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. This obstruction restricts or prevents the passage of urine. Urinary tract obstructions come in a variety of forms.
- 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.
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.
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:
- High-resolution level II ultrasound — noninvasive imaging used to assess overall fetal growth and development, the severity of the obstruction, and the condition of the kidneys.
- Ultrafast fetal MRI — a noninvasive imaging technique advanced at The Children's Hospital of Philadelphia (CHOP) that can be useful in evaluating the genitourinary tract in more complex cases.
- Fetal echocardiogram — a specialized ultrasound evaluation of the fetal heart to assess structure and function.
- Serial renal function (electrolyte) profile — a complete bladder drainage (vesicocentesis), performed three to four times at 24 to 48 hour time intervals, to evaluate kidney (renal) function and establish whether there is serial improvement in the urine electrolytes below established thresholds indicating the potential to save the kidneys.
- Fetal chromosome studies (karyotype) — laboratory studies to confirm male gender (as female fetuses with this type of urinary tract anomaly will not benefit from fetal intervention) and rule out chromosomal abnormalities that would affect the baby’s survival or long-term outcome.
A thorough prenatal evaluation will determine whether or not your baby may benefit from fetal 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 your family to review test results, discuss the diagnosis, explain treatment options and potential outcomes, and answer questions.
You will also meet with a pediatric urologist to obtain additional information about postnatal evaluation and treatment. Consultation with a neonatologist who will care for your child after birth and a tour of CHOP’s Newborn/Infant Intensive Care Unit (N/IICU) can be arranged on the same day.
To learn more about the diagnosis and treatment of LUTO, watch our educational video below.
If your baby is prenatally diagnosed with LUTO, you can return home to be monitored by your local care team for the duration of your pregnancy. Mothers who have undergone prenatal surgery can also return home after a post-surgical follow-up confirms that both you and your baby are doing well. For all LUTO pregnancies, 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 your child after birth. If you have fetal surgery, you will generally be monitored with weekly ultrasound surveillance throughout the remainder of your pregnancy.
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 your baby’s care team.
Following delivery, your baby is stabilized and transported to the N/IICU where neonatologists assess your child’s condition and provide immediate respiratory support, if needed.
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 vesicoamniotic 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. If you are a candidate for fetal surgery, you will receive antibiotics and IV sedation (which also sedates your baby). Depending on the amount of amniotic fluid around the fetus, an amnioinfusion may be necessary. In an amnioinfusion procedure, fluid is added to the space around the fetus.
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, expectant mothers receive antibiotics and are monitored for any post-procedural complications. You will be 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.
Postnatal care for babies born with LUTO
After your baby is born, pediatric urologists and nephrologists (kidney doctors) coordinate imaging studies of kidney and bladder function. After thorough evaluation of your child's condition, the team will counsel your family on what to expect in both the short- and long-term.
Postnatal treatment options depend on the type of obstruction. For posterior urethral valves (PUV), endoscopic resection (valve ablation) 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. Learn more about how PUVs are treated by CHOP's pediatric urologists.
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: June 2014