Renal Agenesis Overview
Renal agenesis is a condition in which a baby is missing one
or both kidneys at birth. Unilateral renal agenesis (URA) describes the absence
of one kidney. Bilateral renal agenesis (BRA) is the condition in which both
kidneys are missing.
According to the March of Dimes, both types of renal
agenesis occur in less than one percent of births annually. Between one in 450
and one in 1,000 newborns has URA. BRA occurs in about one in 3,000 births (March of Dimes).
The kidneys perform functions that are necessary for life.
In healthy individuals, the kidneys:
urine, which removes urea, or liquid waste, from the blood
a balance of sodium, potassium, and other chemicals in the blood
the hormone erythropoietin, helping red blood cell growth
the hormone renin to control blood pressure
calcitriol, a hormone that supplies calcium to bones
At least one working kidney is needed. Without any kidneys, the
body’s waste can’t be properly removed. This accumulation of waste can offset
the balance of important chemicals in the blood and be fatal.
What Causes Renal Agenesis?
Both URA and BRA occur when the
uretic bud (kidney bud) fails to develop at an early stage of fetal growth.
It is not yet clear why this
happens. This and other kidney defects are associated with gene mutations (Yalavarthy, et al., 2003). The mutations occur naturally.
Who Is at Risk for Renal Agenesis?
Certain genetic factors can create a higher risk for URA or BRA. Babies
born with a single umbilical artery and caudal regression syndrome have a
higher risk of URA. Those who have a parent or sibling with either URA or BRA also
have an increased chance of developing URA.
The occurrence of renal agenesis has also been linked with several prenatal
factors (Parikh, et al.,
Risk factors associated with URA include: diabetes mellitus, black race,
younger maternal age, and consumption of alcohol during pregnancy.
In addition, some drugs may contribute to defective renal development.
They include: retinoids, thalidomide, arsenates, and cocaine.
What Are the Symptoms of Renal Agenesis?
Both types of renal agenesis are associated with organ
abnormalities. The most commonly affected area is the respiratory system.
Defects also occur in the digestive, genital, cardiac, and musculoskeletal
Newborns affected with BRA typically have distinct features
separated eyes with skin folds over the upper eyelids
that are set low
nose that is pressed flat and broad
Babies born with URA may not have any symptoms at birth. Symptoms
of URA may not be present until later in life. They can include:
or high protein in the urine
defects in the inner ear, genital tract, head, and vertebrae
glomerular filtration rate (GFR) or the ability of the kidneys to filter waste
in the face, hands, or legs
Diagnosing Renal Agenesis
Renal agenesis is typically found during routine prenatal ultrasounds.
When BRA is identified, prenatal MRI can be used to confirm the complete
absence of both kidneys.
Treatment and Prognosis
BRA is not compatible with life outside the womb. The condition is typically
fatal within the first few days of life. Newborns usually die from
underdeveloped lungs shortly after birth.
Some newborns with BRA survive. They must have chronic peritoneal
dialysis to replace their missing kidneys. Factors such as lung development,
overall health, and family support determine the success of this treatment. The
goal is to sustain these infants with dialysis until they grow strong enough to
have a kidney transplant.
The prognosis for newborns with URA depends on the health of the
solitary kidney and the presence of other abnormalities. Most individuals with
URA do not experience any complications or limitations. Some physicians may
recommend that children with URA refrain from playing contact sports. This is
to avoid injury to the solitary kidney.
Once diagnosed, patients of any age with URA need to have their blood
pressure, urine, and blood tested annually to ensure the health of the
Since the exact cause of URA and BRA is not known,
prevention is not possible. Genetic factors can’t be changed. Prenatal
counseling can help prospective parents understand the risks of having a baby
with renal agenesis.
Women can lower the risk of renal agenesis by reducing known
environmental factors before and during pregnancy. These factors include use of
alcohol and certain drugs that can affect kidney growth.