Children's Hospital Colorado
Colorado Fetal Care Center

Renal Agenesis

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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%.

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