About 1 in 1350 infants is diagnosed with a kidney malformation by age 1, according to a California Birth Defects Monitoring Program study of 2.2 million births. These babies have a variety of diagnoses: renal agenesis (complete absence), dysgenesis (abnormally formed, often small kidneys), cystic kidneys (with multiple fluid-filled lesions) or other defect (such as a single horseshoe-shaped kidney). This rate does not include children with kidney damage resulting from urinary tract obstruction.

BILATERAL ABNORMALITIES MOST SEVERE

Kidney defects can occur in either or both kidneys. Bilateral abnormalities generally cause major problems because little or no urine is produced. Lack of amniotic fluid (which comes from fetal urine) constricts fetal lung growth; babies die soon after birth from respiratory insufficiency. Seeing no amniotic fluid on prenatal ultrasound is often a symptom of kidney problems.

Unilateral kidney abnormalities typically go undetected because urinary filtration and output are normal. In our study, most infants with unilateral defects had other birth defects that prompted evaluation of the kidneys.

More than half of babies with kidney abnormalities have additional birth defects. 63% of babies with renal agenesis/dysgenesis die before age 1. The lifetime cost for medical treatment, educational services and lost productivity averages $250,000.