The important parts of the urinary system are the kidneys themselves, the tubing system and the bladder. The kidneys act as filters removing unwanted water and waste products and passing then into the urine. The tubing system takes urine from the kidneys into the bladder by the tubes called ureters, and then from the bladder by a tube called the urethra. (See the diagram below.) The bladder stores the urine until it is necessary to pass it.
There is a valve at the junction of the ureter with the bladder, and when the bladder is being emptied the valve prevents the urine from travelling up the ureter towards the kidney. In urinary reflux this valve does not work properly and each time the bladder is emptied urine flows up the ureter towards the kidney.
It is not clear how common reflux is, but there are probably many children who have reflux and who never have any problems. Urinary reflux can be present in up to 25% of children who have infections of the bladder and urinary tract and in up to 10% of children who have a dilated tubing system. A dilated tubing system can sometimes be diagnosed before a baby is born when the mother has a special ultrasound scan.
Reflux predisposes children to urinary infections, and particularly infection which not only involves the bladder, but also the kidney (pyelonephritis). Because the valve between the ureter and the bladder is not working properly, infected urine is pushed up the ureter to the kidney. Such urinary tract infections occur in many children who have reflux.
In most cases this kidney damage resolves with time and complete healing occurs through the natural processes of the body. Sometimes the damage due to the infection does not heal by itself and permanent damage results. Usually this damage is only minor, but long term problems like high blood pressure can occur much later in life.
Up to one third of infants with urinary reflux have kidneys which are not formed properly (congenital damage) and have kidney damage before infection has occurred.
Drawing of severe urinary reflux. Free passage of urine up the urinary tract toward the kidney, often associated with urinary infection, can cause permanent damage to the kidneys.
Reflux does not cause any symptoms and does not cause kidney damage on its own, in the absence of infection. Symptoms and damage occur most frequently if urine infection develops. Urine infections commonly cause fever, pain and burning when passing urine. In young children, fever may be the only symptom. If this occurs your child should see a doctor for a check-up and a urine test.
As children grow older, the valve between the ureter and the bladder can mature and reflux then disappears without any surgical treatment to mend the valve. This takes place over several years.
Because the chance of infection (particularly infection that causes kidney damage) decreases as children grow older, persistent reflux usually does not matter in school age children but you should always check with your doctor.
Reflux is diagnosed by a micturating cystourethrogram (MCU). This x-ray test involves passing a fine tube through the urethra (the natural passage into the bladder) and filling the bladder to see whether there is reflux of the dye back up the ureter towards the kidney. Fifteen minutes is usually all that is required, and while the test sounds unpleasant, it is usually quite tolerable for the child.
An ultrasound examination of the kidneys is also done to make sure there is no associated kidney blockage.
A radionuclide dimercaptosuccinic acid (DMSA) scan is frequently done in children with reflux to find out whether kidney damage is present. This involves an injection of a radioactive dye, and three hours later pictures are taken of the kidneys. Movement of the child results in unclear pictures, so they need to be held securely. The state of kidney health can then be accurately assessed.
Reflux of urine during micturition. At the top, events in a normal individual are shown. The valve between the bladder and the ureter does not leak, and the bladder empties completely (2). After passing urine (3) the bladder is empty.
In contrast, at the bottom reflux is shown. During the passage of urine, urine also refluxes back into both kidneys (although in some individuals it may be on one side only). After passing urine, the bladder relaxes and the urine in the expanded ureters falls immediately into the bladder which is never empty, except at the instant of finishing passing urine. Thus, there is always a reservoir or urine which, if it becomes infected, will result in persistence of the infection.
Most doctors would recommend daily antibiotics to prevent further urine infections and new kidney damage occurring. These antibiotics are usually given for several years early on in life, when the risk of urine infection and kidney damage is highest. In these cases, long term antibiotic use is very appropriate and must be weighed against the risk of permanent kidney damage caused by repeated, untreated urinary tract infections. Not all antibiotics are suitable because resistance can emerge quickly e.g. penicillins, or are not suitable for children e.g. tetracyclines. A number of antibiotics have been proven to be useful in smaller doses than for acute infection e.g. Septrin, Bactrim, Keflex. Macrodantin should not be used where there is reduced kidney function. Breakthrough infections (urine infections that develop in children on antibiotics) can occasionally occur, and if they do, different preventative antibiotics can be given or sometimes surgery to fix the leaky valve can be undertaken. If surgery is necessary to repair the valve (and this is not often required), the surgeon remakes the valve mechanism at the lower end of the ureter where it enters the bladder.
Urine samples should be examined whenever a urine infection is suspected and particularly if the child has a fever.
There is no treatment that will make kidney damage resolve, apart from the body’s own healing processes. If complete healing does not occur, it is important that blood pressure and urine checks are done annually.
Reflux is a long-term problem, especially if associated with kidney damage.
However, it is only a small proportion of children with reflux who develop significant kidney problems. In most children the problem is minor, and with regular visits to the doctor and preventative antibiotics, children with reflux do well with no significant long term problems.
Finally, it is important to recognised that after birth it is infection which causes kidney damage and not reflux in itself.
The Renal Resource Centre is a national unit established to provide information and educational materials on kidney disease for patients and health professionals.
The primary objective of the Centre is to ensure that patients have easy access to such information, are well informed and can actively participate in their own health care.
The Renal Resource Centre is committed to providing education and service to the renal community.
RENAL RESOURCE CENTRE, 2010
2C Herbert St, St Leonards NSW 2065
Telephone: (02) 9462 9455 or (02) 9462 9400
Facsimile: (02) 9462 9080
Toll Free: 1800 257 189
Supported by an unrestricted educational grant from Amgen.