Lower urinary tract obstructions (LUTO), also known as obstructive uropathy, are rare birth defects that occur in 1 in 5,000 to 7,000 births, commonly in male fetuses. The underlying cause is a partial or complete obstruction of the urethra — the tube that connects the bladder to the amniotic fluid space around the fetus — which restricts or prevents the passage of urine. Urinary tract obstructions come in a variety of forms.
The prognosis for each individual case depends upon the underlying cause and severity of the obstruction as well as the presence or absence of other findings. Fetal urine is an important component of amniotic fluid during gestation and contributes to fetal lung development.
Urethral atresia (UA) - a complete obstruction of the urethra
Posterior urethral valves (PUV) - a flap of tissue blocking the urethra
Triad syndrome - a constricted narrowing in the mid-portion of the urethra which results in a highly restricted ability for the urine to pass
In cases of complete obstruction, the inability for urine to be released into the amniotic fluid space around the fetus causes the bladder to enlarge and the amniotic fluid levels to decrease (oligohydramnios). Low amniotic fluid levels in turn can result in underdevelopment of the lungs (pulmonary hypoplasia), a life-threatening condition.
Without amniotic fluid, the fetus is not cushioned from the walls of the uterus. Pressure from the uterine walls leads to secondary deformations of the face and extremities (Potter sequence).
Obstruction can also cause back pressure on the kidneys, which may lead to varying degrees of kidney damage. For the greatest potential benefit, early diagnosis and intervention are essential.
A diagnosis of LUTO is usually made by ultrasound in the mid-second trimester. Families referred to the Center for Fetal Diagnosis and Treatment (CFDT) undergo a comprehensive one-day evaluation that may include the following studies:
The evaluation will determine whether or not a fetus may benefit from prenatal intervention. The presence of cysts in the fetal kidneys on initial ultrasound evaluation is an indicator of irreversible kidney damage. In these cases, fetal intervention will not improve the outcome and is thus not performed. An enlarged fetal bladder with normal amniotic fluid volume indicates an incomplete obstruction. These cases are typically followed by ultrasound until amniotic fluid levels decrease.
Upon completion of the evaluation, our multidisciplinary team meets with each family to review test results, discuss the diagnosis, explain treatment options and potential outcomes, and answer questions.
Families meet with a pediatric urologist to obtain additional information about postnatal evaluation and receive written educational information about LUTO. Consultation with a neonatologist who will care for the child after birth and a tour of CHOP’s Garbose Family Special Delivery Unit and Newborn/Infant Intensive Care Unit can be arranged.
Male fetuses with isolated complete obstruction that show serial improvement in urine electrolytes (indicating salvageable kidney function) and no other genetic or chromosomal abnormalities may be candidates for fetal intervention via vesico-amniotic shunt placement.
A shunt is a hollow tube that temporarily bypasses the lower urinary tract obstruction and provides an alternate passageway for urine to go from the bladder through the abdominal wall to the amniotic fluid space around the fetus. This allows for drainage of the urinary tract and bladder and establishes fluid around the fetus, which is necessary for lung development.
In utero shunting is performed as an outpatient procedure. The mother receives antibiotics and IV sedation (which also sedates the fetus). Depending on the amount of amniotic fluid around the fetus, an amnioinfusion (a procedure during which fluid is added to the space around the fetus) may be necessary.
The shunt is loaded into the trocar, passed into the bladder and recoils to a pigtail shape.
The other end of the shunt recoils to a pigtail outside the abdominal wall, releasing urine into the amnionic fluid space around the fetus.
The shunt is positioned as low in the bladder as possible to decrease the risk of displacement.
The shunting procedure itself is performed under ultrasonographic guidance and color-flow Doppler. A large trocar (hollow needle) is guided through the mother’s abdomen and uterus into the fetal bladder, through which a pigtail shunt is then passed. The shunt is placed low in the bladder to decrease the risk of displacement.
After the procedure, the mother receives antibiotics and is monitored for any post-procedural complications. Mothers are discharged the same day and return to CHOP one week later to ensure the shunt is functioning properly.
After post-procedural follow-up, mothers who have undergone prenatal surgery return home and are monitored by their local care team. Our team works closely with referring physicians, discussing any issues or concerns and making recommendations as needed, including referral to a pediatric urologist who will be able to evaluate the child after birth. Ultrasound surveillance throughout the remainder of the pregnancy usually involves weekly imaging to ensure the shunt remains in place and is functioning correctly, as shunt displacement can occur in up to 40 percent of cases.
A vaginal delivery tends to occur around 35 to 36 weeks unless there is a maternal condition or factor that necessitates cesarean section. At CHOP, delivery of babies with LUTO takes place in the Garbose Family Special Delivery Unit (SDU). The world’s first birth facility designed exclusively for pregnancies complicated by birth defects, the SDU is a vital part of our team’s ability to provide comprehensive care. The SDU offers the highest level of immediate care for the newborn, as well as expert obstetric services for the mother — all within the same pediatric hospital, with access to multidisciplinary specialists that may be part of the baby’s care team.
Following delivery, the baby is stabilized and transported to the Newborn/Infant Intensive Care Unit where neonatologists assess the child’s condition and provide immediate respiratory support, if needed.
Urologists and nephrologists (kidney doctors) coordinate imaging studies of kidney and bladder function and counsel families on what they can expect in both the short- and long-term.
Postnatal treatment options depend on the type of obstruction. For posterior urethral valves, endoscopic resection is a minimally invasive technique performed within the first several days of life, along with the removal of the shunt. Urologic surgeons attach specialized surgical instruments to a tool with a light and camera (endoscope) and insert it into the urethra to remove the tissue (valves) causing the obstruction.
In more complicated cases, a vesicostomy — an opening below the belly button that allows the bladder to drain directly into a diaper — diverts urine until the baby is healthy enough to undergo valve resection or urethral reconstruction.
Children with LUTO are more susceptible to kidney infections and kidney failure. A percentage require kidney transplant. Some may also experience long-term respiratory symptoms, including asthma, reactive airway disease and upper respiratory infections, as well as bladder dysfunction, poor growth and musculoskeletal problems.
Long-term follow-up is overseen by a pediatric urologist and nephrologist, with clinic visits typically every three months for the first year of life and regularly thereafter.
Updated: January 2012