What are urinary tract infections and why do some children catch them?

We each have two kidneys, one on either side. Their job is to filter out waste products from the blood and these are excreted in urine which travels down two tubes, one from each kidney, called ureters. These tubes enter the bladder where the urine is stored until the bladder is so full that the need to pass urine is felt. The urine is then passed to empty the bladder.

Sometimes this urine becomes infected. This can result in pain on passing urine and the desire to pass urine more frequently. Often there are no tell-tale symptoms. The child is just generally ill with a fever, tummy ache or vomiting, for no obvious reason. Then the only way to diagnose it is with a urine test.

Normally urine flows downwards from the kidneys to the bladder. In some, urine also flows back up the ureters each time they pass urine: this can result in urine becoming infected and splashing up to the kidneys. Other things which cause urine to stay too long in the body can also tend to cause urinary tract infection. Constipation can interfere with the emptying of the bladder. Not completely emptying the bladder when urine is passed, or holding onto the urine for too long can also be causes.

The tendency for the urine to go back up the ureters when the child passes urine is called reflux. Why it occurs is not entirely known. It may be due to an inborn abnormality in the wall of the bladder. In many children, however, there may be no abnormalities to explain the urinary infection.

Why are these serious?

We know that urinary tract (kidneys and bladder) infections can be difficult to diagnose in children. Unfortunately it is possible for children to have long-standing or recurrent urinary tract infections that go undetected for some time. This can damage the kidneys and if left untreated will eventually cause kidney failure in later life, requiring dialysis or kidney transplantation. For this reason doctors take these infections very seriously and that is why your child may undergo investigations in hospital or as an out-patient and may be asked to take long term antibiotic treatment. The investigations are tailored to the age of the child so that the minimum unpleasantness occurs, but some injections and blood tests may be necessary.

Remember, the point of these are to ensure that your child has healthy kidneys as he or she grows up and is not left on a dialysis machine or requiring a kidney transplant in adulthood. With proper investigation and treatment the outcome is excellent.

What treatment will be offered?

Once the urinary tract infection has been diagnosed, the doctor will prescribe a course of antibiotics for a particular number of days. The course of antibiotics should be completed. They should not be stopped just because the child appears better. It is also important to make sure that the fluid intake is at least 1 to 2 pints a day and that the child regularly passes urine.

Further tests will usually be necessary. It is important to make sure that the ureters and bladder are normal and that the kidneys have not been damaged by the infection. Some blood tests and x-rays of the kidneys may be required. An intravenous urogram /pyelogram (IVU/IVP) involves an injection of dye into a vein. The kidneys will collect this from the child's bloodstream. The dye will show up the kidneys and all the tubes below them. It involves several x-rays and the injection itself may make the child feel flushed and ill. Another type of test is an isotope scan. Here, a small quantity of a safe radioactive substance is injected into a vein. The kidney concentrates the substance and a scanner is used to visualize the kidney by measuring the radioactivity and forming a picture of it. The other main type of investigation is an ultrasound scan. This is very simple and not unpleasant for the child. It involves a scanner being passed over the kidneys and bladder to look at their general.

If any of these tests do show abnormality, if the urine infections are repeated, or if they have occurred at a very young age (below the age of 2 years), a micturating cysto-urethrogram (MCU) may be performed. This is a special test to look for the reflux mentioned above. In this test, the child's bladder is filled by a catheter. This is a thin tube which is passed up the penis or through the bladder-opening in little girls. It is an uncomfortable procedure and in younger children some sedation is usually provided. Once the bladder has been filled, the x-ray is taken while the child passes urine, to see if the urine is flowing back up to the kidneys.

Further treatment depends on the results of the tests. If no abnormalities are found, the child will be seen regularly with urine test checks to ensure that no further infections occur. Some may be given a small daily dose of antibiotic to protect the kidneys from further infection. These children will be seen regularly throughout childhood, and as they get older may no longer need treatment. Some children may need to have an operation to correct the abnormality which is causing the recurrent infection.

Avoiding further infections

Boys rarely get further infections and if they do it usually occurs very soon after the first one.

Girls often do get further infections and while it does not necessarily indicate that something is seriously wrong, it may be an indication that further investigation may be required. In some children it may be necessary to place the child on a low dose of antibiotics over a long period of time. Please ask your doctor about any points which you feel unsure about, so that you can understand the reasons for your child’s prolonged treatment and so you can help your child to get better.

As a parent you can help reduce the chances of further infection by encouraging your child to follow the guidelines mentioned below.