Bladder Outlet Obstruction (BOO)

Bladder outlet obstruction (BOO) occurs when there is a blockage in a developing baby’s urinary tract.  

Also referred to as lower urinary tract infection obstruction (LUTO), bladder outlet obstruction (BOO) is an uncommon fetal condition in which the urethra—the tube that transports the baby’s urine from the bladder to the amniotic space—becomes partially or completely blocked. If BOO is left unaddressed, the obstruction can lead to a buildup of urine in the baby’s bladder and kidneys, forcing the bladder to enlarge and amniotic fluid levels to drop.

Bladder Outlet Obstruction Causes

Bladder outlet obstruction is rare, occurring in about one in every 4,000 live births. It is sometimes linked to genetic disorders or issues with the baby’s chromosomes, in which case several other medical problems may be present. For many male babies, BOO results from a thin membrane (posterior urethral valve) that prevents the bladder from properly draining. Rarely, a narrowly formed urethra may be to blame for blockages.

Some cases of BOO may not have any underlying causes. These instances are referred to as “isolated” lower urinary tract obstructions (LUTO).

Bladder Outlet Obstruction Symptoms

Babies with bladder outlet obstruction may experience medical complications that range from mild to potentially life-threatening. In severe cases, BOO can lead to kidney failure, bladder damage and respiratory insufficiency.

Bladder Outlet Obstruction Diagnosis

Bladder outlet obstruction is often diagnosed through an ultrasound, an imaging test that produces images of the baby’s urinary tract and amniotic fluid levels. It is typically identified between 20 and 24 weeks of gestation.

Other diagnostic methods for BOO include:

• Fetal urine tests to assess kidney function
• Chromosome analysis
• Fetal magnetic resonance imaging (MRI) to view more detailed images of the baby’s body
• Echocardiography imaging to identify signs of heart disease

Bladder Outlet Obstruction Treatments

Careful monitoring plays an important role in bladder outlet obstruction treatment. Expectant mothers at Tampa General Hospital’s Women’s Institute have access to advanced evaluation and high-risk obstetrics treatment services for BOO and other complex fetal conditions.

In addition to attentive, personalized care from a multidisciplinary team, TGH specializes in providing BOO treatments such as:

• Vesicoamniotic shunt surgery – Draining urine through a small tube (shunt) that is placed in the fetus’ bladder and removed after birth
• Vesicocentesis – Removing urine from the fetus’ bladder using a very small needle
• Fetal cystoscopy – Removing a blockage from the fetus’ urinary tract by inserting a thin tool into the urethra