Children's Hospital Colorado

Renal Agenesis

What is renal agenesis?

Renal agenesis occurs when one or both kidneys completely fail to form. This usually occurs at approximately 4 to 6 weeks into pregnancy and is due to failure in the earliest steps of kidney development.

In the past, many people born with only one kidney (unilateral renal agenesis) lived their lives unaware they did not have two kidneys. Today, prenatal ultrasound makes it much easier to diagnose these conditions and provide better treatment for babies. This also makes treatment much easier and improves outcomes for babies missing both kidneys, which is called bilateral renal agenesis.

At the Colorado Fetal Care Center, we offer nationally ranked care for families facing a renal agenesis diagnosis, whether for one or both kidneys.

Renal agenesis is a rare condition in which babies are missing one or both kidneys at birth. In this disorder, one or both kidneys fail to develop between the fourth and sixth week of gestation. There are two types of renal agenesis:

Bilateral renal agenesis

Bilateral renal agenesis, also known as Potter syndrome, means that both kidneys are missing. This occurs in about one in every 3,000 to 4,500 live births and is more common in boys. When neither kidney develops, it causes a lack of amniotic fluid, which is usually the reason for diagnosis as the low fluid levels are visible during a routine prenatal ultrasound.

Babies with no kidneys are unable to survive without treatment and the available treatments are still experimental. With no kidneys, the baby doesn't produce urine, leading to low amniotic fluid and incomplete lung development.

Unilateral renal agenesis

Unilateral renal agenesis means that a baby develops only one kidney. Found in roughly one in 1,000 live births (higher in twins), this condition is not fatal and often causes no additional symptoms. When a baby has just one kidney, the organ grows larger to compensate and perform the functions of both.

Most babies born with one kidney live normal lives, but this condition is associated with abnormal development of the genitals in 12% of males and 40% of females.

What causes renal agenesis?

While the exact cause is unknown, unilateral renal agenesis is more common with intrauterine growth restriction (poor growth during pregnancy) and in multiples (twins, triplets, etc.). Unilateral renal agenesis is sometimes seen an association with a two-vessel umbilical cord, rather than the normal three-vessel cord.

The cause of bilateral renal agenesis, the absence of both kidneys, is also unknown. In most cases, there is no family history of the condition, though in around one-quarter of cases, there is a genetic component.

The risk of a future pregnancy being affected by renal agenesis is approximately 3 to 4%. If the renal agenesis is part of a condition with multiple abnormalities, the chance for it to reoccur in a future pregnancy may be as high as 8%.

How is renal agenesis diagnosed?

Both types of renal agenesis can be identified in sonographic findings. Unilateral renal agenesis is found when the one developed kidney is larger than normal for the gestational age. Hypertension can also develop due to this anomaly, leading to diagnosis and requiring postnatal follow-up examinations.

Bilateral renal agenesis can be observed through sonographic findings that detail complete or severe depletion of amniotic fluid levels at 14 to 16 weeks. The inability to visualize the fetal bladder after 16 weeks of pregnancy should prompt further investigation for bilateral renal agenesis.

As a parent, receiving the news that your child may be missing both kidneys can be devastating. Even a diagnosis of unilateral renal agenesis can be worrisome, but the Colorado Fetal Care Center is a national leader in diagnosing and treating both types of renal agenesis.

Treatment for renal agenesis depends on the severity and type (unilateral or bilateral). For both types of agenesis, the standard treatment protocol involves monitoring the baby with numerous ultrasounds and planning delivery at the Colorado Fetal Care Center. While C-sections are not usually required to deliver babies with renal agenesis, immediate access to our care team after birth is essential to guarantee the best outcomes.

Bilateral renal agenesis treatment

Babies missing both kidneys cannot survive without treatment but the only available treatment is experimental.

Once diagnosed through a prenatal ultrasound, this defect can be addressed in utero with a series of amnioinfusions. This means that physicians inject saline solution into the amniotic sac to help the baby's lungs develop. Once the lungs start to develop, some stress is taken off the baby's system and he or she may be able to survive once outside the womb. The first known baby to survive bilateral renal agenesis did so in 2013 as a result of this new treatment. Two years later, she received a kidney transplant.

The Colorado Fetal Care Center offers a special amnioport procedure to facilitate amnioinfusion and to avoid repeated, potentially risky injections. Once the baby is born, he or she will be dependent upon dialysis until a kidney transplant can be attempted, usually at 1 year or older. The ability to offer dialysis after birth depends on the baby's size, weight and gestational age.

Unilateral renal agenesis treatment

Most babies who are missing just one kidney have no other symptoms, as that one organ grows large enough to perform the duties of both. However, infants with unilateral renal agenesis can have hypertension (high blood pressure) and may be born prematurely.

What is the prognosis for babies with bilateral renal agenesis?

In 2013, the first known baby to survive bilateral renal agenesis provided hope for all families who face this severe diagnosis. In that case, in utero injections of saline solution restored amniotic fluid and allowed the lungs to develop. Once born, the baby was dependent on dialysis for three years, until her father donated her a kidney.

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