange other tests, such as a chest x-ray, a test to check for rotavirus, stool (poo) cultures, or lumbar puncture (a spinal tap).
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