Lower Urinary Tract Obstruction (LUTO)/Bladder Outlet Obstruction (BOO)

Lower urinary tract obstruction (LUTO), also known as bladder outlet obstruction (BOO), is a rare condition which occurs more commonly in males than females. LUTO is a blockage either at the base of the bladder or at the urethra, which is the tube that drains urine from the bladder. Depending on the severity of the blockage, the drainage of urine can either be slowed or completely stopped. 

If the urine cannot drain properly, there may be problems before and after the blockage:

  1. Before the blockage: The urine backs up and the pressure can cause damage to the developing kidneys and bladder.
  2. After the blockage: If little to no urine drains out from the bladder there will be less amniotic fluid around the fetus which can then cause the lungs to not develop correctly.  

LUTO Diagnosis

LUTO can be detected on prenatal ultrasound by looking at the size and shape of the kidneys, bladder, and urethra, as well as the amount of amniotic fluid.  Sometimes, additional ultrasounds or other imaging like fetal MRI is recommended to better understand the problem.

The findings concerning for LUTO on prenatal ultrasound include:

  • Enlarged and/or thickened bladder
  • Dilated urethra (“Keyhole sign”)
  • Abnormal kidneys
  • Low amniotic fluid (Oligohydramnios)
  • Underdeveloped lungs (Pulmonary hypoplasia)

LUTO Complications

LUTO can present with a range of symptoms depending on the degree of urinary tract obstruction and when it developed during pregnancy. Mild blockages in which the amniotic fluid volume is normal tend to have less effect on lung development and kidney function. However, severe blockages in which the amniotic fluid is low or absent, often lead to severe kidney damage and breathing difficulties after birth. It is not uncommon for mild blockages with normal amniotic fluid early in pregnancy to progress to severe blockages with low amniotic fluid late in pregnancy. Long-term, any child born with LUTO can have problems with toilet training, urinary wetting, and urinary tract infections.

LUTO Treatment Options

The Chicago Institute for Fetal Health provides comprehensive evaluation, diagnosis, prenatal treatment, and delivery planning for LUTO of all types. 

If a LUTO is suspected in a fetus, it is important to have a thorough assessment of the urinary tract and other fetal structures. This assessment typically starts with a detailed ultrasound examination but may also include a fetal MRI and fetal echocardiogram. Sometimes, a genetic test is also recommended to help determine any underlying causes of the condition.

Treatment of LUTO is dependent upon the severity of the obstruction and how early it was diagnosed. In some cases, the fetus may benefit from prenatal intervention to restore the amniotic fluid volume such as the placement of a vesicoamniotic shunt or infusion of fluid into the amniotic space. Each situation is unique and each family receives counseling and care that is customized to their specific situation.

Delivery planning is essential for babies with LUTO since they usually need to deliver at a center with immediate access to a Neonatal Intensive Care Unit (NICU). Newborn babies with LUTO require evaluation and care by a multi-disciplinary team including neonatologists, pediatric urologists, pediatric nephrologists and pediatric surgeons. This team is experienced in the treatment of complex breathing problems (due to underdeveloped lungs), kidney damage (due to urine blockage), and urinary tract obstruction. Shortly after delivery, the care team will perform blood work to monitor the kidney function and may place a urinary catheter to relieve the obstruction. Long-term treatments may include surgery on the urinary tract, dialysis and possibly kidney transplantation.