Posterior Urethral Valves
What are posterior urethral valves or PUV for short?
Posterior urethral valves occur only in boys. It is due to a blockage in the urethra or the tube leading from the bladder to the outside (see diagram).
Urine is made by the filtering units (nephrons) in the kidney which filter waste products from the blood and excrete excess water. The urine that is formed flows down the ureter and is stored in the bladder before being passed out in the urethra which passes through the penis.
A blockage to the urine flow through the urethra causes back pressure on the bladder which may enlarge considerably and/or develop a very thick muscle wall. This in turn can lead to further back pressure up the ureters and lead to excess fluid in the kidneys called hydronephrosis.
Each child who presents with PUV has a different amount of damage to the urinary system (bladder, ureters and kidneys) – some may have a mild problem whereas in others PUV may have caused severe damage in the womb.
How might PUV present?
Ultrasound in pregnancy may show an abnormal urinary tract. If PUV is recognised early in pregnancy on the 18-20 week detailed scan then usually the problem is very severe.
The problem may only be recognised on late pregnancy scans. The problem may not have been spotted on the earlier scan as the blockage due to PUV may only occur later in pregnancy.
If the PUV has not been recognised antenatally then the baby may be noticed in the newborn period to have an enlarged bladder which can be felt in the lower abdomen. However, babies’ bladders are sometimes normally palpable and this isn’t a very reliable sign.
If there is a blockage to the outflow from the bladder then baby may only dribble urine and not have a spout of urine which sometimes you can see when changing baby boys’ nappies. Again, there is great variation in the way that babies pass urine but it may be that baby’s stream of urine is poor and baby has to strain to pass urine.
Once the urinary system is blocked by the PUV then infection of the urine (urinary tract infection) can occur and baby may get very sick with a temperature and vomiting and occasionally convulsions.
Some boys have only very mild valves and present later in life with urinary infection or persistent wetting problems.
How is the diagnosis of PUV made?
Ultrasound of the abdomen is the first investigation. This will show us any hydronephrosis (dilatation) of the kidney and how healthy they look. It will also show dilated ureters and changes in the bladder.
Micturating Cystourethrogram (MCUG) or cystogram for short is a definite way of proving the presence of valves. This needs to be performed by an experienced radiologist. It will show the state of the bladder and whether there is reflux of urine back up to the kidneys. If your child has a catheter in place then this may have to be withdrawn to demonstrate the narrowing between the posterior and anterior urethra, the site of the ‘valves’.
Radionuclide Scan will tell us how well each kidney is working and how they are draining. This is usually done sometime after the valves have been treated.
What is the treatment for PUV?
Your child will be managed by a team of kidney specialists (nephrologists) and surgeons (urologists) as well as specialist nurses.
If your child’s problem has been diagnosed before birth then usually your baby will be detained in hospital until the investigations have been completed and the valves have been dealt with.
The first treatment is usually to insert a tube into the bladder to drain the urine constantly. This tube is usually passed into the bladder via the urethra and occasionally can be placed into the bladder from the top (suprapubic catheter).
Your child will be given antibiotics to prevent infection occurring following the catheterisation. Your child is likely to require blood tests which tell us how well the kidneys are working and to check that we are giving your child the right amount of salts and fluids.
If your child’s condition has not been recognised before birth then sometimes they can be very sick with infection (we call this septic). In this situation, they may have severe disturbance of body fluids or salts along with very poor kidney function and infection. Your child may need high dependency or intensive care treatment.
What is the treatment for valves?
Usually your child’s condition improves rapidly with the establishment of drainage from the bladder by a catheter. After the cystogram has confirmed the PUV then the paediatric urologist will use a cystoscope under general anaesthetic. This is a tube that is passed through the penis with a small camera at the end. They can look at the valves directly and cut or laser the valves away.
Following the cystoscopy your child will need a catheter in place for a few more days and coverage with antibiotics. Once the catheter has been removed and your child is passing urine freely and is healthy and thriving, he will be allowed home.
What is the follow up?
Usually the follow up is shared between the paediatric urologist and paediatric nephrologist so that we can monitor your child’s condition throughout the growing years.
Sometimes there needs to be another cystoscopy to check that the valves have all been dealt with.
What are the long-term effects of PUV?
The kidneys may be badly affected by the PUV in the womb and your child may have kidney impairment. In some cases this will result in the future need for dialysis and/or kidney transplantation. However, the majority of children have only moderate or mild damage, although they will need to be followed throughout childhood.
Since the bladder is almost always affected by PUV it is likely that your child may be slow to achieve dryness during the day and night. He may need to have detailed bladder scans in the future.
Will it affect other pregnancies?
PUV is not inherited and is not due to anything that the mother might have done or ate during her pregnancy.
PUV is relatively rare and only occurs in 1 in 8-10,000 pregnancies and affects only boys.
Where will I find more information?
This leaflet is only meant to give you simple background information, please feel free to ask any member of the clinical team if you are unsure or want further information.
If you want to talk to another family about PUV then please let us know.
The National Kidney Federation cannot accept responsibility for information provided. The above is for guidance only. Patients are advised to seek further information from their own doctor.