Lower urinary tract obstructions (LUTO) are simple anatomic defects that can have major consequences for a developing fetus. Proper diagnosis, treatment and follow-up require an experienced, multidisciplinary team that understands not only the pathogenesis of this condition but also the best options for treatment. At the Center for Fetal Diagnosis and Treatment at The Children’s Hospital of Philadelphia, a team of high-risk obstetricians, pediatric surgeons, anesthesiologists, advanced practice and surgical nurses, radiologists, genetic specialists, neonatologists, urologists, and nephrologists sees an average of 25 prenatal cases of this rare, life-threatening disorder each year, offering an unparalleled level of expertise.
LUTO occurs as a result of either a partial or complete obstruction of the penile urethra that restricts or prevents the passage of urine to the amniotic fluid space around the fetus. Lower urinary tract obstructions come in a variety of forms, including posterior urethral valves, urethral atresia, and constricted narrowing in the mid-portion of the urethra, known as Triad syndrome. Long-standing obstruction causes back pressure on the kidneys, which impairs renal function, as well as oligohydramnios, which can result in underdeveloped lungs (pulmonary hypoplasia) and secondary deformations of the face and extremities, referred to as Potter sequence.
An initial diagnosis of LUTO is usually made by ultrasound between 18 and 24 weeks. Once referred to the Center, a one-day evaluation — including high-resolution level II ultrasound, fetal echocardiogram and ultrafast fetal MRI in complex cases — confirms the diagnosis and provides the family with options for care. Serial vesicocentesis is performed two to three times at 24 to 48 hour intervals to evaluate kidney function, a standard established in studies led by Mark P. Johnson, MD, director of obstetric services for the Center for Fetal Diagnosis and Treatment.
Male fetuses that have no other syndromic or chromosomal abnormalities and show serial improvement in urine electrolytes to below thresholds established by outcomes studies at the Center may be candidates for fetal intervention (female fetuses typically have a more complex cloacal anomaly that will not benefit from fetal intervention). Upon completion of all testing, a multidisciplinary team meets with families to review test results, discuss the diagnosis, explain treatment options and potential outcomes, and answer questions. Candidates for fetal intervention also meet with a urologist to discuss postnatal management and treatment options.
The rationale of fetal intervention via vesico-amniotic shunting is to provide an alternate passageway bypassing the obstruction and re-establishing normal amniotic fluid volume. Seamless teamwork is essential during shunt placement, an invasive procedure whose risks include premature rupture of membranes, chorioamniotic separation, intraplacental bleeding and direct trauma to the fetus. Shunting is performed as an outpatient procedure. The mother receives antibiotics, IV sedation and local anesthesia. Under ultrasonographic guidance and color-flow Doppler, a 3 mm trocar is guided through the maternal abdomen and uterus and into the fetal bladder, through which a 2.3 mm pigtail shunt is then passed. The shunt is placed as low in the bladder as possible to decrease the risk of displacement.
Once the shunt is placed and functioning properly, patients return home for the remainder of the pregnancy. Our team works closely with referring physicians to ensure the shunt is working properly and remains in place, as it can migrate into the abdomen or the amniotic space, which may require replacement in up to 40 percent of cases.
Delivery in the SDU
Some families choose to deliver in CHOP’s Garbose Family Special Delivery Unit (SDU) because of the need for neonatal subspecialty care including urology, nephrology and neonatology. The SDU was designed specifically for pregnancies complicated by birth defects and offers the highest level of immediate care for the newborn, as well as expert obstetric services for the mother.
After delivery, babies are stabilized and transported to the Newborn/Infant Intensive Care Unit where they undergo imaging studies of kidney and bladder function that allow the urologists and nephrologists to counsel families on what they can expect in the short and long term. The team reinforces prenatal counseling and educates families about additional findings, if any, and how to manage the challenges their baby may face after discharge, such as urinary tract infections, poor bladder emptying and compromised renal function.
For posterior urethral valves, postnatal treatment typically involves ablation of the valves and removal of the shunt. In more complicated cases, a vesicostomy is performed to divert urine until the baby is healthy or old enough to undergo ablation, or urethral reconstruction is performed in cases of urethral atresia. Limited long-term outcome studies suggest that these pregnancies deliver on average at around 35 weeks, that only a third of the children went on to have complications resulting in end-stage renal disease and transplant, and two thirds were able to spontaneously void without need for catheterization. Follow-up involves outpatient clinic visits with urology and nephrology, typically every three months for the first year of life and regularly thereafter to monitor for kidney infections, renal insufficiency and bladder dysfunction.
By the numbers
CFDT urologic experience January 2001 to November 2011:
- Prenatal referrals: 1,254
- Fetal interventions: 202
- Postnatal surgeries: 3,735
Fetal interventions offered:
- Fetal cystoscopy
- Vesico-amniotic shunt placement