Lower Urinary Tract Outlet Obstruction

Lower urinary tract outlet obstruction (LUTO) is when pee (urine) is partly or completely blocked from leaving the body at the lower urinary tract.

What is Lower Urinary Tract Outlet Obstruction?

Lower urinary tract outlet obstruction (LUTO) is when pee (urine) is partly or completely blocked from leaving the body at the lower urinary tract. The lower urinary tract includes the bladder and the urethra.

This blockage can make the organs swell and cause long-term damage. LUTO also leads to low amniotic fluid during pregnancy. This can make it hard for a baby’s lungs and body to grow the right way. LUTO occurs in about 1 in every 5,000 pregnancies. It is more common in males.

What Are the Causes of LUTO?

The most common causes of LUTO are:

  • Posterior urethral valves - This is when tissue blocks the tube that brings urine from the bladder to the outside of the body. This tube is called the urethra.
  • Urethral atresia - This is when there is no opening from the urethra to the outside of the body.
  • Triad syndrome - This is when in the middle of the urethra is narrow, making it hard for urine to pass through.

What Are the Signs & Symptoms of LUTO?

Signs are normally found on the anatomy ultrasound during the 2nd trimester. They can also be found near the end of the 1st trimester. Possible signs of LUTO include:

  • enlarged bladder
  • enlarged kidneys
  • swollen ureter
  • decreased amniotic fluid
  • underdeveloped lungs
  • abnormalities to the face arms, or legs

How is LUTO Diagnosed?

You will have an ultrasound to find the cause of LUTO. More testing may be needed to get a better understanding of your baby’s condition. Tests can include:

  • Anatomy ultrasound – A high-resolution image that looks at the size and condition of the bladder and kidneys. It can also find other problems.
  • Fetal magnetic resonance imaging (MRI) – This test shows how bad the blockage is and any changes not seen on an ultrasound. This test is non-invasive.
  • Fetal echocardiogram – This test uses sounds waves to take a moving picture of your baby’s heart structure and see how it functions.
  • Amniocentesis/chromosome studies – A procedure that takes a small amount of amniotic fluid from the mother’s womb to study. The fluid is screened for problems 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.

How is LUTO Treated?

Treatment for LUTO depends on the cause of the blockage and the symptoms. If your baby has a small blockage and amniotic fluid is not affected, your baby will be watched closely.

If the obstruction is causing other areas in the urinary tract to swell and there is low amniotic fluid, treatment before birth may be needed. This could include:

  • Vesicocentesis -- A needle is inserted into your baby’s bladder to remove urine. This may be done many times during pregnancy if urine builds up again.
  • Vesicoamniotic shunt - A small plastic tube is placed into your baby’s bladder to let urine flow to the outside of their body.
  • Fetal cystoscopy - A small camera is used to see your baby’s blockage and remove it.

Surgery may also be needed after birth. In some cases, a short-term procedure is done to allow urine to leave the body through a tube just below the belly button. This is called a vesicostomy. It can give your baby time to heal until they are ready for a permanent fix, such as urethral reconstruction (repairing the urethra) or valve resection (removing the blockage).

Possible Problems

Fetal surgeries involve risks, including early (premature) labor or delivery. Your health care provider will talk with you about the risks and benefits of these procedures before any treatment is done.

Babies with LUTO usually need to be monitored in the NICU after delivery. They will have more tests to check kidney and urinary tract function This helps providers decide on treatments. Your child may need surgery after birth to permanently remove the blockage.

Even after fetal treatment, children born with LUTO are at higher risk for kidney infections and kidney failure. Some may have: 

  • long-term breathing problems
  • abnormal bladder function
  • impaired growth and development
  • musculoskeletal (muscle and bone) problems

Lifelong Considerations

After birth, your baby will be seen by a pediatric urologist, a pediatric nephrologist, and other specialists to watch their kidney and urinary function.

If your child had kidney or lung damage, long-term care may be needed. In severe cases, dialysis or a kidney transplant may be needed.