Posterior urethral valves (PUV)

Posterior urethral valves (PUV) is a condition found only in boys that affects the urethra (the tube which runs from the bladder to the outside).

The urinary system consists of the kidneys, the bladder and ureters. The kidneys filter the blood to remove waste products and form urine. The urine flows from the kidneys down through the ureters to the bladder. During urination it passes through the urethra to the outside.

In PUV, the urethra has a blockage in it near the bladder. This makes it difficult for a child to pass urine. As the bladder pushes hard to get the urine out, it causes pressure which may result in urine being pushed back from the bladder into the ureters and kidneys. This causes the kidneys and bladder to swell and may lead to kidney damage.

About one in every 8,000 male births has PUV.

PUV is not inherited in any recognised way and seems to happen in the early stages of pregnancy when the organs, muscle and other tissue starts to form. It is not due to anything a mother did or ate during pregnancy.

There are various symptoms associated with PUV, but they may not affect every child in the same way. The degree of blockage affects the severity of the symptoms.

Some symptoms include:

• an enlarged bladder, so that it can be felt through the abdomen as a lump
• urinary tract infections (UTIs)
• difficulty urinating
• a weak stream of urine
• unusually frequent urination
• bed wetting after toilet training has been successful
• poor weight gain

PUV can be diagnosed by a routine ultrasound scan during pregnancy if the bladder, ureters or kidneys are swollen. It can also be diagnosed in a newborn baby if the bladder is swollen and urine dribbles constantly.

If the blockage was not severe before or just after birth, the condition can remain undetected until the child has symptoms as above.

The severity of the blockage affects how the condition is diagnosed. Each case will be different, but the following tests are usual:

• Ultrasound of the child’s abdomen – this is very similar to the ultrasound scan that most women have during pregnancy. It creates a picture of the organs inside the body and shows how well they are working.
• Micturating cystourethrogram (MCUG) – this test shows urine passing from the bladder to the urethra and then to the outside. It will also show if the urine is flowing backwards towards the ureters and kidneys (this is known as reflux).
• Cystoscopy – this is a scan which uses a small tube with a camera at the end to examine the inside of the bladder.
• Blood tests – these will show how well the child’s kidneys are working and check that there is enough fluid inside the body. Other tests and scans may be needed to check that other parts of the urinary system are working properly. These can include kidney and bladder function tests.

There are several options for treatment, depending on how severely the symptoms are affecting the child:

• The first course of action usually deals with the symptoms and includes putting a catheter (thin, plastic tube) into the bladder to drain away the urine. Any UTIs and fluid imbalance will also be treated with antibiotics and intravenous (IV) fluids, which are delivered directly into a vein.
• The next course of action is to try to remove the parts of the valve which are causing the backflow of urine into the kidneys. This is usually carried out using a cystoscope (a tube with a light on the end) rather than a traditional ‘open’ operation.

The outlook depends on how much damage has already occurred in the kidneys. The doctor will be able to give parents a better idea once they have all of the child’s test and blood results. The child will need follow up appointments on a long term basis to check that no lasting damage has been done to the urinary system.