Fetal lower urinary tract obstruction (LUTO) is a birth defect that consists of blockage of the baby’s bladder. This condition affects approximately 1: 5000-8000 males and can lead to the abnormal development of a baby’s kidneys and lungs. Females can also have an obstruction though it is not as common. The urinary tract consists of two kidneys (where urine is made), two ureters (tubes which lead the urine into the bladder), the bladder, and the urethra (the tube which leads the urine from the bladder to the outside of the body). The urine should flow from the kidney, through the ureter, to the bladder, and out of the fetus through the urethra to the amniotic fluid. There are many causes of LUTO in the fetus such as: “Posterior urethral valves” (when a membrane completely or partially blocks the baby’s urethra), “urethral atresia” (lack of formation of a segment of the urethra), “anterior urethral valves” (valves closer to the urethral meatus, the point where the urine leaves the penis), or prune belly syndrome (a not-so-well understood condition in which the abdominal wall muscles are weak and the bladder and other organs of the urinary tract are distended. Because most of the amniotic fluid consists of fetal urine, the lack of amniotic fluid (oligohydramnios) may hinder the development of the baby’s lungs, as they need amniotic fluid around them to develop normally. Thus, fetal LUTO may result in death of the baby in utero (rare) or after birth (more common) or in chronic lung or kidney disease after birth. Babies with LUTO that survive may require several surgical procedures after birth, or even kidney transplant.

Fetuses with LUTO may have damage to their kidneys beyond repair at the time of the prenatal ultrasound diagnosis. Treatment of such fetuses is not recommended, because the baby may still die from lack of functioning kidneys after birth. Thus in order to offer treatment in utero, the doctor needs to determine that the baby’s kidneys are still functioning adequately. This can be done via a vesicocentesis or cordocentesis.

A vesicocentesis is performed by obtaining fetal urine with a needle that is inserted through the mother’s abdomen and into the baby’s bladder. One or two fetal urine samples may be required. If the first urine sample shows normal values, no further testing is required. However, if the first sample is abnormal, it may be due to the presence of old, concentrated fetal urine. Thus collection of a second sample of fresh urine may be indicated. This is usually done within 48 hours of the collection of the first sample. If the second sample is also abnormal, no further testing is offered at our center. Other centers may offer a third sample collection.

A cordocentesis is performed by obtaining fetal blood with a needle inserted through the mother’s abdomen and into the baby’s umbilical cord. Advantages of cordocentesis over vesicocentesis include a single procedure. Disadvantages include higher degree of difficulty, with increased risk of fetal death from the procedure (approximately 1%) as well as inability to perform the procedure due to fetal position or bladder distention. In addition, fetuses with damage to one but not both kidneys may still show an abnormal assessment when tested via cordocentesis, and become disqualified from treatment.

The goal of in utero treatment of fetal LUTO is to avoid damage to the baby’s kidneys and to allow for the development of the baby’s lungs. These goals can be accomplished by inserting a catheter (small plastic tubing) called a “vesicoamniotic shunt” into the baby’s bladder to provide a passage way for urine to exit into the amniotic fluid (bag of waters). Patients are typically quoted a 4% risk of fetal death from the procedure and 5-10% risk of premature rupture of membranes which may lead to miscarriage (before 24 weeks) or premature delivery (before 37 weeks). In addition, the following statistics are also quoted for fetus having received treatment for LUTO: Approximately 33% of babies will do well after birth without the need for dialysis or renal transplant, 33% will require multiple surgeries, dialysis and/or transplant before age 5, the remaining 33% of babies will die either in utero or after birth from damage to the kidneys, lack of lung development or complications of prematurity. Further, unfortunately the shunt may become dislodged or stop working in up to 40% of patients. When this occurs, patients have then been counseled as to whether they would elect to attempt a repeat vesicoamniotic shunt placement, withhold treatment or opt for pregnancy termination (before 24 weeks in most states). However, recently Dr. Quintero has developed and now offers a modified version of the vesicoamniotic shunt called the “Q-shunt”. It is anchored to the fetal bladder wall and the fetal anterior abdominal wall with the goal of keeping it in place and preventing fetuses from pushing or pulling it out. To date we have obtained patient consent to place the shunt in 6 cases all of which have remained in place.

In addition, if the fetus has been identified as having posterior urethral valves, and if the tissue blocking the urethra can be positively identified as posterior urethral valves by performing “fetal cystoscopy” (inserting an endoscope or medical telescope into the baby’s bladder - also developed by Dr. Quintero); the valves can be perforated using laser energy through the endoscope. The risk of fetal death and/or premature rupture of membranes is similar to vesicoamniotic shunting. If the laser ablation is successful, the baby will be able to urinate through the urethra into the amniotic cavity. A shunt is left in place as a fail safe measure.

INCLUSION CRITERIA:
1) Must be at least 16 weeks' gestation
2) Have undergone or willing to undergo vesicocentesis or cordocentesis
3) Must give written informed consent
4) Normal karyotype
5) Normal fetal urinary parameters
6) Willing to have follow up weekly ultrasounds

EXCLUSION CRITERIA:
1) Presence of major congenital anomalies
2) Known unbalanced chromosomal complement
3) Ruptured membranes
4) Active labor
5) Urine electrolyte values above the threshold upon repeat vesicocentesis