Lower urinary tract obstruction (LUTO)

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 can be detected on prenatal ultrasounds 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. 

What Are the Symptoms of LUTO?

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)

What Are the Complications of LUTO?

LUTO can present with a range of symptoms depending on the degree of urinary tract obstruction and when it developed during pregnancy. Mild blockages or those that develop later in pregnancy tend to have less effect on lung development and kidney function. However, severe obstruction associated with low amniotic fluid and pulmonary hypoplasia as well as diagnosis early in pregnancy can result in permanent kidney damage, significant breathing difficulties, and be life threatening. 

What Are the Treatment Options for LUTO?

The Chicago Institute for Fetal Health provides comprehensive evaluation, diagnosis, treatment and delivery planning for fetal urinary tract obstruction.  

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 further imaging with a fetal MRI or fetal echocardiogram. Sometimes, a genetic test is also recommended to help determine any underlying causes of the condition. 

Treatment of bladder outlet obstruction is dependent upon the severity of the obstruction and how far along the pregnancy is. There are some conditions which may benefit from a fetal intervention, like a vesicoamniotic shunt. Each situation is unique and each family receives counseling specific to their situation.

Delivery planning is essential for babies with LUTO since they usually need to deliver near a Neonatal Intensive Care Unit (NICU) to be close to specialists in case of breathing problems (due to underdeveloped lungs), kidney damage (due to urine blockage), or need for surgery to relieve the urinary tract obstruction. Long term treatments for kidney and bladder damage including urinary catheters or dialysis may be needed. 

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