What is pyelectasis/hydronephrosis?
To understand this condition, it is helpful to understand how the urinary tract works. In simple terms, the kidneys (we typically have two) filter the blood and remove waste products that are then taken out of the body in the urine. The urine is collected in the pelvis, which empties into a tube (the ureter) and then drains into the bladder. From the bladder the urine is drained out of the body through the urethra.
During pregnancy the placenta does most of this work for the baby. The kidneys produce urine starting as early as the fifth week. While the baby is inside the womb, the urine produced by the baby's kidneys adds to the amount of fluid surrounding the baby. The fluid is important to help the lungs develop as well as giving the baby a "cushion" and providing him or her space to move.
Twenty to 30 percent of birth defects found before the baby is born involve the urinary tract. Fifty percent of these babies will have a condition called hydronephrosis.
Hydronephrosis occurs when the pelvis becomes enlarged because urine is collecting in the area of the kidneys. The term hydronephrosis is used when the enlargement exceeds 10 millimeters at 20 to 24 weeks of pregnancy. Hydronephrosis can be the result of:
- A blockage, which can occur in a variety of places along the urinary tract.
- Reflux or backward flow of the urine.
- Immaturity, which allows more stretching of the pelvis than normal.
- An extra ureter (the tube that carries urine from the kidneys to the bladder).
- Multicystic kidney (which means the kidney does not function).
Pyelectasis also is known as renal (kidney) pelvic dilatation. Dilatation means stretching or enlargement. The amount of stretching of the renal pelvis with pyelectasis is typically defined as greater than 4 mm but less than 10 mm in a fetus less than 24 weeks of pregnancy. Enlargement of 4 to 10 mm also may be called mild hydronephrosis and will improve by itself in up to 90 percent of cases. However, in 10 percent of cases, the dilatation will increase. Pyelectasis/mild hydronephrosis does warrant another ultrasound as the pregnancy progresses to examine the urinary tract. This ultrasound will look at the amount of dilatation in the pelvis, appearance of each kidney, how many kidneys are affected, overall fetal growth, gender, amniotic fluid index (the amount of amniotic fluid present), bladder size and thickness and how well the bladder is emptying.
Prenatal diagnosis of hydronephrosis:
Hydronephrosis is usually seen on a routine ultrasound. Follow-up ultrasounds are needed to track the condition. An abnormal urinary tract is seen in about 85 percent of infants who are diagnosed with mild hydronephrosis before birth. The other 15 percent of cases will get better with no problems after birth. Of the 85 percent of babies with a defect, only 15 to 25 percent require surgery to correct it. Amniotic fluid volume is the single most important factor that shows the well-being of the unborn baby. Another finding that causes concern is an enlarged bladder.
Your obstetrician will likely refer you to a specialist that handles high-risk pregnancies. These doctors are called perinatologists. Other specialists you may see during pregnancy include a pediatric urologist or nephrologist and a neonatologist. They will make recommendations for follow-up care during pregnancy as well as follow-up care for the baby once it is born.
How does hydronephrosis affect my baby?
Pyelectasis or mild hydronephrosis will likely have little or no effect on your baby. Most of these babies do very well. Very rarely, a fetus will have severe bilateral hydronephrosis or an extremely distended or filled bladder and insufficient amniotic fluid. These babies will have a more guarded prognosis (see the chapter on bladder outlet obstruction).
The affects of hydronephrosis on your baby are dependent on the cause. Two of the more common causes for mild hydronephrosis and their effects are:
- Ureteropelvic junction obstruction, also referred to as UPJ obstruction, is the most common cause of hydronephrosis. The flow of urine from the kidney to the ureter is blocked. This can affect one or both kidneys. Complete obstruction, very early in the pregnancy (8 to 10 weeks) will result in severe dysplastic changes. If the UPJ obstruction is on one side only and has litte effect on kidney function, testing after the baby is born is recommended. An ultrasound of the kidneys and bladder will be done at about 4 weeks of age to determine if the hydronephrosis is still present. If UPJ is suspected, a renal scan may done to confirm the diagnosis. This scan measures the kidneys' ability to make and drain urine. If the initial ultrasound should show severe hydronephrosis and/or other changes such as thickening of the cortex (the part of the kidney that produces urine), a voiding cystourethrography (VCUG) test may be done to see if urine is backing up. Some babies with prenatally diagnosed hydronephrosis may be prescribed antibiotics after birth to prevent a urinary tract infection. When the baby is diagnosed with hydronephrosis before birth, follow-up is done soon after the baby is born.
In the past, without diagnosis before birth, these babies with no apparent problems would go for years without a diagnosis and kidney function could be severely affected. There is the potential need for surgery if kidney function is affected. Pyeleoplasty is the surgery needed for UPJ obstruction. Pyeleoplasty is the removal of the area that is blocked. However, it is also known that many cases of UPJ will get better on their own in the first 18 months of life.
- Vesicoureteral reflux (VUR) is the abnormal flow of urine from the bladder back toward the kidney(s). This can result from an abnormal flap valve. The backflow of urine allows bacteria from the bladder to enter the kidney. This makes these babies more prone to urinary tract infections of the bladder and/or kidney(s) (pyelonephritis). Pyelonephritis can seriously damage the kidney(s). This can put these babies at risk for hypertension and kidney failure.
Reflux is diagnosed through a VCUG test or radionuclear cystourethrogram (RNC) test. If reflux is found, an isotope renal scan may be done to evaluate kidney function and assess for damage.
When the diagnosis of reflux is made early, treatment is aimed at preventing urinary tract infections or UTI. Antibiotics are part of this treatment as well as c physical exams, X-rays of the bladder and/or kidneys (to monitor the reflux) and urine analysis (to check for infections). Often, reflux will disappear as the child grows and the ureter(s) lengthens and develops. This form of treatment is most commonly used for reflux that is less severe and causes only mild hydronephrosis.
Surgery aims to fix the flap valve problem so that urine is not able to flow backward. It also may fix a twisted ureter or dilated/distended ureter. Surgery is used when reflux causes more severe hydronephrosis that is more likely to result in kidney damage.
How does hydronephrosis affect my pregnancy?
Hydronephrosis may be first seen with a routine ultrasound. You will likely be referred for a follow-up ultrasound that can examine the fetus' anatomy in more detail. The two most important factors for outcome with these fetuses are the volume of amniotic fluid and the appearance of the kidneys. These factors can change either for better or worse as the pregnancy progresses. For that reason, multiple ultrasounds need to be performed to watch for changes in symptoms. The affects on the pregnancy are dependent on the severity of the hydronephrosis. For most, the pregnancy will progress normally and the baby's kidneys will be observed by ultrasound to ensure they continue to function well. The amniotic fluid volume, which is the best clue about how well the kidneys are functioning, also will be watched.
How is hydronephrosis treated?
These babies typically go to the newborn nursery. Some may have an ultrasound of their kidneys and bladder before they go home. Most will have an ultrasound at approximately 4 weeks of age. These babies usually go home when their mother is discharged and are scheduled for an ultrasound later. Even with a normal first ultrasound, another one will be done to make sure that the hydronephrosis hasn't returned. It is rare for mild enlargement to progress. The majority of babies diagnosed with mild hydronephrosis before birth will require no type of treatment except observation.
If the hydronephrosis continues to be seen after birth or if an ultrasound shows there are changes in the kidney(s), tests will be done to determine if the baby has reflux or an obstruction. X-ray tests may be done to look more closely at the renal anatomy and other tests may be done to rule out reflux. If there is an obstruction or reflux, surgery may be required if kidney function is being affected.
What about after surgery?
Very rarely is surgery required for mild hydronephrosis. Occasionally, surgery will be needed to fix an obstruction or reflux. Surgery is almost never needed when the baby is first born, but is scheduled after the child has been allowed to grow and tests have been done to measure the extent of the problem.
Will I be able to help care for my baby?
Yes. Your baby will more than likely go to the newborn nursery and be treated there if hydronephrosis is his or her only problem. The urologist/nephrologist may see him or her in the hospital if you deliver at Froedtert Hospital. If you do not deliver at Froedtert or the urologist/nephrologist does not see your baby before you go home, please call to set up a follow-up appointment soon after you take your baby home. After birth and before your appointment with a pediatric urologist, an ultrasound of the kidneys will be done to look at the structures and for comparison with the pictures taken before the baby was born.
When can my baby go home?
Most babies that were diagnosed with hydronephrosis before birth will go home with their mothers after delivery. Follow-up is done on an outpatient basis. If your baby does require surgery, it will be done later in life.
What is my baby's long-term prognosis?
Long-term prognosis is excellent for most of these babies. Even if the baby has only one working kidney, he or she can live full lives with few limits on activity.
For more information, visit www.UrologyHealth.org.