In some children the urine that is made in the kidney is not able to drain into the bladder as quickly as it is produced. The affected kidney(s) become swollen and this swelling (dilatation) can be seen on ultrasound scans and is known as hydronephrosis. Urine drains from the kidney through a funnel shaped structure called the renal pelvis into a tube called the ureter then down into the bladder. A narrowing, hold up or blockage where ureter meets the bladder is known as vesico-ureteric junction obstruction (VUJO).
This swelling of the kidneys may be noticed on ultrasound scan during your pregnancy (antenatal hydronephrosis) and your baby may need further investigations after he / she is born. On other occasions it is not diagnosed until the baby has already been born, or, in rare cases it may be found in an older child. Sometimes only the ureter is dilated.
About the urinary system
The kidneys are part of the urinary system, which gets rid of things that the body no longer needs so that we can grow and stay healthy.
The kidneys are bean-shaped organs. They filter blood and remove extra water, salt and waste in urine (wee). Most of us have two kidneys, which are at the back on either side of our spine (backbone), near the bottom edge of our ribs.
Other parts of the urinary system are:
- two ureters – long tubes that carry urine from the kidneys to the bladder
- bladder – muscular bag that stores urine until we are ready to pass urine
- urethra – tube that carries urine from the bladder out of the body.
The Vesico-ureteric junction (VUJ, or sometimes called UVJ) is the area where the ureter joins the bladder.
What is vesico-ureteric junction obstruction (VUJO)?
VUJO is one type of congenital renal anomaly:
- congenital – the problem is present at birth
- renal – to do with the kidneys
- anomaly – different from normal
In very rare circumstances, it may be acquired. This means that the child was not born with the problem but it developed over time.
In VUJO there is usually a narrow and stiff section of the ureter as it enters the bladder. This causes a hold up of urine passing into the bladder, causing a build-up in the ureter and kidney which become swollen. This is called hydronephrosis or hydroureteronephrosis and is sometimes first seen on an ultrasound scan, usually during pregnancy.
How does VUJO happen?
As babies develop in the womb, a tube forms that connects their developing bladder to each kidney. These tubes will become the ureters. They should be hollow to allow urine to pass through them from the kidney down to the bladder, and they have a wall that is made of a type of muscle called smooth muscle.
VUJO can happen if there is a problem with the development of the muscular wall of this tube and so part of the ureter becomes narrow and stiff. This narrowing causes a hold up to urine drainage, or rarely complete blockage. Rarely, it may be caused by other things, including scar tissue, infection, a polyp or kidney stones.
Does VUJO affect how the kidneys work?
Usually not. In a small number of cases the swelling could lead to kidney damage on the affected side unless surgery is performed. However, in about half of the affected cases, VUJO gets better without any intervention. In about one third, the dilatation (swelling) will stay the same. In 10-20%, the VUJO causes the kidney(s) not to work as well as usual, or the child to have persistent urinary tract infections meaning that they would need surgery.
How common is VUJO?
VUJO affects approximately 1 in every 1,500-2,000 children, and is not usually associated with any other abnormality, and usually only one kidney is affected.
Most babies and children do not have any symptoms after birth. Some are at risk of:
Urinary tract infections
Symptoms can include fever, vomiting, pain on passing urine, abdominal or back pain, needing to pass urine more frequently.
Symptoms relating to obstruction to the flow of urine
Older children may rarely have these symptoms, which can include pain in the loin (side of the tummy) or blood in the urine haematuria.
If you think that your child may have these symptoms, contact your doctor. If you cannot reach your doctor straight away, contact 111 or NHS Direct or your local out-of-hours GP service.