Bladder Outlet Obstruction

Bladder outlet obstruction, also referred to as lower urinary tract obstruction (LUTO), is a rare birth defect characterized by a partial or complete blockage in the urethra, the tube that allows the bladder to empty into the amniotic sac.

What is Bladder Outlet Obstruction?

Bladder outlet obstruction, also known as lower urinary tract obstruction (LUTO), is a rare birth defect. In this condition, there is a partial or complete blockage (obstruction) in the urethra, the tube that allows the bladder to empty into the amniotic sac.

There are many types of blockages, including:

  • Urethral atresia – a complete blockage of the urethra
  • Posterior urethral valves – an abnormal flap of tissue in the urethra that blocks the flow of urine (occurs only in male fetuses)
  • Triad syndrome – the middle part of the urethra is narrow, making it hard for urine to pass

Bladder outlet obstruction affects about 1 in 4,000 to 5,000 births and is more common in males.

What Causes Bladder Outlet Obstruction?

Some cases of bladder outlet obstruction are caused by a genetic or chromosome disorder. Other cases are random. They result from abnormally formed tissues or structures.

What are the Signs and Symptoms of Bladder Outlet Obstruction?

A blockage in the lower urinary tract can reduce the level of amniotic fluid. This is not safe for your baby’s health and growth. Low fluid levels can lead to:

  • bladder damage
  • kidney damage
  • risk of kidney failure 
  • deformities of the face and limbs 
  • underdeveloped lungs (most serious and life-threatening)

How is Bladder Outlet Obstruction Diagnosed?

Bladder outlet obstruction is typically diagnosed through ultrasound during the second trimester of pregnancy. However, it can be found at the end of the first trimester. Routine imaging may show a large bladder in the fetus, swelling of the kidneys, and/or a low level of amniotic fluid.

If your doctor thinks your baby may have this condition, they may order other tests, including:

  • Anatomy ultrasound – A high-resolution ultrasound to confirm the diagnosis. It will look at the size and condition of the bladder and kidneys and find any other physical abnormalities
  • Fetal MRI – A non-invasive imaging to find changes that may not be seen on an ultrasound. It can show the doctor the degree of obstruction.
  • Fetal echocardiogram – A special ultrasound to look at the baby’s heart structure and function.
  • Amniocentesis/chromosome studies – A medical procedure in which a small amount of amniotic fluid is taken and studied in the lab to screen for issues that could affect treatment and outcomes.
  • Fetal bladder tap – A procedure where a urine sample is taken from the fetus to look at kidney function.

Advanced testing gives the doctor a complete picture of your baby’s health so they can make recommendations for treatment.

What are the Treatment Options for Bladder Outlet Obstruction?

Treatment depends on how bad the obstruction is and how it affects your baby’s kidneys and amniotic fluid. If the blockage is minor and there is enough amniotic fluid, your baby may only need to be watched closely. Other obstructions are more serious, but not life-threatening. These cases may need surgery after the baby is born.

When the blockage is severe and tests show that the kidney damage may be reversed, your doctor may recommend fetal surgery. They will do this if they think your baby will have a good outcome. Procedures help restore amniotic fluid, promote lung development, save kidney function and improve your baby’s chance of living after birth.

How is Bladder Outlet Obstruction Treated During Pregnancy?

The most common fetal intervention is called fetal shunting. This involves putting a tiny, flexible tube (shunt) in the fetus’s bladder. One end of the tube stays in the bladder while the other goes into the amniotic sac. Shunting lets urine move past the blockage and drain from the fetal bladder. This increases the amount of fluid in the amniotic sac to let the lungs develop. While the procedure may relieve pressure on the bladder and kidneys, kidney function cannot always be saved.

You will be sedated during this minimally invasive procedure. Using ultrasound guidance, the surgeon inserts a hollow needle through the mother’s abdomen (belly) and uterus to place the shunt into the fetal bladder. You and your baby will be closely monitored after surgery and during the pregnancy to make sure the shunt stays in place and is working. The tube is not removed until the baby is born.  

Less common fetal interventions include:

  • Vesicocentesis – A needle is placed into the fetal bladder to remove the urine. The procedure may be done one time or many times.
  • Fetoscopic cystoscopy – A tiny, surgical camera is inserted into the fetal urethra and bladder to remove the obstruction and restore urine flow.

Each of these procedures involves risks and possible problems, including premature labor or delivery. Treatments do not always work. Children with this condition may have life-long kidney or lung damage.

Will This Birth Defect Impact my Delivery?

Babies diagnosed with bladder outlet obstruction should be delivered in a hospital prepared to treat babies with rare birth defects. Newborns need treated right away by experienced pediatric specialists and surgical services. After birth, they will go to the neonatal intensive care unit (NICU).

Pre-term or Cesarean deliveries are not always needed unless the fetus shows signs of distress or there are other obstetrical reasons. However, a good birth plan is very important. It should involve pediatric nephrologists, pediatric urologists and other specialists to ensure the best possible outcome.

Treatment After Birth

After birth, a team of neonatologists, pediatric urologists and pediatric nephrologists will evaluate your baby’s condition. Blood tests and imaging procedures, such as renal ultrasound, are typically done within 24 hours of birth. This helps the team assess your child’s kidney and lung function before deciding on a plan of care.

Treatment after birth depends on the type of obstruction and level of function. Some options may include:

  • Endoscopic resection – This is a minimally-invasive procedure. It removes the tissue causing the obstruction in the posterior urethral valves.
  • Vesicostomy – In more complex cases, this procedure lets urine leave the body through an opening below the belly button (into a diaper). A vesicostomy is often a short-term solution until your baby is strong and healthy enough to have surgery to fix the problem.
  • Dialysis and/or Transplant – Some babies may need ongoing renal replacement therapy (dialysis) or kidney transplant.

Your child may spend many weeks, or even months, in the NICU. How long they stay depends on lung development, kidney function and treatment.

What are the Long-term Effects of Bladder Outlet Obstruction?

Children born with bladder outlet obstruction are at higher risk for kidney infections and kidney failure. Some may have: 

  • long-term breathing problems
  • bladder dysfunction
  • stunted growth and development 
  • musculoskeletal (muscle and bone) problems 

Your baby will stay under the care of a pediatric urologist, a pediatric nephrologist and other specialists who will watch their health.