Renal agenesis is a condition in which a newborn is missing one or both
kidneys. Unilateral renal agenesis (URA) is the absence of one kidney.
Bilateral renal agenesis (BRA) is the absence of both kidneys.
Both types of renal agenesis occur in fewer than 1 percent of births
annually, according to the March
of Dimes. Fewer than 1 in every 1,000 newborns has URA. BRA is much rarer,
occurring in about 1 in every 3,000 births.
The kidneys perform functions that are necessary for life. In healthy people,
- produce urine, which removes
urea, or liquid waste, from the blood
- keep a balance of sodium,
potassium, and other electrolytes in the blood
- supply the hormone
erythropoietin, helping red blood cell growth
- produce the hormone renin to
help regulate blood pressure
- produce calcitriol,
also known as Vitamin D, which helps the body absorb calcium and phosphate
from the GI tract
Everyone needs at least part of one kidney to survive. Without either kidney,
the body cannot remove waste or water properly. This accumulation of waste and
fluid can offset the balance of important chemicals in the blood, and leads to
death without treatment.
are the signs and symptoms of renal agenesis?
Both types of renal agenesis are associated with other birth defects, such
as problems with the:
- genitals and urinary tract
- stomach and intestines
- muscles and bones
- eyes and ears
Babies born with URA may have signs and symptoms at birth, in childhood, or
not until later in life. Symptoms can include:
- high blood pressure
- poorly working kidney
- urine with protein or blood
- swelling in the face, hands,
Babies born with BRA are very sick and do not usually live. They typically
have distinct physical features that include:
- widely separated eyes with
skin folds over the eyelids
- ears that are set low
- a nose that is pressed flat
- a small chin
- defects of the arms and legs
group of defects is known as Potter Syndrome. It occurs as a result of reduced
or absent urine production from the fetal kidneys. The urine makes up a large part
of the amniotic fluid that surrounds and protects the fetus.
Who is at risk for
Risk factors for renal agenesis in newborns appears to be multi-factorial.
This means that genetic, environmental, and lifestyle factors combine to create
a person’s risk.
For example, some early
studies have linked maternal diabetes, young maternal age, and alcohol use
during pregnancy to renal agenesis. More recently, studies have
shown prepregnancy obesity, alcohol use, and smoking to be linked to renal
agenesis. Binge drinking, or having more than 4 drinks over 2 hours, during the
second month of pregnancy also increases risk.
Environmental factors may also result in kidney defects like renal agenesis.
For example, maternal medication use, illegal drug use, or exposure to toxins
or poisons during pregnancy may be factors.
What causes renal
Both URA and BRA occur when the uretic bud, also called the kidney bud,
fails to develop at an early stage of fetal growth.
The exact cause of renal agenesis in newborns is not known. Most cases of
renal agenesis are not inherited from the parents, nor do they result from any
behavior by the mother. Some cases, however, are caused by genetic mutations.
These mutations are passed on from parents who either have the disorder or are
carriers of the mutated gene. Prenatal testing can often help determine if
these mutations are present.
Diagnosing renal agenesis
Renal agenesis is typically found during routine prenatal ultrasounds. If
your doctor identifies BRA in your child, they can use a prenatal MRI to
confirm the absence of both kidneys.
Most newborns with URA have few limitations and live normally. The outlook
depends on the health of the remaining kidney and the presence of other
abnormalities. To avoid injuring the remaining kidney, they may need to avoid
contact sports when they’re older. Once diagnosed, patients of any age with URA
need to have their blood pressure, urine, and blood tested annually to check
BRA is typically fatal within the first few days of a newborn’s life.
Newborns usually die from underdeveloped lungs shortly after birth. However,
some newborns with BRA survive. They must have long-term dialysis to do the
work of their missing kidneys. Dialysis is a treatment that filters and
purifies the blood using a machine. This helps keep your body in balance when
the kidneys can’t do their job.
Factors such as lung development and overall health determine the success of
this treatment. The goal is to keep these infants alive with dialysis and other
treatments until they grow strong enough to have kidney transplants.
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 exposure to possible environmental
factors before and during pregnancy. These include use of alcohol and certain medications
that can affect kidney development.
The cause of renal agenesis is not known. This birth defect is sometimes
caused by mutated genes passed from the parents to the baby. If you have a family
history of renal agenesis, consider prenatal genetic testing to determine your
baby’s risk. Babies born with one kidney usually survive and live a relatively
normal life, with medical attention and treatment. Babies born without kidneys
usually don’t survive. Those who do survive will need long-term dialysis.