Urine Blockage in Newborns

What is the urinary tract comprised of?

• The kidneys: the kidneys are the body's filters which remove waste and surplus water in the blood.
• The bladder: the bladder is responsible for storing urine until it is ready to be released from the body.
• Two ureters: the ureters bear urine away from the kidneys towards the bladder, at which point it is stored before being released through urination.
• The urethra: urine flows from the body through the urethra.

The kidneys and other parts of the urinary system are responsible for maintaining the balance of fluids and chemicals found naturally in the body. While an unborn baby is still in the mother's womb, the placenta takes control of the balancing act and is largely in charge of maintaining the balance of fluids throughout the pregnancy (until the final weeks), even though the baby's kidneys start to generate urine around 10-12 weeks into the pregnancy. Waste fluids are removed via the umbilical cord and the baby's urine is freed into the amniotic sac, the fluid sac that surrounds and protects the foetus, adding to the amniotic fluid. The amniotic liquid is involved in the development of the baby's lungs.

In some cases a blockage caused by a birth deficiency in the baby's urinary tract can prevent urine flow. This causes urine to become backed-up and the kidneys and ureters to become swollen. Inflammation of the kidneys is known as hydronephrosis and swelling of the ureters is known as hydroureter.

Hydronephrosis is generally the most commonly identified problem on ultrasound scans of babies while they are in the womb. The degrees of swelling vary and may be very distinctive or hardly noticeable. Hydronephrosis can cause mild or severe problems, but this cannot usually be determined by the degree of swelling. Hydronephrosis can affect the development of the kidneys and diminish their capacity to filter out waste fluids and excess water. Blockages in the urinary tract can also contribute to an increased risk of urinary tract infections (UTIs) and any recurrent infections can cause permanent damage to the kidneys. In severe cases the amniotic sac can be affected and the shortage of fluid can affect the development of the baby's lungs.

Types of defect in the urinary tract

There are many different types of defect that can cause hydronephrosis and doctors classify types by using specific words to illustrate the position of the blockage and type of defect. These include:

• Vesicoureteral reflux (VUR): the openings located at the top of the ureters, at which point the ureters join the bladder, normally function like valves to prevent backflow of urine into the ureters. However, if the valves do not work properly this can cause urine to flow backwards into the ureters and even further down into the kidneys, leading to inflammation. VUR can affect one or both ureters. In severe cases of reflux the development of the kidneys may be affected and this can increase the risk of permanent damage and infections after birth.
• Ureteropelvic junction (UPJ) obstruction: this occurs at the sectional meeting point of the ureter and the kidneys, the ureteropelvic junction. A blockage at this junction causes the kidneys to become inflamed, but the ureters will no be affected. This defect usually affects only a single kidney.
• Bladder outlet obstruction (BOO): this is a term used to describe any obstruction in the bladder opening or the urethra opening and can affect boys and girls. The main type of BOO found in unborn babies and a newborn baby is posterior urethral valves (PUV), which only affects boys.
• Posterior urethral valves (PUV): this affects boys only and occurs when a fold of bodily tissue in the urethra prevents the urine flowing without restraint from the bladder. PUV can also cause inflammation in other parts of the urinary tract.
• Ureterocele: ureterocele occurs when a bulge develops at the ending of the ureter; this can cause obstruction to the bladder or kidney.
• Nerve disease: the process of urination involves the coordinated transmission of nerve signals in the urinary tract. In some cases conditions which affect the nerves, including spina bifida, disrupt the transmission and cause urine to be retained.

Syndromes that can affect urinary tract

As well as birth defects there are also certain congenital conditions (present at birth) which can cause problems for the urinary tract, as well as other structures in the body. Conditions that cause multiple problems, which seem to have no connection, are known as syndromes. Examples of syndromes that concern the urinary tract include:

• Prune belly syndrome (PBS): PBS affects only boys and causes the abdomen to be unusually large due to the muscles in the wall of the abdomen being weak or completely non-existent. PBS causes the urinary tract (in its entirety) to become inflamed and the testicles stay within the body, rather than dropping down into the scrotum. Skin covering the abdomen is screwed up in appearance, which is why the condition is called prune belly syndrome. Most children who have PBS also have VUR (vesicoureteral reflux and hydronephrosis.
• Oesophageal atresia (EA): EA is a birth defect which prevents the complete development of the oesophagus, which is the tube that takes food from the orifice towards the stomach. Around 30% of babies who have EA will also have problems affecting other structures within the body, including the urinary system.
• Congenital heart defects: these can be mild, moderate or severe, and babies that have heart defects at birth are more likely to experience problems with their urinary system. This suggests that there may be a genetic link between urinary tract and heart defects.

Diagnosis

Birth defects and syndromes may be diagnosed during pregnancy, at birth or after birth if the child displays signs of a urinary tract problem.

Prenatal screening

All babies are screened for certain conditions and defects and prenatal screening is designed to check that the baby is growing healthily and identify possible abnormalities or defects. Prenatal screening tests include:

• Ultrasound: ultrasound scans use sound waves to create detailed images of the baby, which are seen on television monitors. Sound waves, which are sent from a wand-like contraption to the womb, are bounced off the baby to create black and white images. Ultrasounds can produce images of the internal organs, enabling doctors to identify areas of swelling.
• Amniocentesis: amniocentesis involves inserting a fine needle through the skin into the amniotic sac, where a sample of fluid is taken and tested. The amniotic fluid contains genetic information and analysis can detect defects.
• Chorionic villus sampling (CVS): in this test the doctor gathers a small sample of placental tissue; the sample contains genetic information which is analysed for symptoms of defects.

Ultrasound scans are routine during pregnancy and are usually carried out at around 12 and 20 weeks. Many women do not require additional tests, but the option is there and tests may be recommended if there is a chance of genetic problems, family history or signs of abnormalities or defects on the ultrasound scan. There is a small risk of damage to the baby with both CVS and amniocentesis, and the risks of the tests will always be weighed up against the benefits.

Examination of a newborn baby

In some cases a newborn baby doesn't urinate normally even if there are no signs of abnormalities on the prenatal tests. This may include urinating not at all or only a little. An examination may reveal an inflamed kidney and imaging techniques can also help to diagnosis the reason for this problem. Imaging techniques include:

• Ultrasound: ultrasound scans can be implemented to observe images of the baby's urinary tract, and the images are likely to be clearer than when the baby is inside the mother's womb.
• Voiding cystourethrogram (VCUG): a VCUG may also be ordered if a doctor believes that urine is retracting up into the ureters or the bladder opening is obstructed. The test involves using a catheter to fill the bladder with fluid containing iodine, which makes it detectable on X-ray. The X-ray images and video records what happens when the bladder is filled and then after when the child urinates, so that doctors will be able to see whether reflux is occurring or if there is a blockage affecting the bladder.
• Nuclear scan: this test involves the injection of a tiny amount of radioactive material into the baby's bloodstream (the exact amount comes down to the weight of the child). A camera is used to capture the flow of material in the course of the kidneys, ureters and bladder.

Later diagnosis

In some cases a blockage will not be diagnosed until later when a child shows symptoms and signs of a urinary tract infection. Signs to look out for include:

• Fever (a high temperature).
• Pain or a stinging sensation when urinating.
• Loss of appetite.
• Unpleasant smelling urine.
• Dark coloured urine.
• Vomiting.

If a child has symptoms that persist it is advisable to take them to a doctor. You should see a doctor as soon as possible if a baby aged 2 months or under has a fever. The physician will take a sample of urine to be sent off for analysis. The clinician may also order further tests including an ultrasound, nuclear scan or voiding cystourethrogram (VCUG).

Treatment

The treatment plan depends on the severity and cause of the urinary tract blockage. Treatment is not usually administered immediately for babies who are diagnosed with hydronephrosis during pregnancy, and the condition usually clears up without any formal treatment prior to the baby's birth, especially if only one side is affected. Doctors will recommend frequent ultrasound scans to allow them to keep an eye on the baby. In rare cases treatment is recommended before the birth of the baby.

• Prenatal shunt: if the blockage is life-threatening a prenatal shunt may be recommended. A shunt is a slim tube which is inserted into the bladder to drain fluid into the amniotic sac. The positioning of the shunt is carried out in a similar way to amniocentesis, when a needle is introduced through the mother's abdomen and the procedure is guided by ultrasound. This procedure carries risks and is only carried out in extreme circumstances when the baby's life is at risk as a result of a lack of amniotic fluid, as this may prevent the development of the lungs or damage to the kidneys.
• Antibiotics: antibiotics are medication used to destroy bacteria. If a doctor suspects that a newborn baby has VUR or a blockage they may prescribe antibiotics to stop urinary tract infections.
• Surgery: surgery is sometimes required if a defect does not correct and the infant still has a urinary blockage. Doctors will decide whether to operate based on the seriousness of the blockage. Surgery is used to remove the blockage and restore free flow. A stent (a slim tube) may also be positioned in the urethra or ureter to allow urine to flow during the healing process.
• Intermittent catheterisation: when the child is found to have urine retention as a result of nerve disease, intermittent catheterisation may be recommended. The parent will be educated in how to empty the bladder using a slim tube known as a catheter. This treatment helps to stop urinary tract infections, kidney damage and overflow incontinence.