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Urinary Tract Obstruction

Our long experience with prenatal diagnosis and planning for optimum care allows us to offer the highest quality treatment whether intervention is indicated before or after birth.

Under the direction of Dr. Michael Harrison, the Fetal Treatment Center was the first institution to develop fetal surgery techniques. The first open fetal surgery in the world was performed at UCSF over 2 decades ago. We presently have more experience with fetal surgery and endoscopic fetal intervention (FETENDO fetal surgery) than any other institution in the world. We are dedicated to urinary obstruction research and treatment innovation.

What is urinary tract obstruction?

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 urinary tract obstruction in the fetus. Most are caused by a narrowing at some point in the urinary tract. This narrowing can slow down or stop the flow of urine, and this in turn can interfere with the development of both the kidneys and the lungs.

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What is the outcome for a fetus with urinary tract obstruction?

Outcome is related to the type of obstruction (where it is in the urinary tract), the severity of the obstruction, and the affect on renal function and amniotic fluid volume. Fetuses who have an obstruction or abnormality in one kidney and have a normal kidney on the other side will do very well. One good kidney can support a normal life.

On the other end of the spectrum are fetuses with severe obstruction to both kidneys. This can be at the level of the bladder outlet (urethra), the bladder inlet (ureterovesical junction) or the kidney outlet (ureteropelvic junction). If the obstruction prevents urine from getting out into the amniotic space around the fetus, and the amniotic fluid goes away (oligohydramnios), the fetus’s lungs will not develop. The small lungs may prevent survival after birth. The obstruction also damages the kidneys, leading to kidney failure after birth. Many of these babies will not survive.

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How serious is my fetus’s urinary tract obstruction?

Fortunately, the severity of damage to both the lungs and kidneys can be accurately assessed by ultrasound and, sometimes, by sonographically-guided aspiration of fetal urine. In most cases, serial sonographic observation is all that is needed. This applies to all unilateral lesions in which there is one normal kidney. These fetuses can be safely followed by serial ultrasounds to make sure they maintain amniotic fluid volume and to help plan the delivery.

Fetuses with obstruction to both kidneys must be closely followed for changes in amniotic fluid volume, further dilation of the urinary tract, and the sonographic appearance of the kidneys themselves.

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What are my choices during this pregnancy?

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Most fetuses with urinary tract obstruction do not require treatment before birth, but should be followed by serial ultrasound. All single-sided lesions, even those where the kidney is destroyed (dysplasia), can be successfully managed after birth. Fetuses with mild partial obstruction to both kidneys who do not have cysts in their kidneys or abnormal urine electrolytes and maintain their amniotic fluid volume can also be successfully managed after birth. It is important to follow these fetuses with serial ultrasound to make sure they maintain enough amniotic fluid volume for lung development and do not develop signs of kidney damage.

This is a good time to plan the time, type, and place of delivery. Although most babies will require some surgery after birth, it is usually not urgent. Most babies will not require intensive care and can be evaluated for surgery in the nursery or even later after they have left the hospital. However, fetuses with urinary tract obstruction that develop very dilated kidneys and have any degree of oligohydramnios and any risk of small lungs should be delivered in a tertiary center with an intensive care nursery.

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What will happen after birth?

We recommend that after consulting with your primary physician, your newborn be started on Amoxicillin, an antibiotic, immediately after birth. This will prevent any infection of the urinary tract. No testing is recommended until the baby is one month of age and the kidney function has matured. At this time we would recommend a renal (kidney) ultrasound and a Diuretic Renal Scan, and an appointment with a surgeon for consultation. Both of these tests will help evaluate the anatomy and function of the kidneys.

On occasion, the surgeon will request a third test, called a “Voiding Cystourethrogram” or VCUG, to examine the urinary system for reflux (or back up) of urine from the bladder into the kidneys. Based on the results of these studies, the surgeon will be able to identify the specific renal abnormality, assess the health of the kidney(s), and make recommendations for the treatment of your baby’s condition. The recommendations for treatment range from periodic testing to operation intervention.

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